من کمتر دیدم یک طراح سیستم صوتی مقاله های زیادی در مورد صدا و نوع طراحی یک سیستم صوتی نوشته باشه و دقیقا رابطه بین فضای Subjective با فضای Objective رو درک کرده باشه. بقول رومی همه ما میتونیم یک AC Regenerator بسازیم که زیر اسیلوسکوپ پاسخ خیلی خوبی داشته باشیم اما کدوم ما میتونیم یک AC ReGenerator بسازیم که تاثیرش روی صدا خوب باشه. این حرف در مورد همه بخشهای طراحی یک سیستم صوتی صدق میکنه (یک طراح میگفت It’s not hard to make an amplifier that measures well, it’s comparatively hard to please audiophiles ).
من فکر میکنم در حوزه های فای همه کسانی که در دنیا فعالیت دارند، چه طراحان سیستم صوتی ، چه فروشندگان بازار ، چه تحلیل گران صدا و چه دوستداران صدا همه و همه کاری که برای های فای انجام دادند کار بزرگی نبوده، اینکه ما بعد از صد سال Solidstate ساختن (جدیدا همه رفتند بالای 1000 وات) بیاییم اعتراف کنیم یک سینگل اندد 3 واتی با یک هورن پاسخ بهتری قراره بده و یا یک ریل 250 هزار تومنی از سورس 70 هزار دلاری صدای خیلی بهتری میده اینها نشون میده جریان اصلی و حاکم بر های فای در دنیا فقط اشتباه کرده.
من فکر میکنم بزرگترین نقش این جریان رو مجلات های فای بازی کردند که با سوء استفاده از اعتماد مخاطب فقط به صنعتی کمک کردند که هیچ گلی به سر دوستداران صدا نزد.
اما فراموش نکنیم خود های فای هم برعکس شاخه های دیگر علم در کل دنیا آرشیو بزرگی از تجربیات خوب نداره، چرا یکی مثل رومی باید همه وقتش صرف شه تا دنبال یک AC Regenrator خوب باشه و آخرش مجبور شه که خودش اونو با صرف هزینه های بالا بسازه که تازه معلوم هم نیست در نهایت چه نتیجه ای بده، آیا منطقی هست که یک کاربر همه راه رو خودش بره؟
من در جواب خیلی از دوستانی که میخواستند وارد این فضا بشوند نوشتم های فای دردسر داره و هزینه های زیادی ازتون میگیره و بهتره واردش نشید. چرا؟ چون این صنعت، این فروشندگان، این مجلات نتونستند به شما اون چیزی رو که باید بدهند.
اما باز جای خوشحالی است که در اینترنت ما جیم اسمیت ، رومی ، آرتور ، ریچارد، مایک ، داگ ، اولسون ، هافمن و استو رو داریم و کسانی هستند که کمک میکنند درست قدم برداریم اما ای کاش تعداد آدمهای باشعور و تاثیر گذار بیشتر از این بود تا های فای روزهای بهتری رو برای همه دوستداران صدا به همراه میداشت.
ای کاش هر رسانه ای و هر مجله ای و هر فروشنده ای به اعتماد مخاطبش درست پاسخ میداد و دو عامل ندانستن و منافع اونها باعث نمیشد به کاربر یک مسیر اشتباه رو نشون بدهند.
بگذریم، داشتم میگفتم کمتر طراح سیستم صوتی مثل طراح Audio Note و یا Pass Labs حرفی برای گفتن داره، یکی از کسانی که من جدیدا با نوشته هاشون آشنا شدم آقای Steve Deckert هست که سازنده آمپلی فایر و بلندگو با نام Decware هست، ایشون سینگل اندد های زیر 6 وات میسازند با بلندگوهایی که اکثرشون بالای 94 دی بی حساسیت دارند (چقدر جالب میشد یکی از فروشندگان این برند رو میا ورد ایران چون قیمت هاش هم خیلی مناسبه).
لیست کامل مقالات ایشون اینجاست :
http://www.decware.com/newsite/articles.html
چیز جالبی که در نوشته های ایشون هست اهمیت آکوستیک در نظر ایشون هست که مقاله زیر رو نوشتند :
http://www.decware.com/acroom.htm
A listening room – what for?
by Steve Deckert
May 1998 – revised June 2002
A listening room is a room where you listen to music – or is it a room that listens to music? Actually it’s a room that plays the music you listen to….
We basically have two things going on here, and we need to clarify which side of the fence you want to be on. There are two basic kinds of listening habits, one of them is called “passive listening” and one is called “active listening”. Passive listening is sometimes referred to as “background listening”. Perhaps we should call it “hearing” since the person doesn’t really actively listen to it.
A Passive listening system can be anything from a clock radio, to a fairly nice home stereo system that seamlessly blends into your decor and gets turned on for the purpose of filling the room with music which can then be enjoyed from anywhere in the room. (We ALL started out as passive listener’s with our speakers along the wall or in the corners didn’t we?)
An active listening style makes the stereo system the focal point of a room dedicated solely for that purpose. This format allows a much higher resolution of playback to occur, and since the stereo sound field can be experienced in three dimensions rather than two, the enjoyment of it can change into an almost holy experience.
In a dedicated listening room, the freedom to control speaker placement and reflections makes having such a room a scientific experiment to see how much resolution can be resolved.
So, we have two rooms, one is a listening room with no furniture, only your stereo system and the other is (usually) a living or family room with the speakers placed in book shelves, or along the walls somewhere. And yes, I’m sure on occasion super intelligent beings can finagle it in such a way as to have combined the two without compromise.
The bottom line is that many people buy expensive “high end” audio gear and set it (improperly unbeknown to them) up in their family rooms and decide they’re audiophiles. They buy and read the high end journals and then wonder what in the world “delineation” and “layers” mean. I’m not saying it’s any fault of their own, only that too many people are spending too much money trying to get better imaging and more depth, or just overall better sound and aren’t realizing the goal they seek is unobtainable in this scenario.
Buying overbuilt machined connectors and garden hose size speaker wire when the fundamental room acoustics are poor (usually the case) is not a real good return on your investment. Ironically the sonic benefits of high end cables and tweaks are largely masked by poor room acoustics.
I would agree that we’re all in a spot because how many people have a spare room large enough to be a good dedicated listening room? I’ve been there and the vast majority of us are still there. Hell, what do you do? All you can do is perform the WASP speaker positioning procedure (Wilson Audio Setup Procedure) or similar procedure and find the single point in your room with the least amount of evils and then hope you can find a way to live with the results.
Oh, and yes, I almost forgot… there are those $250.00 acoustic pillows you can stick to your walls, or even better than that…. magic “tuning” dots that you can also stick – and that by the shear act of using them will free you of the bondage of this dilemma. In fact I heard that if you paint your CD’s green, put an M&M on the top of each speaker and stick a Brazilian carrot in your ass while sipping ginseng tea your stereo will never sound better!
Hmm. how’s that for freedom of speech? Anyway, the point is high end stereo gear was designed and intended to be set up in a symmetrical stereo array with the speakers a good distance from the rear and side walls for one simple reason – to recreate the space, depth, and focus of a live performance. You see, IT DOESN’T TAKE HIGH END GEAR to reproduce two-dimensional sound fields.
You know in the early days I didn’t used to know what “imaging” really meant. And the expression “sound stage” was curious to me as well. Growing up as a young lad my favorite places to put speakers was ON the wall and in the corners. This gave the most punctual and tight bass response. In those days, bass response was about the only obvious thing that changed from one stereo system to another – so I thought. My ignorance wasn’t tied to stupidity, I had just never been exposed to a “sweet spot” where the sound was a good 100 feet deep, twice the width of the speakers and completely three-dimensional. On the day that happened, everything changed. Prior to that day I read about it until I was blue in the face and couldn’t relate. Still I find it magical to sit in my listening chair with two speakers in front of me and not hear anything come out of the speakers. The sound just comes out of the air from different spots as though there were actually musicians there!
Okay, enough AUDIO CLASS 101 and on to the important stuff. (Understand all types of people read this web site, not just engineers and audio geeks.)
For those of you who are on the side of the fence with the living/family/TV/listening room thing happening, this is the end of the article. For the rest, read on to get you own holy chamber for audio induced out of body experiences.
It is common knowledge among those who’ve tried to find out, that the ideal listening room is rectangular and fairly large. The reason for the larger size isn’t so you can put your speakers farther apart, it is so that there is more space between your speakers and the reflective surfaces of your room.
In a small room, wall reflections ALTER what you hear from your speakers and always in a NEGATIVE way. At the same time, room dimensions create a comb filter effect that is responsible for variations in frequency response that can reach 12 dB or more as well as change by that much just from moving your head. Ever wonder why your stereo doesn’t sound the same way twice? If you have, it’s in part the comb filter effect of your room dimensions on the frequency response!
Having a dedicated listening room where the stereo is the main focal point makes it possible to deal with the evils of room acoustics. Even dimensionally problematic rooms and small rooms can be vastly improved if you know what you’re doing and why!
I would encourage you to consider a dedicated room, even if it’s a spare bedroom, garage, or basement. The science behind it is as fascinating as audio gear and the reward will come to those who really listen.
Lets face it, the average listening space in most homes is inferior. I would say 75% or more simply suck. Most show rooms are no better. CES or trade shows are usually worse. Where exactly do you find a reference for understanding what a good sounding room is! Without being able to actually comprehend how vast the improvement would be to your own gear in a better room it is unlikely that you would spend any real money on room treatment. Add to that the complexity of room treatment compared to a designer power cord, it’s no wonder we waist our money on the power cord.
Steve Deckert
About Treated Room:
A well treated room will make even entry level hi-fi gear sound better than an untreated room containing the very best audio gear money can buy.
Understanding what to do and how to do it is actually less difficult then trying to decide what cables to buy.
We want you to address your listening space, especially if you own our gear because we want it to sound great in your home!
Un-treated rooms mask or skew the differences in cables, speakers and all audio components. This is exactly why audiophiles feverishly buy and sell gear, and what fuels the audio placebo market.
In a properly treated listening space the resolution at which you can hear is at least doubled making it easier to hear the fidelity of any component.
People who have treated rooms are more inclined to step off the buy and sell marry-go-round of audio gear and start listening to music.
I calculate the return on investment is 2 to 1. For every dollar spent on treatments you save two dollars on the never ending quest to make your system sound better.
مقاله جالب دیگه ایشون در مورد طراحی آمپلی فایر هست :
http://www.decware.com/paper43.htm
WHY THE SET & HIGH EFFICIENCY SPEAKER APPROACH WORKS
MAY 2003
by Steve Deckert
On our audiophile forums, members have a moniker that usually includes a tag line. Mine say; “If the first watt sucks, why continue?” Having said that, this is not going to be another hard line attempt to convince you that SET amps are the only way to get good sound, or that high efficiency speakers automatically sound better than anything else.
Over the years I have learned that for every assumption about audio there are exceptions that could lead one to conclude the exact opposite. This “law” encompasses every facet of audio, from cartridges to loudspeakers and all the cables and components in between.
Most people for example have assumed that a 2 to 8 watt per channel SET amp wouldn’t have the balls to get out of it’s own way. It couldn’t possibly have any real bass, but we hear the midrange is to die for.
Most people would also assume the only way to hear any dynamics from a flea powered amplifier is to use big nasty horn speakers so really what is the point?
All of these assumptions are probably a side effect of the general direction that high-end audio has taken since the 1960’s. Solid state has made high power affordable for everyone so the loudspeaker industry responded by making speakers less efficient to both reduce their size and flatten their response.
Despite popular belief, you do not need horn speakers to use or enjoy a SET amplifier. You can also find many horn speaker designs that sound wonderful, better than wonderful in fact, so the question then becomes this:
What are the advantages are to using SET amps with high efficiency speakers?
To answer this, lets start with the advantages of a SET amplifier over any other type. A Single Ended Triode is the simplest circuit design there is, using the least number of parts. Typically this is a driver stage coupled to a single output device. Triodes do not require negative feedback, something found in most all push-pull circuits, solid state or tube. Negative feedback is used to lower distortion specs and in the case of solid state devices it is often the only thing keeping the transistors from exploding all over the inside of your amplifier. Feedback a problem? If you don’t mind the time smear it creates and the resulting 2 dimensional sound stage, then no I guess it’s probably not.
Aside from the amplifier’s superiority by simplicity, there is a more profound reason for using SET amplifiers. The magic predominately lies in the first watt. By magic I mean inner detail and most of the dynamics. For example, a pair of 96dB speakers playing with one watt of power against the average noise floor in your listening room (55dB) is 40 dB of dynamic range. (96 – 55 = 41 dB) Adding a second watt increases the dynamic range by only 3 dB. For every additional 3 dB you need to double your power. This should clearly illustrate that there is over 10 times the dynamic range in the first watt as there is in the second.
This brings us directly to loudspeakers. A typical loudspeaker today is 86 dB efficient with 1 watt. It also usually has a complex crossover that attempts to keep the frequency response and impedance flat. The crossover alone will usually dissipate a significant portion of the first watt as heat before it even reaches the drivers. To reach the same loudness level as the 96 dB speaker will with 1 watt requires over 8 watts on the 86dB speaker. If we used 2 watts on the 96 dB speaker the other would require 16 watts to keep up. If we used 4 watts on the 96 dB speaker the other would require 32 watts to keep up.
The problem here is resolution. If you can’t hit a listening level with the 1st watt, you’re not likely to hear what’s happening in that 1st watt. For a driver to achieve a high efficiency it’s moving parts must be low in mass. That makes it dramatically faster or more accurate than a speaker with heavier moving parts. If you like inner detail and want to hear all of the textures and layers of a good recording you need fast, efficient and coherent speakers.
A good SET amp combined with a single full range driver with no crossover or a simple 2-way using minimal crossover parts on the tweeter only, has a purity and depth that you simply don’t find in more conventional systems. It is a benchmark for coherency, and noted for its ability to create hauntingly real holographic sound stage. Bass and dynamics with this combination sound more realistic in part from the tremendous speed and in part from the coherency.
I’ve consulted many people about their audio systems, and the most common complaints include dry somewhat fatiguing sound with a fairly boring soundstage followed by the realization that it simply doesn’t connect you to the music emotionally like it could. Experience has taught me that by far the easiest way to get a liquid sound that becomes holographic with stunning clarity and detail, something that excites the listener, is to set him up with an SET and simple pair of efficient speakers. It also usually ends up being the least expensive solution.
The biggest conformation of this is reports from audiophiles who used to have several hundred watts and many thousands of dollars invested in show winning audio gear, but now report that even a good 2 watt SET on efficient speakers has better dynamics and weight which they find simply amazing. If you’ve ever observed how audiophiles rotate through audio gear during their lifetime you might also find it interesting that the ones who finally land on SET amps and good speakers seldom find anything they like better.
The bigger is better mentality that is directly connected to more expensive the better is certainly the handicap that stunts most audiophiles from discovering truly high fidelity sound. Will the guys at the audio salon laugh… yes the will. Will your fellow audiophiles laugh when they hear you sold everything and got a 2-watt amplifier… yes the will. Is this important to you? Only you can decide, but I would suggest it has little to do with high fidelity.
In closing, remember this – It is dangerous to place amplifiers, speakers, cables etc., into neat little categories in an effort to make some sense of it all. Not all tube amps sound good. Not all solid- state amps sound bad. With the Internet audiophiles have been set free to research things in a far more unbiased way then ever before. Before the Internet there were only trade magazines, and manufacture’s literature to educate us all and it goes without saying – fairly biased sources. Of course the Internet is full of misinformation, some intentional, some out of ignorance, but at least you can find all sides and make your own determinations.
-Steve Deckert
اینم یه مقاله دیگه :
TUBES vs. TRANSISTORS
by Steve Deckert
Dec. 1997
Below is an email I got that refers to our Tube Vs. Transistor articles located in the tube section of this site. I thought is was well written and respect the position enough to say it speaks for a whole lot more people than just Larry.
Gentlemen,
Your posted articles on Tube VS. Transistor amplifier sound are interesting, but they suffer one serious flaw: YOU SHOULD NEVER EVER ALLOW A TRANSISTOR AMPLIFIER TO CLIP!! Just below clipping, a well designed transistor amplifier well have almost unmeasurable distortion. High power transistor amplifiers today are so good and so cheap, there is no excuse for them to go into clipping. The speakers will begin to distort way before the amplifier reaches near its clipping level. The modern MOS FET transistor amplifier can easily reach peak levels of over 200 watts without clipping.
The even-order distortion that tubes produce is still distortion, but some call it “euphonically correct”, and, with a tube amplifier you can’t turn it off, it’s always there. If I want this kind of possibly desirable coloration in my music listening, I would add a tube stage that is voltage starved which will slightly exaggerate this effect (Such as the product the “Tube Head” from PAiA), and then I would have control over the degree of coloration I would like to inject–and I can turn it off, like a tone control defeat switch.
The one common trait all of you Pro-Tube folks have in common is that it is so easy to poke holes in every one of your attempted objectivist assertions (regardless whether you are a member of the prestigious Audio Engineering Society or not). If you keep your Pro-Tube arguments purely subjective, then I have no argument–each to his own.
My response follows:
Dear Larry,
Thank you for your email! You have just narrowed down what I feel to be the pro – solid state position in only 3 paragraphs which I thought was outstanding!
I think it clear that the two articles I posted regarding the differences between tubes and solid state are an attempt to shed some light on the forever ongoing debate, not an attempted objectivist assertion on my part.
I understand where you’re coming from on your first position on clipping, but don’t forget that using your 200 watt amplifier as an example and listening at a nominal level of 10 watts, you would need 1280 watts to reproduce a 20 dB musical peek without clipping the wave form. I’ve spent hundreds of hours watching music on the scope for the sole purpose of seeing clipping in action, and it is my opinion that in the real world almost all amplifiers will and do clip when playing music.
I also agree that most speakers will be into some type of distortion in the above illustration.
The even order harmonic distortion of tubes can be a
non factor before clipping in a good circuit. I’m not sure it is accurate to imply that the distortion is always there as a consistent coloration.
So, this all leading to my personal position on tubes vs. solid state. First off I do not categorically feel tubes are superior. I think each application in unique. For example, I am a musician, and in my studio, I use solid state amplifiers for the mains and wouldn’t dream of using anything else. It is just more practical. I have heard many solid state systems that sound really good.
Where the difference comes in is in the specific application of hard core audiophile listening. By this I mean going into my listening room (where there is no TV or furniture) and getting off on the illusion of a three dimensional presentation. In this scenario I would challenge any solid state amplifier to sound more realistic than for example my Zen amp. For me the goal is to recreate the emotional responses that occur with live music because it’s real, not to make damn sure the (*#&$% specs are perfect and then deciding the resulting presentation must also be perfect.
There are two reasons why I think tubes sound better in this application. One is that triodes (tubes) can be operated without negative feedback. The other is because a solid state circuit needs many more capacitors in the signal path than a tube circuit, hence more parts. The combination of all the additional parts and negative feedback will ALWAYS result in LESS depth, less detail, less involvement, less pleasure.
Some people think that the goal of a perfect playback system is perfect specs, and some people think the goal of a perfect playback system is one that sounds real. These two perspectives are what I feel is really in debate. And the only reason in my experience for the debate is that spec-o-holics have not heard a good single ended tube amp A/B’d with their ideal of a perfect amplifier.
There are TONS of CRAPPIE sounding tube amps out there. I would say way more than good ones. This makes it easier for the pessimist to draw a negative conclusion when comparing the two, however I will challenge anyone to the test any time you want to make the trip over here.
The most recent person to take this test owned the Cello Music System, has a treated listening room, and has spent to date over 400,000.00 on fine audio gear, and even worked with Levenson. After hearing GOOD tube gear at my place, he has come 180 degrees and will be the first to tell you I’m right.
-Steve
TUBES vs.TRANSISTORS PART II
by Steve Deckert
Oct. 1997
I usually don’t do this, i.e…. debate over-debated issues because it starts feeling like a newsgroup discussion. This continuation is the result of a new response that is even better than the first one in the way it perfectly encapsulates one side of this “great Debate”, so I thought I would post it.
Since this email is so lengthy, I am going to respond to it a point at a time. My responses will be in bold face.
Steve,
Thank you for your detailed and thoughtful reply. However, I must take issue with you on a number of things you brought up.
First of all, I don’t listen to music (mostly classical) with my amplifiers operating at a nominal level of 10 watts. The average listening level is closer to 1 watt, which I have measured numerous times with my HP A.C. voltmeter and “Mitey-Mike” based sound level meter. Besides, if your assertion were true that 10 watts is closer to nominal, then how could your Zen Amplifier, Pass’s Zen Amplifier, or any of the other under 10 watt Class-A Single-ended triode amplifier possibly perform without producing excessive distortion at more than moderate levels?
You are responding to the following statement that I wrote in my previous email:
“using your 200 watt amplifier as an example and listening at a nominal level of 10 watts, you would need 1280 watts to reproduce a 20 dB musical peek without clipping the wave form.”
I don’t listen to my system at an average level of 10 watts either, but then I didn’t say that was the average listening level, I said at a nominal level of… thinking at the time what it would take to reproduce live music at live levels on Ave. efficiency speakers of 86 dB.
Make no mistake, solid state cost effectively gives more people the option to play music loud than tubes. As far as average listening levels, I also agree there is more content in the first magical watt than most people realize.
The Zen amp on the same ave. efficiency of 86 dB speakers cannot perform without producing excessive distortion at those levels, nor could (as you point out) any other 10 watt amplifier. The way this is compensated for is by using more efficient speakers. If you wanted to achieve those levels you could easily do so with large horn loaded designs.
My home system is tri-amplified, which I think is the only way to go for true “high-end” performance. The output of my power amplifiers (7 channels, including an extra sub-bass servo-feedback sub-woofer (my design) in the rear of the room) drive my speakers directly, with no passive crossover to attenuate (or otherwise “color”) the signal. My power amplifiers (custom-modified MOSFET -based kits) have massive power supplies–8 amp. toroidal transformers and 80,000 mfd. of power-supply capacitors per stereo-pair. These amplifiers drive the most excellent Morel MW-142 woofer and MDT-33 tweeter in small satellite enclosures, which I maintain provide better imaging and lower coloration than most (if not all) of the larger system designs (which, often have four and five figure price tags). You probably are not all that impressed with measurements, but, using a pink noise source in 1/3 octave bands, my system measures within +/- 3 dB from 40 Hz. to 18,000 Khz., on axis, or 30 degrees off horizontal axis. This is partly due to the very small cross-sectional dimensions of the midrange/midbass driver, the low mid/high crossover frequency of 1,900 Hz., and the egg-shell-like small enclosure design. I hope to perform pulse-response measurements soon, using a spectrum analyzer program on my computer.
Actually I am impressed by measurements (specs), they are the only tangible non subjective thing we have to analyze performance. I just don’t care what the specs are if something sounds good and rather like not knowing what the specs of a particular piece of audio gear are before I listen to it. I like to audition audio gear with an open mind, and the less I know about what I’m hearing, the more I can hear.
With the reserve instantaneous available power provided by my power amps, at even high levels for home-listening in my 12 X 20 ft. listening room (which, by the way has been acoustically optimized for the system, and the satellites and sub-woofers have been optimally positioned–away from the wall, etc.) I can achieve more than adequately high listening levels without audible clipping.
Audible clipping – I assume that means a form of distortion that you are consciously able to detect. At high levels clipping could be harder to consciously detect against the 100 dB “noise floor” created by the music. However, I’m not saying YOUR system is clipping.
Let’s focus on clipping a moment. A good solid-state amplifier will clip a sine wave coming from a test generator with absolute symmetry–perfectly flat on the top with no droop, and absolutely no overshoot or spikes. This was the problem with the earlier transistor designs and caused them to sound harsh. I followed this carefully back in my college days (late 60’s) when I was selling and installing the new Marantz 8B’s and Model 9’s to the more wealthy people in my community when I was working my way through college. Yes, my first amplifiers were tube-types, Dynaco Stereo 70’s and Mark III’s, and they sounded damn good, I almost cried when I finally got rid of them. This was when the new solid-state units were just coming into existence (Carver, et al.).
Let’s also indicate that when a solid state output device clips it is actually shutting off and then turning back on again creating DC on the voice coils of your speakers, and causing the speaker to stop momentarily. Severe clipping means not enough air moves over the voice coil and it over heats, the number one cause of blown speakers. This is why it is possible to blow up a 100 watt speaker with a 10 watt solid state amplifier.
This sort of well designed transistor power amplifier is capable of amplifying the dynamics of music without audible clipping. It has been my careful study throughout the years that the only clipping that occurs, does so only at the relatively fast transient peaks, and because these peaks are fast, they simply cannot be heard. Why? Because these harmonics occur for only a brief few milliseconds and the psychophysics of the human hearing mechanism simply does not have the neurological apparatus to detect them–the way the cochlea and its associated neuro-waystations simply mask these effects is well understood. Read a good book on psychoacoustics to find this out.
Frankly I could write a good book on psycho acoustics. It is my main focus. What happens in the mind to make one think a system sounds good, is the perspective from which I design audio gear and the very reason I can come across as having little respect for specs. And you are right about our inability to consciously hear the relatively fast transient peaks. Again if you like numbers the neurons in the human brain can not fire fast enough to distinguish phase above around 2800 cycles, yet the effects of such can be heard in the way they effect the sound stage.
The simple equation dB = 10 log (P1/P2) Would then indicate that if at my nominal 1 watt for an 85 dBm or so acoustic level, then the loud passages of the orchestra are allowed to obtain over 110 dBm of acoustic level before my amplifier would begin to clip to a point that could be audible. Remember, my amplifier can produce 300 watts or more for a several milliseconds without clipping–long enough to sustain nearly all of these short duration peaks without clipping. That’s what is called reserve power, something that just is not present with your preferred low power Class-A single ended tube designs–all they can do is squash these peaks severely and in so doing throw in the signal all kinds of harmonic content (coloration) that simply is not supposed to be there–if you want reproduction that is close to the original source. It’s ironic that you criticize my 200 watt RMS amplifier based upon its insufficient power and yet advocate the use of a 6+ watt single-ended Class-A amplifier in you Zen Amplifier article. I suspect that such an amplifier would be very effective in driving headphones, but not much else.
I don’t think there is an argument here about clipping, I simply think tubes can sound better. I am sure your system is not clipping 99% of the time at the average listening levels you operate it in.
Reserve power, called “head room” is a monumentally important thing to have a lot of in a good solid state amplifier for reasons we have both pointed out. If solid state amplifiers didn’t clip so aggressively (flat line DC at the peaks) the amount of head room would not be a serious issue to the listener. In a tube, clipping is completely different. Since a tube works by passing electrons from a cathode through a charged screen to a plate by way of different electrical potentials, there is no such thing as “clipping” as we’ve come to know it through this discussion. The tube never shuts off, and never puts DC on the voice coil. It never creates an unnatural flat line at the top of musical peaks. What happens is more like a bucket (the plate) being filled with water (electrons). When the plate is saturated there is no longer a potential difference – so, no more electrons are accepted on the plate until there is room made on the plate by the dissipation of those electrons. Instead of clipping, a form of compression occurs as the difference between the continuous power and peak power are reduced.
I too have spent many hours observing amplifiers clip on an oscilloscope. In fact I have a special oscilloscope (formally used for medical signals) that has a high-persistence (P7) phosphor, which is ideal for catching the peaks of musical content. I have also built a special sample-hold circuit from an LED dB level meter I.C. which has been carefully adjusted to light an LED and hold it on for a half-second any time my amplifier clips (I also have to compensate for changing power line voltages). Using this apparatus, I have found that my amplifiers rarely clip. And, when they do, it is of such short duration that it simply is not audible. Incidentally, as an experiment, I once connected a very fine 30 watt solid-state amplifier to my Morel Woofers and found it to be inadequate–its clipping was indeed audible! Thank god it did not disguise this clipping by squashing it! This was a clear indication that I needed more reserve power.
…or perhaps a 30 watt tube amp. And yes, thank god it did not disguise this clipping by compressing it because that would have been musical by comparison.
OK, what about these clipped peaks? Observing this on the scope, these peaks are again, relatively brief. A properly designed amplifier of adequate power will clip these peaks (which, remember, occur rather infrequently in the context of the rest of the mass of the musical content) cleanly, without overshoot, etc. Thus, the harmonic structure of this clipping is of very high frequency and low power content. It is well above 3,000 Hz., and probably exists mostly as harmonics above the 18 Khz. audible top end–remember, these are harmonics of already very brief peaks–peaks of generally less than 5 ms. which are too short in duration to be perceived.
My observations have been that solid state clipping can happen anywhere from 20 Hz to 20 kHz and usually does. In fact the kick drum centered anywhere from 40 to 100 cycles depending on how it’s tuned, can usually by found on a scope as the number one clipping frequency. I didn’t know you could have harmonics of a fundamental clip that high up the spectrum without either the fundamental itself or one the first three harmonics of that fundamental clipping.
I also need to mention that the load given to the amplifier by the speaker at any given frequency and the amount of negative feedback will largely determine where in the frequency band an amplifier is most likely to clip. To think of an amplifier as a separate entity would be misleading since the speaker completes the circuit, and no two speakers are alike.
It has been demonstrated that the perception of “harshness” occurs in the critical 800 Hz. to 3 Khz. region, and it has to be sustained long enough to be perceived by the hearing mechanism. The distortion produced by the occasional instantaneous clipping of a sharp music spike in an amplifier has most if not all of its power-spectral content well above this critical frequency range.
Yes, on a linear scale it might, but hearing is non linear. Our ears have the highest sensitivity in the 800 Hz to 3 kHz region, so even though the majority of clipping may occur outside this band, any clipping in this band would be perceived.
You say that “even order harmonic distortion of tubes can be a non-factor before clipping in a good circuit”. That’s basically true. A well designed tube amp will probably have less than 0.1% harmonic distortion below clipping, which is inaudible. But the problem comes when the tube-amp runs out of steam and begins to go into clipping. I find 200 watt (RMS) tube amps. insanely expensive, and almost non-existent. The coloration of a tube amp. is more “consistent” (your words) if it is lower in power and thus able to squash the signal more readily. Well designed 200+ watt RMS solid-state amps. are readily available, easy to maintain, fairly power efficient (class A-B), and not too expensive.
The debate is not about practicality, but musicality. Tube amps a not terribly practical. In fact a good one is not unlike a pet, requiring special attention and upkeep. Solid state was a less expensive more reliable means and largely more profitable way to build amplifiers so everyone jumped on it.
The differences between the even order harmonic distortion
tubes generate and odd order harmonic distortion that solid state amplifiers generate are profound. If you had to listen to both types at a level where they were in heavy distortion, the solid state would make your eyes water, where as the tubes would possibly go unnoticed. Clear an issue of psychoacoustics.
So, now comes the High-End (Retro Ghetto?) Politically-correct single-ended Class-A Triode amplifier. Generally, these products can produce about 20 watts maximum. So just imagine how these “waveform squashers” color the signal with all but perhaps the most efficient loaded-horn type of speaker systems (the latter of which really are “colorizers”!–believe me, I spent dozens of hours in listening rooms during my college days listening to these beasts, the only thing worst was the horrible Bose 901). So, Steve, in your Zen Amplifier article, you say that amplifiers contribute more to the quality of the sound than anything else, including speakers. Yes, for these “Class-A Puny-Watt Triode Wonders”, you are probably right. They should definitely have the ability to muck up the sound more effectively than anything else in the signal chain.
Living in this country and market, I clearly expected you would also be an anti-horn person, so let me just say that the horns you listened to sucked, and you probably heard them on solid state gear which is a no no. Good horn speakers have the most intimate coupling to amplifiers of any speaker. For that reason, you do not want to try to separate the two with feedback, and that eliminates almost all solid state circuits. There are no good horn speakers in this country.
And so, is 2nd order or even-order harmonic content distortion really what we want? Does it exist on the original master-tape? These Class-A designs are really tone-controls in disguise, as I mentioned in my last letter. I see people insist on buying preamplifiers (even passive preamps) that are devoid of bass and treble controls (even a tone-defeat is not good enough for these “purists”) and yet connect these preamps up to Class-A amplifiers that are rich in adding the sort of “warm” coloration that is raved about–nice tone control, eh?–except you can’t turn it off!
What we really want is zero distortion, but this is audio where no one can have it all. And IF we ran amplifiers to a level where they begin to distort, even order would be far less of an offense that odd order would it not? You imply again that tubes are always producing even order distortion, yet you yourself agreed that a good tube circuit operated within its parameters can have less than .1% I have been told and have done double blind listening tests to see, that humans can’t detect harmonic distortion until it reaches 3%. I found that to be basically true, so when I see people basing buying decisions on the difference between .01 and .0001 % harmonic distortion I just have to shake my head.
Because of the fewer parts needed to construct a tube circuit, I find a good tube amp not only has LESS coloration than solid state, but it can also sound faster.
What I want to achieve is a music system that does nothing to the signal coming from the source–be it compact disk or master tape. I want all the creativity, artistry, and hall effects to end where the rarefactions of air hit the microphone capsule. At least as much as possible–I know I am still victim of the whims of the recording engineer. But the recording companies are getting better and better all the time. A fine example of this is the improved CD quality of Deutsche Grammophon over the years.
The classic statement made by all engineers and audiophiles absorbed with specifications.. I want the same thing stated in a different way… to achieve a music system that breaths with openness and is not veiled by negative feedback and excessive parts to insure great specs. You see even more important than great specs are the things that specs can not yet measure, like clarity, depth, width, focus, delineation. These are the things that determine how REAL a recording sounds. If you take your average solid state amplifier with perfect specs and compare it with my Zen amp, you will discover that the Zen amp lets you hear several additional levels of detail, the result being far more realistic and involving at moderate listening levels.
Unfortunately phonograph records and vacuum tube amplifiers don’t do this, they add color–something which was not present in the original. After listening to such a system for months or years it would be natural for one to say that a CD/Solid-state system sounds thin or lacking in warmth, etc. But on this basis so would perhaps be the sound of a live performance. This reminds me of the psychology experiment where young chicks are given two containers of “water”. In one container is pure water, but the other container contains mercury. the chicks immediately go for the container of mercury–it is more shiny and reflective than the water–a sort of super-stimulus–more warmth, more air around the instruments. In college I got the same effect smoking a joint!
I can’t agree with that, but I will suggest that getting stoned before listening would be similar to hearing my Zen amp. You would be so lost in the music you wouldn’t care about clipping.
I wonder what would happen if individuals of the Pro-Tube camp were asked to listen to two sources hidden behind a curtain. One curtain would be a live performance–say a string quartet playing Schubert, while being miked. And, they would then be asked to listen to the amplified reproduction of that string quartet through the best Single Ended Triode Class-A amplifier system money can buy. I suppose they would favor the latter, as they would hear the warmer sound and the increased “air around the instruments” produced from the increased coloration introduced by the amplifiers.
They would favor the later because the later would have the ability to deliver a far more accurate presentation. In fact it should be almost impossible to tell the two apart. I can assure you that the triode camp could pin point a solid state amp in the signal path in less than 5 seconds every time.
And, your comment about negative-feedback. You, and many others like to imply that negative feedback is a bad thing. Sorry, but this only indicates your ignorance of electrical engineering concepts. You should refer to articles already written by Tom Nousaine, David Rich, Tomlinson Holman and others who have already gone into depth about such misunderstandings. Negative feedback is part of the reason solid state amplifiers can achieve extremely low distortion figures of say less than 0.05%. But, according the Pro-Tube Camp, low distortion must be a bad thing–something to be avoided, or at least not discussed. It’s no wonder then why manufacturers of tube amplifiers seldom publish any meaningful distortion figures. Besides, according to many who make all those subjective testimonials, careful laboratory measurements are meaningless. If what they claim is true, the laws of physics somehow magically do not apply to audio equipment!
The laws of physics do not apply to the laws of psychoacoustics, nor do specs (as I previously pointed out) define all the variables of realistic playback. Also I do not feel terribly ignorant of electrical engineering concepts. I obviously have done more with negative feedback study than yourself because I was willing to look beyond specs. Oh believe me, negative feedback is the best thing since sliced bread for engineers. It lowers distortion and raises dampening by a considerable amount. The problem is that by taking the output of an amplifier and running it back into the input stage, you create a time delayed input super imposed over the original signal that veils and homogenizes the output. Quite frankly it is a speaker dependent argument, but in general I find negative feedback has the exact same sonic effect as throwing a blanket over your speakers.
Then you mention that solid-state amplifiers have more capacitors in the signal path. Well, nothing could be further than the truth. Besides, a properly spec’ed coupling capacitor has absolutely NO effect on the sound. All it is doing is blocking DC. All of this talk about one brand of capacitor having superior sonic characteristics to another is absurd superstition and could never be proven with objective A-B listening tests. Besides, most modern solid state power amplifiers have only one coupling capacitor. It is at the input–to block any small DC offsets. The rest of the design is direct-coupled, all the way to the loudspeaker. My home system has no passive crossover network at the loudspeaker either. I’m using 24dB/Octave (Linkwitz-Riley) active equalization using 1% matched components for nearly identical response characteristics from both stereo channels for maximum “holographic” effect. The instruments of my reproduced orchestra have excellent spatial placement. In fact, better than anything I have yet heard at my local High-End Saloon listening to five figure-systems, but, of course, this is just my subjective (and therefore biased) opinion. Here, Double-blind ABX testing would be a bit difficult.
Your position on coupling capacitors is depressing and absurd.
Capacitors are the single most worse thing you could ever pass a musical signal through, necessary evils. What kills me is that the time constants associated with capacitor design can be easily measured, and you should like that. BTW, I’ve never heard a system in a High End Saloon (grin) that sounded better than my own either. They typically don’t.
Looking at the sketch of your Zen Amplifier at the top of your article, I believe I see three coupling capacitors per channel, if this is true, aren’t you being a bit hypocritical here? The vacuum tubes and output transformer are much bigger contributors to coloring (distorting) the signal than a coupling capacitor. A coupling capacitor simply exhibits a very low reactance (resistance) throughout the entire audio range–that’s all. And, all the absurd theories by proposed certain tweako capacitor manufacturers are just plain fancy. One 2 Mfd. mylar capacitor will have the same effect as any other 2 Mfd. mylar capacitor–it has no “sound” of its own.
The schematic you’re referring to was an integrated amplifier from which the Zen amp project was born. The Zen amp is only the last stages of that circuit, and does use only one coupling cap. And none is used on the input, the input is direct coupled.
The output transformers do more for creating a harmonious impedance balance between the amplifier and speakers than they do damage by coloration, and are the very reason why horn speakers can sound so good on a tube amp.
I stuck with my Dynaco Mark III’s up until the early-eighties, for my more serious listening of opera and orchestral music. But, as a hobbiest, I began to build better and better solid-state amplifiers. And, when the better MOSFET designs came out, it was clear to me that it was time to make the switch. No more annual replacement of those expensive 6550 matched pairs, or monthly checking of the grid-bias. Better, cleaner, purer sound resulted from my transition to solid state amplifiers.
The Apt/Holman company nearly 20 years ago designed a transistor amplifier that would simulate the squashing effects of a tube-amplifier going into clipping. Using special circuitry they made the edges of the clipping rounded, just like the effect you get with vacuum tubes. They then did some serious blind-testing with a group of listeners, comparing this experimental design with their standard design which clips very squarely, with no overshoot or droop. And, to their amazement, their listeners reported that they preferred the sound of the un-modified square-clipping amplifier to the sound of the vacuum-tube-like clipping effect. I wish I had my hands on the paper they published on this–I would send it to you.
Yes, I should think they would have found the unmodified amp more open sounding , and the other modified amp to be slightly more veiled by the additional complexity of the circuit.
I find the preference much of the High-End community has (as exemplified by Stereophile Magazine) towards the preference to vinyl recordings to the superior CD, and Vacuum Tubes to transistors (especially the Single-ended Class A Triode four and five figure nicknacks probably only purchased by the very rich who, not caring a diddily about the sound quality, only want the stuff to impress their colleagues at cocktail parties) took two equally giant steps backward in the progress of making sound reproduction more real. When these such digressions became rampant, many very brilliant electrical engineers, being designers of fine sound equipment, left the industry to seek other occupations in computer technology, video, etc. I personally know at two of them. They simply could not stand the insanity.
A lot of truth in that statement.
Steve, you are a musician and therefore I applaud you. We need more musicians, especially musicians of a classical music bent. Interest in classical music is waning in the U.S., as witnessed by a progressively declining attendance to live concerts (and NOT the allegedly inferior 44.1 Khz. sampling rate of the CD–how absurd!), perhaps just another indication of the gradual “dumming of America”. Perhaps, it would be more beneficial to humanity that you concentrated your efforts to the making of music, or the reporting of fine musical recordings, than the retrograde and ultimately fruitless interests of yet another vacuum-tube amplifier design. It is probably a waste of your creative potential as an artist. Instead of trying to design amplifiers, have you thought seriously about composing music?
No offense Larry, but I am focused in the correct direction. My work will make it possible for many people to enjoy listening to music again who otherwise may not have.
Lastly, I find interesting parallels between the High-End audio industry and the fashion industry. Insanely expensive stuff–wives thumb through fashion magazines that advertise four-figure designs while their husbands thumb through Stereophile Magazine imagining themselves owning that five-figure amplifier or speaker system advertised. Oh, yes, tubes are definitely more photogenic than transistors.
You’re correct about the similarities from a market perspective, I have no real argument with that.
Well, Larry, you certainly haven’t left anything out.. except possibly an open mind. Let me conclude this, my last response, with a story:
Several years ago I had a friend who I used to involve in my speaker design work because he had good ears. He went to school to become an engineer. As the first year passed I watched the magic of audio leave his spirit as his schooling defined boundaries from which to think inside. Once he knew the laws, there was no point in trying to work outside those laws “because it won’t work”. One day at the repair bench we were finishing up a job, and having a beer when I bet him I could turn the beer can into a speaker. I explained that by cutting it in half and installing a magnet inside, reassembling it and wrapping a coil around the outside that I would have a working speaker. He though about it for a minute and bet me that no sound would come out because there would be no linear travel possible by the voice coil. I still have that beer can and it still measures +/-3dB from 300 to 10K.
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