A 7.5w       101db
B 15w        98db
C 30w        95db
D 60w        92db
E 120w      89db
F 240w      86db
G 480w      83db

عدداي بالا كه نوشتم تقريبا تناسب بين توان امپلي فاير با حساسيت بلندگو هست

يك لامپ خوش صدا 300b تو مد سينگل اندد بيشتر از ٧/٥ وات نميتونه بده

لامپ ٢١١ يا ٨٤٥ گرچه ميتونن بيشتر از 300b توان بدن اما هم كار كردن باهاشون سخت تره و هم ممكنه اون ظرافت 300b رو تو صدا به شنونده ندن.

اگر ايده ال بخواهيم فكر كنيم براي سينگل اندد لامپي راهي جز انتخاب بلندگوي بالاي 100db نداريم و عملا از درايوري خارج ميشيم ميرسيم به هورن

حالا طراحا چكار كردن كه ما از غير هورن هم صدا بشنويم . اومدن دوتا لامپ رو موازي كردن مثل كوندو جكو ps . اومدن از لامپهاي قوي تر استفاده كردن مثل ٢١١ . اومدن بجاي ترايود از مد پنتود لامپ كه غيرخطي تره استفاده كردند. اومدند از پوش پول بجاي سينگل اندد استفاده كردند.

ولي مساله اينجاست كه وقتي خطي ترين حالت رفتار يك لامپ مد ترايود سينگل اندد هست با ولتاژ كمتر كاري هر كاري كنيد كه توان بيشتر بشه ديگه مثل قبل خطي نيست و چه با فيدبك اينو تغيير بديد چه نديد در حالت توان بيشتر شما يه چيزايي رو ممكنه از دست بديد و راه حل ايده ال اينه خود بلندگو حساسيتش بالا باشه.

http://www.goodsoundclub.com/Forums/ShowPost.aspx?PageIndex=1&postID=11455#11455

The problem is that it is completely impossible, even theoretically impossible to be able to hear anything audio-valuable when one uses 200-400 watts SS push-pull and dead tonally and contrast disabled loudspeaker. Why? Connect this 300W SS amp to a PROPERLY BUILT AND PERFORMING 110dB sensitive system and listen what this realy amp does. Sound too revolting? Now connect it back to your 90dB sensitive speakers (even a god one) and see if your SS amp can REALLY discriminate tonal and dynamic charisma of notes? It is it! The game is over and the high power SS amp after this self-education should be sent to hell, or more precisely to the Audiogon to benefits a next idiot out there….

It is 21 century and still there is no good, tonally and contrast capable high sensitively loudspeaker. If all those people who waste themselves by infinite search of high power SS push-pull Messiah would spend the same amount of time and money to discover the potentials of properly done multi-channel (no single driver idiocy please!) high sensitively speaker then ALL those high power, SS, push-pull, gray-sounding amplifiers will die off and will not be applicable for a high demanding home sound reproduction…

Romy The Cat …

تنها راه برای صدای خوب بلندگوی حساسیت بالاست

بين آمپلي فايرهاي ترانزيستوري و هيبريد (خروجي SS) كمترين فيدبك رو برندهاي زير دارند :

Vitus , Ayre , Ypsilon , Dartzeel , Firstwatt J2 , Dan Dagostino , Hovland, Naim

بين آمپلي فايرهاي Tube كمترين فيدبك رو برندهاي زير دارند :

Audiopax , Audio Note , Border Patrol , Wavelength Audio , Leben , Lamm ML3 , PrimaLuna , Sophia Electric , Wavac , Antique Sound Lab

بین مدلهای Lamm فقط مدل Lamm ML3 فیدبک نداره. مدل های جدید Airtight فیدبک منفی دارند.

من نظرم اينه نداشتن فيدبك منفي شرط لازم براي صداي خوب هست و نه كافي و با ديدن اين ليست اول اونايي كه تو ليست فيدبك منفي بالايي دارند رو حذف ميكنم و بعد اونايي كه فيدبك منفي كمي دارند رو سعي ميكنم بشنوم ببينم صداشون چطوره.
لازم به توضيح هست توپولوژي هاي مختلف رو نبايد با هم مقايسه كنيد واسه همين من لامپي رو از ساليد استيت جدا كردم و بين ساليد استيت ها هم اونايي كه ترانس خروجي دارن وضعيتشون متفاوته.

A Future Without Feedback?
When Black proposed negative feedback in 1927, he was trying to solve a specific problem: the deep cascading of imperfect, transformer-coupled tube amplifiers. But has anyone explored the implications of negative feedback for reproduced sound quality in the absolute sense?

Based on my experience of the pairing of a zero-loop-feedback preamplifier and amplifier, and supported by the evidence that amplifier designers consciously or unconsciously attempt to reduce negative feedback to improve subjective quality—even if this means worsening the measured performance—we need to reconsider the subject.

It is possible that engineers need to rethink how audio systems should be designed. Before the introduction of transistors limited to low voltages, which forced the speaker industry down to 8 and 4 ohm impedances, speakers were typically 8 to 16 ohms, did not need thick cable to wire them up, achieved maximum electromagnetic utilization at good efficiency, and were well matched to tube amplifiers. Higher efficiency spells better dynamics, reduced thermal compression, and the potential of using smaller, more perfect power amplification. But if speakers were designed to have smooth impedance curves, to be relatively uncritical of amplifier or cable matching, and to offer higher sensitivity, we would have greater freedom to examine the feedback question and the validity of the low-power, short-path, zero-feedback approach.

We still have much to learn about the art of sound reproduction; ultimately, our responsibility is to our ears, not to established precepts.

هرچقدر فیدبک منفی کمتر باشه امپدانس خروجي بيشتر ميشه و صدا بهتره.

https://www.stereophile.com/reference/70/index.html

Ypsilon Electronics Hyperion monoblock power amplifier its output impedance was relatively high for a solid-state design, at 0.35 ohm

Ypsilon Aelius monoblock power amplifier The output impedance was high for a solid-state design, at 0.44 ohm at 20Hz and 1kHz, 0.47 ohm at 20kHz.

AkitikA GT-102 power amplifier 0.2 ohm at 20Hz, 0.11 ohm at 1kHz, and 0.13 ohm at 20kHz

Constellation Inspiration Stereo 1.0 power amplifier The output impedance was low, varying from 0.11 ohm at 20Hz and 1kHz to 0.12 ohm at 20kHz.

Bel Canto Design Black ACI 600 integrated amplifier The output impedance at the speaker terminals was 0.2 ohm at all audio frequencies

Pass Laboratories XA25 power amplifier The output impedance (including 6′ of speaker cable) was low, at 0.08 ohm at 20Hz and 1kHz, rising very slightly to 0.1 ohm at 20kHz.

PS Audio Stellar M700 monoblock power amplifier The output impedance (including 6′ of speaker cable) was low, at 0.1 ohm at 20Hz and 1kHz.

Pass Laboratories XA60.8 monoblock power amplifier The XA60.8’s output impedance, including 6′ of speaker cable, was 0.07 ohm at 20Hz and 1kHz, rising to 0.1 ohm at 20kHz.

Dan D’Agostino Progression Mono monoblock power amplifier The output impedance was high for a solid-state design, at 0.44 ohm at 20Hz and 1kHz, rising slightly to 0.49 ohm at 20kHz.

Siltech SAGA power amplifier output impedance was higher than is usual for a solid-state design, at 0.23 ohm

Krell OLD KST-100 power amplifier output impedance was close at 0.15 ohms, rising to 0.2 ohms by 20kHz.

Emotiva XPA Gen3 two-channel power amplifier The output impedance, including the series resistance of the speaker cables I used, was very low at 20Hz and 1kHz, at 0.09 ohm, and rose only slightly at 20kHz, to 0.125 ohm.

Mark Levinson No.536 monoblock power amplifier The output impedance was low, at 0.1 ohm at 20Hz and 1kHz, rising slightly to 0.13 ohm at 20kHz.

Audionet Max monoblock power amplifier The output impedance was very low, at 0.045 ohm (including the speaker cable) at 20Hz and 1kHz, rising slightly to 0.07 ohm at 20kHz.

AVM Ovation MA8.2 monoblock power amplifier The output impedance (including 6′ of cable) was very low, at 0.08 ohm at 20Hz and 1kHz, rising very slightly to 0.1 ohm at 20kHz

Boulder Amplifiers 2150 monoblock power amplifier Measurements The output impedance, including 6′ of speaker cable, was extremely low, at 0.02 ohm at low and middle frequencies; this rose only slightly, to 0.026 ohm, at the top of the audioband

Bel Canto e.One Ref600M power amplifier output impedance, including 6′ of cable, was low, at 0.1 ohm from 20Hz to 20kHz.

First Watt J2 power amplifier The output impedance was relatively high for a solid-state design, at 0.5 ohm from 20Hz to 20kHz.

PS Audio BHK Signature 300 monoblock The output impedance (including the series resistance of 10′ of speaker cable) was on the high side for a solid-state amplifier, at 0.16 ohm at all audio frequencies

Ayre Acoustics MX-R Twenty monoblock power amplifier the output impedance was higher than usual for a solid-state design: 0.26 ohm at low and middle frequencies, rising to 0.28 ohm at 20kHz

Simaudio Moon Evolution 860A power amplifier The output impedance, including 6′ of speaker cable, was very low, at 0.09 ohm at low and middle frequencies, rising to 0.11 ohm at the top of the audioband.

Bricasti Design M28 monoblock power amplifier The output impedance, including 6′ of speaker cable, was very low, at 0.05 ohm at low and middle frequencies, rising to 0.06 ohm at the top of the audioband.

Constellation Audio Performance Centaur Mono monoblock power amplifier The output impedance was low for a bridged design, at 0.07 ohm including the cable at low and middle frequencies, rising slightly to just under 0.1 ohm at the top of the audioband.

Symphonic Line Kraft 400 monoblock power amplifier The output impedance was 0.04 ohms or less at low and mid frequencies, and under 0.07 ohms at 20kHz

Mark Levinson No.53 Reference monoblock power amplifier The output impedance at low frequencies was very low, at 0.06 ohm, including 6′ of speaker cable. This rose to 0.25 ohm at the top of the audioband

darTZeel NHB-458 monoblock amplifier The output impedance was high for a solid-state design, at 0.3 ohm (including 6′ of speaker cable) at all frequencies.

Lamm M1.2 Reference monoblock power amplifier The output impedance at the “1–6 ohms” setting was 0.15 ohm at low and middle frequencies, rising to 0.18 ohm at 20kHz.

MBL Reference 9011 monoblock amplifier The output impedance was very low, at 0.05 ohm at 1kHz and below, rising to 0.1 ohm at 20kHz.

Goldmund Mimesis 8 power amplifier output impedance: assessing this by measuring the voltage drop at a 1W level when an open-circuit load was replaced by an 8 ohm resistor gave a figure of 0.04 ohms at 20Hz and 1kHz. Repeating the measurement using a 4 ohm load, thus demanding twice as much current, gave a figure twice this, at 0.08 ohms. Though this is still inconsequential, it puzzles me, as does the fact that at 20kHz, the discrepancy was smaller, at 0.12 ohms (8 ohm load) vs 0.15 ohms (4 ohm load).

Soulution 710 power amplifier The output impedance, including the series resistance of 6′ of speaker cable, was very low, at 0.06 ohm at 20Hz and 1kHz, rising to 0.075 ohm at 20kHz.

Luxman B-1000F monoblock power amplifier The output impedance was 0.125 ohm at 20Hz and 1kHz, rising slightly to 0.15 ohm at 20kHz.

Electrocompaniet AW400 monoblock power amplifier The output impedance is specified as being below 0.01 ohm, which is very low. However, including 6′ of speaker cable, I measured 0.135 ohm at low and midrange frequencies, rising very slightly to 0.17 ohm at the top of the audioband.

Bryston 7B SST² monoblock power amplifier The Bryston’s output impedance was low for a balanced design, at 0.11 ohm at low and middle frequencies, rising slightly to 0.17 ohm at 20kHz.

Aesthetix Atlas power amplifier The output impedance was relatively high for a design with a solid-state output stage, at 0.34 ohm at low and middle frequencies, rising very slightly to 0.36 ohm at 20kHz.

EAR/Yoshino M100A monoblock power amplifier Transformer Coupled It was lowest from the 4 ohm output, at 0.55 ohm across most of the audioband—equivalent to a damping factor of just under 8—rising to 1.05 ohms at 20kHz. The 8 ohm figures were 1.1 ohms, rising to 2.3 ohms at 20kHz, while from the 16 ohm transformer I measured 1.9 ohms at 20Hz and 1kHz, and a very high 4 ohms at 20kHz.

Adcom GFA-565 monoblock power amplifier output impedance was uniformly low—ranging from 0.02 ohms from the bass to the upper midrange and increasing slightly to 0.03 ohms at 20kHz.

Musical Fidelity 750K Supercharger monoblock power amplifier The output impedance was a little higher than usual for a solid-state design, at 0.11 ohm at 20Hz and 1kHz, rising to 0.22 ohm at 20kHz

Electrocompaniet Nemo monoblock power amplifier The output impedance measured higher than specified, at between 0.17 and 0.23 ohms

Accuphase M-2000 monoblock power amplifier The output impedance was a extremely low 0.035 ohm at 1kHz, increasing to a measured maximum of 0.038 ohm at 20Hz into an 8 ohm load, and 0.063 ohm at 20kHz into 4 ohms.

Halcro dm88 Reference monoblock power amplifier The dm88’s output impedance was very low across almost all the audioband, at 0.1 ohm including 6′ of multistrand speaker cable. It rose slightly at 20kHz, to 0.14 ohm

McIntosh MC501 monoblock power amplifier output impedance, I was surprised to find it to be lowest from the 8 ohm tap, at 0.08 ohm, and highest from the 2 ohm tap, at 0.13 ohm

Edge NL-12 power amplifier output impedance was 0.1 ohm over most of the audioband, rising to 0.3 ohm at 20kHz

Pass Labs X1000 monoblock power amplifier The output impedance measured between 0.18 and 0.20 ohms (the higher values were at 20kHz)

47 Laboratory 4706 Gaincard power amplifier I measured around 0.15 ohm at 20Hz and 1kHz, this dropping to 0.08 ohm at 20kHz

Hovland Radia power amplifier The output impedance was a low 0.2 ohm across most of the band, this rising inconsequentially to 0.26 ohm at 20kHz.

Krell Full Power Balanced 350mc monoblock amplifier the output impedance was 0.18 ohms at 1kHz and 20kHz, 0.15 ohms at 20Hz

Musical Fidelity Nu-Vista 300 power amplifier the output impedance was 0.08 ohms/0.04 ohms, left/right, respectively, across most of the audio band.

Linn Klimax 500 Solo monoblock power amplifier The output impedance measured a minuscule 0.043 ohms at 1kHz, increasing to 0.071 ohms at 20kHz, both assessed by measuring the voltage rise when an 8 ohm load was open-circuited. Using 4 ohm loads, this increased by a maximum of 0.01 ohm at 20kHz, to 0.081 ohm.

Mark Levinson No.33H monoblock power amplifier output impedance was extremely low at 0.02 ohms at 20Hz and 1kHz, rising slightly to 0.026 ohms at 20kHz.

Ayre AX-7 integrated amplifier Its output impedance was moderately high for a solid-state design, at 0.4 ohm across the audioband.

ASR Emitter II Exclusive integrated amplifier The ASR’s output impedance was very low: <0.08 ohm across the audioband (including the series impedance of 6′ of multistrand speaker cable).

Mark Levinson No.383 integrated amplifier The power-amplifier output impedance was very low at approximately 0.055 ohms across most of the audioband, this rising to a still negligible 0.065 ohms at 20kHz

Luxman L-509X integrated amplifier The output impedance at the speaker terminals was a very low 0.075 ohm at low and middle frequencies, rising to 0.11 ohm at the top of the audioband.

NAD C370 integrated amplifier output impedance across most of the audioband a moderate 0.16 ohm, this rising slightly to 0.19 ohm at 20kHz.

Ayre Acoustics AX-5 integrated amplifier The AX-5’s output impedance was a little high for a solid-state design, at 0.27 ohm across the audioband, this due to the circuit’s lack of loop negative feedback.

Roksan Kandy K2 integrated amplifier  output impedance was a very low 0.09 ohm at low and middle frequencies, rising slightly to 0.15 ohm at 20kHz due to the usual series Zobel inductor.

Sugden A21ai The amplifier’s output impedance from the speaker jacks was a low 0.12 ohm at 1kHz, rising to 0.39 ohm at 20Hz and 0.25 ohm at 20kHz.

Krell FBI integrated amplifier The output impedance (including 6′ of speaker cable) was very low, at 0.08 ohm at low and midrange frequencies.

darTZeel CTH-8550 integrated amplifier The CTH-8550’s output impedance was quite high for a solid-state design, at 0.4 ohms in the bass, rising to 0.5 ohms at 20kHz.

Devialet D-Premier D/A integrated amplifier I measured 0.04 ohm at all audio frequencies, but thus includes the impedance of the 6′ of speaker cable I used for the test. But the fact that the D-Premier has an extraordinarily low output impedance

Naim Audio NAIT 5si integrated amplifier The output impedance ranged from 0.34 ohm at 20Hz and 1kHz to 0.36 ohm at 20kHz—a very slight increase.

Creek Evolution 100A integrated amplifier The output impedance at the speaker terminals was less than 0.1 ohm, including 6′ of speaker cable.

GamuT Di150 LE integrated amplifier The Di150’s output impedance was very low, at 0.09 ohm (including 6′ of speaker cable) at low and middle frequencies, and rose only slightly, to 0.11 ohm, at 20kHz.

Cyrus 6vs integrated amplifier impedance of 0.08 ohm at low and midrange frequencies, rising very slightly to 0.1 ohm at 20kHz.

Arcam Alpha 10 integrated amplifier The output impedance is comfortably low—under 0.06 ohms up to 1kHz, rising to a maximum of 0.16 ohms at 20kHz

Chord CPM 3300 integrated amplifier the source impedance was a very low 0.06 ohm, rising slightly to 0.08 ohm at 20kHz.

Jadis JA200 Mk.II monoblock power amplifier The output impedance (including 6′ of speaker cable) was very low for a transformer-coupled tube amplifier, at 0.18 ohm at 20Hz and 1kHz, and 0.14 ohm at 20kHz.

PrimaLuna ProLogue Premium power amplifier The output impedance from both output taps was significantly higher than that of the ProLogue Premium integrated amplifier. From the 8 ohm tap, I measured 9.2 ohms at 20Hz, 8.75 ohms at 1kHz, and 8.45 ohms at 20kHz; from the 4 ohm tap, the respective impedances were 4.7, 4.5, and 4.35 ohms.

Thöress 300B monoblock power amplifier The output impedance was relatively low for a single-ended design, at 1.9 ohms at 20Hz and 1kHz, rising to 2.4 ohms at 20kHz

Air Tight ATM-1S power amplifier the Air Tight’s output impedance was high, ranging from 3.6 ohms at 20Hz to 3.3 ohms at 20kHz. This suggests that the single output-transformer tap is optimized for a 4 ohm load

VTL Siegfried Series II Reference monoblock power amplifier he lowest impedance was in triode/MDF mode, at 0.88 ohm in the midband and 0.9 ohm at the extremes of the audioband. The output impedance rose a little with each reduction of feedback, reaching 1.36 ohms at 1kHz and 1.4 ohms at the frequency extremes in the LDF condition.

Sophia Electric 91-01 300B monoblock power amplifier output impedance was also high, at 5.6 ohms at 20Hz, 3.7 ohms at 1kHz, and 8–9 ohms at 20kHz

Lamm Industries ML3 Signature monoblock power amplifier Even without any negative feedback, the 4 ohm tap’s output impedance was moderately low for a single-ended design, at 1.55 ohms at low and middle frequencies, rising to 1.9 ohms at the top of the audioband. Without NFB, the output impedance was much higher from the other taps, the 8 ohm tap measuring 2.9–3.9 ohms

Lamm ML2.2 monoblock power amplifier The output impedance also depended on the transformer tap used. From the 4 ohm tap, the impedance was a low 0.38 ohm at low and middle frequencies, rising to 0.5 ohm at 20kHz. As expected it was higher from the 8 ohm tap, at 0.7 ohm at 20Hz and 1kHz, and 0.8 ohm at 20kHz, and higher still from the 16 ohm tap: 1.35 ohms at all audio frequencies.

Octave Audio RE 290 power amplifier The output impedance was fairly high, measuring 2.2 ohms at 20Hz and 1kHz, rising slightly to 2.4 ohms at 20kHz.

Jadis SE300B monoblock amplifier The output impedance was 2.5 ohms at 1kHz, 2.7 ohms at 20kHz, and 0.76 ohms at 20Hz.

Jadis Defy-7 Mk.II power amplifier with solid-state amplifiers it is usually sufficiently low to be considered negligible: 0.1 ohm or under. With a number of tube amplifiers it can be rather higher. For example, the “1000”—a low-feedback triode amplifier made by Audio Innovations in the UK—has an output resistance of several ohms. This is by no means an isolated example. The Defy-7’s output or source resistance was quite constant over the audio band, ranging from 0.45 ohms at 20kHz, to 0.4 ohms, midband, and 0.45 ohms at 20kHz.

Allnic Audio A-5000 DHT monoblock power amplifier output impedance was impressively low for a single-ended tube design even from its 16 ohm tap, where it measured 1.6 ohms at 20Hz, 1.35 ohms at 1kHz, and 1.5 ohms at 20kHz. As expected, the respective impedances were lower from the 8 ohm tap: 1, 0.8, and 0.85 ohm.

Conrad-Johnson LP125M monoblock power amplifier The source impedance from the single pair of output terminals was a high 2 ohms at low and middle frequencies, rising slightly to 2.2 ohms at 20kHz

VTL MB-450 Series III Signature monoblock power The output impedance also depended on the amount of negative feedback and the operating mode. The lowest impedance was in triode mode with the maximum amount of feedback, where it measured 0.87 ohm in the midrange, rising very slightly to 0.89 ohm in the low bass and 0.9 ohm at the top of the audioband. With the lowest amount of feedback, these figures rose to 1.45, 1.5, and 1.53 ohms, respectively. Operating the MB-450 in tetrode mode gave a slightly higher source impedance, ranging from 0.95 ohm at 1kHz with the maximum feedback, to 1.95 ohms at 1kHz with the lowest feedback.

Balanced Audio Technology VK-55SE power amplifier the output impedance from the VK-55SE’s High and Med taps was high, at 2.7 ohms in the midrange, rising to almost 3 ohms at high and low frequencies

AudioValve Baldur 70 monoblock power amplifier The Baldur’s output impedance, from both the 8 and 4 ohm transformer taps, was lower than usual for a tubed amplifier, at 0.66 and 0.42 ohm, respectively.

Yamamoto A-08 power amplifier The right channel measured 3.2 ohms at 20Hz, dropping to 2.85 ohms at 1kHz and 2.16 ohms at 20kHz. The corresponding figures for the right channel were a little lower, at 3 ohms, 2.73 ohms, and 2.05 ohms, respectively, but these are still high in absolute terms.

Bel Canto SET 80 monoblock power amplifier The measured output resistance was 1.7 ohms, corresponding to a low damping factor of 4

Cary Audio Design CAD-805 monoblock power amplifier output impedance is 0.74 ohm

Cary CAD-1610-SE monoblock power amplifier impedance from the 8 ohm output was high at 3.4 ohms across most of the band, rising to 4 ohms at 20kHz.

Graaf GM 200 OTL power amplifier The output impedance was 0.79 ohms at 1kHz, 0.7 ohms at 20Hz, and 0.83 ohms at 20kHz

Audio Research VTM200 monoblock power amplifier output impedance also varied according to which tap was used: a reasonably low 0.35 ohm from the 4 ohm tap, rising to 0.6 ohm from the 8 ohm tap and 1 ohm from the 16 ohm tap

Sonic Frontiers Power 3 monoblock power amplifier output impedance a maximum of 0.17 ohm at 20Hz and 1kHz, increasing to a maximum of 0.22 ohm at 20kHz

Wavac SH-833 monoblock power amplifier The SH-833’s output impedance was on the high side, at 5 ohms from the 8 ohm transformer tap and 2.6 ohms from the 4 ohm tap. These figures were maintained across most of the audioband, with a rise at 20kHz from the 4 ohm tap to 3.6 ohms. Unexpectedly, the 20kHz source impedance from the 8 ohm tap dropped from 5 to 4.3 ohms.

EAR 890 power amplifier the EAR 890’s output impedance was around 1.5 ohms from its 16 ohm tap and 0.5 ohm from the 8 ohm tap

Wavelength Audio Cardinal XS monoblock amplifier output impedance was a very high 3.4 ohms at 1kHz, increasing to 5.9 ohms at 20Hz and 5.3 ohms at 20kHz.

Antique Sound Lab Explorer 805 DT monoblock power amplifier output impedances were high, at 7.2 ohms (16 ohm tap), 3.65 ohms (8 ohm tap), and 2 ohms (4 ohm tap)

Audiopax Model Eighty Eight monoblock power amplifier output impedance also varied with the control settings. It was lowest with them at full clockwise, but was still very high in absolute terms at 3.5 ohms across most of the audioband. Unusually, the source impedance dropped at low frequencies, reaching 1.8 ohms at 20Hz.

Air Tight ATM-211 tube monoblock power amplifier output impedance measured a high 3.7 ohms at 1kHz. Unusually, this decreased slightly to 3.5 ohms at 20Hz and 20kHz.

Hovland Sapphire power amplifier The output impedance from the 16 ohm tap was a very high 3.55 ohms across most of the audioband, rising to 4.3 ohms at 20kHz.

Wavelength Audio Gemini monoblock power amplifier The low-frequency source impedance with the 2A3 was 3.7 ohms (8 ohm tap) or 1.7 ohms (4 ohm tap); the midrange impedance was 3.1 and 1.5 ohms, respectively; while at 20kHz, the impedance rose to 4.6 and 1.8 ohms, respectively. The respective figures with the 45 tube were 3.2 and 1.5 ohms, 5.5 and 2.6 ohms, and 6.8 and 2.9 ohms.

McIntosh Labs MC2000 power amplifier The output impedance measured a maximum of 0.4 ohm—quite high in comparison with solid-state amplifiers but admirably low for a tube amp.

Nagra VPA monoblock power amplifier output impedance was quite high, varying between 2.23 and 2.26 ohms depending on frequency and load impedance (measurements taken at the 8 ohm output).

Manley Laboratories Stingray integrated amplifier The output impedance, however, was also high, ranging from a maximum of 3.87 ohms at 20Hz to a minimum of 2.83 ohms at 20kHz—values guaranteed to affect the amplifier’s frequency response through real loudspeakers.

EAR V20 integrated amplifier The output impedance from the 8 ohm speaker terminals measured a minimum of 0.77 ohms and a maximum of 1.14 ohms, the latter at 20kHz. The corresponding values from the 4 ohm taps were 0.47 ohms and 0.62 ohms—respectably low values for a tube amplifier. The output impedance at the V20’s tape-monitor jacks was 1k ohm with a 25 ohm source impedance, and 1.56k ohms with a 600 ohm output impedance, indicating an unbuffered tape output.

Audio Note Jinro integrated amplifier The output impedance from the single transformer tap was commendably low for a single-ended-triode design, at 2.5 ohms

Leben CS300 integrated amplifier The output impedance at 20Hz was similar from all three outputs at 3–3.5 ohms. It did differ at higher frequencies: at 1kHz, the impedance was 2.65 ohms (8 ohm tap), 2.25 ohms (6 ohm tap), and 1.8 ohms (4 ohm tap); at 20kHz, it was 2.4, 1.6, and 1.1 ohms, respectively.

Quad II Classic Integrated amplifier The output impedance was on the low side for a transformer-coupled tube amplifier, at 0.28 ohm at 20Hz and 1kHz, dropping to 0.2 ohm at 20kHz.

Woo Audio WA5 integrated amplifier The output impedance from the speaker terminals was also high, at 3.2 ohms across the audioband

این تست مثل تست دیستورشن موج آنالوگ برای بررسی موج مربعی دیجیتال استفاده میشه.

http://www.edn.com/design/test-and-measurement/4389368/Eye-Diagram-Basics-Reading-and-applying-eye-diagrams

https://en.wikipedia.org/wiki/Eye_pattern

در مورد کابل USB میخونم و مشکل کابل USB دو چیز هست یکی مساله نویز و یکی هم انتقال دیتای فرکانس بالا . این طراح ها میان نویز رو کم کنن میزنن دینامیک رو خراب میکنن و مشکل دیگه اینه چون نمیتونن کابل رو خوب Terminate کنن و امپدانس رو ثابت نگه دارند شکل موج خراب میشه. کابل فرکانس بالا نباید با دست Terminate بشه و مشکل USB اینه چون کواکسیال نیست و Twisted Pair هست ثابت نگه داشتن امپدانس براش سخته.

جمع بندی من از مطالعات این چند روزه در مورد کابل USB و کابل SPDIF :

گوردن و تورستن و رومی مطالبی رو که نوشتند تو سایتها رو تا جایی که شد خوندم و نظرات کسانی که subjective تست کردند رو هم شنیدم و این نتیجه گیری ها بدست اومده و دوستان اگر نظری دارند خوشحال میشم بشنوم. این نوشته ها هر کدوم بازتاب نظرات تورستن و گوردون و رومی هست و من تست سابجکتیوی نداشتم تا از خودم چیزی بگم.

اول اینکه انتقال سیگنال دیجیتال توسط کابل چه 90 اهم USB و چه 75 اهم SPDIF تاثیر خیلی زیادی تو کیفیت صدا داره. این تفاوت زیاد زمانی درک میشه که شما کابل های معمول بازار (هم گران هم ارزان) رو با هم تست نکنید بلکه یه کابل خوب رو با کابل های معمول بازار (حتی مدل های خیلی گران) تست کنید. بنابراین به من نگید ما دو تا کابل USB تست کردیم و تفاوتشون خیلی کم بود. باید برای مقایسه یه کابل خوب دقیق رو با کابل هایی که تو بازار هست تست کنید. اینو بگم دنیای کابل دیجیتال ربطی به دنیای کابل آنالوگ نداره. من کابل های 20 هزار تومنی پاساژ توکل جمهوری رو تست کردم واقعا فاجعه بود.

در هر صورت مهمترین قسمت کار این تولید و انتقال درست شکل موج مربعی هست طوری که هم کابل فرکانسهای بالای خوبی داشته باشه و هم انرژی اضافی High فرکانس نداشته باشه. از بابت دیتا روی کامپیوتر خیالتون راحت چون با نرم افزار dbpoweramp و دیسک درایو نوری Apple super drive میشه کل اطلاعات دیسک آئودیو رو آورد روی کامپیوتر. دیتا دقیق و درسته و فقط تو انتقالش ماجرا داریم.

گوردون با کد هایی که نوشته تو ریسیور دیجیتال TAS1020 XMOS (کد ها داخل این XMOS نوشته شده و این چیپ در ورودی Berkeley قرار داره و البته دقت کنید همه اونایی که از XMOS استفاده میکنن 90% شون از کد های دیفالت خود XMOS استفاده میکنند و اون شرکت هایی که از کد های گوردون استفاده میکنند باید پول استفاده از اون پتنت رو به گوردون بدهند مثل Ayre Acoustics Berkeley Audio  Halide Design) بنام Streamlength Asynchronous USB بصورت آسنکرون (یعنی DAC کلاک میزنه و نه کامپیوتر) میاد دیتا رو میخونه تا حد زیادی تونسته یه به بهترین شکل دیتا رو از کامپیوتر بگیره اما موضوع اینه همین دیتا هم به همراه اون 5 ولت که از کامپیوتر میاد بیرون یه شکل موج ایده ال نیست و باید برای انتقال درست اون هم از یه کابل خوب استفاده کنیم و هم از یک مک خوب.

رومی دوست داره کابل دیجیتال رو تو کارخونه با دستگاه های پیشرفته و دقیق Terminate کنن و نه بصورت دستی. ظاهرا اين كابلهاي دست ساز ديجيتال بيشترين مشكلشون اينه امپدانس كابلها وقتي به كانكتور ميرسه بدليل درست ترمينيت نشدن از عدد اصلي فاصله ميگيره.

I would prefer them to be cupper-made and made by a large company where the cable will be soldered my machine but not a human. Companies like Apogee, Belkin, Tektronix, Hewlett Packard are preferable.  I hope their production line still do cables and do not outsource everything outsourcabvle…

Romy the Cat

گوردون میگه ما کابل های 3000 دلاری دیجیتال داریم که جیتر زیادی دارند چون این کابل ها غیر از اینکه امپدانس ثابت و درستی ندارند بلکه کانکتور هاشون هم امپدانس متفاوتی دارند و شکل موج دچار اعوجاج و برگشت میشه. دقیقا برای همین اعوجاج هست که Berkeley پیشنهاد میکنه کابل رو بالای 1.5 متر بگیرید که بخاطر عدم تطبیق امپدانس اگر موج برگشت روی فرستنده تاثیر نگذاره اما همه میدونیم اگر همه چیز ایده ال باشه قاعدتا کابل هم باید کوتاه تر باشه. این مشکل امپدانس غیر دقیق باعث میشه ما ریسک نکنیم و همون 1.5 متر کابل رو بخریم و البته گوردون هم میگه دیگه طول کابل بیشتر از 2 متر هم نشه. پس بهترین حالت طول کابل چه برای USB و چه برای SPDIF همین رنج 1.5 تا 2 متر هست.

رومی رفته Belkin خریده 7 دلار و نوشته از کابل های 2000 دلاری بازار خیلی بهتر بوده.

دقت کنیم تو انتقال دیتای دیجیتال گراند و نداشتن گراند لوپ خیلی مهمه و سیستم رو باید چک کنید گراند لوپ نداشته باشید چون من گراند Berkeley وصل نبود و بعد وصل شد خیلی صدا فرق کرد.

طبق حدس های من شاید اگر کابل تک رشته باشه تو دیجیتال بهتر جواب میده و رومی و تورستن مس دوست دارند و بعضی برندها سیلور میزنند. همین کابل پیشنهادی Berkeley هم استرایت وایر تک رشته سیلور هست. همه اینها هم کواکسیال رو به XLR ترجیح میدهند اگر فرستنده و ریسیور درست طراحی شده باشه.

این نوشته گوردون هست که اشاره داره به اینکه بسته به نوع انتقال باید به انتخاب کابل دقت کرد:

Cables can have a big impact on the sound. Not all USB cables are the same. They need to both provide good data stream and also sheild the dac from noise at the PC side.

“Look there are 2 cables inside a USB cable. There is the DATA differential pair that must be designed for traffic up to at least 12Mhz and the POWER cable which is VBUS 5V’s and Ground.

I have like tons of cables now and some do sound different. But remember it will be device dependent.

All of the PCM27xx devices require VBUS to determine the computer is there. This means there is current running from the computer to the USB Device via the POWER side of the cable.

Other devices like the TAS1020 look for signal on the DATA portion of the cable only. Therefore the VBUS is not used and only the Ground connection on the POWER side is used.

On the DATA side termination on the Device side or endpoint will have an effect on transmissions. I usually get the 5M cables put them on a couple of computers with my USB analyzer on the DAC side and check for errors.

It’s not suggested to use a 5M with streaming audio. These cables were meant for low speed devices. 2M and under for audio will make all the difference in the world.

With the POWER side being used it can bleed noise from the computer into the dac.

It would be nice if you could switch the VBUS signal on the computer side from VBUS to Ground if your device doesn’t use it.

Anyways another thing about the POWER side of the cable is that noise from the computer can end up on the device. The cable should do all it can to make sure that doesn’t happen.

It’s best like all aspects of this hobby to try this stuff before you buy it.

Remember using these expensive cables on a hard drive is worthless they are in Block mode not Streaming and will not be effected by the use of costly cables.

Thanks
Gordon
J. Gordon Rankin “

در ادامه :

He said a number of things that really took me aback. The first thing he said was that yes, USB cables do sound different. They shouldn’t but they do. He says the reason is because most manufacturers are unable or unwilling to make their cables with the correct 90 Ohm impedance and be able to pass up to a 2.6 GHz perfect square wave. He says that unless those two parameters are met, the USB feedback mechanism doesn’t work because reflections get the signal confused on the computer end. Without it, there’s no way for the computer to know that it’s sending the data at the proper rate and bits get dropped. Since USB receivers have no error correction (this was news to me) a dropped bit gets interpolated at the DAC, and distortion increases. He says that this situation is not helped by the fact that Windows, including Win 8, generate 12% more hard errors in a digital audio bitstream than does Apple’s OSX! He also says to play your computer audio directly from memory for lowest error rate on either platform, and if possible, keep your music on a Firewire, eSATA or Thunderbolt drive rather than USB.
So, If you want your computer sourced digital audio system to sound it’s best, find a cable manufacturer that will guarantee his cable’s impedance at 90 Ohms* and that his cable can pass, ideally, a 2.6 GHz, or at least a 0.5 GHz perfect square wave (seems like a pretty high frequency to me), and that your music server runs OSX rather than Windows.

*Gordon also told me that virtually NONE of the cable manufacturers out there have any way of measuring the impedance of their cables and many believe that a lower than 90 Ohms is preferable because it allows them to sell longer runs. He says that because any deviation from 90 Ohms (higher or lower) is damaging to the data stream, lowering the impedance of the cable doesn’t work. Also, an apps engineer at Belden just told me that most cable companies buy their actual wire from suppliers who will customize things like sheath color and dielectric material, and it’s possible that many suppliers supply essentially the same cable to multiple audio cable makers. Fred

در ادامه هم تورستن جواب داده :

Fred,

I was hoping GR said YOU were wrong about USB Cables, but alas it turns out it was not you.
Too bad, I will support anyone who says you are wrong, because statistically speaking you are wrong precisely 87.537% of the time and not quite right the remaining 12.463% of the time.
Yes, I made that statistics up on the spot, but within common error levels I am confident I am 83.73% likely to be right.
Few cables other than printer cables from Belkin and/or similar sources are correct impedance.
Many of those “high end” ones that are handmade, even if the cable is not actually hand twisted silver or Cat6 twisted pair or variations on that theme and that are close to 90 Ohm (talk small minority in high end) give substantial breaks in impedance at the plugs…
Now USB is incredibly robust to bad cables, which is why the cheapest chinese rubbish that is miles off 90R and 1m long still prints pictures on your printer (it probably went to USB 1.1 fallback and operates at 1.5MPS, enough to not slow a printer down).
It is a bit like that SPDIF BNC Lark. Actually “75R” BNC Plugs are around 63 Ohm, 12 Ohm below nominal 75R, 13 Ohm above nominal 50 Ohm.
And of course, even if neither source nor load nor cable impedances are close to 75R, replacing evil RCA’s (which often are not much worse on a TDR than BNC’s) with Good BNC’s elevates sound quality from “rubbish” to ultra high end” in a single stroke.
Or maybe that’s just a load of old bollox and a 75R cable with 20mm worth of a 37 Ohm break (some bad RCA’s) matters Jack Schiit at the frequencies involved?
So actually, I fail to see what your beef with GR’s stuff is (I mean other than that he is usually right, when you are usually wrong).

Ciao T

https://www.google.com/search?q=audio+asylum+gordon+rankin&ie=utf-8&oe=utf-8&client=firefox-b#q=gordon+rankin+site:www.audioasylum.com

https://www.google.com/search?q=audio+asylum+Ciao+T&ie=utf-8&oe=utf-8&client=firefox-b#q=Ciao+T+site:www.audioasylum.com

برندهای زیر رو سرچ کنید هرکدوم یه اطلاعاتی دادند در مورد این بحث:

Revelation Audio Labs Prophecy USB Cable (کابل تک رشته نقره خالص با شیلد خوب)
TUBULUS Argentus USB Cable (کابل تک رشته نقره با دی الکتریک هوا)
Straightwire (کابل تک رشته نقره)
Acoustic Revive USB cable (کابل تک رشته مس با خلوص بسیار بالا)
Oyaide (کابل تک رشته نقره خالص با قیمت بسیار عالی)
Locus Design Cynosure v2 Audiophile Quality USB Cable (کابل خیلی گران)
Vertex AQ (فیلتر)
Black Cat Cable (طراح معروف کابل دیجیتال)
Curious Cables
Audiocadabra optimus dual
GoldNote Firenze Usb

تئوری خطا بخش اول

تئوری خطا بخش دوم

تئوری خطا بخش سوم

تئوری خطا بخش چهارم

تئوری خطا بخش پنجم

اینم از بخش آخر:

بحث این بود چرا یه کابل اینهمه تو میکرو تفاوت ایجاد میکنه حتی وقتی کل سیستم تو میکرو خطی نیست؟؟؟؟ آیا این کابل از خودش صدا رو میسازه و چیزی اضافه میکنه؟؟؟؟

گفتم دلیل تاثیر خطای کامپوننت های سری جمع جبری نیست بلکه جمع لگاریتمی یا همان ضرب هست. برای همینه که کابل چیزی از خودش اضافه نکرده بلکه چون ضرب تاثیرش مشهوده اینطور میشه .

برای همینه وقتی حتی اون میکرو صدا توسط آکوستیک بد و دیجیتال بد و Solidstate بد خراب شده باز هم تاثیر کابل رو میشه حس کرد براحتی و برای همینه که حتی تو آکوستیک و شرایط بد همچنان مردم سیستم عوض میکنند.

من معتقدم نباید تو استودیوها اون میکرو رو خیلی خراب کنند تا مجبور بشیم 250000 دلار پول امپ Micro linear Audio Note رو بدیم و باید یه تناسبی در Micro linearity همه قسمتها باشه.

بنظرم هر بخش مثلا 5% افت ایجاد کنند منطقی هست تا اینکه استودیو بیاد 80% خرابی ایجاد کنه بعد ما بریم 500 هزار دلار پول Audio Note بدیم که تو میکرو خطی هست تا اون 20% مونده رو با زور نگه داریم.

http://www.stereophile.com/content/lamm-industries-ml3-signature-monoblock-power-amplifier-measurements

شاید بشه گفت بهترین میژرمنتی که یک آمپ میتونه داشته باشه از دید من تو میکرو همین Lamm ML3 هست که پاسخش مثل خط کش صاف و هموار هست.

جالبه ببینید حتی بدون فیدبک امپدانس خروجی اش کم هست و تو شکل تابع دیستورشن رو بدون فیدبک و با فیدبک نشون داده.

من معتقدم این صدای خوب از Lamm فقط با هورن درمیاد اگر بخواهیم تو ماکرو صدای متعادلی داشته باشیم و اگر کسی این لامپی ها رو به امثال بلندگوهای بزرگ درایوری بزنه پاسخ مطلوبی نمیگیره، حداقل پتانسیل این آمپ ها مشخص نمیشه.

it is important to use the lowest-possible output-transformer tap with any particular loudspeaker

رومی میگه :

http://www.goodsoundclub.com/Forums/ShowPost.aspx?PageIndex=4&postID=9095#9095

The wire, the coupling caps, the cathode resistors and many other things are superbly important but it is after the strategic topology is settled. In my view caps, resistor, wire and other things are responsible for the sounds, the minor things, the tactics. The big picture of the sound, the strategy is made by the macro topology. I properly, or I would say sonically-pretentiously, designed amp would sound strategically -properly with any, even with very poor parts and even with not the best assembling methods.

آئودیو نت هم با یک توپولوژی ثابت میاد تو 5 سطح کیفیت المان ها رو تغییر میده و قیمت رو بالا میبره.

خب پس دور از منطق نیست اگر برای ساخت اول بریم سراغ یک توپولوژی موفق مثل آئودیو نت.

معتقدم طراحی یک آمپلی فایر سی دی پلیر یا بلندگوی ایده ال تو ماکرو به این معنی که پاسخ ماکرو خوبی تو فرکانس و دیستورشن داشته باشه تو دسته علم جا میگیره و یک علاقه مند diy یا هر کسی که میخواد دستگاهی تو ماکرو بسازه نیاز به علم الکترونیک داره.

این علم الان خیلی دور از دسترس نیست تو بحث آئودیو، کافیه ببینید مثلا Boulder یا Soulution چکار کردند، استفاده از فیدبک منفی ، استفاده از بهترین ترانس و ترانزیستور و خازن و بهترین برد و راه هایی هم برای کم کردن نویز مثل جداسازی پاور از بخش مدارو …

اسامی سازندگان خوب المان ها هم با کمی تحقیق مشخصه ، مثلا ترانس رو یک برند معروفی C Core میسازه ، ترانزیستور رو ژاپنی ها مثل سانکن یا توشیبا خوب میسازن ، دک رو فیلیپس تو مدل مالتی بیتش 1541 خوب میسازه ، ترنسپورت رو CEC یا Teac یا فیلیپس خوب میسازند و …

برای بلندگو هم همینه ، مثلا خرید بهترین درایورها از دانمارک ، استفاده از کراس آور Duelund یا همین 6 دی بی ساده که پاسخ فاز رو درست کنه و جعبه آنچنانی و …

نمیگم کار خیلی ساده است اما حرفم اینه این فیلد فیلد خیلی دست نیافتنی اصلا نیست و میشه بهش رسید همونطور که تو دنیا 200 تا برند هستند که تو همین گروه قرار دارند و کارشون هم خوبه.

اما بنظر من طراحی در میکرو کار ساده ای نیست ، یه جورایی بیشتر هنر محسوب میشه تا علم و مثلا کاری که آئودیو نت ژاپن کرده فقط علم نیست بلکه از نظر من تلفیقی از علم و هنر هست.

اول اینکه تو میکرو تو باید بدونی مفهوم خطی بودن تو میکرو چیه و بعدش باید اونقدر تلاش کنی تا بتونی با المانها ، شماتیک و چیدمان اونها و نهایتا تیون به اون خواسته برسی.

برای این خواسته یکی مثل آئودیو نت حتی خازن اش رو هم خودش میسازه چه برسه به ترانس  و …

تو این حالت شاید حتی 20 کمپانی هم تو دنیا نیستند که میتونند حرفی برای گفتن داشته باشند.

باز هم میگم بحث من دست نیافتنی بودن نیست فقط حرفم اینه مسیر ماکرو نزدیکتره تا میکرو و اگر با X ساعت وقت میشه تو ماکرو به پاسخ خوبی رسید شاید  5X ساعت لازم باشه که به میکرو خوب برسی تازه اگر قبلش فهمیده باشی میکرو چیه.

این نوشته طراح Tron رو بخونید جالبه :

The Art

یکی از کسانی که متفاوت فکر میکنه مثل آرتور و رومی و مایک و جین و لین اولسون و … آقای گیزمو هست. مقالات ایشون رو تو آدرس زیر میتونید بخونید:

 http://www.meta-gizmo.net/Tri/index-1.html

 بنظر من دکتر نوشته های جالبی داره و یکی از قوانینش اینه کیفیت صدای آمپلی فایر رابطه معکوسی با توان اون آمپلی فایر داره. R=1/P

این دکتر در مبحث ترایود ها مطالب جالبی نوشته و همونطور که میدونید طراحان این سیستمها مثل ریچرت Herb Reichert، کوندوسان Kondosan ، شیشیدو Nobu Shishido ، ساکوما Susumu Sakuma هر کدوم نظری برای کوپلینگ بین طبقات و طبقه آخر دارند. گیزمو  (Inverted Interstage Transformer coupled) شیشیدو رو دوست داره (به اختصار IT-coupled) و البته از سیستم جدید دیوید برنینگ هم خیلی خوشش میاد. دیوید راهی کاملا متفاوت رو طی کرده ، بعضی ها بدون ترانس هستند OTL بعضی ها با ترانس و دیوید برنینگ اومده از سیستم جدیدی استفاده کرده که هم OTL نیست و هم ترانس نداره تو خروجی.

در مورد دیوید و کارش بخونید :

Established in 1974, The David Berning Company manufactures vacuum tube audio amplifiers based on an unique Impedance Converter that replaces the traditional audio power output transformer and greatly extends and improves amplifier performance. We call our technology “ZOTL” for Zero-Hysteresis Output Transformerless.Operating at a fixed high-frequency without traditional audio output transformers, the ZOTL Impedance Converter eliminates the frequency-dependent performance limitations inherent in all transformer coupled tube amps.Berning amplifiers using the ZOTL technology exceed the performance of traditional OTL tube amplifiers by properly matching the tube impedance to that of the speaker. Berning amplifiers depart from traditional OTL amplifiers in that they do not require a large number of hot power tubes to supply adequate current for driving speakers.Berning amplifiers convey the musical transparency of tubes without the limitations imposed at the frequency extremes by audio output transformers. This limitation at the frequency extremes is a major contributing factor to what some negatively call “tube sound”. ZOTL extends the desirable musical transparency of tubes to the frequency extremes and provides the quickness of the high and low frequencies that are cherished by those who prefer solid-state amplifiers.

لیست زیر کسانی هستند که کارهای جالبی در رابطه با طراحی مدارات انجام دادند، در ادامه لیست برندهایی رو میبینید که از IT کوپل استفاده کردند، اون لینک ها رو دنبال کنید مطالب جالبی نوشته.

Nobu Shishido
Susumu Sakuma
David Berning
Anzaï Zaïka
Jean Hiraga
Herb Reichert
JC Morrison
Arthur Loesch
Hiroyasu Kondo
Ken Shindo,
Mr. Atarashi
Don Garber
Noriyasu Komuro (Nori Komuro)

 http://www.6moons.com/audioreviews/trafomatic2/sidebar1.html

 To map out a terrain familiar to me solely on hearsay, I identified the following, currently available commercial single-ended IT-coupled 300Bs :

Mike Morrow’s Morrow Audio 300B1S monos – $6,500/pr;
Hans-Jürg Dorn’s Althea Musica Royale 300B Concept Mono;
Sun Audio’s SV-300BSM – ¥810,000;
SAC Thailand’s custom-order WE 300B monos;
WAVAC’s EC-300B, MD-300B and MD-300Bm – from $8,500 to £16,500;
Promitheus Audio 300B monos – $1,500;
Audio Note UK Kegon – $49,000;
and the Border Patrols with outboard power supplies – €10,600 for the paralleled Model S20.
Allnic from South Korea
TruLife Audio from Greece, €1000 per watt, interstage transformer bandwidth beyond 2MHz
For kits or published DIY circuits with interstage transformers, reference AudioNote UK kits and Lynn Olson’s Nutshell HiFi Karna (6H30 or 5687/7044/7119 input, 45 driver). For further ‘open’ circuits, Nobu Shishido’s IT-coupled 300 SE Topology was published in Glass Audio in 1994. For perhaps the most generic non-IT 300B SET circuit, think 3-stage affair running 6SN7 dual-triode input/drivers. Much present Chinese offerings seem to fall into that category. Other designers don’t see the need for two voltage amplification stages with their higher complexity and cancellation of harmonics. They favor less stages. The earliest 2-stage circuits used pentode drivers like Western Electric’s legendary movie house amps. Shishido used 6L6s. Gordon Rankin’s 2-stage Wavelength Cardinal sports a shunt-regulated push-pull stage (SRPP) to drive its power triode. Other 2-stage topologies use single rather than dual triode drivers. Japanese audiomaniacs seem fond of the classic Western Electric 417A/437A drivers when transformer-coupled to the power triode, championed particularly by Shishido and Sakuma. SAC too adopted this recipe for its current flagship monos. Then there’s direct-coupling and the Loftin-White approach.

ژاپنی ها همونطور که قبلا گفتم ماسفت و ترازیستور های آئودیویی که میسازند به نسبت بهتر از آمریکایی هاست مثل توشیبا که ASR ازش استفاده میکنه و Sanken که ویتوس باهاش کار میکنه و تو ترانس هم قضیه دقیقا همینطوره و ترانس های ساخت ژاپن (مثل تامورا) در مجموع بهتر از بقیه ترانس هاست و حتی تو موضوع شماتیک مدارات هم پیشرو هستند مثل همین شماتیک شیشیدو که خیلی ها از روی اون مدار میسازند. ژاپنی ها تو انتخاب نوع ترانس هم از بقیه جلوترند و اونها زمانی که آمریکایی ها از ترانس های حلقه ای توروید استفاده میکردند ژاپنی ها بیشتر به C Core و EI Core و UI Core علاقه داشتند.

تو کل سازندگان غربی (البته بین ترانزیستوری ها و تا اونجایی که من میدونم) فقط  Vitus و ASR و Howland و Ypsilon از توروید استفاده نمیکنند و بقیه برند های ترانزیستوری از توروید استفاده میکنند.

برگردیم به نگاه دکتر گیزمو که مقالات جالبی نوشته مثل http://www.meta-gizmo.net/Tri/mag/KINGTONE.html که نگاهش رو بیان میکنه. مطلب زیر رو دکتر در مورد کار دیوید برنینگ نوشته :

First and foremost an output transformer, or any transformer for that matter, is an impedance-matching device. Impedance matching is used to transfer a source of power to a load so that both the power source and the load are operating under optimum conditions for maximum efficiency. What other kinds of impedance matching devices are there? Some such mechanical devices include an automobile transmission, bicycle gears, and a simple lever. Besides the transformer, a dc-to-dc power converter is an electrical type of impedance matching device. The dc-to-dc converter can convert a high voltage at low current into a low voltage at high current, or vice versa. Dc-to-dc converters form the basis of the switching power supply, but usually contain added complexity for regulated power supply applications. In its simplest form, the output voltage or current of the dc-to-dc converter is always related to its input by a proportionality constant which is just like the turns ratio in a transformer. Like the transformer, impedance matching goes as the square of this constant.

All current Berning amplifiers use the dc-to-dc converter to form the basis for impedance matching between the tubes and the speaker. The patent for this technology is US patent 5612646 (March ’97), and is reprinted on the Berning web site at http://www.davidberning.com This patent describes the many advantages of this amplifier over the transformer-coupled amplifier, so this will not be repeated here. Unless the reader is well versed in switching power supply design, it is unlikely that he or she will understand exactly how it works, and it is too complicated to try to explain it here. Perhaps the best explanation to read is the one given by Chuck Hansen in his technical review of the ZH270 that appeared in Glass Audio, vol. 12, issues 1&2, 2000. This is also reprinted on the Berning web site. In his review, Mr. Hansen reaffirms the success that this new technology has with preserving the tube’s transfer characteristics at the speaker.

رومی خیلی اوقات مخالف بازی درمیاره که این موضوع به جذابیت اش کمک میکنه اما من معتقدم همونطور که خود دکتر میگه نباید ما به یک نفر تکیه کنیم و فقط ببینیم اون چی میگه ، بنظرم همونطور که دکتر میگه تو این مسیر آئودیو نباید دنبال بودا بگردیم و فقط و فقط ملاک تجربه شنیداری ما باید باشه.

Kill All Audio Reviewers Including Me

THE HIGHEST WISDOM ABOUT THE AUDIO ARTS IS YOUR COLLECTIVE WISDOM..AND NOW IT IS YOUR TRIBAL RESPONSIBILITY TO INSPIRE YOUR BROS’.

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