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In Reply to: RE: How Good Are Bryston Amps Compared to Other High End? posted by Disbeliever on March 26, 2014 at 00:20:28
I thought that was your cup-o-tea, Class AB, pushpull and high power? Should be the perfect amp for you.
Follow Ups:
Class AB certainly but not from a Bryston Integrated
Edits: 03/28/14
Quality of sound varies so much within the family of solid-state Class AB amps. Bryston was not for me. At the other end of the spectrum, I'm loving the Ampzilla 2000 2nd Edition. Pass Labs was also very nice. I'd even take the high value Odyssey Stratos Extreme over Bryston.
Abe-
are the Ampzilla amps still in production?
Original Ampzilla are no longer made but the current production includes the Ampzilla 2000 2nd Edition mono blocks, and the stereo version.
Information on the Spread Spectrum Technologies Ampzilla website does not appear to be completely current since the death of designer James Bongiorno in 2013.
Wyred4Sound manufacturers the Ampzilla amps but I didn't find any info on them on the W4S website. However, they sometimes advertise Ampzilla amps on Audiogon, linked below.
If you search "Ampzilla" on Audiogon, you will also find the stereo version Son of Ampzilla.
Don't know about the 2nd edition but the 1st were a bit warm, dark and not too resolving. Pleasant enough for an SS amp, at least no real nasties, but not close enough to SOTA for me.
Morricab : What is SOTA for you ?
Edits: 03/30/14
For SS, probably the current state of the art are the First Watt SIT amplifiers. Unique transistor, utterly simple design, superb sound. This from a guy who is making his money feeding the vanity of big spenders with his huge Pass X series amps, which don't sound half as good but sure are big. It is unlikely that any Class AB amp can touch a SIT amp driving a speaker for which they are both compatible. I have heard the darling Soulution and Vitus SS monsters and they don't sound really good, despite what the reviewers and the high price say. The Reimyo KAT-777 might be an amazing good SS amp (haven't heard it though). Oh and the edge NL series were probably the best AB I have heard to date.
For Tube, it is likely a big SET from the likes of Lamm, Wavac, Kondo, Ayon, NAT, Reimyo etc. For Push pull it is likely VAC or CAT. Or an OTL from Atma-Sphere.
For hybrid it is the likes of Ypsilon, Siltech and KR Audio
I have not heard the First Watt SIT, but have yet to hear amp with FET input or Jfets that I like. Mosfets are OK.
Edits: 03/30/14
Your statement is completely contradictory. You don't like FET input or JFETs but Mosfets are ok? For what? Only the output stage. Are you telling me that you only like in particular Class AB amps with bipolar transistors?? Probably the best amp I have ever heard is the KR Audio Kronzilla DX monoblocks and like all KR Audio amps they use a JFET on the input and a MOSFET as a driver.
The best mono blocks I have heard are made by a friend of mine an electronics engineer they have mosfet output and bipolar input. He says JFETs have higher distortion and are more suited for PA amps. I would not waste my time listening to any amplifier that had FET/JFET input irrespective of what any reviewer might say.
Edits: 03/31/14 03/31/14
I would not waste my time listening to any amplifier that had FET/JFET input irrespective of what any reviewer might say
Why, because your engineer friend is not too partial to them...well that is plain silly!
Morricab: Not silly , all the amps I have auditioned over many years with FET of JFETS sound poor.Latest example the new Sony TA-1AES amplifier.
Edits: 04/01/14 04/01/14 04/01/14
Poor selection of amp choices then? I can tell you if they are run the right way they perform very well indeed. They probably should not be run Class AB for example. If run heavily in Class A they offer very benign distortion...again without feedback...add feedback and all bets are off.
Try listening to FETs in some top Class A implementations...you might change your mind.
I have zero interest in any Class A amplifier, the latest Sony TA-1AES is Class A with FET input IMO it sounds lousy, but has got rave reviews in Andrew Everards Words & Music & in Hi-Fi News & RR both reviews in my opinion are totally inaccurate and very misleading. I took the Sony amp for a second opinion to a audio engineer & speaker designer he agrees with me. The Heat sinks are small, the amp runs hot, distortion due to the FET input at HF is on the high side as measured by HFN & RR. There are distracting bright white light circles around the facia line input indicators, & there is no unity gain by pass facility. WHF? says "Does,nt convey rhythms particularly well,needs more sonic punch" I find the Sony amp conveys nothing particularly well, Bass is just a thud or thump with no proper resolution or natural definition, the overall sound is artificial. I have read on a Forum that this new amp was not designed by Sony,s Chief designer Mr Kanai this does not suprise me.
Edits: 04/02/14
I have not heard this design but if it is not designed properly then you can hardly blame the damn transistors!
I have an amp that runs Class A and uses 1 big industrial mosfet per channel on the output. Yes, it is single ended and yes it uses tubes on the input and driver stages. Yes it sounds very good...far better than any Class AB amp or push pull amp I have owned or heard.
The KR Audio amp I owned before had 1 JFET, 1 MOSFET and 1 big tube for the output and also sounded far better than...well than anything else I know. Also better than the amp above but for safety reasons I had to sell the KR.
Just for your information, I have owned or heard at great length the following Class AB and A amps:
Onkyo Integra A-9711
Sumo "The Nine" amp with Hafler 915 preamp
Sumo Andromeda
Sumo Polaris III (worst amp I ever owned)
Nakamichi PA5E (Stasis design curtesy of Threshold)
Sim Audio Celeste W-4250
Sim Audio Moon W5
Sphinx Project 18 (friend of mine had this for a couple of years)
Ampzilla 2000 monos (same friend for about 1 year)
Krell (various KSA series from original KSA100 to Reference monos)
Musical Fidelity KW750 (different friend and he had some of the Krells)
McIntosh MC501 monos (third friend and had them for several years so I heard them with lots of speakers, dacs, wires etc.)
Plinius SA-102 (another friend still has them)
Accuphase A45 (Class A friend 5)
Mark Levinson ML27
Karan integrated (big don't remember the model friend 6)
Pretty big list there and I am sure to be missing some. Now here is the funny part:
Friend 1 has KR Audio SET hybrid now after switching to tubes completely with many many years with all SS of various kinds
Friend 2 has KR Audio, Lamm hybrids, Sphinx hybrids and sold the KRell and Musical fidelity
Friend 3 sold the McIntosh but even before got an Einstein preamp and now couples that with Octave tube monoblocks
Friend 4 Stil has the Plinius (he has two biamped)
Friend 5 oscillates around a lot but currently has an all Audio Note setup (obviously all tube)
Friend 6 sold the Karan and now has a VAC 30/30 all tube amp.
I have been a SET hybrid man for the last 8 years and before that I was a conventional hybrid man for about 4 years and had started dumping pure SS a few years before that going with PP tube amps.
Nearly all my friends "grew up" and dumped their unsophisticated sounding Class AB SS amps...I just did it several years before they did.
In some cases tubes work well, but Im so used to the quick attacks, snap, and kick of a high current solid state amp, that I keep coming back to it. Im currently in talks with a seller to possibly buy his YBA 2 HC amp at a later time frame, since money is tight right at this time. I only went to the audition today at HiFi Center to see if Bryston was worth getting. Apparently not. Bryston is a very clean sounding amp that does voice presentation very well, but the depth and space to the music is missing. I have also heard a Sumo 9 Plus at one time, and almost bought it. I should have. I didn't like it because it was weak on the bass side of things. And I don't think it had the quickness of sound that I like. So YBA might be my solution. Plus its a lot cheaper (in used condition) then spending 5 grand on a new amp.
I'm curious, and I realize this is a bit off topic, but whats your impression of Goldmund amps. I'm using the JOB 225, but it has the same house sound as the house offerings. I like tube amps too, but I find the JOB to be incredibly fast and detailed.
--Ze'ev
Well I had my audition of a system today at Hifi Center in Vancouver BC. To cut to the chase- I wasn't really that impressed with what I heard today. The sound from the speakers didn't really fill the room as much as I heard even on my own system. The sound had a hard time escaping the speakers. It only did that to maybe a small amount away from the speaker, but not the "I feel like Im in that space" kind of sound. The amp did have balls however- like Rotel I've heard before. Maybe it was the source material. All of it was digital files. What I heard was a Bryston 4B SST2 amp on B&W 804D speakers. Now I've heard the 804s from the Matrix to the 804S, and now the 805D. The best sound to me came from the 804 Matrix. The most non colored neutral sound is from both the 804S and 804D. I didn't really think the diamond tweeter really made that much of a difference compared to the older versions. Again maybe it was source material. What I will say were voice presentation was very good. That I'll give it. Bass was tight, but it really struggled to produce sub type bass. It was more reserve non colored bass. I don't know what was really restricting the sound. The speakers or the amp. I didn't really notice the bass too much, even though this amp is supposed to do bass quite well. Probably the speakers there. For what these speakers cost, I think you can do better today. The only thing B&W had going for it was the realism in the voice, but the speaker itself wasn't very musical. I don't know if I should keep looking for another amp or speaker, but I haven't found nirvana yet. I have one classical piece I use for a reference at how real the sound can be, and the only time it sounded its best I ever heard- was the first time on a YBA amp and B&W Matrix 804. All other combos struggle to produce that in the air horn sound that one song can do. Maybe I should look for some Matrix speakers. And I wasn't too impressed with the salesman either. He kept interupting my music listening session and we wasted a lot of time screwing around with equipment that wasn't really necessary.
I was picking on the Bryston earlier but I will now pick on B&W speakers. They a pure engineering for engineers speaker and frankly miss most of the point of music. First they use drivers of all different materials that each have their own sound signature...bad start. Then they use steep filters (except the new diamond tweeter apparently) to separate the drivers, which is bad when each driver has it's own "voice" leading to bad blending of the drivers. This also makes any form of time alignment impossible. The midrange is far to flexy in the upper frequencies and has nasty breakup modes. This colors the upper mids and lower treble ranges. Bass seems often neither tight nor tuneful in many models and difficult to drive.
All-in-all one of my least favorite loudspeaker brands driven by a very run-of-the-mill amplifier...a match made in hifi but not music IMO.
The only B&W I heard make some music was the Silver Signature stand mount speaker driven by some reissue Marantz Model 9 monos...that was pretty good.
Of course there is the B&W Nautilus...the real Nautilus that Laurence Dickie designed but does not follow the ethos of B&W at all...except the tapered tube tweeter and midrange head...an idea they got from Dickie not the other way around! Now Dickie makes the Vivid speakers, which are very good indeed!
That sound not getting free from the speakers and the "restricted" nature was mainly the amps (along with whatever preamp was used).
The old 3BST was known for having an overly tight bass...don't know if the SST2 models fix that or not.
Worst amp I've ever owned, aside from numerous class D beasties...
I am also allergic to Class D amps, as well as tubes
Edits: 04/03/14
Tripath- and International Rectifier-based: both very good with good recordings -- neither sugar coating bad recordings.
I prefer my current Pass Labs but I could live my Class D Audio SDS very well, especially for 1/9 the price of the Pass.
I love the music of ... ... Gustav Mahler
And yet, you decided not to live that way and now have the Pass even though, by your own admission, it was quite a financial stretch for you. That is telling....
nt
I love the music of ... ... Gustav Mahler
I seriously doubt you have heard an OTL amp or I don't think your opinion would hold up...or are you blinded by your opinion? I think that might have something to do with it...
Listen to 12 antique tubes in one mono block ? I am not crazy I have excellent central heating.
Edits: 04/04/14
Antique does not equal obsolete. That simple really. Besides, KR Audio, Ayon and Emission Labs have all designed new tubes in the last 15 years.
TRIODES versus BIPOLARS from a friend of mine
It all depends on how one interprets "facts" for example a pretty standard bipolar stage with a current mirror load and a constant current source at relatively low cost will produces vanishingly small levels of distortion, whilst producing much of the required gain in an amplifier.. The sort of values in distortion terms are typically 0.00001% at I kHz and 0.0006% at 50kHz this sort of circuitry with a CCS, the VAS stage will and can produce a total distortion of better than 0.0015% in what is called a blameless amplifier at full power of 50 watts and 30+ kHz. Quote Douglas Self , there is no valve amplifier out there that can get anywhere near these values and for a very good reason. The triode suffers one distortion which is rarely measured or noted , that of an early effect , which basically is this, that when the grid goes positive the anode current increases and in doing so reduces voltage on the anode due to the voltage drop across the anode load , this drop will cause the signal during + half cycles to have a significantly different amplitude to the - half cycles , effect of this is that if you take a high Mu triode used to get the gain required and introduce current negative feedback by not decoupling the cathode resistor the lowest distortion you wil get is about 0.2% or worse. CCS's have been tried with Triodes but the early effect still remains.
You may already know that the second grid was introduced to make the valve less dependant on this effect but because of the screen grid alone caused a kink in the curves , they introduced the suppressor grid to even it out again, the new valve the pentode has unremarkable distortion characteristics... in summary it is unfair to try to make comparisons with such devices because they are so totally different in the way in which they can be used , one other factor that must be considered is that a thermionic valve will be swinging across its transfer characteristics significantly higher voltages than a transistor, effectively stretching its distortion range because you are using more of its curve area , a transistor is concerned with just a few volts and so a much smaller area is being used.
There is no doubt at all many valve designers have today pushed the limits of circuit design to produce some overall sweet sounding amps which many people prefer , Tim de Paravicini for instance who also has OTL designs and has used mosfet O/Ps to simplify the heat & current requirements , but in any event many people are not after distortionless amplification , rather they want a sound that does not fatigue after long term listening and in which the very nature of valves presenting even order harmonics is perhaps better suited to those requirements which will also be commensurate with the speakers thay are using, meaning that many speakers have a very bright presentation and usually reflexed so that a tight bass from the valve amp will largely go unnoticed anyway and the easier top will be more acceptable to those modern speaker designs which I frankly find irritating on any amplifier.
regards etc. Humble
Edits: 04/05/14
"It all depends on how one interprets "facts" for example a pretty standard bipolar stage with a current mirror load and a constant current source at relatively low cost will produces vanishingly small levels of distortion, whilst producing much of the required gain in an amplifier.. The sort of values in distortion terms are typically 0.00001% at I kHz and 0.0006% at 50kHz this sort of circuitry with a CCS, the VAS stage will and can produce a total distortion of better than 0.0015% in what is called a blameless amplifier at full power of 50 watts and 30+ kHz. Quote Douglas Self , there is no valve amplifier out there that can get anywhere near these values and for a very good reason"
First: Show me ONE amplifier out there with numbers that good other than Halcro, which if you ever heard them you would know why the numbers don't mean anything when massive feedback is used.
Second: Those numbers are not achieveable without negative feedback... a lot of negative feedback. It is also a fact that negative feedback does not cure the ills of a Class AB amp's residual crossover distortion.
Third: When are you going to learn that it has become clear after the last 50 years of "blameless" amplification that psychoacoutically transparent and Oscilloscope transparent are NOT the same thing.
Quote from Geddes paper I:
"To be useful the metric must be consistent and reliable the same number must mean the same thing in every context and there must be a close correlation between the metric and the response that it is intended to scale."
"This is precisely where the signal-based distortion metrics fail. In our next paper we will show that .01% THD of one type of nonlinear system can be perceived as unacceptable while 10% THD in another
example is perceived as inaudible. Even one of these simple examples is sufficient to invalidate THD as a viable metric for discussion of the perception of distortion. Furthermore, 1% THD is not at all the
same as 1% IM, but we will show that neither correlates with subjective perception. While some of the signal-based metrics may be better than others, it is our opinion they all fall short of what we are seeking."
"If we take these facts and join them up with our Perception Principles then we can make the following statements, which are, perhaps, not exact, but they are, none the less, more valid than not.
The masking effect of the human ear will tend to make higher order nonlinearities more audible than lower order ones.
Nonlinear by-products that increase with level can be completely masked if the order of the nonlinearity is low.
Nonlinearities that occur at low signal levels will be more audible than those that occur at higher signal levels.
Again these may seem intuitively obvious."
"If the amplifier has crossover distortion then this type of nonlinearity violates both of our principles it is both very high order and it increases (as a proportion of the linear terms) with decreasing signal level. Based on our hypothesis, one would expect that this type of distortion would be highly objectionable and it is."
Quote from Geddes Paper II:
"Of primary interest in the present study was the correlation between the mean subjective ratings and the various metrics. Table 5 provides the Pearson product-moment correlation coefficients between the
mean ratings across subjects of the twenty-one stimuli, and each of the three metrics. A negative weak relationship was observed with the THD (r = -0.42, p=0.06) and the IMD (r=-0.35, p=0.13) metrics. These results suggested negligible predictive values when utilizing THD and IMD metric in this context."
"These results supported the skepticism that THD and IMD metrics were poor predictor of subjective perception of sound quality ratings."
http://www.gedlee.com/downloads/Distortion_AES_I.pdf
http://www.gedlee.com/downloads/Distortion_AES_II.pdf
Based on their studies, they found that there was a slightly NEGATIVE correlation with THD and IMD and sound quality!!!
That is because of how modern amps make distortion and that the negative feedback trick doesn't make it much more listenable.
CHeever also made the same observations and he said that THD once upon a time was a pretty good indicator of quality when amps were all SET and none used negative feedback. Once they went to PP, AB and lots of feedback then THD and IMD no longer correlate with sound quality.
You can take your numbers all you want, I listen to music not numbers and I can tell you that the WORST sounding amps I have ever heard were all the best measuring ones. Your engineer friend and also Doug Self are just delusional and brainwashed by 50 years of engineering "best practice" that had nothing to do with sound quality.
OK Have it your way to say 10% THD is inaudible ? However I would agree that at the end of the day it is all about how it sounds and I would not waste my time again listening to any valve or Class D amplifier. I have auditioned the Devialet Class AD at Home gets highest SQ rating from Paul Miller HFN & RR best Class D to date but I still prefer my old Class AB amplifier, had the Devialet been better I would have bought it despite only being interested in the power amp section.
Edits: 04/07/14
I don't say that 10% is inaudible but 1 or 2% of mostly 2nd harmonic is almost certainly inaudible. How can you say that for you it is only about the sound when you are wantonly ignoring the psychoacoustics of sound and catergorically dismissing whole technologies...one of which clearly more closely matches psychoacoustic ideals of what kind of distortion an amp should make...seeing as it is impossible to have a zero distortion amp. I don't offhand dismiss any technology based on my "feelings" of the technology (your comments about tubes being antique for example), I base it on my current understanding of psychoacoustics and the types of distortions made by each technology. This along with lots of listening tells my Class AB ANYTHING (transistor, tube or hybrid) isn't the way to sonic nirvana. Class D is also not the solution because of the noise and distortion pattern it generates. The signature is obvious even if somewhat more subdued with the Devialet.
As I said, I haven't used a pure tube amp for several years. I find that the current SOTA without spending a king's ransom comes from hybrids running Class A or a VERY simple transistor design like the First Watt SIT amps. For pure tubes, either you need OTL or VERY expensive output iron and then you get there.
There was a review of the KR Audio Kronzilla monos in a German magazine many years ago (that version is now about 2 generations behind). The measurements showed about 3% THD at around the rated power (droping like a stone with lower power I might add) but nearly all of it (over 2%) was 2nd harmonic some 3rd, a bit of 4th a tiny 5th and not much else above -120db.
It follows Cheever's Aural harmonics nearly perfectly and as a result SOUNDS nearly perfect. I had a generation newer at home as a reviewer and it made other highly regarded amps (like the ASR Emitter II Exclusive) sound broken by comparison...it was not subtle. Another German magazine had the older version monos as their highest rated amp for 10 years!!! (2002-2012) and it is still in the top 3. It was FAR ahead of the competition and still among the very best. It is a hybrid. My current NAT is also a hybrid.
Speaking of the Devilet, I too had it at home and it did not compare favorably against the amp I had at the time, The Einstein "The Absolute Tune", which was one of my least favorite amps that I have owned in the last 10 years (still it is quite good just not compared to what I owned before it and not what I own now). The Einstein was notably more musical and just as resolving. The Devialet failed to move me to think higher of Class D. I have also heard the Devialet 110 in a friend's home...he now has an all Audio Note system with the Devialet long gone.
What is your current Class AB amp that you find so realistic sounding? The ONLY one I have heard that truly competes at the highest level is the now defunct Edge NL series amps. They were GOOD. BAT VK amps are pretty good too but a bit darkish sounding to me that reduces their realism. BATs tube amps are better.
Amps I have heard from Accuphase, Soulution (current darling), MBL, Krell and others have failed to move me at all (either AB or A offerings). Who in your mind is making the best amps out there?
Morricab: Triodes versus Bipolar from Humble
You may be interested to learn young man that between Disbeliever and myself there amounts to over 100 years of listening to both valve & transistor amplifiers , we do not essentially disagree with you about sound quality and can concur that many amplifiers that measured well were largely overrated. However you appear to be widening the goalposts, originally stating that triodes had less distortion than bipolar transistors being a blanket statement without any circuit references, so I had to challenge you. You then go on to rubbish any form of feedback as if it were the bane of any design concept in the audio domain.So firstly allow me to clarify a few points, it is true that taken as as an individual device transistors do have more intrinsic distortion than say a high mu triode but the point I have re-iterated is that a solitary transistor is rarely used in isolation as a straight amplifying device in a high quality amplifier, so the point about distortion becomes irrelevant , simply put, a circuit topography is used because the way in which transistors work allows it to be used to cancel out the very distortion that nonlinearities produce, but in such a way that it essentially still remains within the domain of a single device, meaning no phase anomalies an increase in speed thus widening the bandwidth and significant reduction in all distortions, yes it is essentially within the realms of current negative feedback, but the electrical reaction within the topography is without detriment , it,s now a symbiotic unity. The simplest of which is the longtailed differential pair to the more complex Current mirror load and constant current source, the same CCS is often used to feed the next stage the VAS to improve its linearity.
Now it is also true that with this type of topography very high intrinsic gains are achieved and further distortion from the output devices and drivers are also reduced by negative feedback, however many articles have been written about the proper use of feedback and all those other artifacts of SID, TID etc. which includes nested feedback to reduce phase anomalies , but you can not rule out the fact that many very good amplifiers have been designed with both high & low amounts of feedback, and some like Onkyo with no Global feedback which still produce relatively low amounts of distortion because the circuits are an amalgam of topographies used to reduce the additive stage distortion and if I remember correctly the Onkyo produced around 0.02% that Company believing as you do that an amp with limited distortion sounded better but in fact did,nt.
Referring to Geddes and Lee have you considered what happens when when say an audio amplifier of the transistor variety uses differing devices throughout the amplifying stages , for instance a J.Fet front end with it,s slope character followed by a standard B.polar VAS stage then followed by by say Mosfets, here you have three different slopes all adding their own particular distortions , feed all these back into the early stage and you have a disparity of control which results in both odd and even harmonics but more importantly some of the harmonic intervals are not amplitude consistant meaning some harmonics in the higher reaches have a larger than those proceeding, perhaps this is one reason why feedback can have rather unpleasant sounds with some designs , but is not generally known as a casual link,.. but in the end preferences will always be the deciding factor, however for proof of the proverbial pudding just take a well respected modern amplifier of each variety , in the case of the transitor version remove the input filter if it has one , then feed it with a square wave set at the same level as a valve version , then monitor the output into a dummy load , I think you will be very suprised at the result, because all the other factors of the amps will come into play which include the reaction by capacitors in the signal path and the interelectrode capacitance of the triodes CGK+(A+1)CAG, this then becomes a measure of accuracy not necessarily distortion, because it is measuring the filtering effect of both types of amplifier .
I have already conceded that there are many amplifiers of the valve variety out there which sound very sweet, so essentially we are not in any conflict whatever, I simply believe that a properly designed Transistor amplifier will give very satisfactory and pleasing results and can be blameless, I have had many debates with well regarded audio engineers , consultants and other speaker designers. Everyone has a preference for their particular beliefs and experiences , but they would all tell you that sound quality is of paramount importance but more often than not are convinced that their way is the only way forward and so sometimes get caught up in a negative feedback loop. ha ha.
Humble
Edits: 04/09/14 04/09/14 04/09/14 04/09/14
No need for the condescension. Maybe you guys have learned something during all your years of "experience" but based Disbelievers amps of choice I am inclined not to think so. Experience is not a substitute for talent.
As for the linearity of devices there is no debate, triodes are more linear than bipolar transistors by a long way. So are FETs for that matter...at least running Class A. Adding more non-linear devices in a circuit doesn't make the circuit more linear, it makes it less so. This is only logical and it can also be shown easily if you build any kind of circuit with them and don't wrap it up in negative feedback...fact is that if you go with multiple stages you MUST use some negative feedback and often it won't be stable without it. At least with a FET or SIT you can take one, run it Class A and it will be stable, sound very good and measure ok to a few watts. With a tube amp you need probably at least two stages but the whole thing will run without feedback and still measure ok and sound really good as long as you used good parts.
Making an amp with multiple stages (this is also true for FETS or tubes) only makes it less linear and then NECESSITATING the use of local and/or global feedback just to control the way too high gain and stability issues.
"essentially within the realms of current negative feedback" Heard amps with this topography like Accuphase and well YAWN, they didn't sound very good despite the glowing press...They sound gray and dead.
"believing as you do that an amp with limited distortion sounded better" Their problem is the same as others, the use of the wrong design gives a poor sound not the absolute amount of distortion. The design dictates what the form of that distortion will be and it is that pattern that is important. Find the design parameters that deliver the right pattern and you get good sound...stray into ultra low distortion techniques and you pay in sound quality. It is not as you think that it is because the distortion is low it is because of what was done to the signal to get it low that is the problem.
"Referring to Geddes and Lee have you considered what happens when when say an audio amplifier of the transistor variety uses differing devices throughout the amplifying stages , for instance a J.Fet front end with it,s slope character followed by a standard B.polar VAS stage then followed by by say Mosfets, here you have three different slopes all adding their own particular distortions , feed all these back into the early stage and you have a disparity of control which results in both odd and even harmonics but more importantly some of the harmonic intervals are not amplitude consistant meaning some harmonics in the higher reaches have a larger than those proceeding, perhaps this is one reason why feedback can have rather unpleasant sounds with some designs"
Once you have multiple stages and complex topologies in each stage AND feed all that back to the input I don't think it matters anymore what the elements are. Especially if one of the stages is Class B. Like I said, a tube push/pull amp in Class AB that is not triode and uses negative feedback will suffer many of the same problems because a non-triode tube is also highly non-linear, feedback exacerbates the problem AND it is likely to have transformer saturation issues unless the output iron is very good. I don't cut them any more slack than most transistor designs.
I have found that one thing that works very well is a hybrid design with two stages only, running Class A or very high bias AB (so like Class A 10 or more watts). With a FET output this can be run without any feedback and will sound very good with low absolute and low order distortion primarily. Make this single ended and it will sound even better but the amp will have to be physically huge.
Of course the pure tube variant and reverse hybrids (like KR Audio) can also sound phenomenal.
"I simply believe that a properly designed Transistor amplifier will give very satisfactory and pleasing results and can be blameless,"
And I would simply argue that no such animal exists or has ever existed, nor will exist until a truly linear amplification device is invented. Until that device is invented then I will stay with the psychoacoustically correct path for sound reproduction.
I also don't really care too much what engineers think on these matters...they are usually designing by what they learned is proper circuit design and to price points for the market. The majority of them are not scientists and don't know how to make the proper observations about what their products are doing. I am a scientist, which makes me a professional observer, which means i hear things in their products that they don't or wish not to hear. I may or may not know how to design various cool and tricky circuits but I know how to tell when one is doing the right thing and one is not. THen I bother to find out what was used and how it was implemented and wait to see other similar examples and how they sound. One can build a mental library of what sounds consistently good and what doesn't and start to draw conclusions about various "innovations" in circuits. I have done so and came up with some guidelines for a good sounding amp. I would share them with you but I doubt you would take them seriously. I have posted them before so feel free to search under my name and you might find my ideas.
"in the case of the transitor version remove the input filter if it has one , then feed it with a square wave set at the same level as a valve version , then monitor the output into a dummy load , I think you will be very suprised at the result"
Why on earth would you remove the input filter? That's silly. All systems have finite bandwidth and dynamic range and I think that one of the biggest failures of home audio gear is NOT limiting the input to what the device can swallow. Many audio people think the world stops at 20Kc. and removing input filters just punishes those that know better.
But... I am very much in favor of evaluating systems by using square waves, I'm just not in favor of modifying them first.
Rick
From HUMBLE
Input filters were originally used amongst other things to prevent the main amplifier from suffering SID especially , when the pre-amp was much faster. Bearing in mind that many earlier amplifiers had relatively slow Bi-polar output devices which meant that as the frequencies increased less feedback was available and distortion crept up sometimes significantly, modern out put devices like Sankens and some Toshiba audio devices are extremely fast with an FT up to 40mhz making the amplifier much faster and thereby keeping the distortion lower at much higher frequencies. BY removing the input filter and some amplifiers don,t have them ,enables you to see what the amplifier is capable of without the inhibiting effect of that filter which often comes into effect depending on the designers criterion of frequencies as low as 150kHz, taking the filter out of the Hafler 200 series enables a beautiful square wave to be reproduced above 10kHz, with the filter in the square wave was much more rounded as you would expect.. There is a strong correlation between the speed of transistors and point of roll-off in the treble particularly prevalent with slow output devices a factor that feedback does not totally compensate for, of course Mosfets enable a much faster performance and often noted for a detailed treble especially with supertweeters. When the JL Linsley-Hood 75 watt amplifier was first produced it had 2 t 3 mhz FT O/P devices, later these were substituted with BDY56 10 MHZ devices and immediately the distortion dropped by almost a decade and that amplifier had 78 db of NFB, it also sounded faster and easier on the ear.
Humble
Good Post!
I have no problem with injecting test signals after an input filter, or any place else for that matter to evaluate a system's response. I also believe that using square-waves and a scope are far more likely to get you to the root cause of audible problems than peering in the frequency domain with a spectrum analyzer, especially an FFT one that doesn't go very far out-of-band.
All "properly designed" systems need to make a reasonable attempt to not accept signals that they can't handle. I think the best case is to have enough bandwidth margin to allow a simple RC LPF as the dominant pole and still be high enough to not mange the treble.
Regards, Rick
I have no idea who is making the best amps out there. My own 18 year old close coupled design ( similar to Hafler )Class AB stereo amplifier Prime Design A100 has the following specification:
Transistors two 17 amp. 40 mHz per side. High grade 500 Va toroidal transformer, 80,000 mfd capacitance, damping factor at 40Hz in excess of 200, THD 0.005% has had a few upgrades and still sounds excellent.
.005% THD, at which frequency? I bet at higher frequencies it is significantly worse (above say 1Khz)...that would be typical for a high feedback design (the only way to get THD that low).
However, it is irrelevant because as I have said and the research shows there is even a slightly NEGATIVE correlation between THD/IMD and sound quality...That is what Geddes found and Cheever as well and many others before them...at least since the dawn of PP circuits and negative feedback.
I wonder what you'd think of the Matrix speakers if you have heard one? My B&W 602 S3 speakers produced 3D depth to music very well, and when I had vinyl on- it did fill the room. I was expecting better from their 800 series. There is a YBA amp on Craigslist right now. Shame I can't afford it at the moment. Its only a 60 watter, but was very musical if I remember correctly. Don't recall how dynamic YBA was though. It is a high current design- is it not?
I have heard the B&W Matrix 801 whatever the last version was (they came out with the Nautilus 801 not long after that) and the 802. They weren't bad but at that time I heard as well the Monitor Audio Studio 50 and it was WAY better overall. THen I heard big planars and realized that both were way behind the best speakers.
I haven't heard a YBA but I believe it really depends on the model if it was a good design or not.
This is all way off original thread topic however you can also forget B & W 804D , tweeter output is up by +6dB around 12kHz giving audible brightness in the treble ,even a treble sting. (from Hi-Fi World Measured performance)
Edits: 04/03/14 04/03/14
Yeah that would seem pretty deliberate on their part...naughty boys.
Haven't heard the JOB or other Goldmund amps, sorry. But when I hear the first descriptors used by someone about an amp as "fast" and detailed, I think "lean" and "fatiguing". If someone describes and amp with "tone", "transparency" and "presence" then I start to perk up and take notice.
Thanks. Sorry I didn't perk you up with the right verbiage.
--Ze'ev
I agree quality of sound varies a lot with Class AB amps or any other class. I was referring to Bryston Integrated amps which sound harsh and you are coming up with a pair of expensive large Godzilla ha. mono blocks which would be of no interest to me despite the rave reviews. I am mainly concerned with 150 watt into 8 ohm amps, have you auditioned the Quad Platinum amplifier which sounds very good into my TL speakers but I could not use it as I got unresolved hum problems when it was connected to the pre-outs of my excellent Sony DA5400ES AVR no other amp I tried has this problem.
Edits: 03/29/14
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