I'm delighted you acknowledge that.
Congratulations.
Hopefully, it's never used with the symphony!
Burson Audio V6 Vivid Opamps review: “Put some smack in yer DAC!!!”
wyn palmer
Addicted Member
Alas, it will be. However, the hall will probably be worse without it as it was designed primarily for Musicals and excellent sight lines and not for quality live music reproduction.
If the potential loan of some Burson opamps is realized, "this individual" will report on at least some measured results. It may well offer some insight for some people. Who knows...
If that happens- I will be back, and we can continue our exchange then.
Sorry to hear that. That decidedly compromises the concert experience for me.
Some of us do not require "measurements" in order to be able to observe qualitative aspects of musical reproduction. If anything, I avoid those with overly low THD metrics as such is easy to achieve using crutches that I find compromise the overall presentation. I learned about the irrelevance of that metric in the 70s when I was a teenager. Dave O' Brien measured and handed me a fancy chart of my AR integrated at a Mac clinic. Great numbers. Poor sounding at low levels. Nothing has changed since IMHO...
Oh, OK didn't expect that. Since I already have them I might as well try them just to see. I also have some of those lil' DIP sockets so I can swap in something else easily.
Perhaps one of you should contact John Saio and tell him he doesn't understand how his own amplifier works. LOL!!!!
“The AHB2 is comprised of both a Class AB and Class H design (this is reflected in the product’s name if you’re attentive). I asked John if he could explain the topology of the Benchmark amplifier in a bit more detail and what were some of the limitations of the topologies that they had to overcome.
'Class AB amplifiers require precise control of the biasing in order to minimize push-pull crossover distortion. Class-H designs add at least two more crossover regions. The AAA technology virtually eliminates this distortion, even when no biasing is used. We have chosen to keep the output stage lightly biased, but we could operate in full Class-B mode without much of a distortion penalty.'”
You guys really need to give this a rest having taken this topic WAAAAYYYY far afield of the OP. Sheesh!
Phaceless56
Active Member
ok so from the discussion The Burson op-amps work great in DAC's the question was how do they fair in the Basic C2
Both are used in analog output stages at similar output levels so results should be similar. Especially since the JRC4580 used in the C2 is a rather unremarkable choice.
Phaceless56
Active Member
I already changed them out to njm2068dd and I did notice an improvement in sound I think from the recap or both I would love to try a few op-amps also I have a Denon DVD-2910 I would like to change the op-amps there are some articles from a company that mods these players out then asking $1200 to $1500 for them
wyn palmer
Addicted Member
Just to add more confusion...
A quote from the Stereophile review;
"It was also explained to me that the AHB2 was based on designs by Benchmark's founder, Allen H. Burdick (whose initials it bears)"
It's all quite fascinating, really.
A quote from the Stereophile review;
"It was also explained to me that the AHB2 was based on designs by Benchmark's founder, Allen H. Burdick (whose initials it bears)"
It's all quite fascinating, really.
Kinda sorta. The feed forward amplification stage design (building on Peter Walker's "Current Dumping" and Nelson Pass "Stasis" work) was performed by the THX group while the power supply is designed by Benchmark.
wyn palmer
Addicted Member
Just for reference sake, for those that may be interested.
https://en.wikipedia.org/wiki/Power_amplifier_classes (yes, I know that this is Wikipedia- but in this they are correct).
"There are a variety of amplifier designs that enhance class-AB output stages with more efficient techniques to achieve greater efficiency with low distortion. These designs are common in large audio amplifiers since the heatsinks and power transformers would be prohibitively large (and costly) without the efficiency increases. The terms "class G" and "class H" are used interchangeably to refer to different designs, varying in definition from one manufacturer or paper to another.
Class-G amplifiers (which use "rail switching" to decrease power consumption and increase efficiency) are more efficient than class-AB amplifiers. These amplifiers provide several power rails at different voltages and switch between them as the signal output approaches each level. Thus, the amplifier increases efficiency by reducing the wasted power at the output transistors. Class-G amplifiers are more efficient than class AB but less efficient when compared to class D, however, they do not have the electromagnetic interference effects of class D.
Class-H amplifiers create an infinitely variable (analog) supply rail. They are sometimes referred to as rail trackers. This is done by modulating the supply rails so that the rails are only a few volts larger than the output signal "tracking" it at any given time. The output stage operates at its maximum efficiency all the time. This is due to the circuit ability to keep the rail transistors (T2 and T4) in cutoff until a music voltage peak is of a sufficient magnitude to require the ..."
There is indeed a clear definition of "Class H" that is not what Jon Saio, despite his engineering chops, says. I have used both class G and class H power amp/supply designs in a different area- hand sets- and the implementations are distinct.
In science/engineering words should have precise, and commonly understood, meanings. We generally don't employ Humpty Dumptys- and I'm not inferring Saio is one in a non-literary sense.
What Saio is apparently describing is class G.
From the initial THX feedforward patent
https://patents.google.com/patent/US8004355B2/en
Quote from the patent.
"The driver and main output stages may be operated in Class AB and B modes respectively, and/or in Class G or H modes"
So clearly, the original THX corp. inventors understood the distinction.
Many references are cited in the patent, most notably the progenitor of the whole idea- Peter Walker of Quad (incidentally, they use a truly crappy opamp at the heart of the Quad design), and Bob Carver.
However, as far as I can determine, and please correct this if it is wrong, no reference is made to any of Nelson Pass' works, or any derivative therof.There are other subsequent THX patents in the area. However, my knowledge of those is less complete.
I'm delighted you finally acknowledge what I observed almost fifty posts ago! Whether G or H, it uses multiple rails, NOT "fixed ones just like my preamp" as you averred in post #26.
And most likely, no reference to Harold Black either who introduced negative feedback amplification used by the design.
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First I hear of Nelson Pass regarding Feedforward too, yet the member you quoted doesn't mention Sansui engineers.
It's my understanding that Peter Walker used a current dumper design (some debated if it was actually feedforward) so he did not invent Feedforward. As mentioned, that distinction goes to Harold Black way back in 1928 (although it was for communication devices).
In 1980 Sansui used a variation of Black's invention (giving him credit) and called it Super Feedforward. They claimed to be the first to use NFB & FF simultaneously in an audio amp, which I believe is similar to what Benchmark is also doing now.
https://secure.aes.org/forum/pubs/journal/?elib=3934
https://www.hifiengine.com/manual_library/sansui/super-feedforward-system.shtml
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wyn palmer
Addicted Member
I found a web link to the original Walker et al patent- "distortion free amplifier"- assigned to the acoustical manufacturing company- Filed June 10 1975 ser no. 539954, patent 3970953.
https://patents.google.com/patent/US3970953A/en
The only reference it provides to prior art seemingly is a US patent assigned to Ketchledge, 1956.
Indeed the basic feedforward concept was not Walker et al's invention, and I didn't intend to imply that the essential concept was his - only that the initial circuit implementation was (hence the Walker et al patent)- which is remarkably similar to one which is described in the Benchmark patent. And no, do not read into this that I am saying that the Benchmark design is a copy- it's not, but it does use the Quad design as a starting point of sorts.
www.audiocircuit.com/A-PDF/AA-Brands/Q/Quad-QUA/Current-dumping-audio-amplifier-A-EN2-920-QUA.pdf
Here you will see a reference to Black, and a claim that the current dumper employs relatively small variations on the original concept, which is a pretty modest statement by Walker.
The circuit implementation uses both feedforward and negative feedback, both global and local, and you can see why it's been argued that it's not "true" feedforward.
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No worries, I never thought you implied that he invented it. I didn't read it that way at all. My second paragraph was more of a general statement, sorry for the confusion.
On a side note, I also have an AHB2 and even subjectively I think it's sound quality is excellent. Very clean, lean, detailed, open and musical. IMO, a sound signature that is very similar to the best of the spec driven Japanese amps from the early '80 (not all of course). As for Harry Pearson, something tells me that if the AHB2 would have come out in 1980 he wouldn't have liked it's sound either. It's nice to see that the high-end press has finally come around to agree that an amp with superb specs can and does sound wonderful. How times have changed.
What Benchmark has accomplished with this unconventional amp should be applauded.
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wyn palmer
Addicted Member
No problem.
Sometimes I'm not as clear in my wording as I should be and the meaning gets misinterpreted.
I generally try to avoid subjective statements on the quality of sound. However, I and others do think that my system sounds excellent, although, I must admit, this afternoon I think it sounds quite poor...
I think that I have a cold or something coming on. Often when I'm going "out of sorts" things start sounding off. It's probably time to stop listening for a while before I become tempted to tweak or buy something.