From Volume 3 of "Linear Audio". It sims out very well. Here's a possible PCB 3D image:
An externally hosted image should be here but it was not working when we last tested it.
Hmmm, this is just a combination of two well known circuits, both of which I have showed here on this forum. The input is the buffer as shown by JLH, the second part is as I described in Mpp thread to tweak JLHs headphone amp. Does this designer frequent DIY audio ??
Anyway it will sound and measure very well indeed.
Anyway it will sound and measure very well indeed.
Richard Marsh has been writing "do-it-yourself" audio articles since before Compuserve! The genesis for this particular article was some work he had published in "The Audio Amateur" 3/80 with credit to R. Baker from MIT.
I have no idea who these people are. The person who he should be crediting is JLH who developed these type circuits back in the late 60s.
I didnt expect people to admit or reveal exactly where their ideas came from anyway.
I have a headphone amp which is 95 % this exact design with the tiny difference that the input stage is further bootstrapped to lessen the load of the output, just lowering distortion further.
Its a excellent headphone amp either way, well worth building.
I didnt expect people to admit or reveal exactly where their ideas came from anyway.
I have a headphone amp which is 95 % this exact design with the tiny difference that the input stage is further bootstrapped to lessen the load of the output, just lowering distortion further.
Its a excellent headphone amp either way, well worth building.
Baker was the inventor of the "Diamond Buffer" and "Baker Clamp". I believe that he has over 80 patents, dating from the early 1960's.
I still have Dick Marsh's article "Picking Capacitors" from Audio Magazine in 1980. This was co-authored with Walt Jung and is archived on http://waltjung.org/PDFs/Picking_Capacitors_1.pdf Dick wrote one of the first TAA articles on passive RIAA equalization.
At any rate, I am going to have some boards burned and offer them at cost -- just as I did for SY's "Impasse" and "His Master's Noise".
I still have Dick Marsh's article "Picking Capacitors" from Audio Magazine in 1980. This was co-authored with Walt Jung and is archived on http://waltjung.org/PDFs/Picking_Capacitors_1.pdf Dick wrote one of the first TAA articles on passive RIAA equalization.
At any rate, I am going to have some boards burned and offer them at cost -- just as I did for SY's "Impasse" and "His Master's Noise".
from the Linear Audio site . . .
"If you are looking for that ultimate headphone replay amplifier, you couldn’t do any better than with this discrete circuit. Richard Marsh develops his circuits from the well-known diamond topology but with a twist. His headphone amp is a very clean and linear discrete design that’s equally at home driving low-impedance or high impedance ‘phones. But Richard doesn’t stop there; he realizes that many headphones do not produce flat frequency response at your ears. Therefore, he borrows from ‘room equalization’ technology and develops a simple way to use that to equalize the headphone response at your ears.'
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An externally hosted image should be here but it was not working when we last tested it.
"If you are looking for that ultimate headphone replay amplifier, you couldn’t do any better than with this discrete circuit. Richard Marsh develops his circuits from the well-known diamond topology but with a twist. His headphone amp is a very clean and linear discrete design that’s equally at home driving low-impedance or high impedance ‘phones. But Richard doesn’t stop there; he realizes that many headphones do not produce flat frequency response at your ears. Therefore, he borrows from ‘room equalization’ technology and develops a simple way to use that to equalize the headphone response at your ears.'
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An externally hosted image should be here but it was not working when we last tested it.
"Richard Marsh grew up with music in the home - piano, singing and records playing. He builds his first tube preamp and power amp at age 16. Richard was drafted out of college to work in High Energy Physics R&D at Lawrence Livermore National Laboratory. There he held the rare 'Q' clearance (above top secret) for 23 years. In this position, he developed a talent and expertise in precision test and measurements. Eventually, he became responsible for coordinating development of several high profile DOE and DOD projects, including experimental test accelerators, fusion energy systems, and nuclear engineering systems programs (nuclear weapons). During that time he also continued to write articles and develop circuits and systems for audio. He is a member of IEEE and AES and holds many patents. After retiring from government R&D, he pursued his musical and audio interests as a consultant to consumer electronics companies in USA and Asia. He has now started learning to play blues bass guitar. Richard also spends time every year in S.E. Asia helping poor children in Nepal get an education thru direct support."
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John: his picture certainly looks like "Sheridan Whiteside" (played by Monty Wooley in "The Man Who Came to Dinner".)
The boards cost just under $3.00 then with bubble mailer, PayPal fees, postage etc. let's make it $6.50 for non US and $5.00 US and I should be about break even. I'm not going to set anything up until the boards get back and I can test them out.
Can someone help me understand this circuit? I'm looking to learn something here. It looks like unity gain buffer to me, but can't be sure. I'm confused about the input jfet's function, for example. I can see that Q1 and Q3 are emitter followers, and that Q7 appears to be a constant current arrangement. Thanks.
The full development of the circuit, description and determination of component values etc are in Linear Audio Vol 3.
jan didden
jan didden
OK. I guess that means I have to buy the magazine (or article?) in order to understand this circuit. Thanks.
Both stages are both so close to Sziklai connected devices (1956) that I don't see much of a point to press.
Boards arrived this morning. I could probably tweak this up a bit by matching the input JFETs. The values of R3 and R4 aren't specified in the article, so I used some machined female pins and inserted values of 47R5 and 150R to see what an FFT would look like:
Attachments
The above was into a 250 ohm load -- similar to my Sennheiser HD-650's -- tomorrow i will run the amp into the "worst case" 30 ohm load.
The DC offset changed by only a milliVolt after a few hours which is very good indeed. The output transistors should be happy bolted to the chassis with the appropriate insulators.
I don't know if I'm going to run it off a wall wart and a couple of DC-DC converters, or make up a quiet push-pull switcher.
This would probably be a tremendous line amp if A=10.
...edit...and the bandwidth is much greater than suggested in the article.
The DC offset changed by only a milliVolt after a few hours which is very good indeed. The output transistors should be happy bolted to the chassis with the appropriate insulators.
I don't know if I'm going to run it off a wall wart and a couple of DC-DC converters, or make up a quiet push-pull switcher.
This would probably be a tremendous line amp if A=10.
...edit...and the bandwidth is much greater than suggested in the article.
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