I just checked, it was 'small signal audio design' Where DS analyses this. For those who don't have that the addendum to that chapter is here. Discrete design: 2-transistor RIAA preamp . I still think its fascinating how readily performance can be very significantly improved, even if a 50p op-amp will still outperform it 
Thanks for the description. Definitely understand what you're trying to achieve, but there's just some details I'm not perfectly getting (that's on me). I just need to sit down and hash out why this is/isn't more sensitive test (or same) than the description Samuel gives in his thesis, which is to flip/flop in the 2s/2p for a single DUT in a simpler RC. Cheers!
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The A77 wasn't a pro recorder, but the pro ones probably was not better eider. On the other hand they filled the purpose ,recorded all kind of beautiful music for our enjoyment and we still listening to them. That shows our high threshold of sensitivity to distortion.
depends.... my 1/2 track 15/30 ips A77 would be in the Pro catagory. Electronics the same.
The sound was a lot better from my own recordings than what i was hearing thru my TT/LP system.
usually, I have no issues with technical talk here but as soon as I say i heard this or that, all hell breaks loose. But, I use both listening and measurements and accept both as valid to within certain limits.
THx-RNMarsh
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Hi Richard,
Having worked on many of those, yes. They could sound pretty good. Still, I would prefer a B-77 in the same configuration. The A-700 was nicer and they all used the same heads. I think the attraction to the A-77 must be mostly romantic, or it could be that sound they had.
-Chris
Having worked on many of those, yes. They could sound pretty good. Still, I would prefer a B-77 in the same configuration. The A-700 was nicer and they all used the same heads. I think the attraction to the A-77 must be mostly romantic, or it could be that sound they had.
-Chris
Of course there were several others that are better - maybe even great but I didnt own any of them. I did have a nice 8 channel Otari MX-8080. used the high speed A77 for mix down to 2 channel master.
Just saying this is the topology popular at the time in preamps and recorders and tuners (audio section) etc. The A77 used 8 polar caps per channel on just the playback side. The polars were a lot worse than polars are today, but still. This is what got me to thinking how to be rid of all those caps via topology change. No one has looked back since..... But then we see the Sony FM HD tuner is back to the junk designs for the audio portion, again.
Though we have found better parts and topologies since then... big high volume companies keep doing this sort of thing so i guess it will keep the debates going for centuries.
We have 'fixed' many of the big problems in circuit design for audio and are left with fine tuning them. Except we havent got to fixing the speakers yet. I had lunch today with Keith Yates (Keith Yatees Design - acoustician-architect) and he agreed 100% from his studies of speakers and rooms and designing hundreds of high-end rooms for audio and A-V --- about the low dynamic range and wide polar patterns lingering for decades. Other than Myer Sound Labs and JBL (M2) he could not think of a #3 speaker to use that comes close to what is needed.
THx-RNMarsh
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On that speed a live recording would be out of this world. I never seen one 30 ips one. What I found irritating with the Revox A77 (if I remember correctly) is the fact it didn't had a Pause function. In case of recording you couldn't put it to Stand By. I made some live recordings in the eighties (nothing serious , just for fun) with a Sony WM-D6 and an amateur copy of a Sennheiser kunstkopf with electret mics, the best stereo I ever heard.
Miklos
I was curious whether our departed friend would find time to say anything interesting or at least about DIY, but then he wasn't lashing out at me.
That is my experience also. Way better than LP. Until recently, it was the standard to use as source. But, we have HD direct down-loads now. very nice.... too bad it took so long to get back to the future in high quality sound.
Thx=RNMarsh
So did I miss something? I am still wating for JC to actually say something about the Hirata test and how it helped him detect and fix a flaw in an amplifier, and why no other test would have revealed that flaw. I am not a professional nor even a competent amateur, but I am curious ro see how Hirata's paper actually informed product design and how it was more revealing than more conventional tests.
Hi Richard,
I agree with you on that. How did you get around the channel swap that the A-77 does? I guess knowing about it is most of the problem solved.
Hi Miklos,
30 ips with tape has issues. The head bumps that were in the bass region now show up in a more audible range. Studer EQ'd them out, but that is expensive. I wouldn't recommend going to 30 ips for 2 dB of s/n improvement. At 15 ips you're already up in the 22 ~27 KHz range for top end response (on a Teac too). That's got to be enough top end for anyone.
A 15 ips half track sounds glorious. I just sold my BR-20 to a friend. Just wait until he hears what this can do!
-Chris
I agree with you on that. How did you get around the channel swap that the A-77 does? I guess knowing about it is most of the problem solved.
Hi Miklos,
30 ips with tape has issues. The head bumps that were in the bass region now show up in a more audible range. Studer EQ'd them out, but that is expensive. I wouldn't recommend going to 30 ips for 2 dB of s/n improvement. At 15 ips you're already up in the 22 ~27 KHz range for top end response (on a Teac too). That's got to be enough top end for anyone.
A 15 ips half track sounds glorious. I just sold my BR-20 to a friend. Just wait until he hears what this can do!
-Chris
When it comes to analog tape recorders, I have a lot of experience. 50 years ago, I bought a semi-pro Ampex tape recorder called an AG-500. It had a pretty good transport, 15ips, 1/2 tr. and the typical 3 transistor circuits with a single supply, like what was described here earlier. It had a number of small problems at first, but I worked it over, without actually changing the topology much, and made it into a better tape recorder than most were at the time (early 70's). The GD recording engineers thought so as well, certainly better than the AG440 electronics used also in the Ampex MM1000. Actually, BIASED Tantalum caps are not as bad as UN-BIASED Tantalum or Aluminum caps. They do have some DA, but when biased, less than Aluminum caps and the low frequency distortion drops to almost nothing. In 1974, I started working with the electronics of the STUDER A80, and the first model that I had was sort of OK, but they changed to a second model that had typical IC's in the audio path with a Class C output. This sucked! I made some measurements, took photos of the distortion in the line stage, and personally showed Willi Studer and his engineers what I found. Did they fix it? No. So, 4 years later, in 1979, I threw away the analog electronics of a brand new A80, and designed new electronics. This was for Mobile Fidelity. I did another unit, as well with a preview head for the same company. The company tried to take the design away from me, so they could make it independently themselves, but they did not have access to the schematics, so we had one big battle, almost winding up in court, and I dropped making another tape machine for awhile. But in 1983 Dave Wilson commissioned me to do another Studer, and that unit is still being used today. It is considered one of the best analog tape machines in the world today, still. However I had to triple the bias frequency, and more than double the track width (full tr. 1/2"), EQing to 10 Hz at 30 ips to get it right. It was expensive and time consuming to make the electronics for these analog recorders, but I did appreciate the STUDER tape transports, the are VERY NICE. Those Swiss are great with mechanical stuff.
Now why do I appreciate the Revox A77 electronics? It is very similar to my Ampex AG-500, and I know how it can be made to sound very good, better than most analog transports. As proof, Dave Wilson used a 15ips 1/2tr A77 for several master recordings that he put out on vinyl, before my machine was ready. They sound pretty darn good too!
Now Studer, you might think would learn about electronics, and improve them, but they didn't, so far as I can determine. The earliest electronics, whether tube or transistor were better.
Now why do I appreciate the Revox A77 electronics? It is very similar to my Ampex AG-500, and I know how it can be made to sound very good, better than most analog transports. As proof, Dave Wilson used a 15ips 1/2tr A77 for several master recordings that he put out on vinyl, before my machine was ready. They sound pretty darn good too!
Now Studer, you might think would learn about electronics, and improve them, but they didn't, so far as I can determine. The earliest electronics, whether tube or transistor were better.
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