If you've decided no progress is possible then there isn't much else for me to say, and, perhaps, more to the point, no question for you to answer.
Just because I think this may be useful
Check out YouTube
Download here HP Prime Virtual Calculator Emulator (32-bit) 2.1.14181 (2018-10-16) - detailed information
There’s no EQ error on an all-active RIAA EQ amp. Easy enough to build one and measure it. On solid state +-15V (typical) based designs you get best noise performance and best overload performance.
Due to circumstances I had to live for a few years with a noisy phono stage. The mute switch on the preamp made it a mute problem on all bar 2 records in my collection
Noise figure drag racing is fun, but ultimately pointless below a certain level. Richard Lee published a 2 transistor MC head amp that will beat practically anything out there for Lo-z coils, yet no one builds it for audio.I don’t buy the ‘why worry about the noise’ thing. Agree, it’s not as critical as a LIGO instrumentation amplifier, but just because it’s audio does not mean you should not make some effort - kind of like the whole cart resonance thing. Just sayin
Define great. LF grot is more vertical than lateral. Vinyl has no LF vertical information., Hmmm just maybe there is a better solution out there?
At one time, progressively blending (reducing separation) with lower frequencies was more common than now.
All good fortune,
Chris
In the late 60s we had access at grammar school to a pdp-10 and pdp-8 at the county Uni. We had a 300bps acoustic coupler, and a teletype with a paper tape punch / reader to load and save programs. This scheme was available to a lot of schools. basic and Fortran available.
They had to forcibly drag me out of the computer rooms most days to get me to other lessons. I was hooked!
The uni would also lease time to commercial interests. Helped pay for it all.
So yes, one way or another computer time was readily available.
Time flies... I wonder how useful are the "ancients" today? Attached is from my course material illustrating what half a century brings. Fast forward to the 80's, and I remember struggling with a thing called Turbo Pascal on a PC AT: no good for math because of a hopeless floating point library.
Attachments
You don't know Roy Underhill? Roy Underhill - Wikipedia
In one show he made one of those bouncing folk dolls of Norm Abrams holding a router, it was one of the funniest inside jokes I've ever seen.
An active, non-inverting RIAA stage approaches unity gain at hf, instead of following
an asymptote down to zero gain. This is true of any non-inverting amplifier topology,
and is due to the 1+ term in the transfer function. At hf, the circuit reduces to a follower.
An inverting active RIAA does not have this particular bug/feature.
Remember that an inverse RIAA network has a related problem. Its hf boost reaches
a limit and flattens out, instead of following an asymptote upward. The two errors can
compensate (more or less) for each other, and make it appear that everything is ok.
An inverse RIAA can be designed to have a high loss, and will then have a much wider
useful bandwidth. It will then show up the problem with the non-inverting active RIAA
circuit more clearly.
Last edited:
If you built a super low noise RIAA preamp and then added the mute-when-needle-not-in-groove stunt as well, you could install a PCB options jumper (shorting header etc.) labeled Mute Disable or some such. Then when Mr. Smarty Pants reviewer comes along to unmask your treachery and by God he is going to measure The Real Noise Level so he can tell The Real Truth, he disables the muting stunt and aha! he discovers ... a super low noise RIAA preamp. Oh snap.
Due to circumstances I had to live for a few years with a noisy phono stage. The mute switch on the preamp made it a mute problem on all bar 2 records in my collection
You had a very sub-optimal system then. As an engineer, I thought you would have lashed something half decent up rather than living with the problem and a switch. If you had to mute it when not playing a LP it must have been pretty horrendous. Is it a case of 'the unshod cobbler' or challenging Scott for the lowest performance phono amp?
Noise figure drag racing is fun, but ultimately pointless below a certain level. Richard Lee published a 2 transistor MC head amp that will beat practically anything out there for Lo-z coils, yet no one builds it for audio.
Anymore of this type of talk from you and Scott and we'll all be building LM741 based phono EQ amps . Building a low noise MM amp that's 10-20 dB quieter than LP surface noise is as easy as using an NE5534. Others prefer more esoteric solutions. What's the problem? MC head amps of the type Richard showed have been around for decades - see Marshal Leach et al. I think Richard spent some time optimising his version of the classic design - I agree it is very elegant.
Define great. LF grot is more vertical than lateral. Vinyl has no LF vertical information., Hmmm just maybe there is a better solution out there?
Great = when your bass speaker cones are flapping around with it switched out and are not with it switched in and there is no apparent loss of LF programme material. The single resistor solution peaks at about +1.5 dB between 60 Hz and 25 Hz before dropping off rapidly - so not flat, but given the discussion on the other thread about cartridge response I don't thing its anything to lose sleep over. I have a wonderful Art Blakely LP (A night in Tunisia) and a very old (c. 1979) Manhattan Transfer LP - both are not playable without a subsonic filter, so its a useful function IMV
You had a very sub-optimal system then. As an engineer, I thought you would have lashed something half decent up rather than living with the problem and a switch. If you had to mute it when not playing a LP it must have been pretty horrendous. Is it a case of 'the unshod cobbler' or challenging Scott for the lowest performance phono amp?
Noise figure drag racing is fun, but ultimately pointless below a certain level. Richard Lee published a 2 transistor MC head amp that will beat practically anything out there for Lo-z coils, yet no one builds it for audio.
Anymore of this type of talk from you and Scott and we'll all be building LM741 based phono EQ amps . Building a low noise MM amp that's 10-20 dB quieter than LP surface noise is as easy as using an NE5534. Others prefer more esoteric solutions. What's the problem? MC head amps of the type Richard showed have been around for decades - see Marshal Leach et al. I think Richard spent some time optimising his version of the classic design - I agree it is very elegant.
Define great. LF grot is more vertical than lateral. Vinyl has no LF vertical information., Hmmm just maybe there is a better solution out there?
Great = when your bass speaker cones are flapping around with it switched out and are not with it switched in and there is no apparent loss of LF programme material. The single resistor solution peaks at about +1.5 dB between 60 Hz and 25 Hz before dropping off rapidly - so not flat, but given the discussion on the other thread about cartridge response I don't thing its anything to lose sleep over. I have a wonderful Art Blakely LP (A night in Tunisia) and a very old (c. 1979) Manhattan Transfer LP - both are not playable without a subsonic filter, so its a useful function IMV
I don't experience this. An open-loop, cascoded JFET I to V, differential current out, the impedance is so high the exact RIAA is easy to compute, ~0.1dB with NOS TRW 2% PS caps and Dale RN55 resistors out of the box and the zero at infinity is really at infinity. I Muntzed Bob Cordell's Linear Audio article down to about as little as you can get away with, Patrick made some welcome changes to accommodate more users.
With a chance to thoroughly check layout, grounding, EMI, and PS issues I would put it up against anything I have ever listened to in the context of real LP listening. Of course rigorous DBT (of any mutually agreed upon protocol) is required, so as with most things here just P****** in the wind. Remember though my 8-legs microphone won the Triode Fest, one needs to know when to hold them and when to fold them (would anyone fold Aces and 8's, maybe with a gun pointed at the back of your head).
@Mark J - I finally unpacked some tubes of unmarked parts, and popped the lid on some and found the ceramic 797's they are on the way.
Last edited:
Count yourself lucky you will never meet my ex-wife
. I have new wife now and better equipment. Note that Scott and I are both fully balanced. And my MM stage is so esoteric only one other person has been brave enough to build it.
. The fact that I say one thing then do another is just part of the fun So zero analysis of the actual problem or solution? Shame on you. Have my cobblers awl (northampton boy).
Correct me if I'm wrong, but you are a MM/Grado user? For a MM "low noise" amplifier you don't need anything but the next JFET opamp with 3nV/rtHz (many available today).
Not saying that MMs are anywhere inferior to MCs, if used correctly (no resonances, etc...).
- Status
- Not open for further replies.