Assuming we are still discussing this circuit, https://www.diyaudio.com/forums/att...bjt-input-phono-preamp-lt1792-riaa-preamp-jpg , an OPA637 should theoretically work somewhat better than an OPA627 - both should be stable, but the OPA637 will have five times more loop gain at high audio frequencies. The OPA627/OPA637 noise specs are fine for moving magnet and the offset is quite low.
Over the years, before they became so ridicously expensive, I have used dozens of OPA627’s in different projects and never had a taming problem with any of them.
Just ordinary decoupling with two 100nF caps as close as possible to the supply pins as you normally do with all opamps and that’s it.
And my very subjective opinion is that it is one of the best sounding opamps around.
But I haven’t had the opportunity to compare it to the OPA164x and the OPA165x.
But in general, many modern opamps in the OPA16xx series are very good such as the 1612 and the 1632 that I have used.
Hans
Just ordinary decoupling with two 100nF caps as close as possible to the supply pins as you normally do with all opamps and that’s it.
And my very subjective opinion is that it is one of the best sounding opamps around.
But I haven’t had the opportunity to compare it to the OPA164x and the OPA165x.
But in general, many modern opamps in the OPA16xx series are very good such as the 1612 and the 1632 that I have used.
Hans
This should be last time I play my LP records again, and then will go back to their storing place.
Even if I think the quality you could get with LPs was never reached with standard 16bit/44KHz CDs, LPs were a very poor mechanical system as a design. And very few people (considering the large universe of people playing LPs in the world) could own a system that could extract all the info in the LP.
Besides that, the LP started desintegrating the first time you played it, no matter how careful you were or how well engineered your system was. The friction and physical contact was deadly.
A standard CD player, particularly a good one like Philips, Marantz or Sony, could play things as well as a basic turntable system, say a Dual, but not reach what you could get with a Thorens, a Linn or a Rega, just to name some affordable ones. Things got expensive when you used better arms and cartridges and a good preamp. No CD player, then or now, could get close to that quality.
The industry refused to go further, using DVDs, to make 24bit 384 KHz records, which would then surpass the LP quality.
This was clearly explained by Tim de Parravicini, one of the best valve amp and professional recording consoles designer, in Studio Sound magazine.
Anyway, I don't want the preamp to be a limiting factor. That's why I have been researching so much.
The only thing I will not discuss is MM versus MC cartridges.
Yes, the circuit should basically be that one. But if possible I would like to build two versions, perhaps using that PCB I had mentioned which is very cheap, one passive (as the one you showed) and a passive/active hybrid one, and see how different they sound.
Then it would only be a question of plugging the opamps in one and then in the other one.
evey guy here has its own opinions on vinyl and digital...the only problem with digital today is that the 50's to 90's singers recorded on analogue: tape, valve, etc...As very few had acces to professional tape machines and recordings vinyl was the poor's affordable choice.It happened that Vinyl could last over decades better than tape was able to do it.Most probably that's the best option we have today: to get the best setup for one time analogue to digital transfer.That in no way can be a very high dynamics discrete phono preamp used on dirty vinyls as it would easily saturate the ADC input. So either you wash thoroughly your vinyls and have a decent phono setup for digital transfer or you have a valve preamp doing that, providing enough good sounding saturation to get through to ADC .There's also a solution provided by Scott Wurcer based entirely on j-fets to solve this saturation problems but that comes very expensive due to the extensive use of rare j-fet's.There might be other solutions i'm not aware of ...but at least i exposed my opinions here.
I was a professional sound recordist, for film & TV, for more than 40 years. So I got to know the best you could get in tape systems.
Listening to the original tapes, when your material went to an LP, and listening when it went to CD, was quite disappointing for the latter.
You insist on talking about dirty vinyl LPs, which seems to imply you should be using such a system continuously, actually playing the LP every time.
Sorry, but I do think that's a thing of the past. LP surface wear and every type of dirt is not something you can avoid. But you can convert your LP to a high resolution format, and record it on a DVD, and play it through a good quality DAC. That is the best of both worlds.
In my case I intend to put the files on a computer server, both for audio and video.
Listening to the original tapes, when your material went to an LP, and listening when it went to CD, was quite disappointing for the latter.
You insist on talking about dirty vinyl LPs, which seems to imply you should be using such a system continuously, actually playing the LP every time.
Sorry, but I do think that's a thing of the past. LP surface wear and every type of dirt is not something you can avoid. But you can convert your LP to a high resolution format, and record it on a DVD, and play it through a good quality DAC. That is the best of both worlds.
In my case I intend to put the files on a computer server, both for audio and video.
I didn't own the studios I worked in, and they didn't care of phono preamps there: only mic preamps
Nothing special about it, and I don't think it will sound better than the circuits I have shown. Nakamichi was good for other things, not phono preamps.
There's a mic preamp design that has the same architecture, with two low noise BJTs on first stage. It just sounds OK.
You need to see their CA-5e, Ca 5EII(Ca-50II) , CA 7 and Ca70 control preamplifiers before saying anything about Nakamichi phono preamp skills...Besides CA-5E is a Nelson Pass design.They were good in anything they did.I am impressed with that little phono preamp because it solves some basic problems of phono preamps in a very simple manner.
All audio engineers will be able to design a phono preamp, but whether it sounds good or not is a different matter.
The problem, not really open to discussion, is what anyone will consider "good". Many audio engineers think amplifiers or preamplifiers do not have any sound of their own, or that if they measure the same they will sound the same. Neither is that open to discussion, or at least a discussion I am interested in.
I'm aware of the many things NP did for Nakamichi, particularly the power amps. And it stops there. If you were impressed for something he did, that's very fine.
The problem, not really open to discussion, is what anyone will consider "good". Many audio engineers think amplifiers or preamplifiers do not have any sound of their own, or that if they measure the same they will sound the same. Neither is that open to discussion, or at least a discussion I am interested in.
I'm aware of the many things NP did for Nakamichi, particularly the power amps. And it stops there. If you were impressed for something he did, that's very fine.
Been following this discussion with interest, and noted a few things on the way.
Reading the Muffsy page it seems that he simulated using the LT1792/LT1037, but recommends using OPA2134/LM4562. In other words his PCB seem to be for dual op-amps and hence not very suited for "singles".
My first choice would be the RJM Emerald. Single channel boards with two single op-amps per board. Active shunt regulation of the PSU. Available as a kit or as PCB-only.
RJM Audio - The Emerald Phono Stage
RJM Audio Emerald Phono Stage Help Desk
The op-amp based design posted by J.Curl in a thread here on diyaudio, the Rotel Rq-970bx, the NAD S100 discussed previously in this thread and the above mentioned Emerald are other examples.
Marcel, I know that you have done a lot of work on analysing noise in RIAA stages. I would appreciate if you could expand a bit on this topic. Specifically; how will the impedances of the passive network influence noise generated by the second stage?
Attached is the first stage and passive Low Pass of a two stage RIAA amp published by Erno Borbely. In the article he makes a comment that he has been able to reduce the value of the series resistor in the LP filter (R36) to 750 ohm for noise reasons. The JC published RIAA uses 1600 ohm, the Emerald 2K26 ohm and the Rotel is all the way up at 75K. Without having done the calculations, I suspect that the high impedances in the Rotel LP passive networks warrants the use of JFFET amp also in the second stage. The Emeralds value of 2K26 seem be good in the sense that most op-amps can drive this load and the filter network would pose a low source impedance for the second stage.
Reading the Muffsy page it seems that he simulated using the LT1792/LT1037, but recommends using OPA2134/LM4562. In other words his PCB seem to be for dual op-amps and hence not very suited for "singles".
My first choice would be the RJM Emerald. Single channel boards with two single op-amps per board. Active shunt regulation of the PSU. Available as a kit or as PCB-only.
RJM Audio - The Emerald Phono Stage
RJM Audio Emerald Phono Stage Help Desk
The arguments I've seen for this topology make make me lean towards this type splitt-Eq also. Borbely is not the only one to advocate this split passive LP active Bass boost.
The op-amp based design posted by J.Curl in a thread here on diyaudio, the Rotel Rq-970bx, the NAD S100 discussed previously in this thread and the above mentioned Emerald are other examples.
Marcel, I know that you have done a lot of work on analysing noise in RIAA stages. I would appreciate if you could expand a bit on this topic. Specifically; how will the impedances of the passive network influence noise generated by the second stage?
Attached is the first stage and passive Low Pass of a two stage RIAA amp published by Erno Borbely. In the article he makes a comment that he has been able to reduce the value of the series resistor in the LP filter (R36) to 750 ohm for noise reasons. The JC published RIAA uses 1600 ohm, the Emerald 2K26 ohm and the Rotel is all the way up at 75K. Without having done the calculations, I suspect that the high impedances in the Rotel LP passive networks warrants the use of JFFET amp also in the second stage. The Emeralds value of 2K26 seem be good in the sense that most op-amps can drive this load and the filter network would pose a low source impedance for the second stage.
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No I don't. Stop playing the textbook internet troll when asked a question.
Or just go to ChannelD website, read their AES paper and come back with a critique why they are wrong.
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