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wanted RIAA schematic

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sam8888ysl

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Joined 2005
#1
I had built some tube amp, but never built RIAA. I want to built a tube RIAA amp. Now I still heave some 5670.5687.5965.6922.5963.WE407A.6BK7B.5844...... and I prefer simple is the best, so, anyone can give me some idea, Thanks, Sam 🙂
 
#2
I have an Audio Research SP-8 -- the RIAA section is very, very acurate -- you can find a schematic on the Audio Research database: http://www.arcdb.ws/ Also www.tubecad.com has some very good schematics.

Unfortunately Tritschler who wrote a very nice article in AudioXpress 2003 with a passive tube RIAA preamp seems to have gone off the air. I bought two boards from them and they were very, very acurate indeed, but radio silence for months.
 
#9
Corrections done, refresh your browser page if you still see the old schematic. This is the good one:
 

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#12
Giaime said:
Corrections done, refresh your browser page if you still see the old schematic. This is the good one:
Click to expand...

G-Man

I tweaked your design just a tiny bit -- I really like passive RIAA's -- changing C1 to 220nF, R6 to 4.75k and R7 to 270k -- these are simulations, not real ECC83s so YMMV.

Given that standard values of R's C's are used this circuit is very nice -- if the ECC83's are up to it! Here are the deviations from RIAA:

An externally hosted image should be here but it was not working when we last tested it.
 
#13
Good work jackinnj! 😉

By the way I see you use Multisim... am I right? I never made the tube models to work. They gave me tons of errors: now I use Spice (with Duncan models) and I'm happier, but I miss the "real time" feel of Multisim. You could even change a trimmer's value during the simulation and watch the results...
 
#14
yes, I use Multisim -- I have models for 6DJ8, ECC83, etc. courtesy of your fellow countrymen. I was having troubled with the "nested parenthesis" a few months back. These use the Koren "phenomonological" method -- I thought phenomonology was something you took if you were a graduate philosophy student.

the Multisim 12AX7 seems to replicate the real world pretty well, however.
 
#16
Would it not make more sense to do a mod for the russian tube, the 6h23? Gobs of current, if it's the one I'm thinking of. In my feeble understanding of things tube, high current might be just the thing to deal with thew whole RIAA as an EQ issue?

Likely under 'today's dumb question', but...any ocatal based circuits out there?
 
#17
The dangers of SPICING

I found some other ECC83/12AX7 SPICE parameters on the net and compared the Multisim version with Koren -- neither is "bad" per se. I normalized the gain so that what you see is is set with a 1kHz midpoint, with a little windage -- G-Man's circuit is intriguing for a passive RIAA with off-the-shelf components. This one is tweaked slightly from the verion I referenced a couple posts ago.

An externally hosted image should be here but it was not working when we last tested it.
 
#18
Even though i have not yet built Giamie's design, i plan to because of its simplicity, and the lack of expensive components. however i would like to applaud him because a vast majority of the parts are common values!, and hence it is easier, and cheaper to build
 
#19
Hello Alexmoose, and thank you,

but believe me: standard values are a wonderful thing, but the BEST can be obtained still cheap by series-paralleling standard parts.

On my schematics I tend to put *actual* resistance values, you are free to choose what standard components to put in parallel to obtain that value, the math is trivial.

For example, R5 in my design could be 47k || 470k, 56k || 180k...

(a little note about R5: do not set for a precise value, I suggest you put 47k in there and try paralleling it with high value resistors: start from 1M and go down to 220k, try what sounds best to you. Or try the suggestions made here for the other components).

I prefer to use, however, 1% resistors because of their lower noise.

But also note that extreme precision in resistors is nothing when you don't have control on capacitors. For the people willing to build something definitive, I reccomend the purchase of a LCR bridge and match your capacitors.
 
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