trying a solid state RIAA

[PhaseLockLoopy]

Perfectly correct guys -- I have stripped back the design - I found the MPP thread informative especially on detailing performance and input impedance on the different types of current mirrors.
I've never done a discrete RIAA stage before and I'm having fun with this...
If you look at Krell, Mark Levinson and Naim - they are all transistor - I wonder if this gives designers more choices to make in producing the high end kit? This idle curiousity of mine continues because I'm going to now convert those two op-amps into all transistor as the big hi-fi names have and see what design compomises can be attacked.

[mlloyd1]

the input devices, q3 and q10, need a dc path to ground. you were on the right track before; you needed to pick another value than 47K to parallel with the 100K to get 47K.

[stratus46]

Originally Posted by mlloyd1

the input devices, q3 and q10, need a dc path to ground. you were on the right track before; you needed to pick another value than 47K to parallel with the 100K to get 47K.

Restore the 100K and change the 47K to 88.7k and it will be spot on - unless your amp has some input loading problems.

G²

[godfrey]

Originally Posted by infinia

Why? There are advantages to monolithic...

Because it's fun?
Opamps are boring - 90% of the work is done for you.

Originally Posted by Bonsai

Have done a noise sim on this circuit? I think it will be quite noisy.

So what?

Vinyl is noisy anyway. You have to screw up a preamp pretty bad before the electronic noise is worse than the surface noise. I remember some phono preamps using shunt feedback getting good reviews because they sounded good, despite their "high" noise.

[OT]
I actually built a phono preamp once with a single 741 - stereo input with a couple of "blend" resistors and mono output. I expected it to be terrible, but it actually sounded OK (in a lo-fi context). Noise wasn't too bad subjectively.

Disclaimer
Maybe I should have prefixed the above with "Hello, my name is Godfrey and I have a confession..."

It was an emergency build. After a burglary, I was left with no audio electronics. Short term, the only way to hear music involved digging into the junkbox to see what I had that could possibly be fashioned into a preamp.

Result: a breadboard with a 741 and some passives that got it almost in the ballpark of RIAA. IIRC, the power supply involved a car battery charger and some caps.

Picture that lying on the floor, hooked up to a horrible Maplin-style power-amp module nailed to a piece of wood via loose trailing wires and a naked pot as a volume control.

Audiophile quality: NO, but it sounded better than I expected and at least I could hear music again. I was happy!

That's probably the most rewarding "DIY audio" project I've ever done.

Purists, feel free shriek now (if you haven't already started).
[/OT]

Cheers - Godfrey

[davidsrsb]

A simple 50 Hz low pass would not sound THAT different from a correct RIAA circuit, just a bit dull

[djsb]

Hi,
This post may be of interest

Turntable Forum :: View topic - The HART RIAA Phono Stage

I use this JLH discrete phono preamp with my Systemdek 11x900.

David.

[Conrad Hoffman]

It only takes a couple active devices to make a surprisingly good sounding RIAA preamp. See here. IMO, you should first build a very good inverse RIAA network. I found this to be quite interesting (scroll down to the RIAA article) and it's the one I built. Still, I run a fairly conventional circuit using the National LME opamps. It's hard to beat 'em, and their app note for an RIAA preamp is a very good place to start.

CH