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Old 21st March 2010, 01:30 PM   #1
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Default trying a solid state RIAA

I was idle this morning looking at converging several ideas to attept to come up with a precision RIAA stage - duinno if anyone else has mucked about with RIAA before? - I'd prefer to remove the op amps and have an all transistor stage.
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Old 21st March 2010, 01:39 PM   #2
Bonsai is offline Bonsai  Taiwan
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Have done a noise sim on this circuit? I think it will be quite noisey.

Q9 to Q12 and the associated resistors all add noise.

Sor SOTA see Syn08's stuff in the analog front end forum - you should get some good ideas.

If you are looking for a basic mag input RIAA, I'd suggest an op-amp based design.
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Old 21st March 2010, 02:06 PM   #3
infinia is offline infinia  United States
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Quote:
Originally Posted by PhaseLockLoopy View Post
I'd prefer to remove the op amps and have an all transistor stage.
Why? There are advantages to monolithic low noise designs, like low drift direct coupled, matching offset, depends really on what your end result goals are.

Op amps like L1037 are low noise optimized for mag inputs while LT1028 for MC's. Depending on topology you can even run them class A with buffers.
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Old 21st March 2010, 03:40 PM   #4
RJM1 is offline RJM1  United States
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The LT1115 has a nice one on the front page of it's data sheet.
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Old 21st March 2010, 04:15 PM   #5
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Quote:
Originally Posted by Bonsai View Post
Have done a noise sim on this circuit? I think it will be quite noisey.

Q9 to Q12 and the associated resistors all add noise.

Sor SOTA see Syn08's stuff in the analog front end forum - you should get some good ideas.

If you are looking for a basic mag input RIAA, I'd suggest an op-amp based design.

You're right of course, but you obviously havent read my sig
It's not bad at the moment - 2mV signal in to 550mV out - noise of course will be a function of gain also and there is the performance of those two op-amps
anyway, with all of that gain in there it doesnt have much choice but to have some noise - I am just doing this as an idle exercise for fun. I'd like to know if it is possible that the better transistors made today could actually offer more design choices?

Yeah I was just idling trying to figure out how a discrete transistor only RIAA with the proper corrections would look - getting the envelope shape right is a challenge.
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Last edited by PhaseLockLoopy; 21st March 2010 at 04:18 PM.
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Old 21st March 2010, 04:41 PM   #6
Bonsai is offline Bonsai  Taiwan
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. . . you should go with infinia's advice on this one.
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Old 21st March 2010, 04:51 PM   #7
Salas is offline Salas  Greece
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Moved to analogue source where all the Riaa people commonly visit.
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Old 21st March 2010, 04:58 PM   #8
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Quote:
Originally Posted by PhaseLockLoopy View Post
- duinno if anyone else has mucked about with RIAA before?
From my pov these exercises are just a waste of time compared to the wealth of info in the currently running MPP thread or the older - Real Vendetta.
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Old 21st March 2010, 06:21 PM   #9
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Quote:
Originally Posted by PhaseLockLoopy View Post
I was idle this morning looking at converging several ideas to attept to come up with a precision RIAA stage - duinno if anyone else has mucked about with RIAA before? - I'd prefer to remove the op amps and have an all transistor stage.
I thought the input loading is supposed to be 47K. Isn't this one 32K?

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Old 23rd March 2010, 05:47 AM   #10
mlloyd1 is offline mlloyd1  United States
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yes, if not lower.

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Originally Posted by stratus46 View Post
I thought the input loading is supposed to be 47K. Isn't this one 32K?

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