2 stage C3g LCR RIAA build...schematics please

the road not taken.
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rob3rt5
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Joined: Mon Feb 22, 2016 6:52 am

2 stage C3g LCR RIAA build...schematics please

Post by rob3rt5 »

This is my first post an I'm hoping my query will not be futile. I'm searching for someone that can create a schematic for a phono stage that I might hand off to a friend that has considerable build experience. (I have none but hope to remedy this soon).
The details are as follows:
*Two gain stages (both based on Siemens C3g)
*LCR networks based in double T filter
(2123Hz pole formed by air core inductor at the first gain stage)
(50-500Hz poles are formed in high signal level directly at the output of the second gain stage)
*somehow the first gain stage is decoupled from the 2123 pole coils
*Passive LCR RIAA
*Power supply rectified by EZ81 and a choke filter
*Tube heaters are DC passive regulated (?) for the first stage and AC in the second stage
I make no apologies that this is an attempt at copying a phono stage that costs thousands of dollars. I don't make a habit of theft but I see no way of obtaining this audio goal unless I can DIY. Please help if you can.
Many thanks in advance for your kindness and generosity.
I believe many can benefit from the shared advice.
I also welcome any advice and guidance anyone can give.
Last edited by rob3rt5 on Mon Feb 22, 2016 7:44 pm, edited 1 time in total.
dave slagle
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Post by dave slagle »

Hey,

I'm not sure futile is the right word but what you ask is not a small task and would require a lot of work which would require some form of compensation for a person to undertake.

My plate is full at this point but maybe someone else will jump in.

dave
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rob3rt5
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Joined: Mon Feb 22, 2016 6:52 am

Post by rob3rt5 »

Thanks for the reply Dave. Of course, I would be happy to compensate whomever undertook this task. I'm embarrassed to say the thought hadn't yet occurred to me.
What is the normal fee for such a thing, if you don't mind me asking? I wouldn't want to seem rude or parsimonious.
rob3rt5
Posts: 4
Joined: Mon Feb 22, 2016 6:52 am

Post by rob3rt5 »

I must also add that I was very much hoping you'd be overseeing, if not directing, this endeavor personally as you understand passive amplification so very well. but, I do understand that you must be inundated with requests for your time. Very kind of you to nudge me on the proper path.
Daniel
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Joined: Fri Jan 10, 2014 4:50 pm

Post by Daniel »

There are some design points in there that seem a bit strange and/or limiting, like the EZ81 rectifier. By "choke filter" you mean a choke input filter? At least I hope so.
Why do you want to heat the input stage with DC and the output with AC?

I recommend you contact Thomas Mayer (www.vinylsavor.com) and get one of his LCR RIAA kits. There's a good change you will get something better than what you are trying to copy.
rob3rt5
Posts: 4
Joined: Mon Feb 22, 2016 6:52 am

Post by rob3rt5 »

Thank you so much for your reply Daniel. Great advice.
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