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Simplistic NJFET RIAA
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Old Yesterday, 11:20 PM   #17411
Hikari1 is online now Hikari1  United States
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Quote:
Originally Posted by Salas View Post
Good screening for sensitive circuits in traditional diy fashion comes with dead bug style construction on a raw board's copper back housed in a tin can.

I prefer direct high gain input where hum and buzz problems can be solved without a step up transformer.
I think some of the problem with this is my turntable, a Rega. It has no separate ground wire and I was using the step up as dual mono (2 battery packs). The only way it was quiet was if I tied the Left and Right RCA grounds together.

Also, I experienced a strange loud BUZZ when I my hand was about one inch away from the record on the platter...Not touching, just hand above platter.
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Old Today, 12:08 AM   #17412
Salas is offline Salas  Greece
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Is there continuity between metal parts of your TT and its signal cable ground (?) someone would have wondered
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Old Today, 11:15 AM   #17413
escucalin is offline escucalin
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Quote:
Originally Posted by Salas View Post
Good screening for sensitive circuits in traditional diy fashion comes with dead bug style construction on a raw board's copper back housed in a tin can.

I prefer direct high gain input where hum and buzz problems can be solved without a step up transformer.

Hello Salas,


I was contemplating the same these days ; and started by acquiring tined steel boxes(1/chanel) composed by top and bottom plate and moving both gain stages in there. The main drawback is the ridiculously large inter-stage 100n russian mica capacitor that is at this point an antenna for 50Hz hum.


How one solves that ? a Polypropylene capacitor is linear enough at that point (anyone compared different builds with different interstages? R-Cruz maybe ?)


My status: In process of finding 100n mica's that are comparable in size to a jfet so all the stages except buffer to fit in a 3cm/5cm shielded enclosure(but it seems impossible).

Last edited by escucalin; Today at 11:21 AM. Reason: adding the question :)
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Old Today, 12:44 PM   #17414
Salas is offline Salas  Greece
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If the big Soviet era cap has a metal shell see if you can scratch it somewhere and put solder on to run a wire from it to a ground point.
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Old Today, 01:33 PM   #17415
escucalin is offline escucalin
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Originally Posted by Salas View Post
If the big Soviet era cap has a metal shell see if you can scratch it somewhere and put solder on to run a wire from it to a ground point.

is aluminium


and funny you mentioned it; i managed to create a soldering point using a 22000uF @35V and some thin copper wire discharging it repeatedly in a pad like area

It seemed too much of a improvisation to mention or use it.


But after a couple of hour seeking an alternative; incorporating it seems a better option. But i will build a steel enclosure for it ; aluminium is worth nothing when it comes to shielding.

Cheers.

P.S So no comparison to just use a different capacitor or none ?
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