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Capacitors for RIAA Circuit
Capacitors for RIAA Circuit
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Old 3rd September 2019, 09:59 PM   #1
WntrMute2 is offline WntrMute2  United States
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Default Capacitors for RIAA Circuit

I am looking for some recommendations as to what kind and brand of caps to use in a tube phono-stage's RIAA circuit. I've had recommendations from REL-TFTs to Charcroft's Silver/Mica to Copper foil and propylene. Looking for help in selecting these.

Thanks in advance
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Old 3rd September 2019, 10:23 PM   #2
ticknpop is offline ticknpop  Canada
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Capacitors for RIAA Circuit
I have 1% Relcap TFT teflons for RIAA caps, John Curl recommends them.
Relcap Polystyrene ( and MIT RTX) are a lot cheaper, but all are hard to get in 1% values especially if the cap values are not a common one, I had to custom order mine from Parts Connexion. Do not use silver mica.

I burn them infor 500 hours ( 2 weeks) before auditioning, in the right presmp they are wonderfull, smooth, detailed, but you have to have your power supply, resistors, and circuit topology all top notch before considering them., theres no sense in putting them in a $200 phono stage.
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Old 3rd September 2019, 10:26 PM   #3
JonSnell Electronic is offline JonSnell Electronic  United Kingdom
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Polystyrene or anything other than ceramic or mica.
Components do not 'burn in' the bad design of schematic or your ears do!
5% are ideal your ears cannot detect anything more close tolerance.
Polyester are really nice;
Polyester Film Capacitors | RS Components
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Last edited by JonSnell Electronic; 3rd September 2019 at 10:28 PM.
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Old 3rd September 2019, 10:27 PM   #4
analog_sa is offline analog_sa  Europe
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Capacitors for RIAA Circuit
Apart from personal taste the choice depends on whether the caps see a high dc voltage across or not.

Silver mica has never worked for me but was preferred by Thorsten in comparison to film in situations with a high polarizing voltage.
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Old 3rd September 2019, 10:28 PM   #5
rayma is offline rayma  United States
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With tube circuits, make sure the voltage rating is at least adequate, and preferably more.
The channels should be closely matched in values.
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Old 3rd September 2019, 10:31 PM   #6
analog_sa is offline analog_sa  Europe
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Capacitors for RIAA Circuit
Quote:
Originally Posted by ticknpop View Post
Relcap Polystyrene ( and MIT RTX)

My favourite. The Relcaps come in 2% but the Mit RTX are next to impossible to match.
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Old 4th September 2019, 09:58 AM   #7
DF96 is offline DF96  England
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Quote:
Originally Posted by rayma
The channels should be closely matched in values.
Yes, this is far more important than capacitor dielectric. Capacitor brand matters not at all.

5% components are fine but it will help if you match them more closely than this. Buy a few extra and pick the two which are closest in value.
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Old 4th September 2019, 02:02 PM   #8
RajkoM is offline RajkoM  Bosnia and Herzegovina
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Tefon or polystyrene/styroflex cap`s is on top for RIAA network.
BTW, one of Thorsten`s last RIAA preamp had Painton wirewound resistors (which are great, btw) and many Ansar MKP capacitors everywhere. In RIAA network, Ansar was bypassed with ERO MKP1837 (3.18e-3) and caramel (Sangamo ??) silver-mica (3.18e-4) equalization, to make a proper value.

Of course, capacitors should be around 1% tolerance.

You can put on the capacitors any way you want, but you'll quickly change them, I'm sure.
This is is pic of Thorsten last RIAA preamp.

Best diying.
Attached Images
File Type: jpg Phono Torsten.jpg (66.5 KB, 259 views)

Last edited by RajkoM; 4th September 2019 at 02:09 PM.
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Old 5th September 2019, 10:24 PM   #9
WntrMute2 is offline WntrMute2  United States
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F461BK104F630L KEMET | Mouser
F461BB333F630A KEMET | Mouser

This is what I could find after a long search. High enough voltage capability, 1% tolerances and polypropylene. I'm a little worried about the 1000 hour life-span.

Comments or further suggestions?
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Old 5th September 2019, 10:30 PM   #10
rayma is offline rayma  United States
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That's a maximum stress rating, and is not important here. They'll last indefinitely.
Very cheap for 1% tolerance parts.

Last edited by rayma; 5th September 2019 at 10:37 PM.
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