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Simplistic NJFET RIAA
Simplistic NJFET RIAA
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Old 26th February 2009, 03:00 PM   #1201
RCruz is offline RCruz  Switzerland
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Simplistic NJFET RIAA
Hi Salas

I am about to order the obbligato output caps.

The difference in size and cost for 4.7u to 6.8u is not uge.. should I try the bigger ones ? (Can I expect even more bass ?)

Ricardo
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Old 26th February 2009, 03:09 PM   #1202
nicoch58 is offline nicoch58  Europe
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Optivol

is a simple shunt LED/LDR optocouplers, the series resistor are 27k (at fist I put a Dale but tantalum is a must ) that work well in jfet riaa (you can remove the resistor on out caps) change if the amp need...

the pot control the light on led ,ie you can put where you want !and ldr near the out

need 24vdc or so ,for 17 shipping incluse you can only win !! a lot better then alps blu

problem,now is out of stock but contact Greg ,is fine men ,for preorder


alternative the ligthspeed on Diyaudio that are full ldr but parts and match are problem (you can order two matched optivol)

decent pot start with TKD at 61$

alternative 41-step Attenuator but $$$ link
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Old 26th February 2009, 03:14 PM   #1203
nicoch58 is offline nicoch58  Europe
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from Zen mod, ldr+JC buffer kit .....are you sure that need buffer?

http://www.diyaudio.com/forums/showt...hreadid=139113
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Old 26th February 2009, 03:19 PM   #1204
RCruz is offline RCruz  Switzerland
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Thank you nicoch... I will email Greg.

What about the 6.8u output caps ? Can I expect any gains ?

Ricardo
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Old 26th February 2009, 03:26 PM   #1205
nicoch58 is offline nicoch58  Europe
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no

the amp gain/speakers db/room and if you like blast

Rload do a bit ,
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Old 26th February 2009, 03:31 PM   #1206
RCruz is offline RCruz  Switzerland
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You mean 6.8u is not suitable as an output cap ?
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Old 26th February 2009, 03:32 PM   #1207
nicoch58 is offline nicoch58  Europe
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Quote:
Originally posted by salas


Means a John Curl buffer. But your RIAA is already buffered so it will not lose from its own gain. And a further buffer after the pot will not add gain either. It may interface the pot nicer, but that is all. The main thing is if you get enough drive for your habits to the main amps, speaker, room, system.
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Old 26th February 2009, 03:46 PM   #1208
Salas is offline Salas  Greece
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Quote:
Originally posted by RCruz
You mean 6.8u is not suitable as an output cap ?
4.7uF is more than enough even down to 10k loading. Bigger means more aluminum foil for no reason.
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Old 26th February 2009, 03:48 PM   #1209
RCruz is offline RCruz  Switzerland
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Thank you again.

I believe I will try to feed the Riaa directly into the power amp using a pot only and see what gain do I have.

It might clean up things a lot.

PS:
I like the optocoupler option, so I will mail Greg about them.

Ricardo

Thank you Salas... 4.7u it will be.
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Old 26th February 2009, 04:00 PM   #1210
nicoch58 is offline nicoch58  Europe
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with 27k can be 1mf if I remember well ,I have used 2,2//0,47....

with optivol if you lower to much the rserie (now my is 18k) you lost a bit the 0 volume out.....(no signal)
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