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Old 3rd April 2009, 07:37 PM   #1571
Salas is offline Salas  Greece
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Ricardo, that question gets general answers by definition. A. Surely if a Fb cap helps also other op amps than original there, it is not the same value. B. What value or no capacitor, needs measurements for high frequency square waves and THD so to know. C. General tweaking practice info found mainly in forums of compensation and decoupling for certain popular op amps, may apply or not, but needs measurements for any different PCB and/or PSU design/components. D. If you still wanna tweak, trust your ears for the certain preamp with certain op amp substitutions, but never think that you really got an idea of what each op amp model can really do if surely properly implemented. The faster, the more rebellious.
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Old 3rd April 2009, 07:47 PM   #1572
RCruz is offline RCruz  Switzerland
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Thank you Salas

I must read a lot before I do more modifications here.

I really need a good pre with loads of inputs.

Before commiting to the Riaa, I built a jfet buffer but did not finish the project because;
1st - it has output caps
2nd - I am not sure if my amp needs some gain.

Can a jfet buffer + caps sound better than a opamp without caps ? (I could live with less gain)

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Old 3rd April 2009, 07:48 PM   #1573
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mastering
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Old 3rd April 2009, 07:51 PM   #1574
Salas is offline Salas  Greece
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Ricardo:

It depends on the quality level you have reached with op amps so to compare. Also on the needs of the main amp and speakers. My general practice is. A. If it sounds good, don't destroy it for checking out new quests. -} B. Make something from ground up if researching alternatives. Just my2c.
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Old 3rd April 2009, 07:51 PM   #1575
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use zen mod kit , optivol plus buffer without caps...cheaps too
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Old 3rd April 2009, 08:22 PM   #1576
RCruz is offline RCruz  Switzerland
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Thank you so much.

I will start building from scratch.

Ricardo
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Old 3rd April 2009, 08:28 PM   #1577
RCruz is offline RCruz  Switzerland
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Where can I find Zen mod optivol ?
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Old 3rd April 2009, 09:15 PM   #1578
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link

or order optivol(+minireg) and add the zen buffer ie JC buffer ,
forgot you need gain ? Salas can help ?
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Old 3rd April 2009, 09:50 PM   #1579
RCruz is offline RCruz  Switzerland
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Yes

I need some gain.

I like the optivol idea, and Zenīs 1 buffer per output, but I need gain.
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Old 3rd April 2009, 09:54 PM   #1580
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sure ?connect the phono direct to pw amp and play lower tracks
look at amp input.....
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