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TL084CN upgrade on a Musical Fidelity Nu-Vista 300 power amp.
TL084CN upgrade on a Musical Fidelity Nu-Vista 300 power amp.
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Old 12th October 2018, 07:08 PM   #21
zavan is offline zavan  Greece
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I would like also to add to the "opamp equation" question, the factor of trimmer. The pcb of opamps is currently using a single turn 10% Bourns 3362 trimmer per opamp. (two) What about the replacement with the following trimmer.



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Old 12th October 2018, 09:58 PM   #22
Bigun is offline Bigun  Canada
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TL084CN upgrade on a Musical Fidelity Nu-Vista 300 power amp.
You got bad case of upgrade-itis

Curious- Why are there thick ceramic spacers between the power devices and their heat sink on one side and not the other ?
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Old 12th October 2018, 11:00 PM   #23
zavan is offline zavan  Greece
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Originally Posted by Bigun View Post
You got bad case of upgrade-itis

Curious- Why are there thick ceramic spacers between the power devices and their heat sink on one side and not the other ?

Hehe nice one :-) The right side of the amp is the side which I have recapped. ELNA Silmics are surely bigger. I have also used an aluminum oxide ceramic insulator from AAVID. Better thermal performance, you never need to replace it mpla mplah for the precious Sanken SAP15. They are very expensive and hard to find. (at least the originals)
Also this upgrade gave me the opportunity, (since it's 2mm thicker) to put the whole channel pcb on rubber washers for reduced microphonics. Something that the discreet line amp pcb had already from "mama" MF.


And to finally answer your question: I haven't start the left channel yet.


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Last edited by zavan; 12th October 2018 at 11:10 PM.
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Old 13th October 2018, 12:36 AM   #24
jan.didden is online now jan.didden  Europe
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One thing to watch out for when replacing these opamps is oscillation. More modern opamps are generally faster and wider band, which is a good thing IF the circuit is designed for it.
Many people have replaced opamps with newer/faster ones and ended up with singing amps.
Doesn't always happen but you need to be aware and have some way of checking for it.

Jan
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Old 13th October 2018, 12:48 AM   #25
zavan is offline zavan  Greece
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Originally Posted by jan.didden View Post
One thing to watch out for when replacing these opamps is oscillation. More modern opamps are generally faster and wider band, which is a good thing IF the circuit is designed for it.
Many people have replaced opamps with newer/faster ones and ended up with singing amps.
Doesn't always happen but you need to be aware and have some way of checking for it.

Jan



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Old 13th October 2018, 01:20 AM   #26
zavan is offline zavan  Greece
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Originally Posted by jan.didden View Post
One thing to watch out for when replacing these opamps is oscillation. More modern opamps are generally faster and wider band, which is a good thing IF the circuit is designed for it.
Many people have replaced opamps with newer/faster ones and ended up with singing amps.
Doesn't always happen but you need to be aware and have some way of checking for it.

Jan
I feel that MF has designed the pcb with the opamps exhaustively for this kind of cases that could cause such problems with opamps.
I surely don't know what will happen with a much newer op amp. But I know that other amplifiers, who people tried to upgrade opamps, didn't even have a trimmer for op amp offset voltage fine tuning.

So I am just curious to see the end result.
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