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Old 5th May 2008, 04:25 AM   #1
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Default Upgrading an op amp in mic pre??

Hello, newby question for everyone. WHat would be an upgrade in quality from a " JRC 4558dy" op amp

I know very little about what I am looking for in compatibility between op-amps.

the reason I ask is I have a old Yamaha MR1642 that needs work, I want to try to upgrade a few things on it to help my DIY skills, before I tackle something that I would care if I destroyed.

anyone know where I can get schematics for such a board?
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Old 5th May 2008, 04:24 PM   #2
Minion is offline Minion  Canada
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Location: Cowican Bay , vancouver island
The JRC 4558 is a standard Dual BJT Opamp, there are a Lot of Replacements for it...Pretty much any Dual opamp would work but here are a few suggestions:

OPA2134
TL072
NE5532
LM4562

The OPA2134 or the LM4562 would probably the the best out of the ones I listed...

Good luck
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Old 7th May 2008, 03:57 AM   #3
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Thanks alot!

can you upgrade transistors aswell? they have some "A970 BLo" Transistors in them.

also I have come to the understanding that the power supply has a lot to do with the performance of the components, how true is that and what would be a good power supply and power transformer to use to power the modules . How does powering multiple modules affect the power supply? I want to power 4 - 8 modules with one power supply.

I have seen these power supplies on Five fish studios called PSU-2448 how well would this work?
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Old 7th May 2008, 02:26 PM   #4
Minion is offline Minion  Canada
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Location: Cowican Bay , vancouver island
Hi, Yes you can change Transistors also but it isn"t nearly as easy as swapping opamps, why? Because Some transistors have different pin assignments and won"t swap in directly, you also have to make sure the new transistor has simular or better specs than the original ,and some Transistors just aren"t suitable for audio...

And yes a Good power supply can help reduce noise buy useing low noise regulators ,Bridge Diodes ,Good quality bypass caps and in some cases a Snubber, there are also very low noise discrete regulators but these are more complex to build...

You can make a very good Low noise power supply by useing a couple LM317/LM337 regulators a few resistors, a bridge rectifier and a few good quality caps....The Five Fish studio"s PSU is a good one and uses these components....

There shouldn"t be any problem powering 8 channels of mic pre with a Five fish PSU ,Just as long as you practice proper grounding schemes (Common star ground for all channels)...
As Long as you have a suitable transformer you should be able to power quite a few channels ,most Mic pre"s don"t use up a lot of Current.....

Good luck
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