Mods to Your Amps

**Old Guy** · March 14th, 2020, 11:07 AM

Originally Posted by markw51

I'm pleased to report that I finished the refurbishment. It was a big job but am pleased with the results. The 10 mfd cap following the input board into the main board was replaced with a Panasonic film cap but it sounded like hell so I took it out and replaced it with an electrolytic as was the original. Sounds much better. I was surprised by that. My total investment is about $200, including the purchase price for the amp. I'm quite certain I would not be able to beat that in the consumer hifi world for what I have now.

I plan one more change. I ordered a LM4562 op amp and will use it to replace the NE5532 op amp in the input section. Some guys claim the LM4562, which was specifically designed for audio, is sonically better.

The NE5532 is surprisingly good. Lots of high end gear used it. Were I going to the trouble, I'd go one better with a Burr Brown OPA1642.
Drawback is newer opamps are using surface mount, but adapter boards are available.
Whether it makes a difference is going to depend on the total circuit. But it's a higher performance unit that would fit without circuit mods. The FET front end is potentially a plus.

In audio, improvements on paper often don't translate to audible improvements.

And of course, if the person doing the mods wants to hear a difference, they will.

**endeeinn** · March 14th, 2020, 02:50 PM

Originally Posted by Old Guy

I'd go one better with a Burr Brown OPA1642.

I agree with Old Guy. I currently use the OPA1642 in my Marchand XM44. Went from stock OPA2134 which was good to the LM4562 which was about the same or slightly better but the OPA1642 (on a brown dog adapter) is really heads and shoulders. If you are going to the trouble of removing the 5532 then replace it with a socket. As Old Guys says what works or sounds better in one application may not in another so with a socket going back (or experimenting) is easy.

**markw51** · March 14th, 2020, 05:10 PM

Originally Posted by endeeinn

I agree with Old Guy. I currently use the OPA1642 in my Marchand XM44. Went from stock OPA2134 which was good to the LM4562 which was about the same or slightly better but the OPA1642 (on a brown dog adapter) is really heads and shoulders. If you are going to the trouble of removing the 5532 then replace it with a socket. As Old Guys says what works or sounds better in one application may not in another so with a socket going back (or experimenting) is easy.

The 9444a has a socket for the op amp so that's no problem. Thanks for the advice. What adapter should I get?

Question about the adjustment procedure. The manual says set the bias by adjusting R27 for 1.2 volts across resistor R40. Then you adjust the same pot for a 10mv reading across the emitter resistors. That then drops the voltage across R40 to less than 1.2 volts. I don't understand the logic of adjusting the same pot for two different things.

**endeeinn** · March 15th, 2020, 11:51 AM

Originally Posted by markw51

The 9444a has a socket for the op amp so that's no problem. Thanks for the advice. What adapter should I get?

Question about the adjustment procedure. The manual says set the bias by adjusting R27 for 1.2 volts across resistor R40. Then you adjust the same pot for a 10mv reading across the emitter resistors. That then drops the voltage across R40 to less than 1.2 volts. I don't understand the logic of adjusting the same pot for two different things.

Someone else will have to help with the adjusting question. Doesn't seem right to me either.

You can get a Brown dog adapter for $2.50 ready for your OPAMP to be installed or with an OPA1642 mounted on it already from $9.50

SOIC-8 to DIP Adapter - BrownDog Adapters - 970601

**markw51** · March 15th, 2020, 05:24 PM

Originally Posted by endeeinn

Someone else will have to help with the adjusting question. Doesn't seem right to me either.

You can get a Brown dog adapter for $2.50 ready for your OPAMP to be installed or with an OPA1642 mounted on it already from $9.50

SOIC-8 to DIP Adapter - BrownDog Adapters - 970601

OK thanks for that. I happened to have a LM4562 so replaced the NE5532 with it and its a definite improvement. More musical, better low end, smoother and all the other adjectives I can't think of.

Next I will get that OPA1642. Amazing how you can roll op amps like tubes.

**Old Guy** · March 16th, 2020, 07:58 AM

Originally Posted by markw51

OK thanks for that. I happened to have a LM4562 so replaced the NE5532 with it and its a definite improvement. More musical, better low end, smoother and all the other adjectives I can't think of.

Next I will get that OPA1642. Amazing how you can roll op amps like tubes.

Manufacturers spend millions designing gear. Woe be the Op Amp maker who obsoletes all that design work. Incremental changes. not revolutionary.

**markw51** · March 21st, 2020, 04:45 PM

I got the OPA1642 and put it in and you guys are absolutely right about it. After listening to the LM4562 for a while it sounded too laid back and mushy. I put a new NE5532 back in. That was actually better but it has a certain hardness to it. The OPA1642 has the right balance between the two. Thanks very much for your help!