Ampeg VL-1002 fx loop problem

[chunkitup]

When the loop is in the circuit the volume drops off, no low end, crackles and in general sounds bad. When switched out it sounds normal. The loop utilizes a NE5532N for send and return. The supply rails read +/-13.9v. I was just going to replace the chip unless I should check something else. Also mouser doesn't have the 5532N. It brings up a OPA2604AP for $6 a piece or a 5532AP for $1. What is a good replacement or should I put a socket in and try different ones? Or could I use a 4558 I pulled from a PV? Given the pins are the same.

[Jazz P Bass]

I do not know the difference between a 5532 N or the AP.
I do know the AP is the lowest noise version.
Are you using the pad switch?
That is supposed to increase the loop output by 12db.
Manual: http://www.amparchives.com/Amp%20Arc...ce%20Guide.pdf
Full Schematic:Amp Archives/Ampeg/Schematics/Ampeg VL-502, VL-1001 & VL-1002

[Enzo]

Before you change anything, plug a cord from send to return. Does this bypass connection restore the sound? If so, clean the cutouts on those jacks.

The 5532 is just a plain old vanilla op amp. it is a low noise type. But ANY plain old vanilla op amp will work. A 4558 would work just fine, and while the 4558 has potentially higher noise levels, it may not. This is not a high gain stage anyway, so noise may not be an issue at all. A 4580 is more recent , darn common, and just as good a sub.


Even if the noise went up a hair, it would still show whether the problem was the IC or not. Hell, put in a DIP socket, you can swap it out for a fancy chip later. DOn;t order a $1 IC just for this.

A chip like the 5532 or the 4558, usually the first couple letters mainly identify the maker. NE5532 is a TI part, while NJM5523 is a NJR part. The letters after the number mostly refer to packaging. 5532P as in P for plastic. 5532A is just a later version of 5532. 5532AP is the same in plastic. Other brands might use a D or an N for plastic, you have to look up the data sheets when in doubt.

I sincerely doubt you will get any real improvement by spending $6 for an op amp in this application.


But please just bypass the jacks first.

[Enzo]

Before you change anything, plug a cord from send to return. Does this bypass connection restore the sound? If so, clean the cutouts on those jacks.

The 5532 is just a plain old vanilla op amp. it is a low noise type. But ANY plain old vanilla op amp will work. A 4558 would work just fine, and while the 4558 has potentially higher noise levels, it may not. This is not a high gain stage anyway, so noise may not be an issue at all. A 4580 is more recent , darn common, and just as good a sub.


Even if the noise went up a hair, it would still show whether the problem was the IC or not. Hell, put in a DIP socket, you can swap it out for a fancy chip later. DOn;t order a $1 IC just for this.

A chip like the 5532 or the 4558, usually the first couple letters mainly identify the maker. NE5532 is a TI part, while NJM5523 is a NJR part. The letters after the number mostly refer to packaging. 5532P as in P for plastic. 5532A is just a later version of 5532. 5532AP is the same in plastic. Other brands might use a D or an N for plastic, you have to look up the data sheets when in doubt.

I sincerely doubt you will get any real improvement by spending $6 for an op amp in this application.


But please just bypass the jacks first.

[chunkitup]

Thanks for posting the schemes and manual. Computer took a dump and I have to post using my phone.
There is no difference with loop in and pad on or off.

[chunkitup]

Enzo you replied while I typed last post. I put a patch in and there was no improvement. Same problem

[Jazz P Bass]

What exactly are you using the loop for?

[chunkitup]

What exactly are you using the loop for?

My buddy uses a pedal board full of fx

[Jazz P Bass]

Have you proven that it is Not a component on the pedal board?
Had to ask.

[chunkitup]

Have you proven that it is Not a component on the pedal board?
Had to ask.

He has 2 more amps I worked on and they work perfect with the fx in the loop.
Problem is with the loop on/in with no pedal board in the loop it still has the same affliction

[Jazz P Bass]

Put the 4558 in & try it.

[chunkitup]

Finally got time to work on this. I put in socket and used the 4558 and it works great. I can't notice any increase in noise. Case closed. Thanks guys