New high quality opamps...

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Thanks again for the replies.

Originally posted by fmak

If its 5534 with comp cap, you need to remove. Otherwise no.

Is this because the OPA627 is internally compensated?

The original is actually NJM5532 with, what looks like, a bad layout around it.

Originally posted by fmak

I personally have never liked the up-with-it 'clean' sound of the 627 and prefer the AD825 current loaded with fets to about 3mA, or the bypassed LM6172. The newer AD opamps are all 12V only.

I also have OPA2134, OPA2604, LM6172 and AD8065/6 and would like to work out a good way to try all of these in their optimum environment. I will probably add a new PS for this stage, so changing to 12V is no big deal.

 

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Hi cdl

Originally posted by cdl

If making new circuit board, also make new groundplane connected to star ground with a very thick wire. But that's not necessary unless you want to change a lot of the circuit - I would just start replacing opamps.

The main reason I was thinking of making a new circuit board is that the existing circuit containg the NJM5532 seems to be far from ideal. The components are spread far apart and connected with long traces. The output circuit also uses smd's for one channel and full size for the other. Not very symmetrical!

So, can I just use generic proto board with point to point wiring?
OR
Does there need to be a complete copper side to the board to form a groundplane?

Originally posted by cdl

Adding extra decoupling caps close to the opamp will never do any harm, you might consider a combination of two or three sizes in caps.

Can you explain a bit more about using a combination of two or three sizes?

Originally posted by cdl

I would check that there is an output resistor, ~100 ohm or so, between the output of the opamp and the output jacks (there probably is one already), it reduces sensitivity to load capacitance..

There are two 200ohm resistors in series and amongst the muting circuit.

Originally posted by cdl

And, as Fmak also suggests, you can current load the opamps..

I would like to investigate this further.......