Sound of parallel opamps.

[Bernhard]

Hi,

my CD880 headphone amp has 2 opamps parallel ( 1 NE5532 package ) for each channel.

This sounds not as good as if one opamp from each package is disconnected.





Bernhard

[Nelson Pass]

I have played with massively paralleled circuits, including
ordinary op amps, and there are definite improvements to
be had. At Threshold we nearly launched a preamp with 25
parallel stages for each section. Until we costed the parts out.

[Christer]

Maybe I misunderstood Bernhard, but I think he meant that he
found the sound better if using only one opamp instead of two
in parallel as in the original design. There are right ways to
parallel op amps and there are wrong ways to do it. Perhaps
posting a schematic will help people to give useful comments
on this observation.

[Fred Dieckmann]

Originally posted by Nelson Pass
I have played with massively paralleled circuits, including
ordinary op amps, and there are definite improvements to
be had. At Threshold we nearly launched a preamp with 25
parallel stages for each section. Until we costed the parts out.

Nelson....... April fools day is not for 13 days. If that was a practice run the official entry is going to be a real whopper!

[Christer]

Fred,

Please don't get us started on Whoppers again. Last time it
happened it seemed everybody preferred to talk burgers
instead of discussing the original thread topic.

[Bernhard]

One sounds better than two.

Here is the schematic, followed all the tracks on the double layer pcb

Why do they take the feedback before the 150ohm resistors ?

Better remove the muting circuit ?

Better remove the 47ohm resistors on the power supply pins ?

[millwood]

Originally posted by Bernhard
One sounds better than two.

Here is the schematic, followed all the tracks on the double layer pcb

Why do they take the feedback before the 150ohm resistors ?

Better remove the muting circuit ?

Better remove the 47ohm resistors on the power supply pins ?

the 150ohm resistors are summing resistors. They are there to even out any minor differences between the two amps / gain resistor networks so you don't end up in a situation where one opamp is driving the other like crazy.

You can eliminate the muting circuit if you don't need it.

the 47ohm resistors are for decoupling. yes, you can take them out.

[analog_sa]

One sounds better than two.

Parallel anything (tube, fet,opamp) sounds different than single. There is often loss of immediacy and focus but there are also some virtues. Many believe that the negative effects can be minimised by precise matching of gain - the resistors in your case.
A commercial product should be able to drive a wide variety of loads - if it sounds better to you single that's how you should set it.

Of course it will sound better without the mute.

Why don't you build a new amp with less comromises using better chips?

[Bernhard]

Originally posted by millwood

They are there to even out any minor differences between the two amps / gain resistor networks so you don't end up in a situation where one opamp is driving the other like crazy .

Nontheless it sounds like that.

[Bernhard]

Originally posted by analog_sa

Of course it will sound better without the mute.

Why don't you build a new amp with less comromises using better chips?

Searching for a bug in a CDP is like going to hospital...

Go there because of one illness, and they will find another ten.


Better rebuild the whole mainbord.