Help with OpAmps frames & Sound Changes

[irgendjemand]

Dear friends (may I ?),

Trusting your remarks, I have just experiment in completely different direction & locations in my all HiFi chain.

Indeed, once the OpAmps have been mounted directly on the PCB, the all sound became very strong: It was not anymore possible to handle it just “as it is”: There has been much too much midrange, no transparency, not enough highs, all that what I described before…

The mistake had to be found indeed somewhere else: First of all, I simply changed now the polarity of ALL 3 palatine-rhodium power cables: On the Active Subwoofer, on the Power-Amp and on the Pre/DAC. Already with this, almost everything came to its place "at once".

Not yet being done, I noticed that I have a new matched-pair of the Bursons Discrete OpAmps which I was about to replace sometime (I am normally using s pairs of them in the I/V - behind the DAC). One of the old was indeed damaged before!! Now there is a new pair inside...

Wow! What shell I say? I listen to your advices and decided NOT to go backwards to the sockets. So what I did find is that it has been this combination of 1x damaged OpAmp and total wrong compensation through the rhodium cables.

Removing the sockets indeed yielded in small improvements. Smal improvements? I am not sure if it is so small... Well, putting the OpAmps directly on the board caused a tremendous impact on the all system. Not a bad conclusion after all!

Special thanks to all of you!

IY.

[nigelwright7557]

Originally posted by irgendjemand

Can anybody help with an explanation for this?

Regards, IY. [/B]

I found a similar problem with a job I did.

The IC pins were shorting out tracks on the PCB !

I have also found the opposite to be true too and the sockets didnt have insulators on them which shorted out on tracks on the PCB.

[unclejed613]

burr brown data sheet. here's the small signal gain charts. notice the peaking around 150 and 200 Mhz. that's instability.

did a search on www.datasheetarchive.com

the first gain curve on page 1 LOOKS like unity gain stable, but look at the bottom of the Y axis. it begins at +66db

[Jan Dupont]

The Burr-Brown datasheet I got, shows circuits on several pages that the OPA627 is Unity-Gain (can't post it here as it's 258kb but you can get it from www.alldatasheet.com)...

Furthermore I have many times used the OPA627 with a gain of 1 and never experienced any problems what so ever......

[janneman]

Originally posted by irgendjemand
Dear friends (may I ?),

Trusting your remarks, I have just experiment in completely different direction & locations in my all HiFi chain.

Indeed, once the OpAmps have been mounted directly on the PCB, the all sound became very strong: It was not anymore possible to handle it just “as it is”: There has been much too much midrange, no transparency, not enough highs, all that what I described before…

The mistake had to be found indeed somewhere else: First of all, I simply changed now the polarity of ALL 3 palatine-rhodium power cables: On the Active Subwoofer, on the Power-Amp and on the Pre/DAC. Already with this, almost everything came to its place "at once".

Not yet being done, I noticed that I have a new matched-pair of the Bursons Discrete OpAmps which I was about to replace sometime (I am normally using s pairs of them in the I/V - behind the DAC). One of the old was indeed damaged before!! Now there is a new pair inside...

Wow! What shell I say? I listen to your advices and decided NOT to go backwards to the sockets. So what I did find is that it has been this combination of 1x damaged OpAmp and total wrong compensation through the rhodium cables.

Removing the sockets indeed yielded in small improvements. Smal improvements? I am not sure if it is so small... Well, putting the OpAmps directly on the board caused a tremendous impact on the all system. Not a bad conclusion after all!

Special thanks to all of you!

IY.

There are many, many very excellent amnps out there without sockets (sockets are for the diy-ers and amateurs; they add unneccesary costs to a product).

Furthermore, almost everyone recommends leaving out sockets to AVOID the extra interpin cap that can cause oscillations.

This is typically a case of thinking that if something is possible it must be true. Sure, sockets or not change mech vibration characteristics of a board-with-opamp. Therefore it MUST be audible? No way Jose!

Bottom line: everybody says no sockest is best. You say: I removed sockets and now it sounds bad. I say: there's something else going on.

Jan Didden

[irgendjemand]

jenneman,

this is pure misunderstanding!!

Originally posted by janneman
Bottom line: everybody says no sockest is best. You say: I removed sockets and now it sounds bad. I say: there's something else going on. Jan Didden

I wrote on my very last post (which you are quoting here) that "I listen to your advices and decided NOT to go backwards to the sockets". Instead, I did find that the problem was somewhere else: I came to a conclusion that you have been right!

What I was saying in addition is that I didn't expect such huge different in the all sound characters after removing the sockets. Sound became bad, but obviously NOT because of removing the sockets themselves!!

I see it as a matter of balancing the system: While the sockets have been in (only for trying different OpAmps !!) the sound was not so strong as without them now. I compensate for it at the time with cables, etc.

Once the sockets are out – AND THEY SHOULD BE OUT! – I got a “wrong” sound at first. But, once again, this was indeed for different reasons. Just as you said, there was something else going on. Thanks again.

[janneman]

Originally posted by irgendjemand
jenneman,

this is pure misunderstanding!!

I wrote on my very last post (which you are quoting here) that "I listen to your advices and decided NOT to go backwards to the sockets". Instead, I did find that the problem was somewhere else: I came to a conclusion that you have been right!

What I was saying in addition is that I didn't expect such huge different in the all sound characters after removing the sockets. Sound became bad, but obviously NOT because of removing the sockets themselves!!

I see it as a matter of balancing the system: While the sockets have been in (only for trying different OpAmps !!) the sound was not so strong as without them now. I compensate for it at the time with cables, etc.

Once the sockets are out – AND THEY SHOULD BE OUT! – I got a “wrong” sound at first. But, once again, this was indeed for different reasons. Just as you said, there was something else going on. Thanks again.

OK, yes, I see. You were ahead of me . Sorry.

Jan Didden

[Jan Dupont]

Lesson to be learned.......
Only make ONE mod at a time between listening tests

[irgendjemand]

You are absolutely correct!

I managed to “keep track” on this rule for so many years, until very lately…

If the lesson will be learned, then al least we all got something out of this. As for myself, I surely got the point, quite brutally... Thanks for your very kind help nonetheless!