Tl audio pa2 moded and noisy

[Deepdark]

Hi there

I recently moded a tl audio pa2 for a friend. I replaced the stock quad opamp with some lme4940. Now there is a hiss and the unit is noisier than before. I seriously wonder why because i only change the opamp in it. Anyone?

 

[Deepdark]

Lme49740  sorry. The stock were tl074. I mount them on sockets so i dont think it's a thermal issue while soldering them. It's on both Channel so i was wondering what could be possible hiss trouble/source . Both opamp are feed in 15v

 

[gyraf]

...maybe the stock TL074's were in there for a reason?

Did you do your homework on the LME regarding stability etc.?

Jakob E.

 

[Deepdark]

thanks Jacob. actually it was the power chord that wasn't fully pressed. now it sound good XD so stupid me

 

[pucho812]

I am wondering what the need was to replace the tl074 in the first place?

 

[Deepdark]

Simple to test the pre with another opamp that was reportés to be an upgrade of thé tl074 (un that particular case). And i put socket to ease the removal for futur test. At the end yes the sound has changed a little for thé best but the major upgrade is tube replacement.

 

[My3gger]

Replacement of good tube for the same type is mostly waste of time and money in circuits like this. You might hear little differences if plate has full voltage and low to no NFB. If you want tube sound, one simple approach would be building separated SRPP or other colored circuit with OT trafo, 1k pot ala Neve at the output is nice addition to it. This can be added to gear's output for example, it has other uses too (DI, more gain, etc.).