prr varimu compressor

[Svart]

yeah you should NOT get DC on the output.  The transformer IS the isolation.  If you get DC then something is not hooked up right with your output transformer.

 

[Matthew Jacobs]

Slowbass, I hooked up my power transformers like you did but it made no difference.

Svart, in PRR original design the output comes directly out of a 5532 op-amp. I checked the 5532 schematic, it appears that it could output DC from it's power rails. I'm not sure because of my limited knowledge of electronics. Most designs I've seen either have a transformer or DC blocking caps after an op-amp.

Just wondering if this compressor needs blocking caps? Or if it's normal to have DC coming out of a op-amp?

As for my comp, can't get it to work... I'm gonna give it a rest and get back to it in a couple of days cause it driving me mad.

Thanks for your help guys...

J

 

[jdbakker]

Svart, in PRR original design the output comes directly out of a 5532 op-amp. I checked the 5532 schematic, it appears that it could output DC from it's power rails. I'm not sure because of my limited knowledge of electronics. Most designs I've seen either have a transformer or DC blocking caps after an op-amp.

Just wondering if this compressor needs blocking caps? Or if it's normal to have DC coming out of a op-amp?

A few tens of mV is not abnormal for many op-amps in sane configurations; sometimes more (100-200mV), especially in higher gain configurations. Many semiconductor inputs don't care, but switching signals with a DC offset can cause clicks and transformers can get saturated and/or magnetized. In those cases a coupling cap or a servo is in order.

[...]About -9.43V, is this normal?

No, that's definitely not normal. Either operator error or a fried 5532.

JDB.
[safe money always says operator error, no matter whether you, I or anyone else here has built it.]

 

[Matthew Jacobs]

A few tens of mV is not abnormal for many op-amps in sane configurations; sometimes more (100-200mV), especially in higher gain configurations. Many semiconductor inputs don't care, but switching signals with a DC offset can cause clicks and transformers can get saturated and/or magnetized. In those cases a coupling cap or a servo is in order.

Thanks for explaining that bro...

[safe money always says operator error, no matter whether you, I or anyone else here has built it.]

Totally agree... 90% of the time operator error.

I will have to carefully check each component in the circuit.

J