[tiagoncalves]

I finally received all the parts, and yesterday I finished the A47 amp, using the next schematic, but with a 1,8 kohm resistor in R2 (instead of the 4,7 kohm):
 

 
Unfortunatly, I have a lot of distortion, and the DC offset is very high: 150 and 90 mV in each of the channels. What tests can I perform, to check the origin of this offset?
Can i try to remove the input caps to see if they are the problem, or can I make some tests to the opamps?
The opamp before the buffer is the same as the other two (opa2132), but I just used one of the channels.
Thanks.

 

[Avro_Arrow]

Given the values in your schematic, I would not expect an offset higher than 1.5mV.
Check carefully for construction errors.
Also make sure to tie the unused inputs on the GND op amp to GND to keep
it from oscillating.

 

[tiagoncalves]

Ok, so in the opamp before the buffer, because I have one free channeI, have 3 pins unused (in+, in- and out). Should I plug all to GRD, or just the IN+ and IN-? I have soldered them just to fix the opamp to the board, but they are not connected to anything.

 

[Avro_Arrow]

Just the + and - inputs, not the output

 

[tiagoncalves]

Thanks,I'll try it as soon as I get home!

 

[tiagoncalves]

Done!! I made what you said, and also I notice that I had miss the connection between the OUT of a half op-amp to the IN+ of the other, in each op-amp... now, with no source I have just more or less 0,5 mV. It's all assembled, and the case closed... the amp is ready, and with the Grado sr80i, is just fantastic!
In the other thread I'll post some photos, but I need the thank you again, because you gave me so much help!

 

[Avro_Arrow]

I'm glad your project turned out successfully!
It is my pleasure to help out