2.45 V dc on inputs

[Luco]

Hi,

I fuond a 2.45 V dc offset on inputs of alle three amp9 I built. This causes some problems to my external signal generator used to drive the amp9. There is the same dc offset also between the capacitors and the pin 1-2-3-4 of the tripath.
If I try to short the inputs to gnd, the offset disappears, but after some minutes I find it again.
Any suggestion?

[krilli]

This DC offset is normal, and SHOULD be between the input capacitors and the Tripath chip, but the input caps should also block it on the outputs.

I would think that there is a short from the 2.5V bias (between input caps and amp chip), to output. Maybe break out the magnifying glass and continuity tester?

[Luco]

It can't be a short: I have the same problem on three different amps!

[krilli]

Hmm! That's pretty strange. Is the Tripath chip slug connected to the amplifier case? - Is the amplifier in a case at all?

- if it is cased and heat-sinked, I think you have to isolate the chip

I'm just guessing, I don't know anything for sure here , I haven't had this problem myself -- hope my ideas help and don't hurt!

[V-bro]

The input caps decouple any kind of DC present on the inputs of the amp/outputs of the source.

However they would be charged when the amp is unmuted and this will give a small pulse on the source outputs, perhaps this is what makes the generator go crazy?

There should not and basically can't be continuous DC voltage present on the inputs when the caps are in place...

------X-max. can be several meters on any driver, too bad it can be done only once...------