[kp93300]

I build a preamp  recently and unable to trim the dc offset to zero and this result in a dc offset of  0.1 v dc at the preamp output and a dc offset of  0.7 v at the amplifier output.
i tried it on test speaker without problem.
Is this level of DC offset acceptable for OB5 ?

thanks and cheers

kp93300

[jdbrian]

Hi

  IMO .7v is way too high. Normally you would try to be under 25mv. You say you have .1v out of the preamp . Does your Power Amp  have a gain of only 7? You need to use a coupling cap. or deal with the problem causing the offset.
   I don't know what the crossover looks like in your speakers but if the bass drivers are DC coupled (no series cap.) then there would be a current of something like .7v/6ohms(DCR) or .117A for a typical 8 ohm speaker which is not good IMO.

Brian

[kp93300]

I check . The lower woofers are  dc coupled .
I will try to rectify the problem at the pre.
thanks
kp93300

[Danny Richie]

It sounds like you definitely will need some coupling caps on the output.