Aquaboy v2 issue

[v00d00blues79]

I just built up a Aquaboy v2 PCB for a MN3005 and I'm getting a high pitch whine on the MN's pins 3&4 with a lot of distortion that I can't seem to bias out.  I'm going through and verifying resistor values to make sure I don't have any invalid values, but what could possibly be causing this?  I've verified my MN3005's in my Dirtbag, so I know they work which is a great relief, but even the ones i have in my Dirtbag exhibit this problem.

Could the clock cap, which measured dead on 100pF, drift and cause this type of issue?  This is going to be a learning exercise for me as my Dirtbag build went sooo smooth. 

I've audio probed the audio path and I have audio all the way to pin 7 of the MN3005, so I know that the board is at least passing signal.  Just looking for some hints as to what it might be.

Thanks,

Andy

[giantrobot]

I'm having the exact same issue.

[v00d00blues79]

Bump... I've been working on this one still and haven't found anything yet.  If anybody has any hints I'd really appreciate it!

Thanks,

Andy

[gtr2]

Whine while using an audio probe?  You were not clear.

If so, there will be whine on 3 & 4 because it hasn't been filtered out yet.  Just bias them to be as clean as possible.

Josh

[v00d00blues79]

Sorry, yes I am hearing the whine while probing pins 3&4 with an audio probe.  The issue is that I cannot get the whine biased out.  I've checked all of the values, including the bias trim pot, and they are good.  I've socketed the recommended resistors and tried different values based on the notes in the build document. 

Thanks again,

Andy

[gtr2]

Your not biasing out the whine, that's what the filtering after the BBD's is for.  You just want the repeats as free of distortion as possible.

[gtr2]

Once you bias the BBD's and have delay you adjust the clock trim.  Put in a testing rig of probe the out pad and turn the clock trim following the instructions in the build doc to find your max delay time before you get whine on the output.

Josh

[v00d00blues79]

I guess I'm using the wrong term applied to what I tried, but that is how I approached it.  I used the bias to try and get clean repeats and then the clock trim to dial out the whine.  What I'm also  experiencing is that the output of the MN3005, pins 3&4, have a really low distorted volume to them.  In my Dirtbag the volume on pins 3&4 is the same as the input. Ill mess with it tonight and see what I can come up with.  Thanks for the help!

Andy