CE-2, Questions on wet/dry ratio

[cab42]

I just finished a CE-2, using a pcb from Tonepad, I bought years ago.

http://www.tonepad.com/getFile.asp?id=101

No debugging needed, worked right away.

However, the chorus effect is much more subtle than I had expected.  I did the vibrato mod and I noticed that the level of the modulated signal was much lower than the mixed signal. So it looks like the clean signal is dominating the mix.

Is this expected behavior or should I look for an error?

I would have expected the levels of two signals to be fairly equal as the mixing resistors, R21 and R22 have the same value. I guess I could increase R21 in order to lower the level of the clean signal. The effect level mod won't help in this situation as far as I can see, as it just lowers the wet signal even more.

Would it be possible to replace the two mixing resistors with a mix pot that goes from clean to vibrato, instead of the vibrato switch and effect level mod?

Regards

C.

[Rob Strand]

Is this expected behavior or should I look for an error?

There's *many* places an error could creep in.
It would be easier to say check all the part values from C2, through to R22 along the delay signal chain.   Be extremely careful about not being a factor of 10 off because you misread a band.

Transistors with reversed E and C for Q2 and Q3 could cause a subtle volume drop.

The right way to go about it would be to inject a 200Hz signal and find what point along the signal path the level drops.   Keep in mind C3 and R5 cause some boost at high frequencies.  It could turn out the MN3007 has a loss because it's a little dodgy and in that case you don't have much choice but to reduce the value of R22.

[cab42]

Thanks Rob,

Using an audio probe and the signal generator I found in the trash a few years ago, It was pretty easy to find the location of the volume drop.

It appeared to be a bad solder joint on  R18 just before Q3, I missed when I checked yesterday. Now the chorus is anything but subtle, and I did the effect level mod to be able to tame it a bit. I think I'll experiment with the chorus intensity mod as well.

Lastly just a follow up question: why 200hz?

[Rob Strand]

Lastly just a follow up question: why 200hz?

It was chosen to keep under the point where C3 and R5 starting boosting the highs.
That way you get more of a constant level at all points.

A more common choice would be 400Hz or 1kHz.

[cab42]

You inspired me to do some reading on filters today. Very useful!

Thanks again, Rob.