Bass Chorus build not working, need some help please.

[ElectricDruid]

Sorry, I think you might have misunderstood me - and I accept that's my fault, given the somewhat unusual labelling on the schematic we're looking at, which I ignored.

When I talked about the bias of the BBD, I was talking about the "1/2V" supply, which is not totally fixed and can be adjusted slightly by the trimmer VR4/25K. That's important, and if that trim isn't right, the BBD won't be happy.

The "Vb" supply is a separate question (and I totally see why you'd think that was what I meant by "bias" since that's often the abbriviation that's used for a bias supply), and is separated from the main supply by a lowpass filter made from R42/C20. This is just to prevent noise getting into the BBD. You could run the chip from the main +9V supply, at the cost of slightly higher noise potentially. Changing this voltage to the 1/2V level is bound to stop stuff working, since running the clock and BBD at a much lower voltage would necessitate other changes too. Put them back on the Vb supply as in the schematic. Vb is not the problem.

Ok, moving on..

As you say, it sounds like you've got a solid clock, so that's good. Before we move to the LFO, we need that BBD making sound. After all, that's the whole point of this thing! Without the BBD doing it's job, we're never going to have any chorusing at all.

Connect up the Vb supply to the MN3102 to the MN3207. Get the clock howling, then push it high enough you can't hear it any more. Then feed some audio through the input and monitor the BBD output. Then adjust the VR4 "1/2V" trimmer until you get audio coming through the BBD. At that point, we crack open the first bottle of champagne. We're saving the other one for after the LFO is working!

[flon_klar]

Ok, it's all back together and I have a very distorted bass signal coming from the output of the BBD.  What's next?

[flon_klar]

I guess I've been abandoned. 

[Rob Strand]

I guess I've been abandoned. 

Electricdruid mentioned adjusting VR4 (twice).   For me that would be at the top of the list if you have distortion.  (I'll admit I haven't read over the whole thread.)

You need to try it and report your results.

[ElectricDruid]

Yep, adjust that BBD input bias VR4 until you get clean audio. Settling for distorted is no good!

It's all good though. You've made progress, and we're almost to fixing that LFO and the LED.

[flon_klar]

Hey guys, thanks for coming back! 

I haven't touched this thing for over a month, but when I set it up tonight, the distortion was no longer present, and I have a perfectly good audio signal at pin 8 of the BBD.  In fact, the chorus sound WANTS to emerge- I can hear the momentary fluctuation in pitch as I turn the depth pot, so it looks like I'm still missing an oscillator.  I await your next advice.

[Rob Strand]

Hey guys, thanks for coming back! 

I haven't touched this thing for over a month, but when I set it up tonight, the distortion was no longer present, and I have a perfectly good audio signal at pin 8 of the BBD.  In fact, the chorus sound WANTS to emerge- I can hear the momentary fluctuation in pitch as I turn the depth pot, so it looks like I'm still missing an oscillator.  I await your next advice.

If the depth pot does something that would mean the clock etc is probably working - ie. everything after the depth pot.

I'm presuming the LED doesn't flash?

For the parts around IC3 (IC3a and IC3b):
- Check your rate pot wiring
- Check the soldering
- Check the part values
- Check electrolytic caps are orientated correctly.

[flon_klar]

Correct, the LED was not flashing.

The effect is currently set up on a breadboard, to verify functionality before soldering.

I started removing the IC3 components one at a time, measured them, and put them back on the breadboard.  As I returned Q4 to its position, the LED began to flash.  I plugged in, and  I had a chorus!  Must have been a bad connection in the breadboard sockets.  So we got it going- thanks to you Rob, and Druid, and the other guys who participated.  I really appreciate your time and knowledge throughout this process.  You guys do good work!

[EBK]

bass. chorus.

I'm chewing on that concept a bit.  My bandmates would've hated me if I showed up to rehearsal with one.   

[Rob Strand]

bass. chorus.

I'm chewing on that concept a bit.  My bandmates would've hated me if I showed up to rehearsal with one.   

Flangers and Chorus were all the rage in the 80's.

[bluebunny]

bass. chorus.

I'm chewing on that concept a bit.  My bandmates would've hated me if I showed up to rehearsal with one.   

I had a board with a Boss bass chorus, bass flanger and digital dimension.  It came with shoulder pads and a questionable haircut.   

[flon_klar]

WTF?

[EBK]

WTF?

You ok?

[EBK]

Flangers and Chorus were all the rage in the 80's.

I'm not doubting its utility.  I just had bandmates who would tell me I was being "too loud" if I widened my signal.  It's an interesting idea for an effect.  I don't hate it at all.

[Rob Strand]

Flangers and Chorus were all the rage in the 80's.

I'm not doubting its utility.  I just had bandmates who would tell me I was being "too loud" if I widened my signal.  It's an interesting idea for an effect.  I don't hate it at all.

Me either.  I played a lot of bass through that era but I'm not someone that leaves it on all the time.   It has its place that's for sure.

To me things like finger run/solo at 3:34 sound amazing with the flanger,

[DIY Bass]

I think a bit of Flange can help make those basslines that are just all eighth note root notes all the time a bit more interesting.  I do use chorus on bass a bit as well, although not as much as I used to.