Ghost Echo / spirit box

[comradehoser]

I kind of get the fuzz dog mods, but don't really know much about the Belton brick and how it works

R4 from 10k>18k to increase volume (because I'm increasing resistance to ground?)
R8 from 22k>12k or 10k to move the range of the reverb into self oscillation (because I'm reducing the resistance the signal has to overcome to initiate a feedback loop?)

Why also change the dwell pot from b5k>b25k or b10k? Is it to adjust so the self oscillation hits further down the range of the potentiometer, or...?

 

[BuddytheReow]

posting a schematic will get you more traction on your request

 

[comradehoser]

 

[BuddytheReow]

I could be wrong. It's been a minute since I've done some circuit work. R4 affects the output gain of IC1.2. R8 in series with C4 creates a EQ filter and altering that would change the frequency. Increasing the DWELL pot would slow down the sweep of the 2399 control.

 

[comradehoser]

Hmmm.

Well, the R8 and pot mods were published by fuzz dog and folks in this forum with respect to modding ghost echo v.1 to be like ghost echo v.2, where the dwell pot permits oscillation and maybe has a more pronounced effect.

I did the R8 swap (10k, socketed), and have self -oscillation, so I am wondering what the pot swap accomplishes/ changes at all, before I go desoldering those legs.

 

[comradehoser]

[edit: this is a record for posterity's sake to help whoever else goes through the build and wants to modify it]

Tried 10k and 12k for the dwell resistor at R8. Definitely like 12k more. I like hearing reverbs on the cusp of feeding back, that's more doable with 12k and the dwell and depth pots near the end of their ranges. 10k puts you early q straight into Belton brick "heee-hoooo-heeee-hooooo" self oscillation, which I have more than enough of with moonn's "space is fun" reverb, and which actually gets on my nerves after about 2 seconds. It's not an interesting or variable texture.

Replaced the pot from b5k to b10k. Makes the range more useable, think. Think I will try the b25k for funsies even though I lifted a trace.

 

[comradehoser]

The fuzz dog mods, 12k at r8 and a b25k pot for dwell gives me all the best ambient reverb this circuit can give, as far as i care to have it. 10k and b10k was too much.

 

[han-tyumi]

I have my own mod of this and from what I can discern my changes are aligned to your goals. Point being let me find my documentation and I’ll attach