Hi-Freq Sweep on CE-2

[Baran Ismen]

Hey lads,

Today I've finished the Tonepad's famous CE-2 with success. Used the original MN3007/3101 combination, along with RC4558 and 1458 instead of TL022 (didn't have any at hand), apart from that I've made no changes or mods. Rin is 1m, Zener is 12v, trim pot is set around %20-25. Used 10k, but after halfway, it doesn't seem to work and I only hear the clean sound, maybe it should be 5k?

I only have a little issue that, there's a hi-freq sweep parallel to LFO speed bleeding into the sound. It's present between 11khz to beyond 20khz and sweeps according to speed. I've made a short record below.

1st part is with the guitar volume at 0.
Rest is some crappy play with various settings. I also tried max settings and it sounds actually like outer space, sort of ring mod, which is kinda cool. Also, this sweep can be heard in the background.

Sound clip



What would be the cause?

[Baran Ismen]

Ok just disregard, it was totally my stupidity that I've soldered 470pf for C22 instead of 47pf, which is the rate cap. That also solved the weird space sound. But I'll add a switch for that mod anyway.

It's dead silent now.

[ElectricDruid]

Well spotted.

Rate cap 10x too big would bring the BBD clock frequency way down into the audio range where you hear it (as you discovered) and below the frequency the filters are set for, so they don't remove it either.

Glad it's good now it's working.

[Baran Ismen]

Well spotted.

Rate cap 10x too big would bring the BBD clock frequency way down into the audio range where you hear it (as you discovered) and below the frequency the filters are set for, so they don't remove it either.

Glad it's good now it's working.

Definitely. I've ended up with 100p for that, its a good balance between a lush and a tad much chorus effect. Was too lazy to add a switch, so I'll leave it like this. Maybe change the R32 for LFO speed, I don't know.

[Baran Ismen]

Another thing is, the output is kind of clipping. I know it's about the trimpot setting, as mentioned above, the trim is set to around %25 (above %50, no chorus, on 0 to around 10 distorted), and the sound is just fine when the guitar's volume pot is around %80.

I think these pickups I use are overpowered for most pedals I have & make, I watched this movie before (xp-100 input clipping, tuner clipping, now this). Is there any way to decrease its volume, or gain, or whatever it is without losing the tonality?

[ElectricDruid]

It would depend a bit on where exactly the clipping is occurring. It might be in the first transistor stage, for exampple, in which case your only option would be to turn your guitar down!
R6/C4 in the first pre-emphasis op-amp stage look like a good bet though. Decreasing R6 will reduce the gain (maybe halve it?) and C4 will need to be altered to compensate (so double it if you halved the resistor).

[Mark Hammer]

I usually recommend lifting one end of the resistor that carries dry signal to the mixing stage, for the purposes of setting the bias voltage to the BBD.  They will use a signal generator and scope at the Boss factory, but since us mere mortals usually have to set these things by ear, it's easier to listen for the quality of the delay signal when the only thing you hear is the delay signal.  Once the  bias is set for cleanest delay signal, THEN you can solder the free end of the mixing resistor in.

[Baran Ismen]

Another question I'd like to ask is how can I add a pulsating LED as per LFO. I've seen a video on YT that shorts Pin 8 and 13 on the original board, yet when I compare the original schematics with the Tonepad, I see that both leads do not exist on the Tonepad version; Pin 8 goes to TL022's 8th leg, and Pin 13 goes to 3.3k resistor, both of which are completely different on Tonepad.

Ok after a quick check on the original schematic, I think I've found it, basically 3rd (or 1st) leg of Rate pot provides that.

[Baran Ismen]

It's me again.

I've noticed that there's a slight volume drop when the pedal is engaged. Any ideas on how can I fix that?

[antonis]

Schematic..??

[Baran Ismen]

Schematic..??

Good old Tonepad's CE-2 

[ElectricDruid]

Schematic..??

Good old Tonepad's CE-2 

He means he'd like a link so he doesn't have to go searching for it. It's good practice to always provide the schematic you're talking about. Here, I've done it for you:

http://www.tonepad.com/project.asp?id=53

[antonis]

For about 20% output raise, make R24 56k..
(for less, you'll need E24 resistor value, like 51k or a small trimpot..)

[Baran Ismen]

For about 20% output raise, make R24 56k..
(for less, you'll need E24 resistor value, like 51k or a small trimpot..)

Thanks, antonis, I've read on PedalPCB that decreasing R21 and R22 help (from 47k to 10~-ish K's), but I'll try this one first.

[antonis]

Thanks, antonis, I've read on PedalPCB that decreasing R21 and R22 help (from 47k to 10~-ish K's)

Same result..

IC1b is a mixer of unity gain (R24/R21 and R24/R22 for clean and wet signal respectively)(*), so it should be more convenient to replace 1 resistor (R24) instead of 2 (R21 & R22)..

(*) to be more accurate, gain is R24 // (R23 + X_C15) divided by R21 & R22 respectively, where X_C15 is C15 capacitive reactance (0.159/C*f, where f=frequency of interest)
So, mixer gain is always less than unity (lesser for high frequencies)..

In case you wish to retain original circuit gain/frequency propotion, you haver to replace 2 resistors..
Either R21 & R22 (as read in PedalPCB) or R24 & R23 (both raised by the same percentage)..

P.S.
I presume you'll be fine with only R24 replacement..