Author Topic: Collosalus unity gain mod?  (Read 416 times)

Spenzerleehorton

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Collosalus unity gain mod?
« on: April 30, 2017, 05:33:06 AM »
Hi everyone,

I'm finally there with a working Collosalus pedal, I had rushed the build and missed a solder joint and two transistors I had the wrong way round!!!
Works ok apart from a slight drop in volume, I've noticed on a few other videos of other builds this seems to be the case as well, so could anyone suggest either a gain control or a unity gain fix?

Regards

Spence.

Spenzerleehorton

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Re: Collosalus unity gain mod?
« Reply #1 on: April 30, 2017, 12:12:13 PM »
well what i'm going to try is take one leg of R7 and R8 up and use trimmer, R7 i'll add a 20k trimmer and R8 i'll add a 10k trimmer and do some tweaking.

Spenzerleehorton

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Re: Collosalus unity gain mod?
« Reply #2 on: May 04, 2017, 01:05:07 PM »
Going to try upping R7 to 150k so it should reach unity?

Spenzerleehorton

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Re: Collosalus unity gain mod?
« Reply #3 on: May 05, 2017, 06:03:01 AM »
after messing around with R7 and R8 i gave up and replaced R5 with 42k, i get unity gain now, must be something wrong in the design of this?
will test how it sounds now.

madbean

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Re: Collosalus unity gain mod?
« Reply #4 on: May 05, 2017, 06:28:54 AM »
You should have some gain just at the input so make sure you've got R3/R4 values correct. Lowering R5 will increase dry output but not wet. If you want to increase the wet output, you could lower R9 to 47k.
I own madbeanpedals (duh). I am part owner of Function F(X).

Spenzerleehorton

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Re: Collosalus unity gain mod?
« Reply #5 on: May 05, 2017, 07:04:19 AM »
yeah, R9 39k sounds good to my ears, R7 - 100k R8 - 10k and R5 - 75k, much better balance of level on output, but still tweaking, still havent ruled out finding a problem and it all being fine without tweaks!!!!

Scruffie

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Re: Collosalus unity gain mod?
« Reply #6 on: May 05, 2017, 07:31:27 AM »
Don't fiddle with R7 & 8 just to increase gain, they set the de-emphasis to counter the pre-emphasis formed by R3 & 4 so you'll alter the frequency response.

Spenzerleehorton

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Re: Collosalus unity gain mod?
« Reply #7 on: May 05, 2017, 10:05:19 AM »
yeah, im leaving R7/R8, i've resoldered everything and put pins in to solder too, to save the pcb, everything is sounding much better now!! must have been a bad contact, will put back to stock and see how it sounds!!!
one other note, one or all of the pots must have been shorting out to the case or something cause at one point it turned into a really cool delay pedal!!!
might investigate this further and if possible put some switches in to get this effect, or possible a external volume pedal which could adjust speed!!
« Last Edit: May 05, 2017, 10:51:13 AM by Spenzerleehorton »

Spenzerleehorton

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Re: Collosalus unity gain mod?
« Reply #8 on: May 06, 2017, 06:33:23 AM »
Well it sounds really good now, little bit noisey but it's such a great sound I think I can live with it, I've got to finish the current lover and compare them!

Spenzerleehorton

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Re: Collosalus unity gain mod?
« Reply #9 on: July 21, 2017, 05:50:18 PM »
have revisited this mod as not happy with the sound.
The level is a little bit too loud now between bypass and effect, i have altered R7 and R9, just put another of the same valued resistor in parallel on top of them.
There is still too much bottom end coming through, could someone suggest a fix for this please?
Should i change 3.3nf cap to lower? 2.2nf?

regards

Spence.
« Last Edit: July 21, 2017, 05:53:08 PM by Spenzerleehorton »

Scruffie

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Re: Collosalus unity gain mod?
« Reply #10 on: July 21, 2017, 05:56:56 PM »
R5 & 9 set the wet and dry level, you need to reduce them equally and leave every other value as they were.

Spenzerleehorton

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Re: Collosalus unity gain mod?
« Reply #11 on: August 26, 2017, 12:48:37 AM »
unfortunately i have reduced both R5 and R9 ive put another same value resister on each and the bottom end is too much?
im going to try and change 3.3nf to 4.7nf, 6.8nf and see if the bottom end improves.

regards

Spence.

Spenzerleehorton

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Re: Collosalus unity gain mod?
« Reply #12 on: October 05, 2017, 10:53:34 AM »
well i've put it all back to stock and the bottom end is too much, i need to find out why i've got so much bottom end when the effect is engaged?

does anyone know where in the circuit this could be happening please?