Colorsound - Power Boost / Overdriver

Discussion regarding early stompbox technology: 1960-1975 Please keep discussion focused and contribute what info you have...
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Dingleberry
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Post by Dingleberry »

Hi.
Hello.
I'm now making a vero layout for my overdriver from the factory schematic and I have few questions.

I got some 2u2 poly caps, 5mm leg spacing. Could it be possible to replace those signal chain electrolytics (6,4uf and 25uf) with those? I could easily fit them to my layout.
I can't remember correctly where I read that if you replace signal chain electrolytic with poly cap, the value of poly cap could be way smaller, even 1/10 of the value of electrolytic because of the better bass response of poly caps.
If that is correct then those 2u2 caps would be more than fine or am I missing something?
Probably the 6u4 could be replaced with 1u poly. I have those in hand also.

Also I have bunch of 2K2 trimmers, that I was planning to use to bias the second and third transistor. Probably 1K resistor in series with 2K2 trimmer so I can set the collector to 5V. Does this make any sense?

Why I am asking because I usually design my vero layouts with those parts that I have on hand at the moment and those poly's and trimmers will take take little more room from board than electrolytics. So if there is no sense soundwise replacing those electrolytics with polys then I can make a tighter layout.

-T
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snail
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Post by snail »

Other guts

snail

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JRM
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Post by JRM »

Hi,

I'm new around here.
I want to build this Power Boost as part of one of my custom made Pedalboard (a project to take a few months to finish). I've already managed to select the schemes for the other pedals I want to include (Fuzz Face, Dyna Comp, Big Muff, Phase 90 and Electric Mistress) but for this Power Boost I have too many doubts...
1: Is there any Power Boost 9V version? I only have found the Overdrive schematics.
2: Does anybody have tried out and knows if there is any great diference between the 18V Powerboost and the 9V version? And between the 18V and the 9V Overdrive scheme (if this later one is different from the 9V Powerboost)?
3: The hand draw version (issue date: 14-06-1971) has some 0.25uF 25V capacitors that harder to find and pricier (I've found them although) but the other drawings available (including one posted in this topic's page 4) replace it by .22uF capacitors. Does that make any big diference?

Thank you in advance for your patience with a beginner :oops:

ashtronaut
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Post by ashtronaut »

Wow! Just finished my first ever diy pedal -this one- and it's awesome! The only issue is the gain knob which ramps infintely in the last 5% of it's turn....okay now it's time to make a new pedal!!! soooo many choices hmmmm

JRM
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Post by JRM »

ashtronaut wrote:Wow! Just finished my first ever diy pedal -this one- and it's awesome! The only issue is the gain knob which ramps infintely in the last 5% of it's turn....okay now it's time to make a new pedal!!! soooo many choices hmmmm
wich version did you made?

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Post by mictester »

Dingleberry wrote:Hi.

I can't remember correctly where I read that if you replace signal chain electrolytic with poly cap, the value of poly cap could be way smaller, even 1/10 of the value of electrolytic because of the better bass response of poly caps.
Complete nonsense. The bass response is only determined by the value of the capacitor, not by its type. The frequency response is determined by the value of the capacitor and the values of the source and load impedances either end of it. I suggest a close reading of "The Art of Electronics" by Horowitz and Hill!
"Why is it humming?" "Because it doesn't know the words!"

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Electric Warrior
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Post by Electric Warrior »

New Schematic - the 12k resistor doesn't connect directly to Q1's emitter in the Overdriver (the factory schematic has it wrong :) ).
PBODschematics.png

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Post by analogguru »

And here is the original Valvo-application (taken from elektor magazine 1971) printed in the 1970 Valvo application book (shown below) as a further proof, that neither Gary Hurst nor Colorsound ever invented something remarkable.

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Post by borislavgajic »

:applause:

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Post by Bernardduur »

Electric Warrior wrote:New Schematic - the 12k resistor doesn't connect directly to Q1's emitter in the Overdriver (the factory schematic has it wrong :) ).
On mine it did :D

Great to see that!
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Post by bootle »

has anyone who ever built this got a squealing/whistling sound when rolling the guitar volume down to about 6 or 7?
not that much of an issue, but still curious.
I ended up with bc549b trannys with gains around the 300 mark and it sounds pretty good and the squealing is gone, though there is still a little hump of noise around that point of the guitar's vol pot.
putting a 330pf cap in for the 220 helped a bit too.
the 10k rev log drive pot is a must too.

really like this circuit, very versatile, should have built one ages ago!

giando
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Post by giando »

Hi guys! :)
A little question: the pots (100k for master, treble and bass and 10k for gain) are log, lin or what else?? :D

Btw, it's not a problem if I use a 220pf capacitor and 2n4904 transistors on the veroboard schematic posted some pages ago? Can't find bc109 from my supplier :(

One last nooby question: how can I bias this circuit if I want to have 5v on collectors? :) thanks!

bootle
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Post by bootle »

pots:
drive 10k rev log
bass/treble 100k lin
vol 100k lin or log

220pf and 2n3904 is fine.

look at the resistors at q2 and q3 collectors to bias, anywhere from 5v to 5.5v is fine,
the stock value resistors got close enough for me.

giando
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Post by giando »

Thanks!
I've seen in another forum that is suggested just a standard 10k log pot for the gain... is there so much difference between the log and the rev log?
Btw I choose the BC549C transistors... much closer to bc109c! :)

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Post by SPeter »

giando wrote: is there so much difference between the log and the rev log?
Yes, they have opposite characteristics!

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Post by TheLemon »

SPeter wrote:
giando wrote: is there so much difference between the log and the rev log?
Yes, they have opposite characteristics!
If you wire up a C10k like a normal log pot it will sound more balanced gain sweep throughout the rotation.. Or even try a smaller C5k or C1K pot

giando
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Post by giando »

Just build it! This pedal is GREAT! :D Built it on veroboard, adding the master volume pot

2 minor issues:

1. sometimes I can get a squelch sound (a la fuzz factory!) when I turn gain pot (c10k wired as seen in the vero layout a few pages ago) to the max...
2. sometimes, with mid gain settings, if I play strings with emphasis, the sound breaks up but not as a distortion/overdrive (like it would normally do), but as a "noise" like "Krrr" (sorry for the poor explanation, I'm Italian and I don't know some technical terminology :D )

Does anyone have some solutions? It works very well, it cleans with volume variations on the guitar, it's very powerful and nice sounding... I already keep it always on on my pedalboard! :) And it works great with muff and fuzz (even with my ge-7 with treble and bass boost for solos!)

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Post by giando »

No one? :(

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Post by joeboo88 »

I built the overdriver a few months ago and love this thing.
answer to question #1 mine does this as well and from reading through the thread i think its supposed to do that.
I also love this feature cause you can dial down the volume and get good fuzzzzzzz.

Question #2 ...? i dont know wxactly what you mean, maybe and issue with transistor types?
I think i used 2n3904's i cant remember right now, but my pedal sounds smooth.
Hope this helps a bit, maybe one of the more expierenced can help more.. :D
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Post by pandadandan »

Im currently suffering from the same symptom
giando wrote: 2. sometimes, with mid gain settings, if I play strings with emphasis, the sound breaks up but not as a distortion/overdrive (like it would normally do), but as a "noise" like "Krrr" (sorry for the poor explanation, I'm Italian and I don't know some technical terminology :D )
It's less of an overdrive and more of a spluttery crackle when the gain is between 12 and 3. If you dig in, it doesn't really overdrive as much as crackle in a non-musical way.
Mis-biased transistors, perhaps?

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