Colorsound - Power Boost / Overdriver

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

Bernardduur, any updates? :)

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Post by Bernardduur »

Sorry, I had a wedding in Finland this weekend, so I just came home. Hope to check it tomorrow as I haven't slept in days.......... 3 days of beer, Finnish women and sauna :)
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Post by bajaman »

lucky boy :lol: :wink:
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pf_fan
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Post by pf_fan »

Indeed... ;)

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Post by jg »

pf_fan wrote:
I think that I noticed one more thing. I counted 15 resistors on PCB. Schematic have only 14. To make things more complicated I found another picture of the PCB which has... 16 resistors! I circled this additional one :)

Image
Looks to me like it is a 100K on the jack side of the .22uF output cap. "Anti-pop".

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Post by Bernardduur »

Yes, that was it! I added it to the unit's notes underneath the picture. There is a 1M resistor used as a pull down on the input.

Now, do we miss anything?
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Post by pf_fan »

Bernardduur wrote:Now, do we miss anything?
Looks clear to me. But here's yet another picture of the Power Boost's PCB where two additional resistors goes from PCB to volume pot. Other one is connected between switch and PCB. Any ideas? Are they 'anti-pop' resistors as well?

Image

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Post by Bernardduur »

The ones to the volume pot sets the volume range. The volume can't go to absolute 0, the other one attenuates the signal a bit.

Mine doesn't have those.
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Post by pf_fan »

Once again, big thanks for your help!

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Post by pf_fan »

Bernardduur, On your schematic "Gain" pot is 2k2 linear (labeled 2K2A) and wired backwards compared to original schematic (10k log). Is it working backwards too?

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Post by Bernardduur »

pf_fan wrote:Bernardduur, On your schematic "Gain" pot is 2k2 linear (labeled 2K2A) and wired backwards compared to original schematic (10k log). Is it working backwards too?
Nope....... maybe I misplaced the potmeter but it works in the normal way

Not that it adds that much. More like on 95% suddenly the gain kicks in :)
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Post by pf_fan »

Maybe a different value of the pot will help? I've seen Power Boosts/Overdrivers with 2k2, 10k and 470k pots...

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Post by Torchy »

pf_fan wrote:Bernardduur, On your schematic "Gain" pot is 2k2 linear (labeled 2K2A) and wired backwards compared to original schematic (10k log). Is it working backwards too?
2K2A is actually a log pot. Which would explain why all the action takes place at one end of the travel ?

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Post by patafix »

Always the same :

With pots it's hard to find the right curve : xxA can be either a log or a lin... europeans and americans using a different letter to describe the pot...
Patafix... so sticky

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Post by pf_fan »

Torchy wrote:2K2A is actually a log pot. Which would explain why all the action takes place at one end of the travel ?
I think patafix is right - look at this picture:

Image

It's 2k2A but there's LIN written next to it...

And a small collection of various Gain/Volume pots from Power Boosts/Overdrivers (both vintage and reissue):

https://img213.imageshack.us/img213/6380/05vb0.jpg
https://img529.imageshack.us/img529/3607/01kd0.jpg
https://img522.imageshack.us/img522/4599/03vl0.jpg
https://img515.imageshack.us/img515/6153/04qw1.jpg

:)

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Post by Torchy »

Youre right, sorry - I just read the 2k2A code.
Those look like Omeg P16's :- european made so they follow the european "standard" of A=Linear, B=Log. Total pain in the arse when the rest of the world follows the USA standard A=Log, B=Linear so why they go against the majority of manufacturers beats me. Typical european arrogance I suppose. Having multiple "standards" for the same thing seems an oxymoron to me.

http://www.omeg.co.uk/pc6bubrc.htm

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Post by analogguru »

Total pain in the arse when the rest of the world follows the USA standard A=Log, B=Linear so why they go against the majority of manufacturers beats me. Typical european arrogance I suppose. Having multiple "standards" for the same thing seems an oxymoron to me.
Hey, Hey, Hey.....:
This is NOT US-standard, this was "invented" by the Japanese.
And the "european standard" was invented long before that - by Radiohm. And it would make more sense: Standard is linear so "A", logarithmic gets "B" and Rev.Log gets C.

Only some stupid guys couldn´t keep this in mind defined logarithmic as "A" - like "Audio Taper".

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Post by clintrubber »

Hi,

I've seen various layouts, or could breadboard etc,
but does anyone know if ready made PCBs for this FX are around ?

Thanks

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Post by controller700 »

Can someone give me an advice??
The Overdriver Schematic has three 25uF caps, but I can only find 22uF and 27uF caps... Which value should I use?

I´m going to use these files for my project:

Image

Image

Has anybody verified this??

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Post by Bernardduur »

Just use 22 uF
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