Sola Sound - Tonebender MkIII  [schematic]

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

Numbers without units always cause lots of confusion. 0.19mA/190µA does sound like a nice amount of leakage.

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Post by sinner »

My bad

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nooneknows
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Post by nooneknows »

Since I 'don't like positive ground and charge pump and I wanted a normal power supply still using a PNP do you think this partial redraw of the schematic could work? (the sound comes from the last tranny the most, so I just flipped the germanium PNP)

thank you!
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tonebenderNPNandPNP.jpg
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Post by Bogart_sci »

KindaFuzzy wrote:Thanks man, collector voltages are as follows with respect to 9v+:

Q1 -3.5v
Q2 -3.5v
Q3 -1.9v (depending on the time of day and rotation of the moon, it's very sensitive)

Since the supply voltage to Q3's collector is ~4.5v, I was aiming for about half, and found that negative 1.5v-2.0v sounded best to my ears.

Thank you thank you thank you! I have been building a few tone benders ove the last few years and have never been totally happy with them. This is because I have been making the collector voltage to -4.5V. After seeing this post I tried a 33k and a 10k trim and got the collector voltage on Q3 down to 1.9V! Woo Hoo! This is the shit I've been looking for.!! I will be modifying all theTBs I have built to this. It sounds the bomb!

Great tip. I'm so happy :)

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Post by LucifersTrip »

I found an easy way to trim is to turn the tone to full bass, then use that trim on Q3 to set the max bass you want. and yes, for me it's usually in the 2-3V range. you don't have to worry about the treble side since it always has more than enough.

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Mbas974
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Post by Mbas974 »

Hi, I try to figure out the classic layout of mkIII
but i get mess in 220p cap zone....

Can anyone post the image or the link to to be back of original PCB (or any similar....)

thanks
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mkIII.jpg
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Post by dbat69 »

Just a noob here but its like one of the games I played on my daughter's tablet.

On the suggested layout, if you delete the blue line with pink dots, replace the orange line with the light blue, and put in the green line, it should do what I think you are after? :thumbsup

I hope the picture is attached - first time attempt :roll:
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Mbas974
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Post by Mbas974 »

Yes, that's a way... and I thank you for that.

What I'd like to check is the orginal design solution ( maybe the same maybe not ).

So if anyone has the image of the PCB... i will appreciate it.

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Post by ringworm »


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Mbas974
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Post by Mbas974 »

....happy sharing !
Have a nice fuzz.
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mkIII-PCB.png
mkIII-Layout.png

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Post by sinner »

Was it something wrong with mine?

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Mbas974
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Post by Mbas974 »

what ?

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Post by sinner »

Nufin'

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Mbas974
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Post by Mbas974 »

OK.

Any concern if I'm planning to use 3PDT switch and a led indicator (original TB has no led) ?
I think it will influence the sound anyway right ?

Thanks

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Post by sinner »

Status LED is ussualy off the signal patch ;-)

Wont affect the sound at all

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Mbas974
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Post by Mbas974 »

Ok, buit it and it sound very good.

But I'm wondering about C5 Value (Q2 source cap)...
I bought GE Transistors from smallbear (very good quality and service !!) and into his schematic it is 22uF while in every schematic I see it is 10uF (or less)

Any comment is appreciated.
Thanks

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Post by sinner »

Q2 source cap?

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Mbas974
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Post by Mbas974 »

Yes.
I get the answer directly from smallbear support mail (very efficient and gentle !!) :

" The capacitor C5 has be to be large enough to sink all audio frequency to ground. 10 mf. is enough but a 22 mf. cap will not effect the performance either "

The pedal I built sund amazing ! thanks to all.

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Post by sinner »

Actualy it will. And it's emitter bypass cap not Q2 source cap

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Mbas974
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Post by Mbas974 »

Yes...
sorry mixing BJT with Jfet... My meaning ref to Emitter (not source)
thanks for pointing out it.

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