BAJA Ampeg SVT bass amplifier pedal 9v 010418  [documentation]

Original effects with schematics, layouts and instructions, freely contributed by members or found in publications. Cannot be used for commercial purposes without the consent of the owners of the copyright.
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tuck
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Post by tuck »

Changed the cap and resistor, the signal is increasing in volume and it is brighter but the other way around. Turning bright off is loud, turning it on is not as loud :-)

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bajaman
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Post by bajaman »

Hello Tuck
yes - exactly like the Ampeg ;-)
You could always remove the input jfet buffer and connect the input socket directly to the normal/bright switch - in this case you would have to scale up the resistor values x10 (100k, 47k, and 5M6) and decrease the capacitor value x10 (220p) - then it will be exactly the same input impedance as the Ampeg SVT ;-)
cheers
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mcrowe
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Post by mcrowe »

I was just experimenting with running this pedal at 12v instead of 9v. With the higher voltage, I'm getting more headroom, but also a low-level hum that's absent otherwise. Any ideas why that might be?

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Tassieviking
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Post by Tassieviking »

What sort of 12v supply are you using ?
It could be your 12v supply that is causing the noise, especially if it is plugged into a power point.

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mcrowe
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Post by mcrowe »

Yeah could be. I haven't tried any others yet. It's just a generic wall wart supply, and it's labeled as 9v even though I happened to measure it one day and found out it's putting out 12. I'll try another.

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mcrowe
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Post by mcrowe »

Whoops...I plugged in a 12v supply but forgot that its polarity was the opposite of what the pedal expects, and now it's distorting in a way it wasn't before. Did I fry an opamp maybe?

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Paul_5
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Post by Paul_5 »

Looking at the schematic there's very little else to go wrong. Check your voltages at the IC pins.
The sounds in my head don't match the sounds from my amp, I guess that's why I'm here...

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mcrowe
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Post by mcrowe »

I'm way out of my depth here, but I'm reading some mismatches of 50-150 mV on most of the + and - input voltage pin pairs, which, if I understand correctly, is often a sign that something is wrong. I'll just replace them, use sockets this time, and hope for the best.

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pedrocucaracha
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Post by pedrocucaracha »

OK, this pedal is every bassist's dream. It makes any amp sound great. I went to a studio the other day, where the amp was crap, but with this pedal, it was night and day.

Would I want to produce it for commercial purposes (at this point, just an idea), how would I need to license your work?
Pedro Cucaracha
(Easy, cheap and dirty)

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bajaman
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Post by bajaman »

Hello Pedro
No need to license it but a mention of it being a design published on freestompboxes.org would be a nice gesture - glad you like it
cheers bajaman
be kind to all animals - especially human beings

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pedrocucaracha
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Post by pedrocucaracha »

bajaman wrote: 18 Jul 2023, 20:46 Hello Pedro
No need to license it but a mention of it being a design published on freestompboxes.org would be a nice gesture - glad you like it
cheers bajaman
Excellent! if I move ahead with this initiative, I'll make sure to provide the credits. Thanks a lot!
Pedro Cucaracha
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Paul_5
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Post by Paul_5 »

What’s the best way to boost the output on this? Would I be ok using the last opamp stage as a boost instead of a buffer?
The sounds in my head don't match the sounds from my amp, I guess that's why I'm here...

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Post by NazarDaniel »

Here's a test of the SVT, compared to a clone of the Sansamp VT Bass.

Treble caps and pot were updated to the Rev1 specs, but I didn't decrease the bass pot.


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skizoide
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Post by skizoide »

NazarDaniel wrote: 13 Dec 2023, 15:50 Here's a test of the SVT, compared to a clone of the Sansamp VT Bass.

Treble caps and pot were updated to the Rev1 specs, but I didn't decrease the bass pot.

Sansamp VT clone? Schematic?

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Tassieviking
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Post by Tassieviking »

bajaman wrote: 18 Jul 2023, 20:46 Hello Pedro
No need to license it but a mention of it being a design published on freestompboxes.org would be a nice gesture - glad you like it
cheers bajaman
I personally would also write "Design By Bajaman" on the PCB and also include it on any instructions you make up.
I think we all should honor the designer if we make up PCB's of someone else's design, especially Steves great pedal designs that have been made available for everyone to use.
Credit where credit is due is my philosophy.
Thanks BAJA

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tedsorvino
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Post by tedsorvino »

Hi everyone.
Before start building the pedal.
i would like to know if it’s ok to use either j109 or j112 instead of the 2sk170 jfet (for buffer use).
Thanks in advance

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