Finally, here is my recording of different settings on this pedal.
Quality is really bad, like my bass playing, but it's all I can share right now

I definitely have to record sound clips, even if the quality will be bad, just to make realize how it sounds.
But I can already tell you that the mid pot is anything but subtle. It makes a great difference between when it's cut and when it's turned !

Here is a Beta Lead version, without reverb section.
The only modifications are C138, C140, C141 and C143 values.
If a moderator or administrator have a look on this thread, maybe it could be renamed to "Sunn Beta Bass and Beta Lead preamp schematic" as they are very similar.

my converter breaking me bad it send ~+15v/-7v :mrgreen: my layout seems good but without this ******** ***** ********* , i can't verify it :applause: diode,cap,IC? I borrowed a voltmeter from a friend and I have measured voltage values from my converter with 3 different transformers. with 9,08V in...

To be honest, I don't have the required equipment to measure the voltage of my converter.
I simply used the Bipolar Voltage Converter of Tagboardeffects, but maybe I have the same issue.
I will try to find a Voltmeter to check it

And here are pictures of my build.
It makes sort of oscillation at low values on the level pot. But it disappears beyond about 9 o'clock.
I wish I could record sound clips, but I don't have recording system for the moment.

Here is my veroboard version of Sunn Beta Bass preamp, based on Sunn Service Manual. I kept the components numbering from original diagram. For the +15V/-15V section, I used a daughterboard from Guitar FX Layout called Bipolar Voltage Converter with 1N4001 diodes : http://tagboardeffects.blogspot.fr...

Ok, so I think you could use a 4P3T toggle switch (I don't know if it's the right designation), that are like two DP3T in a case.
For example APEM 5664. You will have to check how are the connections in middle position, but the wiring could be like this :

Hi guile31 ! I think you should use a rotary switch, with 4 poles and 3 positions like this one : http://www.banzaimusic.com/Rotary-Switch-1x4x3.html http://www.brimal.co.uk/components/com_virtuemart/shop_image/product/Rotary_Switch_4__4e2529fdc1db4.jpg Link A and B poles together and to "Maste...

It still some points to clarify. I was chatting with guile31 by private messages about the resistor and capacitor at the end of the schematic. Both arcaarca and grrrunge schematics are ending after points 2 & 3 of the volume knob, but on the original Sunn schematic, it leads to the effect loop &...

I just finished to build and debug a veroboard version.
I will correct my design and post it here very soon

I admit I'm a bit lost with pot numbering. Fortunately, it is very easy to verify when plugging a pedal for the first time (and to correct mistakes :lol: ) Just in case, if you want to build a Beta Lead version, you will have to swap the following values in your schematic : C15 : replace 56n by 22n ...

The service manual is a little blurry, but the way i see it, the VCC-pin is connected to +15V through a 470R, and then there's a test point that should read +8V directly at the VCC-pin. Connecting it to both a 15V and an 8V supply makes absolutely no sense, whereas a 7V voltage drop across 470R imp...

Sorry, I meant just specify that the circuit is powered with -15/0/+15 on your schematic (not especially the CMOS),
on the top left with the connecting points or in the indications at the bottom right.

If the CMOS can be powered with 0/+15V so you're right, let's skip the +8V

I think this one is correct, I don't know how CD4049UBE should be powered, but on the original schematic 74C04 is powered with +8V Why don't you use 4069 instead ? Maybe you should indicate +V is +15V and -V is -15V The volume pot is not wired as the Sunn schematic, but I don't know if it's important.

Hi ! Please excuse my bad English because I'm French. It seems like two resistors have been forgotten on the first post schematics. R123 100k on channel 1, should be placed between lug 2-1 of Drive pot (R5/2 1M lin), and lug 1 of IC2A 4069N = R152 100k on channel 2, should be placed between lug 2-1 ...