Sunn Coliseum Bass Pedal

[johnk_10]

I've always been a huge fan of Sunn amps (mostly the tube models) and I've owned quite few Sunn Coliseums in the past and had another mint one about 8 years ago. Here's pic of it:



IMO, it didn't really sound as good a I remembered, lacking low end, so I sold it.

About 4 years ago I decided to build the preamp of one in pedal form using the original factory schematic with original vintage transistors.
the hardest part was getting the power supply circuit solved for it as it required a lot of different voltages as well as a lot of filtering. With Frank Appleton of FEALABS help, i finally got it sorted and the result was awesome. It did require a 28 volt power supply (wall wart type) with a lot of filtering on another PCB to obtain the +28 +23 and -15 volts for it. IMO, it sounds a lot better than the actual head.
Here's a couple of pics of the pedal:


gut shot:



It was a pretty daunting task but I'm glad that I finally got it right and it was worth it.

 

[anevilspar7an]

Power can probably be simplified a little using an LT1054 charge pump to obtain 36V out of 9V like the Integral Preamp and using some voltage regulators to get those target voltages. Love to see more Sunn Bass builds so awesome job dude.

 

[johnk_10]

Power can probably be simplified a little using an LT1054 charge pump to obtain 36V out of 9V like the Integral Preamp and using some voltage regulators to get those target voltages.

that was my first thought too, but i tried that and unfortunately, it didn't work.

 

[johnk_10]

Love to see more Sunn Bass builds so awesome job dude.

i've built a few other Sunn preamps.

Sunn 200S preamp:




Black Hole Sunn (Model T):


Sunn Bass Buzz (modified Sunn Buzz):

 

[anevilspar7an]

Those are sweet. Any chance I can get schematics for those, or the links you got them at?

 

[johnk_10]

here's the coliseum, bass schematic:

 

[anevilspar7an]

Thank you @johnk_10, I'll have to breadboard this once my current projects are finished.

 

[johnk_10]

Thank you @johnk_10, I'll have to breadboard this once my current projects are finished.

let me know if you want any of the other other ones.

 

[anevilspar7an]

I'll gladly take them, I have a folder for schematics that I can put them in.

 

[johnk_10]

FET 200s:


Model T (solid state):





Sunn Buzz:

 

[DSV]

Good job , John. Very inspiring. Would you mind sharing the schematic for the PS and the filtering section ?

 

[johnk_10]

it's been a while ( and my old computer crashed) so i no longer have it, but i do still have the two board layouts that i used to make them for it:
this one filters the 28 volt power supply (wall wart type):



and this one supplies all of the necessary voltages: