Supro Sahara

[CJ]

Here is the preamp, all the controls are dual pots, there are some cut traces and jumper wires so it looks like it was in between revs,

clever cathode cap scheme, as the volume is turned up, the first stage cathode cap starts to boost low end by getting  it's ground leg closer to ground,

bass pot looks like it would work backwards, we will see when we fire it up,

the second cathode cap can be switched in or out by way of a foot switch for more gain,

will get some voltage readings after reassembly,

 

[PRR]

> first stage cathode cap starts to boost low end by getting its ground leg closer to ground

No; wide-band boost.

> bass pot looks like it would work backwards

No; max resistance is max bass. If you wish to draw so "11" is "up", this is the right way to draw it.

 

[Gene Pink]

clever cathode cap scheme, as the volume is turned up, the first stage cathode cap starts to boost low end by getting  it's ground leg closer to ground,

1M pot vs 1.5K resistor, that pot won't do anything until within the last 1% of rotation.

Gene

 

[CJ]

good catch, i bet they have a different value paired up with the 1 M vol pot, we will get out the ohm meter and check that out,  can not read value of bottom pot as it is covered up,

 

[CJ]

that is a dual !M-L pot so the cap is going to make the amp go to 11 when you hit 10.

 

[CJ]

voltages right here, only does 18  watts,

 

[CJ]

as predicted up post, vol boost from cap only occurs at very end of pot rotation,

here are the  before and after boost wave forms>

 

[abbey road d enfer]

voltages right here, only does 18  watts,

18 W @20%THD, 25W square-wave, 12W clean...nothing new

 

[fazer]

How does the guitar sound compare to say a tweed deluxe CJ?  I have a project I'm working on.  Also did the transformer rewinds fix issues with the sound and stability in your opinion?

 

[CJ]

those el 84's are known for the "chime" they put on the high end, with that 4700 pf cap across the primary, you lose a lot of that magic, so the new transformer allows for an extended high end compared to the stock setup,

we can wind you a tweed deluxe transformer like the original Triad if you want,

 

[fazer]

I have a standel chassis with el84s and it has a nice transformer . On another subject , I want to build a tweed champ.  How about a transformer for that.

 

[CJ]

tweed champ right here, you could probably roll your own it is so simple>