Let's Figure out the PI with Cathode Follower Driver Tube

[mhartman]

Would this work? I worked this up using the values from the SSS #02 schematic that was posted. But, I've never worked with one of these before, so I figured that I would share and look for some input before wiring it up.


****USE AT YOUR OWN RISK -- THIS IS TOTALLY UNCONFIRMED AND PROBABLY DOESN'T WORK***

[boldaslove6789]

AFAIK The driver tube on SSS #2 is a 12ax7 (as is the rest of them), the 12bH7 is whats was used in the Dumble lands and 300SL's I think.... correct me if I'm wrong though.

[mhartman]

AFAIK The driver tube on SSS #2 is a 12ax7 (as is the rest of them), the 12bH7 is whats was used in the Dumble lands and 300SL's I think.... correct me if I'm wrong though.

I've got to be honest, I'm not sure. The schem that I was working from didn't specify. I would think that at least the reverb driver is a 12AT7, but, again, not sure. Does anyone know for sure?

[mhartman]

Greg, this comment from Tony A seems to agree with your comment about the driver tube:

All SSS I know of have the 7025 PI and the 7025 Driver instead of the 12 AU7 and 12BH7 of the Dumblelands

Other than the tube compliment, any comments on the layout?

[talbany]

Greg, this comment from Tony A seems to agree with your comment about the driver tube:

All SSS I know of have the 7025 PI and the 7025 Driver instead of the 12 AU7 and 12BH7 of the Dumblelands

Other than the tube compliment, any comments on the layout?

If you read further into that thread Max was kind enough to add..

The only thing that I would like to add is that AFAIR there's at least one SSS 150W with a 12AU7 PI and a 12BH7 driver.

If you dig around here you will find a hand written schematic and internal shot of Mayers 002..Take the schematic and pics and use some creative imagination and design one up..IMO it's not all that complicated..A 12Au/12Ax/12bh7/ 12at7(current)are all inter changeable so select the one that best suits your tone needs..Just be sure they are balanced and check bias after each change..
BTW..the cathode resistors on the 02 schematic are labled 1k..These should be 100k at min 5w
Good Luck!!

Tony

[dcribbs1412]

Looks great...any reason not to use a (250k) trimmer in place of the 130k resistor?
nice work mhartman

Darin

[mhartman]

Thanks guys!

Tony, your message was a huge help. I didn't realize that that picture and schem corresponded to one another. I guess I'll be staring at that pic and schem until I get it!

[Stratoblaster]

Would this work? I worked this up using the values from the SSS #02 schematic that was posted. But, I've never worked with one of these before, so I figured that I would share and look for some input before wiring it up.

I tried this driver circuit from SSS #002 but had no luck with it. Output tubes would red plate fairlyquickly. I eventually gave up on it & used the circuit posted here
http://ampgarage.com/forum/viewtopic.ph ... c&start=75
Labeled SSS #004 which seemingly works fine. 7025s work properly.
There are comments on that post that agree on 7025. I got this to work with
both 6550s & 6L6s with relevant bias changes.
Though I wish I knew more about the basic design mathmatics behind it

Cheers Mark

[boldaslove6789]

Would this work? I worked this up using the values from the SSS #02 schematic that was posted. But, I've never worked with one of these before, so I figured that I would share and look for some input before wiring it up.

I tried this driver circuit from SSS #002 but had no luck with it. Output tubes would red plate fairlyquickly. I eventually gave up on it & used the circuit posted here
http://ampgarage.com/forum/viewtopic.ph ... c&start=75
Labeled SSS #004 which seemingly works fine. 7025s work properly.
There are comments on that post that agree on 7025. I got this to work with
both 6550s & 6L6s with relevant bias changes.
Though I wish I knew more about the basic design mathmatics behind it

Cheers Mark

I think that Schemo is labeled wrong, #4 doesn't have the CF Driver tube (only has a standard dumble PI)

[mhartman]

I think that Schemo is labeled wrong, #4 doesn't have the CF Driver tube (only has a standard dumble PI)

Agreed. SSS#4 is setup differently. I think that that schem is actually for SSS#1, which has tremelo and a CF Driver.

@Stratoblaster: Thank you! You've saved me some time redplating and swearing. I'll focus more on the schem that you referenced. By the way, do you know what "-VBias" voltage you are feeding into the bias adjust pot?

Thanks again guys!

[mhartman]

So, I'm thinking something like this (see attached, full pic located here: http://ampgarage.com/forum/download/file.php?id=22326 ). Anyone stared at this one long enough to know if I've got it right/wrong?

Edit: The bias is labled a bit wrong -- it goes to the bias adjust pot, not straight in from -VBias. Also, the ground/accept switch lead is coming off the wrong side of the 100R resistor (the .01uf on the switch should parallel the 100R to ground when the switch is closed).

[Stratoblaster]

I think that Schemo is labeled wrong, #4 doesn't have the CF Driver tube (only has a standard dumble PI)

Agreed. SSS#4 is setup differently. I think that that schem is actually for SSS#1, which has tremelo and a CF Driver.

@Stratoblaster: Thank you! You've saved me some time redplating and swearing. I'll focus more on the schem that you referenced. By the way, do you know what "-VBias" voltage you are feeding into the bias adjust pot?

Thanks again guys!

Ive been tooling around using my dirty old S/F Fender Bassman and Australian made Eminar (not Enimar ).Trying out different ideas as sort of an on going thing. Here it is in action before I changed to CF Driver. http://www.youtube.com/watch?v=U5FP-w4CDlQ

Lazily I just used the stock Fender Bias supply values & 10k pot. I got about -71 volts at -V Bias and correct voltage for 6L6 , about -52 volts. Changing the 27k resistor to around 47k for 6550s.
It all seems to work perfectly ok but I dont know if it is running as it should be.

I havent used any high wattage resistors for the moment & Ive had no problem with any of them even getting warm???? though I expected it from what Ive read. Maybey failure is just around the corner

I myself dont know enough behind the design concepts of this circuit
so I cant really verify that what I have is "correct" though it sounds & works perfectly fine.
I hope it helps some.

[mhartman]

Thanks Stratoblaster! I've got some experimenting to do - I appreciate you giving me the benefit of your experience with yours!