Dual supply...

slideman82 · 3rd February 2009, 01:15 AM

... in a tube preamp... So, I do it as with single supply, or do I have to trim some bias to grids? Thanks!

Iain McNeill · 3rd February 2009, 01:43 AM

Can you post a schematic of your pre-amp?

You don't give us enough information

slideman82 · 3rd February 2009, 10:53 PM

Well, it will be like any guitar amp preamp, but I want to build some hybrid, so, with SS output, I have dual supply, 50Vdc, and I have a couple of 6SN7 and a pair of ECC84 (yes, I know, they're not for audio purposes...) and I wanted to make them work with that supply, not just single 50V dc... would be like the old-style marshall preamp, like plexis.

slideman82 · 5th February 2009, 10:32 PM

So, anyone?

makeb4break · 5th February 2009, 10:43 PM

6SN7 does not compute at those voltages, well maybe they do, but they don't sound good. ECC88 types would be better and could probably be run of a split rail if you like

however, since it's for a guitar amp, you might like the distortion and limited swing a 6SN7 with a low B+ will give. i'd forget about curves and such and just throw a 10k on the plate and a 1k on the cat and take it from there

i've never seen any old style amp run off anything like 50V, btw

cheers,

mb4b

wakibaki · 5th February 2009, 10:55 PM

2 posts, you still don't give us enough information. This is plain rude.

Post something sensible, like a drawing, since you obviously got no talent for explanation.

No wonder you not getting any replies.

w

slideman82 · 6th February 2009, 01:12 AM

That was kinda rude, wakibaki, it's pretty simple!

2 or 3 triodes stage, b+ to resistor to plates, cathode to resistor to b-, and don't know what I can do with grids! 6SN7 are pretty linear, so, make them work with 100V would make them distort easily, right?

I could use some trimmer as plate resistors... maybe...

Ok, I'll post some drawing later.

Iain McNeill · 6th February 2009, 01:44 AM

Oh! I see. You're trying to run a tube amp off your dual 50V power supply.

Putting the two outputs in series would give you 100V to work with. I would ignore ±50 with a 0V tap and just think of it a 0V and +100V.

Can you make a tube preamp work on 100V? I'm sure the answer is yes. Someone else is probably better able to suggest designs than me.

wakibaki · 6th February 2009, 08:39 AM

I'd go for something like this:-

You can steal the tonestack values from a fender champ, the data is for 6sn7, 90V is close enough.

w

slideman82 · 6th February 2009, 12:22 PM

Great data! The fact is I want to use a mosfet power amp, with 50V dual suply, and that's why I wanted to use dual supply! Tubes can run with lower voltages... they just become less linear...

Thanks!

3rd February 2009, 01:15 AM	#1
slideman82 diyAudio Member Join Date: Oct 2007	Dual supply... ... in a tube preamp... So, I do it as with single supply, or do I have to trim some bias to grids? Thanks!

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3rd February 2009, 01:43 AM	#2
Iain McNeill diyAudio Moderator Join Date: Oct 2007 Location: Santa Cruz, California	Can you post a schematic of your pre-amp? You don't give us enough information

3rd February 2009, 10:53 PM	#3
slideman82 diyAudio Member Join Date: Oct 2007	Well, it will be like any guitar amp preamp, but I want to build some hybrid, so, with SS output, I have dual supply, 50Vdc, and I have a couple of 6SN7 and a pair of ECC84 (yes, I know, they're not for audio purposes...) and I wanted to make them work with that supply, not just single 50V dc... would be like the old-style marshall preamp, like plexis.

5th February 2009, 10:32 PM	#4
slideman82 diyAudio Member Join Date: Oct 2007	So, anyone?

5th February 2009, 10:43 PM	#5
makeb4break diyAudio Member Join Date: Jan 2009	6SN7 does not compute at those voltages, well maybe they do, but they don't sound good. ECC88 types would be better and could probably be run of a split rail if you like however, since it's for a guitar amp, you might like the distortion and limited swing a 6SN7 with a low B+ will give. i'd forget about curves and such and just throw a 10k on the plate and a 1k on the cat and take it from there i've never seen any old style amp run off anything like 50V, btw cheers, mb4b

5th February 2009, 10:55 PM	#6
wakibaki Banned Join Date: Jan 2008 Blog Entries: 2	2 posts, you still don't give us enough information. This is plain rude. Post something sensible, like a drawing, since you obviously got no talent for explanation. No wonder you not getting any replies. w

6th February 2009, 01:12 AM	#7
slideman82 diyAudio Member Join Date: Oct 2007	That was kinda rude, wakibaki, it's pretty simple! 2 or 3 triodes stage, b+ to resistor to plates, cathode to resistor to b-, and don't know what I can do with grids! 6SN7 are pretty linear, so, make them work with 100V would make them distort easily, right? I could use some trimmer as plate resistors... maybe... Ok, I'll post some drawing later.

6th February 2009, 01:44 AM	#8
Iain McNeill diyAudio Moderator Join Date: Oct 2007 Location: Santa Cruz, California	Oh! I see. You're trying to run a tube amp off your dual 50V power supply. Putting the two outputs in series would give you 100V to work with. I would ignore ±50 with a 0V tap and just think of it a 0V and +100V. Can you make a tube preamp work on 100V? I'm sure the answer is yes. Someone else is probably better able to suggest designs than me.

6th February 2009, 08:39 AM	#9
wakibaki Banned Join Date: Jan 2008 Blog Entries: 2	I'd go for something like this:- You can steal the tonestack values from a fender champ, the data is for 6sn7, 90V is close enough. w

6th February 2009, 12:22 PM	#10
slideman82 diyAudio Member Join Date: Oct 2007	Great data! The fact is I want to use a mosfet power amp, with 50V dual suply, and that's why I wanted to use dual supply! Tubes can run with lower voltages... they just become less linear... Thanks!

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