6SN7 voltages?

[dehughes]

I'm new to the 6SN7, so I'm not sure where voltages should be and I'm wondering what you all have found to be a good range in which to run this tube. Basically, I've replicated the Komet Constellation 6SN7 circuit, albeit with a different power transformer (so the voltages won't be exact, most likely). I have an instinctive feeling that I'm running the tube a bit cold, but then, again, I'm new to the tube so maybe it's just fine.

[Andy Le Blanc]

The design-center max is 450. Any where from 200 to 350, to taste.
The thing to mind is the heater-cathode voltage, you don't want to exceed
100v +/-. So, for cathode followers or srpp you gonna want to elevate the
heater voltage 30 to 50v

[Phil_S]

I've got a pair running as a power section in a PP amp (so, it's like a 4 tube power section). Plate voltage is right up there. As I recall, it's about 440V at idle. I've got two 470 ohm/25uf on each pair of cathodes, to allow me to pull one tube. The amp is a Fenderish front end with TMB, concertina PI, and the PP 6SN7's into a 9K output transformer. Sounds good, too, very clean.

It doesn't take much to push a triode into clipping and then they sound like poo PDQ. At least, that's my opinion.

[dehughes]

Right on. Thanks. I'm running this as V1 in the preamp, so I'm thinking preamp voltages...

[Phil_S]

Oh, in that case, treat it exactly like you'd treat a 12AU7. It is essentially the same tube, but in a big bottle with big plates.

[rhinson]

Right on. Thanks. I'm running this as V1 in the preamp, so I'm thinking preamp voltages...

depends on the b+ rail to that section and the plate/cathode resistor pairs you choose. all things being equal, if you tried to do it like a 12ax7 in standard fashion, it would have much lower plate voltages than the 12ax7 because it's a lower gain/higher current draw tube (like a 12au7). you'll probably need to choose like a 47k- 100k plate and like a 3.3k - 4.7k cathode to get it not to be too low. take a look at the connie and just do it like it does. rh

[dehughes]

Right on. Thanks. I'm running this as V1 in the preamp, so I'm thinking preamp voltages...

depends on the b+ rail to that section and the plate/cathode resistor pairs you choose. all things being equal, if you tried to do it like a 12ax7 in standard fashion, it would have much lower plate voltages than the 12ax7 because it's a lower gain/higher current draw tube (like a 12au7). you'll probably need to choose like a 47k- 100k plate and like a 3.3k - 4.7k cathode to get it not to be too low. take a look at the connie and just do it like it does. rh

Cool. Thanks.

I did it EXACTLY like the Connie, but the thing is I don't know the supply B+. I have a feeling my supply B+ is lower than the Connie's, and that's why my tube seems a bit cold...which would mean that I'd have to lower the dropping resistor, yes?

Also, does anyone have the voltages for the Connie? I have (partial) schematics and lots of pictures, but I don't know the voltages.

[Phil_S]

Maybe the attached will help.

[rhinson]

Right on. Thanks. I'm running this as V1 in the preamp, so I'm thinking preamp voltages...

depends on the b+ rail to that section and the plate/cathode resistor pairs you choose. all things being equal, if you tried to do it like a 12ax7 in standard fashion, it would have much lower plate voltages than the 12ax7 because it's a lower gain/higher current draw tube (like a 12au7). you'll probably need to choose like a 47k- 100k plate and like a 3.3k - 4.7k cathode to get it not to be too low. take a look at the connie and just do it like it does. rh

Cool. Thanks.

I did it EXACTLY like the Connie, but the thing is I don't know the supply B+. I have a feeling my supply B+ is lower than the Connie's, and that's why my tube seems a bit cold...which would mean that I'd have to lower the dropping resistor, yes?

Also, does anyone have the voltages for the Connie? I have (partial) schematics and lots of pictures, but I don't know the voltages.

i believe the main b+ is only in the 300v - 320v range or thereabouts and the droppers fan out in parallel after the screens (jut like vox/matchless, etc.). of the 3 droppers one is 4.7k and the others are either 10k or 20k (can't remember off the top of my head) but i can't remember which goes to which of the 3 sections (ie---6sn7, 12ax7, p.i. 12ax7). just give those values a try and see what you like the best. rh

[dehughes]

Great. Thanks guys! I'll get to it on Wednesday and see what comes of my tinkering...

[dehughes]

So...the plates on my 6SN7 are right at 100 to 110v, which I assume is about normal. A little low, but then this is a high current tube, right, so that makes sense?

The supply voltage right off my PT is 350-ish, which is then kicked down by 1k, 10k, and 10k dropping resistors. I figure this is pretty close to what the Komet would be, though probably actually higher. Again, all values in the 6SN7 circuit are identical to the Constellation, so I'm probably running the tube at a higher voltage, actually. Hmm....

[Phil_S]

100v is not giving you much headroom. If that's what you want, well, OK then. I'd suggest it will sound better (subjective) at 250v.

[dehughes]

100v is not giving you much headroom. If that's what you want, well, OK then. I'd suggest it will sound better (subjective) at 250v.

Really? Even given the Rk (2k7, both triodes) and Ra (100k, both triodes)?

[Phil_S]

You've got me at a disadvantage, as I don't know much about the Comet. I've worked with the 6SN7. It is very much like a 12AU7. It can take a lot of plate voltage. At 100V I think you are not getting the most from this tube, but if that's what the Comet calls for, you should probably leave it alone.

I'm looking at your B+ supply ladder. I think those 10K dropping resistors each probably gobble up 15-20V of B+. You might consider lowering them, as low as 500 ohms. You can simply tack in a small resistor in parallel to see if you like what it does. If you like it, do it right and make it permanent. You don't like it, just remove it.

[dehughes]

You've got me at a disadvantage, as I don't know much about the Comet. I've worked with the 6SN7. It is very much like a 12AU7. It can take a lot of plate voltage. At 100V I think you are not getting the most from this tube, but if that's what the Comet calls for, you should probably leave it alone.

I'm looking at your B+ supply ladder. I think those 10K dropping resistors each probably gobble up 15-20V of B+. You might consider lowering them, as low as 500 ohms. You can simply tack in a small resistor in parallel to see if you like what it does. If you like it, do it right and make it permanent. You don't like it, just remove it.

Wonderful. I'll try tacking some in parallel with the existing dropping resistor and see how that goes. Thanks!

I'll leave the other dropping resistors in place as I want the Brown Deluxe side to stay as it is, so it should be perfect if I can raise the voltage to the Constellation side....