your opinions on preamp tubes

[blandman74]

I'm planning a new project -- a preamp using vacuum tubes I've got in a box.  I have a bunch of tubes, and I want to make it a three-channel preamp based on different preamp tubes.  The key is to get a sound that's different from the "usual" 12AX7. Which ones should I use?

6SL7
6SN7
6AU6
12AU7
12AT7

I'm leaning toward making one of them a 6SN7, cause I got quite a few.  I'm also willing to buy some other tubes -- I'm off to a hamfest in Bal'mer in late July. Thanks!

[Paul Marossy]

I have heard that the 6AU6 sounds cool.
IMO, the 12AU7 and 12AT7 are more or less like a 12AX7, but with lower gain factors.
Don't know anyhting about the other two tubes you listed.

[Lonestarjohnny]

Good Idea, The 12 stuff has been Beat to death if you know what I mean, You should stick with the octal's for a sound your not use to hearing, you might be very pleased with what you hear, there are a good selection of octal's also, 6SK7, 6SL7, 6SH7, 6SJ7,
there are more and I would be glad to donate the tube's you choose to use for your project, I have quite a selection of these tube's.
Just let me know, I would be glad to help you on this.
JD

[blandman74]

I forgot to say I'll be using an old 6X5 rectifier as well....

In light of the fact that the 6X5 is octal, I think I *will* go all-octal.  The 6AU6 is tempting, but more as a teeny-tiny power amp tube that I could overdrive.  JD, what are your opinions of the 6SK7 and 6SH7 tubes?  The 6SL7s and 6SN7s I think were used in old Fender amps, and others, before they moved to 12AX7s (I assume because of cost).  The word on those octals is they're "smoother" without the midrange cut of the 12AX7s. Is that true about the others?

I'm sure I could find something to swap with you for a few of those old octals.  Maybe I could post a few sound samples to taste-test the various tubes....

[Lonestarjohnny]

I think it would make for a great thread, and very educational for some of the younger people on here that may have not seen or heard this part of Tube History, Beside's that, as Smart as some of the young generation is, who know's, maybe you'll hit on somethin new.
and Yes, there are some neat thing's about the octal's that are worth dicussing, the Smooth Mid's, The high's are'nt piercing like some of the 12 V. family of tube's and a good strong bottom end, Might just be the thing for some of these Drop Tuner's to experiment with.
I know they sound good with different pedal combination's, and for some good idea's just look back at some of the amp's that used these, one of the best sounding low powered amp's I own is an old Vega 1X15 combo, it has an octal pre/amp and it's ver touch sinsitive. has great tone.
some idea's to hash around, an octal in a tube driver, an octal in a Tube O Vibe, there are all kinds of thing's like this that no one has even touched on.
JD

[Paul Marossy]

Octal tubes would probably sound great in a stompbox. The only disadvantage (if you want to call it that) is that octal tubes are quite a bit larger than a 12____ preamp tube. So that means bigger enclosures and probably a higher plate voltage, too. Then you will end up with something that is comparable to a Matchless Hot Box in size and complexity. Not saying that is bad, just pointing that out...  

[Lonestarjohnny]

You know what they say down here in Texas, " Bigger Is Better " LOL !
:wink:
JD

[blandman74]

Vega huh.  Any ida what the preamp schematic looks like?  Couldn't track it down via google

[Lonestarjohnny]

It's a Valco, Chicago 51 amp, Supro,National,Valco,Vega, and a bunch of other little amp's made for Sear's, Montgomery ward's, and a lot of other retail outlets, look under Valco, if you find nodda, just shout, I may have somethin here you can use.
JD

[Mike Nichting]

I have alot of the 6SN7 and 6SL7 GE tubes myself. How could I connect one to the Tube Driver I working on?? Would I have to change the entire circuit to use an Octal tube??

 I have a schematic for an Octal tube amp as well.

Peace,
Mike N.

[Peter Snowberg]

The 6SN7 has two triodes that are VERY similar to a 12AU7 while the 6SL7 is very similar to a big 12AT7.

Look up the pinouts using TDSL Personal Edition at http://www.duncanamps.com and you can substitute the connections easily. The only thing to watch for is the fillament since the 6Sx7 tubes run on 6.3V. Sometimes you can just wire fillaments for two tubes in series if you're running from 12V but keep in mind that a 6SN7 draws 600mA for the heater while the 6SL7 only draws 300mA so you can't make a series connection of these two tube heaters.

In my very general experience, the larger the plates (to a degree) the better the sound can be and the less nasal the tone when overdriven.

Take care,
-Peter

[blandman74]

God, I should be working right now .....

You probably couldn't swap the tubes, even if the socket size and pinout were identical to whatever you presently have in the tube driver, because you would want to bias each tube properly.  Assuming it's a cathode bias voltage amp you would have to make sure, at the very least, you've got a cathode resistor that does not drive the 6SN7 ot 6SL7 into saturation, or otherwise clip the signal. (Although I guess you could want that for some hard clipping, right?)

Probably, tubes that are considered "high-gain" are fairly interchangeable; those  that are "medium-gain" are probably interchangeable.  You just get different sounds.

But the short answer is, yes, to switch from 9-pin to octal, you'd have to make a few changes to the actual circuit.  Me, I'm gonna keep it all-octal, mostly for looks as well as tone.

[Arn C.]

I like the sound I get from 6SN7 and 6SL7.   I think they are much smoother in sound.  Great for playing blues.   I made the Tube Driver with 6SN7, 6SL7 and 6CG7 and I put a switch in to switch between them.

Peace!
Arn C.

[Mike Nichting]

Hey Arn can you send me some info on what you did to get the 6SL7,6SN7 to work??
I would very much appreciate it~!!!

Peace,
Mike N.
NUKLHED