EL84 Tube Shoot Out/ Rocket

[Bruciep07]

I picked up (10) 6P14P-EB's for $20 without boxes sometime last year, figured I'd be able to at least get a matched pair out of them. If nothing else they'll make great start up tubes if I ever get this rocket build going... Anyone wanna test some tubes for me?
Bruce

[DustyBadlands]

I think I read some where that KF wasn't big on matching the tubes. Gave the amp some mojo or something. I could be wrong. Anyone know about this? Db

[redshark]

Uhmm that is one of the urban myths I don't believe. I don't think Ken used unbalanced tubes for mojo. I believe he used diferent brands in the preamp until he got the best sound but I think his power tubes were all a close match.

[RJ Guitars]

There is a thread running somewhere else on TAG recently where they discuss the virtues of mismatched tubes. I have read and heard of Ken Fischer being a tube swapping maniac but not any real discussion on whether the output tubes were matched up or not.

I have one experience where I replaced a matched set of JJ's in a Pro Junior with a couple unmatched (different brands even) Old Stock tubes and the amp sounded really great after I made the swap. I was never sure if this meant that the JJ's really sucked or the random matchup of the other two was touched with a bit of Mojo.

I do think that Pro Juniors are great sounding amps especially for $300 and you can carry them with one hand.

rj

[dartanion]

Uhmm that is one of the urban myths I don't believe. I don't think Ken used unbalanced tubes for mojo. I believe he used diferent brands in the preamp until he got the best sound but I think his power tubes were all a close match.

I believe we are talking about mismatched power tubes, and there is merit to having slightly mismatched tubes as it adds complexity. Having nuts on matched power tubes can sound a bit sterile. Great in a HiFi amp, not super desirable in a guitar amp, but again it's preferential.

Differing brands of preamp tubes is almost necessary to find ones that work well in a Wreck. V1 is a pain to find good tubes to place there, so I don't care if it's NOS, used, or new prod. If the tube is low noise, non-microphonic, and sound good, then I use it.

[redshark]

I agree with the pro jrs. being good sounding cheap amps. Those amps always make me think...if you can get a good sounding amp with everything wrong on them, cheap tubes, cheap trannys, cheap caps, cheap pcb how would it sound if the amp was re designed with good stuff, better layout, better components....
Maybe an experiment worth trying...."the wrecked jr."
Use aluminum chassis, solid core wire, etc, etc and make it a 1x12 combo with a celestion blue in a birch cabinet.

[Cliff Schecht]

Perfectly matching the output tubes will dramatically cut down that great sounding power amp 2nd harmonic distortion. This is great for hi-fi amps but is actually undesirable for guitar amps. This is why I don't waste my money on burned in tubes, it's not necessary or even desirable for guitar amps. The fact that tubes drift over time is a good thing.

[wicker]

I picked up (10) 6P14P-EB's for $20 without boxes sometime last year, figured I'd be able to at least get a matched pair out of them. If nothing else they'll make great start up tubes if I ever get this rocket build going... Anyone wanna test some tubes for me?
Bruce

Don't be shocked if you don't. Russian tubes (NOS) have tendency to have really different parameters between the same type of tube. But it is of course chance that you will find some pairs or quad. I had some time ago a perfect quad od 6P14P-EB, I needed cash so I sold it, damn, now I regret that.

As for matching tubes, I think that in guitar tube amp differences up to 10% are acceptable .

[dartanion]

I agree with the pro jrs. being good sounding cheap amps. Those amps always make me think...if you can get a good sounding amp with everything wrong on them, cheap tubes, cheap trannys, cheap caps, cheap pcb how would it sound if the amp was re designed with good stuff, better layout, better components....
Maybe an experiment worth trying...."the wrecked jr."
Use aluminum chassis, solid core wire, etc, etc and make it a 1x12 combo with a celestion blue in a birch cabinet.

You mean something like this:

http://www.youtube.com/watch?v=vNgZHJXxJI4

Although this uses 6SL7s and 6V6s and retained the original chassis. Everything else was gutted.

[redshark]

Something like that, I'm sure it sounds better in person that in youtube format video. Very nice, I would like to still leave the el84's and the 12ax7's. Why not use a long tail PI? what does the pro jr uses? Also I would like a bigger cab and a 1x12 but yes, this is a good example. Great Job!!!!

[dartanion]

Something like that, I'm sure it sounds better in person that in youtube format video. Very nice, I would like to still leave the el84's and the 12ax7's. Why not use a long tail PI? what does the pro jr uses? Also I would like a bigger cab and a 1x12 but yes, this is a good example. Great Job!!!!

The original chassis socket holes are too big for noval sockets, but octals popped right in without fuss. The noval sockets were mounted on a pcb and not to chassis, they just stick through the holes. I used a concertina PI for 2 reasons, one is that I only had 4 socket holes in the chassis, the other is that this thing is tiny and to keep things under control, a low gain approach was taken. It's hard enough to get a full blown Express/Liverpool to be stable in head morphology, so trying to cram that into a Pro Jr. chassis Not easy. So, low gain approach. 6SL7s in V1 and V2 with DC filaments, with V2b used as the concertina PI, which is a zero gain affair. Anyway, that recording was done off the cuff with a crappy camera and it's built in microphone. In person, that little thing is a beast. The client I built it for loves it. Small, but packs a wallop!

I would have kept the EL84s if it were not for how the Pro Jr is built. Really flimsy pcbs and the chassis is not so great either, so I would have had to make an adapter plate to mount the sockets on that bolts to the chassis. More work that it was worth since octals dropped right in. I just had to drill 8 holes for the mounting screws.

[redshark]

What I meant Dartanion by redesigning the amp was to use the schematic of the pro jr. as a starting point but use diferent chassis, layout and components, not actually use an original amp.
I'm not an experienced builder by any means but I have my own philosophy about amps and it could be a great challenge to reengineer the amp and probably voice it a little bit better considering that the size of the cabinet, the better wood and a 12" speaker would demand to tweak certain values to compensate for the changes.

[Bruciep07]

I picked up (10) 6P14P-EB's for $20 without boxes sometime last year, figured I'd be able to at least get a matched pair out of them. If nothing else they'll make great start up tubes if I ever get this rocket build going... Anyone wanna test some tubes for me?
Bruce

Don't be shocked if you don't. Russian tubes (NOS) have tendency to have really different parameters between the same type of tube. But it is of course chance that you will find some pairs or quad. I had some time ago a perfect quad od 6P14P-EB, I needed cash so I sold it, damn, now I regret that.

As for matching tubes, I think that in guitar tube amp differences up to 10% are acceptable .

Like I said, for $20, even if I have 10 start up tubes, I'm happy... I'd still like to have them tested just to see what I can get out of them, you never know... There was a guy down in florida that was gonna do it for me for a couple bucks a tube but he stopped responding to emails when school started again...

[dartanion]

What I meant Dartanion by redesigning the amp was to use the schematic of the pro jr. as a starting point but use diferent chassis, layout and components, not actually use an original amp.
I'm not an experienced builder by any means but I have my own philosophy about amps and it could be a great challenge to reengineer the amp and probably voice it a little bit better considering that the size of the cabinet, the better wood and a 12" speaker would demand to tweak certain values to compensate for the changes.

The better Pro Jr. is an 18watt Lite IIb.

[mlp-mx6]

I put a Wreck-ish circuit in a Blues Jr. for a friend. It rocked hard. It was great fun, and easy to carry. I had to build a circuit card to hold the noval sockets, because as mentioned the holes in the chassis were too big. Other than that, the build was no big deal. I took the control taps from the PT (brown wires, IIRC) and made a bias circuit from those. Worked fine. That amp with a Tele was magic.