Tooooobs...choices...

[FrankenFretter]

I'm thinking about re-tubing my Vox Night Train, and I have a couple options: I can get JJs from Eurotubes, or I can get some NOS tubes from a guy I met through work that may have some Mullards and such. What would you do in my situation? The vintage tube guy is willing to let me borrow several brands to try out, and just return the ones I don't want. I don't know what all he has, and to be honest, other than Mullard, RCA, Zenith, Sylvania and GE, I wouldn't know what might sound nice and vintage-y in the Vox.

Comments? Suggestions?

 

[oldguy]

It's always fun to experiment w/ different tubes. If your amph doesn't require re-biasing w/ a tube change, I'd say try some of those NOS in there and see if you can hear a difference.
As long as you know how to change to them and there's no re-bias required you should be OK. Be careful w/ the pins when putting the tubes back in the socket.
OTOH, I've changed tubes around in my little Valve Jr. just to see if there was a difference, and other than lower gain tubes (12AT-7 in place of 12AX-7) I didn't see a huge difference. I did find one power tube that was screechy and didn't translate the guitar sound well at all, but I think it was microphonic. With good tubes the VJ sounded pretty much the same.

So that was an afternoon I would've been better off practicing, not screwing around with tubes.
Half a day working on new licks and technique would've done way more for my toans.........."sighs".........

 

[Algonquin]

So that was an afternoon I would've been better off practicing, not screwing around with tubes.
Half a day working on new licks and technique would've done way more for my toans.........."sighs".........

I think this advise holds true for many sitiations we've all been in. Golfers have it as bad (or worse) when it comes to chasing equipment that will help their game.

 

[ZMAN]

If you had any glassiness or microphonics with the old tubes, you probably won't with the NOS. They were built better period.
If you know what tubes he has you can usually go online and get a description of how they will effect the tone.
My local tube guy is really good. He has deiscriptions of what they will do for your sound. Those are with the new tubes though.

 

[oldguy]

I think this advise holds true for many sitiations we've all been in. Golfers have it as bad (or worse) when it comes to chasing equipment that will help their game.

Are you a golfer, David?

 

[piebaldpython]

I think this advise holds true for many sitiations we've all been in. Golfers have it as bad (or worse) when it comes to chasing equipment that will help their game.

Yeah....sad to say.....but this is true too......balls....clubs.....and worst of all, a myriad of different grips and swing theories to forever complicate the issue and render the golfer, damn near impotent out on the golf course. UGH!!!!

 

[otaypanky]

I'd call Bob.

 

[FrankenFretter]

I'd call Bob.

Yeah, I decided to order the power tubes from Bob (Eurotubes). I may play with some vintage ECC83s still, but the power stage is now covered.

 

[tunghaichuan]

You're better off using new production tubes for new amps. NOS tubes can sound great, but in the past there have been problems with NOS EL84s due to slightly different pinouts. There may not be a problem, but just to be safe, it is a good idea to use only new production tubes where EL84s are concerned, unless you know for a fact that there will be no pinout problems.

 

[FrankenFretter]

You're better off using new production tubes for new amps. NOS tubes can sound great, but in the past there have been problems with NOS EL84s due to slightly different pinouts. There may not be a problem, but just to be safe, it is a good idea to use only new production tubes where EL84s are concerned, unless you know for a fact that there will be no pinout problems.

Thanks, Tung. I guess ordering the power valves from Euro was the right choice, then. From what I've read, there's no biasing to be done when replacing these in the NT. Interestingly, what would normally be the V1 position is the V3 position on the NT. Is it just the first 12AX7 I should be tinkering with, or does the PI tube have much to do with the gain/tone? I'm not terribly knowledgeable when it comes to this stuff, and most of what I've learned has been here.

 

[tunghaichuan]

Thanks, Tung. I guess ordering the power valves from Euro was the right choice, then. From what I've read, there's no biasing to be done when replacing these in the NT. Interestingly, what would normally be the V1 position is the V3 position on the NT. Is it just the first 12AX7 I should be tinkering with, or does the PI tube have much to do with the gain/tone? I'm not terribly knowledgeable when it comes to this stuff, and most of what I've learned has been here.

There was an amp made a few years ago called the Lexicon Signature 284. It was based on a MacIntyre amp. The Lexicon used a PCB, but the amp couldn't use some NOS EL84s due to a slightly different pinout. I'm not sure if the NT would be affected, but it is a good thing to think about when replacing tubes.

As far as the PI goes, it depends what type it is. This site has the NT schematic:

http://www.prowessamplifiers.com/schematics/Vox/Night_Train-5.75_Watts_Triode_13_Watts_Pentode..html

The PI in your amp is the Cathodyne type, that is one triode of the 12AX7 is used to split the signal and the preceding triode is used as a gain stage. The plate drives one EL84 and the cathode drives the other. This is in contrast to the Schmitt/LTP type PI which uses both triodes. Each triode's plate drives a power tube in that type of PI. Generally the Schmitt/LTP type is used in higher wattage amps as the Cathodyne has difficulty driving larger power tubes (EL34, 6L6, 6550) to full power. Historically the Cathodyne type is used in lower power push pull amps using EL84s (as they are especially easy to drive) and 6V6s. For example the Fender tweed Deluxe and Black Face Princeton Reverb amp both use the Cathodyne PI and put out about 12W each. The Black Face Deluxe Reverb uses the Schmitt/LPT type and puts out about 18-20watts, although to be fair the BF DR uses higher plate voltages to boost the wattage, but the Scmitt/LTP type PI does contribute.

So bottom line, you can basically stick an working 12AX7 in the PI slot in your amp. And don't be taken in by "matched triodes." It makes no difference in the Cathodyne PI.

 

[FrankenFretter]

There was an amp made a few years ago called the Lexicon Signature 284. It was based on a MacIntyre amp. The Lexicon used a PCB, but the amp couldn't use some NOS EL84s due to a slightly different pinout. I'm not sure if the NT would be affected, but it is a good thing to think about when replacing tubes.

As far as the PI goes, it depends what type it is. This site has the NT schematic:

http://www.prowessamplifiers.com/schematics/Vox/Night_Train-5.75_Watts_Triode_13_Watts_Pentode..html

The PI in your amp is the Cathodyne type, that is one triode of the 12AX7 is used to split the signal and the preceding triode is used as a gain stage. The plate drives one EL84 and the cathode drives the other. This is in contrast to the Schmitt/LTP type PI which uses both triodes. Each triode's plate drives a power tube in that type of PI. Generally the Schmitt/LTP type is used in higher wattage amps as the Cathodyne has difficulty driving larger power tubes (EL34, 6L6, 6550) to full power. Historically the Cathodyne type is used in lower power push pull amps using EL84s (as they are especially easy to drive) and 6V6s. For example the Fender tweed Deluxe and Black Face Princeton Reverb amp both use the Cathodyne PI and put out about 12W each. The Black Face Deluxe Reverb uses the Schmitt/LPT type and puts out about 18-20watts, although to be fair the BF DR uses higher plate voltages to boost the wattage, but the Scmitt/LTP type PI does contribute.

So bottom line, you can basically stick an working 12AX7 in the PI slot in your amp. And don't be taken in by "matched triodes." It makes no difference in the Cathodyne PI.

Thanks, Tung. I haven't tried to read a schematic since high school, but I'll have a gander. I know the trannys are supposed to be overbuilt.

Glad you pointed out the thing about matched triodes, because I was wondering about that. What about "current balanced"?

 

[FrankenFretter]

Well, the JJs came a few days ago, and they're in place. It seems to have given the NT more throat, if that makes any sense. Could be the power of suggestion, but I think it sounds better. I'll try calling the vintage tube guy tomorrow to see what he's got on hand in the way of ECC83s.

 

[tunghaichuan]

Well, the JJs came a few days ago, and they're in place. It seems to have given the NT more throat, if that makes any sense. Could be the power of suggestion, but I think it sounds better. I'll try calling the vintage tube guy tomorrow to see what he's got on hand in the way of ECC83s.

If you don't mind my asking, what tubes were in the amp originally?

 

[FrankenFretter]

If you don't mind my asking, what tubes were in the amp originally?

They were Sovtecs. I'm assuming the preamp tubes are the same brand, although I haven't pulled them to look.

 

[tunghaichuan]

They were Sovtecs. I'm assuming the preamp tubes are the same brand, although I haven't pulled them to look.

In my experience, JJ EL84s are an improvement over Sovtek EL84s. Not that the Sovteks are bad sounding tubes, but the JJs do sound better, IMHO.

 

[FrankenFretter]

In my experience, JJ EL84s are an improvement over Sovtek EL84s. Not that the Sovteks are bad sounding tubes, but the JJs do sound better, IMHO.

Then maybe it's not just the power of suggestion. The amph just seems more...alive. Does that make sense?

 

[NWBasser]

Then maybe it's not just the power of suggestion. The amph just seems more...alive. Does that make sense?

That's consistent with my JJ EL84 experience on my H&K.