Tube Help Needed

[rplace]

One channel on my NOSValves modded MK IIIs was not working. I gave it the once over and one tube was glowing a brilliant purple. It was actually quite pretty. I swaped it out for the same tube in the working amp and all was good. So I guess I have a bad tube. I am a know-nothing-tube-guy. I use them, but don't know much about the details.

I am pretty sure it is the 5AR4/GZ34 tube. There are two small ones on the circut board thingy, two that are huge and look alike (KT88???) and the bad one in question (sort of medium sized). Does this sound right? The bad one looks pretty old so I am guessing it was nice. It is marked Sylvania GT. Brittian, made in England and tested in U.S.A. I can't read any numbers on it.

So now the questions:
1. Is this the 5AR4/GZ34?
2. Do I need to replace them in pairs? i.e. get two and replace the good one on the other amp?
3. If I need to shop around and get a killer pair where can I get a quick cheap one to get me up and running? Are these the type I might be able to get at a guitar shop or something like that?
4. What else do I need to do?

[garymd]

Rich,

That's your rectifier tube. I have a spare you can borrow until you get a pair. Call me tomorrow anytime and we'll work out a time to meet.

Too bad. Those Mullards are expensive!

BTW - You can get a new pair cheap. They don't have much if any impact on the sound although some will argue that point.

[rplace]

Wow Gary, that is great. I have long time friends coming into town this weekend that have never seen my new room/system. I'll give you a yell later.

Thanks man!

[paully]

Consider buying Japanese made rectifiers (www.upscaleaudio.com has

some). They are half the price and pretty close to full

performance. The rectifiers matter, why I don't know, but they

do. Mullards ($100 a pop) are regarded as the best, but I would

avoid the JJ and Sovtek varieties if you can afford NOS.

[anarchist]

Mullards are the only way to go IMO.

Vintage Tube Services provides fantastic tubes at great prices which are fully tested. You get buy Andy's Perfect Picks (used tubes rather than true NOS) if you don't want to spend the money on NOS. Great guy and beyond knowledgeable on NOS tubes. Website is a bit quirky and requires more navigation than should be required - find the phone number and just call him.

Oh yeah, how do I know? I have upgraded Dynaco's and am running NOS Mullards GZ-34's, NOS RCA 12BH7's and NOS GE 5 Star 5751's.

[paully]

I won't argue the point too strongly as I upgraded my Dynaco as well

and put in a Mullard GZ34 in place of a JJ. Massive improvement,

and not subtle. I was stunned. So if you can afford

Mullard, I say more power to you (no pun intended). They are the

best (never heard Amperex or any of the truly expensive ones

though). I put mine in 5-7 years ago and fully expect it to run

another 5-7 so you do have to look at the value proposition, in the

long run Mullard are cheaper. But I would also recommend for

those that want an even cheaper option to take a look at the Matsushita

5AR4. I have a couple and my opinion is that they are also a very

good value at $45 a pop.

[jcmusic]

I second Vintage Tube Services Andy is a great guy and knows what he's talking about, a little slow sometime but worth the wait.

Jay

[stringmun1]

I haven't tried the Mullard 5AR4, but I recently installed a NIB 1964 Amperex Bugle Boy (treble clef) in my Quicksilver Full-Function preamp with marvelous results.

Hal