matching triodes

I wanted to buy some 12DW7 tubes for my ST-35, and the company that had what I wanted (Antique Electronic Supply), told me that they don't match triodes. I know some companies claim that it doesn't matter, but I've found that it does. I got a pair of JJ's from one company and a pair of EH's from another and discovered that my readings between channels was almost perfect for the JJ's and out-of-whack for the EH's. Maybe the JJ's were matched, or maybe they weren't, and I just lucked out.

 Does anyone know of a vendor who, first of all handles this particular tube, and secondly, would match them? I'm looking at GE and Philips which Antique Electronic Supply has, but don't match. Or maybe even RCA if not ultra expensive.

Captain Coconut wrote:I wanted to buy some 12DW7 tubes for my ST-35, and the company that had what I wanted (Antique Electronic Supply), told me that they don't match triodes. I know some companies claim that it doesn't matter, but I've found that it does. I got a pair of JJ's from one company and a pair of EH's from another and discovered that my readings between channels was almost perfect for the JJ's and out-of-whack for the EH's. Maybe the JJ's were matched, or maybe they weren't, and I just lucked out.

 Does anyone know of a vendor who, first of all handles this particular tube, and secondly, would match them? I'm looking at GE and Philips which Antique Electronic Supply has, but don't match. Or maybe even RCA if not ultra expensive.

12DW7 is 2 dissimilar triodes, thus matching a singular 121DW7 is not possible.
One can however select 2 12DW7 from a batch to get 2 tubes with simular properties.
The JJ 12DW7 is usually quite close to spec in my experience, chances are that two randomly
choosen JJ 12DW7 ( or ECC832 as they call it)  will perform equally well.
I do sell these, but i have no routines for selling to us.

( I could use a PA522 transformer for dynaco PAS-3, if you have one we could switch gifts :-)

Upscale doesn't handle this tube and Jim didn't have any the last time I checked with him. I'll check e-bay.

Look for the industrial tube type 7247, too.

Might not help a whole lot, because if anything they are less common than NOS 12DW7.

EICO liked using the 12DW7. I don't remember who they sourced them from, but many of
the originals supplied by EICO had microphonic problems.

Small triodes, 2 tubes in one case, are individually cathode resistor biosed for each half so they can be different and still sound the same in the circuit. Like individually biosing all four output tubes. The one exception is in a long tailed pair used for splitting a signal in some but not all driver stages. In that case both halves use the same cathode resistor so matched halves is very desirable.
Oh, I guess 2 exceptions, also when the 2 halves are different such as the 12DW7. In the case of the 12DW7 one side is a 12AX7 equivalent, and the other side is a 12AU7 equivalent. If both sides are equal then you would have a major problem with that tube. What is really special about the 12DW7 is you get maximum gain for a triode in the first stage [12AX7] while getting lower impedance miss match in the second or splitter stage [12AU7]. For those who don't know, when you split a signal with one tube section, which is common in EL84 amps, the plate half has a higher impedance than the cathode half. This is many time worse if you use a 12AX7 to do the splitting in stead of a 12AU7. That is why I have a problem with most of the new EL84 amps out there with there "improved circuits" . All that I have seen use a 12AX7 for the splitting. This miss match does not apply to a long tailed pair as the split signal comes of the plates of the two sections.

I would suggest, in addition to Jim McShane, Andy Bowman at Vintage Tube Services
http://vintagetubeservices.com/page23.html
Call Andy, don't email him. He hates emails. Very pleasant chap to deal with.

Captain Coconut wrote:Upscale doesn't handle this tube and Jim didn't have any the last time I checked with him. I'll check e-bay.

I have these in stock - it's one of the few JJ tubes I carry. I'll be happy to help if you like.

So the 12DW7 is the same as the ECC832? I have a pair of JJ marked ECC832 I got from Jim and my ST-35 sounds wonderful.

daveshel wrote:So the 12DW7 is the same as the ECC832? I have a pair of JJ marked ECC832 I got from Jim and my ST-35 sounds wonderful.

ECC832 = 12DW7, yes.

Not to hijack the thread, but what are some other tube choices for someone who wanted to experiment with tube rolling in the ST-35?

daveshel wrote:Not to hijack the thread, but what are some other tube choices for someone who wanted to experiment with tube rolling in the ST-35?

Dave,

The 12DW7/7247/ECC832 is a dissimilar dual triode. One section is like a 12AX7, one is like a 12AU7. There really aren't any other tubes that I'd recommend for that socket.

Jim McShane wrote:

daveshel wrote:Not to hijack the thread, but what are some other tube choices for someone who wanted to experiment with tube rolling in the ST-35?

Dave,

The 12DW7/7247/ECC832 is a dissimilar dual triode. One section is like a 12AX7, one is like a 12AU7. There really aren't any other tubes that I'd recommend for that socket.

How about in place of the EL-834s? Isn't the output tube the one that tube rollers like to change to get different sound character?

daveshel wrote:

Jim McShane wrote:

daveshel wrote:Not to hijack the thread, but what are some other tube choices for someone who wanted to experiment with tube rolling in the ST-35?

Dave,

The 12DW7/7247/ECC832 is a dissimilar dual triode. One section is like a 12AX7, one is like a 12AU7. There really aren't any other tubes that I'd recommend for that socket.

How about in place of the EL-834s? Isn't the output tube the one that tube rollers like to change to get different sound character?

Not really. The 6BQ5/EL84 is about it. The 7189 can go in, but it's really not much of a "roll". You CAN try different EL84s.