Power Tube Matching

Cardinals · « **on:** 18 Feb 2011, 06:27 pm »

Hello everyone. I just recently found this site and since I'm in St. Louis, I figured somebody might be able to answer a question I have.

Is there somewhere in St. Louis where I can have 6550A output power tubes matched? My amp requires 2 matched pairs of 6550A and uses 1 6550A as a regulator. I have the tubes, but I have no way of knowing if they are matched. Also, if I found out they are not matched, can they be made into matched pairs? I'm not exactly sure how that stuff works.

Thanks for any help!

Scott F. · « **Reply #1 on:** 18 Feb 2011, 07:38 pm »

Welcome Cardinals!

I don't think any of the shops around town sell matched pairs (or quads) of tubes. Most of the shops simply call up somebody like The Tube Store or Tube Depot and order sets in.

Regarding the shops, I'm not sure what kind of tube testers they use...and you have to be careful. There are only a few styles of tube testers that will give you a true transconductance reading on a tube. The Hickok TV7, the Tripplett and 3423 and a (very) few others. The majority of the tube testers that are floating around out there are Good/Bad testers which won't give you the info you need to 'match' tubes.

As for making your tubes into matched pairs, you can measure the existing tubes and get them placed in your amp where they have (somewhat) even readings. That is about the best you can hope for with used tubes. You're only way to get truly matched tubes is to buy new (or NOS from someone you trust has the right meter).

I'd invite you out and test your tubes for you but my basement is completely trashed as I'm in the middle of rebuilding it. If you are still interested in about a month or six weeks, It should be most of the way back together again.

Cardinals · « **Reply #2 on:** 18 Feb 2011, 07:56 pm »

Thanks for your reply Scott. My tubes have never been used, but since I don't know if they are matched, I'll probably just buy some that I know for sure have been matched. I appreciate the help, thanks again.

Ericus Rex · « **Reply #3 on:** 18 Feb 2011, 09:47 pm »

You can send them down to Florida to AC member Doctor Cilantro for matching on his Amplitrex.

daves · « **Reply #4 on:** 18 Feb 2011, 10:48 pm »

Cardinals, what Audio Research amp are you running?

electricbear · « **Reply #5 on:** 19 Feb 2011, 02:34 am »

If you are using an Audio Research amp get your tubes directly from ARC. They will have already been checked out and matched. You might pay a little more but your baby is worth it.

Scott F. · « **Reply #6 on:** 19 Feb 2011, 02:57 pm »

Hey Cardinals,

If you are going to Daves today, I'm bringing my Triplett tester to check a couple of Blackmores tubes. I could check yours while I've got it there.

Hope to see you there.

Cardinals · « **Reply #7 on:** 20 Feb 2011, 12:30 am »

Dave, thanks for having me out at your home for the gathering! Thank you Scott for taking the time to test my tubes, that was very nice of you. I'm happy to know they are already matched. See you guys in the near future.

daves · « **Reply #8 on:** 20 Feb 2011, 01:55 am »

It was a lot of fun having you, Adam! here is a photo of Scott doing his magic..

Blackmore · « **Reply #9 on:** 20 Feb 2011, 03:13 am »

The goofy look on my face is due to Scott telling me my 1959 Mullard 5AR4 tested better than my 2007 EML 5U4G. Thanks again to Scott for the testing and the 30 rectifier tubes he lent me to try out in the Yamamoto.

Scott F. · « **Reply #10 on:** 20 Feb 2011, 04:14 am »

We expect a write up of all 30, waxing poetic, bestowing the virtues of each new valve

FullRangeMan · « **Reply #11 on:** 20 Feb 2011, 04:30 am »

Quote from: electricbear on 19 Feb 2011, 02:34 am

If you are using an Audio Research amp get your tubes directly from ARC. They will have already been checked out and matched. You might pay a little more but your baby is worth it.

Hi,
I was told by a tube expert of my country, that the AudioResearch VT series amps, needs output tubes so closely matched, that only the AR company can match this tubes.

Also I was told even UpscaleAudio will not sell output tubes for AR-VT amps due risks in running this amps with non-AR matched tubes.

This info is very important to know before one buy an AR amp, after the purchase it is too late, the audiophile already in the hands of AR company.
Hope this help, Gustavo

> Never go to a psychiatrist, adopt a cat or dog from the street. On the streets pets live only two years average.

KenSeger · « **Reply #12 on:** 20 Feb 2011, 02:13 pm »

FullRangeMan,

The ARC amp in question is a 1970's D76 so there should be no problem. I worked for an AR dealer back then, and at that point in time, no dire tube related warnings were issued from ARC

Besides, these milspec tubes had identical millimhos, dead on. What tube measurement was considered critical and what manner of risk would be involved? I.E., how could the amp be damaged by non-perfect matched tubes?

Thanks in advance for your reply,
Ken

Blackmore · « **Reply #13 on:** 20 Feb 2011, 04:09 pm »

re: Rectifiers
Hey Scott, is what you were thinking?

"While the Sovtek was angular with an austere finish and the EH drifted towards a Gewurztraminer (for those of you that really know that grape) the Mullard was briary and suggested malolactic fermentation in its presentation."

My GE made in Holland (Mullard) sounds great right now. I'll pm you what made the biggest difference. I don't want to share every trick. Hint...my wiring in the apartment.

FullRangeMan · « **Reply #14 on:** 20 Feb 2011, 11:29 pm »

Quote from: KenSeger on 20 Feb 2011, 02:13 pm

FullRangeMan,

The ARC amp in question is a 1970's D76 so there should be no problem. I worked for an AR dealer back then, and at that point in time, no dire tube related warnings were issued from ARC

Besides, these milspec tubes had identical millimhos, dead on. What tube measurement was considered critical and what manner of risk would be involved? I.E., how could the amp be damaged by non-perfect matched tubes?

Thanks in advance for your reply,
Ken

Hello Ken,
Good to read this owner is not the case in question.

I unware the tech details and not wish ask at the time, cause I do not own a AR nor know any AR owner, but I translate what he said as below:
I do not suggest changes or substitutions in this amplifier(VT100). Many who have experimented with the replacement of the VT100 or VT200 tubes repented bitterly, because the output tubes have to be robust and both 6550 and the 6922 have to be matched at the specific voltage and current of your amp(VT100). If using pairs or quartets married for a third party, will not give good results.
The Upscale Audio, which is the largest retailer of matched/special valves in USA recommends to buy only matched by factory valves, i.e. Upscale will not sell tubes for VT100 and VT200, so specialized that it is the marriage (matching) necessary.
I believe this tube expert, he is very friendly and have many years on the road.
Iam sure AR factory know all about it, but maybe do not want inform details to the public.
Regards, Gustavo

> Never go to a psychiatrist, adopt a cat or dog from the street. On the streets pets live only two years average.

Scott F. · « **Reply #15 on:** 21 Feb 2011, 01:50 am »

Quote from: Blackmore on 20 Feb 2011, 04:09 pm

re: Rectifiers
Hey Scott, is what you were thinking?

"While the Sovtek was angular with an austere finish and the EH drifted towards a Gewurztraminer (for those of you that really know that grape) the Mullard was briary and suggested malolactic fermentation in its presentation."

Perfect! Now you just need to do that 27 more times

Blackmore · « **Reply #16 on:** 21 Feb 2011, 02:26 am »

Good thing I only used the "a and b" sections of wine descriptions. I'll need plenty of adjectives to describe all 30 tubes.

I'm going to try our a few of the 5U4G tomorrow. My little 5AR4 is doing a pretty good job, but I'll be interested to see if any of your tubes can beat out my GE Mullard.

Highs are much improved over the Sovtek and EH, but not as smooth as the EML. More extended, though. Interesting results so far. Thanks again.

Scott F. · « **Reply #17 on:** 22 Feb 2011, 07:49 pm »

Quote from: Blackmore on 21 Feb 2011, 02:26 am

Interesting results so far.

You're right. Lots of folks don't realize just how large of impact the rectifier tube has on the sound of your amp.

Once you make it through those, I've got about a dozen more if you are feeling really adventurous

KenSeger · « **Reply #18 on:** 22 Feb 2011, 10:44 pm »

I remember when ARC was coming out with circuit updates for their D76 amp several times a year, I think it was between version F and version G, there was a noticable difference in the bass. What was the change in the audio circuitry? None. Just a change in the power supply, period. Big change like new transformer or twice as much capacitance? Nope. Just a small but audible change.
Ken

gooberdude · « **Reply #19 on:** 4 Mar 2011, 01:31 am »

Guys,

Are there any local shops you trust who can test tubes with a proper Hickok (or equivalent) tester?

not to match pairs, just to test for good or bad?

matt