• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

buying matched quad on ebay

B

brad44

Active Member
Im new to buying old tubes, I always bought new as I am confused by all the testing and difference. Now I need a matched quad but would like to try some old stock tubes.

What constitutes a matched quad?

Im looking on ebay. I'm confused as some directly say they are matched but they are of different manufatures in some case appear to have different results from testing. Some don't really say "matched quad" but they have the same numbering on the tubes.

Its all pretty confusing, what if anything can I do to assure I am getting what I pay for?
 
Register to hide this ad
What tubes are you looking for?

I'm far from expert, but as such, I tend to want to pay a little more for known quantities. Jim McShane is a name that keeps coming up as having the ability to truly match tubes well. I bought a quad of Tung-Sol 7591s from him a while back, but I have to admit, due to my own personal time constraints, I have yet to recap the unit that they were intended for.

Also - what amplifier are these tubes going in? It is less critical to have matched tubes in units with individual bias adjustments as it is in units where there's only a single pot per channel.
 
For power tubes you need to match for current and voltage to insure that the push pull pair work together closely and thus sound the best. In NOS tubes this is hardly ever matched in both areas. A tube tester will usually give you a reading which is usually voltage based. There are testers like Amplitrex which can measure the current used by the tube at a certain voltage. If the sellers gives you a pair of tubes or more that are matched by a tester like that you should have good performance. But for old stock used tubes even if they are matched you don't know how many hours are really on the tube and this may make them wear out sooner if they have many hours on them. So getting used tubes even if they are matched is always a crapshoot.
 
Matching means different things to different people. What you often find is that 4 tubes that have the same labels are "matched" even if they're nowhere close electrically. The set of Sylvania 7868's I bought fall into that category.

What it should mean is the tubes have similar transconductance and idle current numbers. This means at least testing them on a machine that can give that data like a Hickok or more ideally something like an Amplitrex.
 
Yes, I have frequently seen sellers on the bay offering "matched" tubes which are no more than matched labels. It is very difficult to find a truly matched quad of NOS tubes. One would need to have many of them and then spend time testing each one to match. Matched new, re-issued tubes are commonplace and easy to find. To find truly matched NOS quads you usually need to go to a respected tube seller, like a Jim Mcshane or Brent Jessee. Even Upscale Audio, a well known tube dealer, doesn't always match NOS. Same goes for many of the sellers here on BT, I once bought a pair of tubes from a highly respected AK member and they were terribly mismatched.

If you have an amp which allows you to individually bias each tube, then you don't need a close match. But if there is just one adjustable bias point, then you need matched tubes.
 
my collection of 7868's has grown to 12, of which, i can put together a quad or two. i just keep buying up cheap pairs and singles. i've spent less than the cost of a new old matched quad, plus, i know i'll let some go later and re-coup. i'm still working on a cosmetic/tested matched quad though, i have 3 labelled "the fisher" that are pretty good together, but i stopped buying for now.

I probably should have just bought from a reputable dealer, but the fun is in the hunt for me.
 
Ebay can get frustrating, often times sellers know nothing about tubes. I tend to trust my own tester and nobody elses. The one exception is Jim Mcshane. I'f he has the bottles you need forget ebay. Also there are some very trustworthy vendors of used and NOS tubes right here in our own barter town section. In my experience, the savings from your first purchase will cover the membership fees.
 
To take this question one step further,,, could it be possible to add an ammeter to a typical voltage tube tester to add the current test to output tubes? seems it would be a pretty easy mod or just make a separate test socket with a switched ammeter to check current in the different tube sections that plugs into the tester socket... Of course results would still be dependent on the supply V of the tester...
 
Tom Bombadil said:
Matched new, re-issued tubes are commonplace and easy to find
Click to expand...

Even with new tubes, I don't understand how a seller is matching these. Are there product codes or something on new tubes that tells them they are matched?

I assume most big time business's aren't burning in tubes in real life situations and then putting them on testers. From warehouse directly to you right?
 
knockbill said:
To take this question one step further,,, could it be possible to add an ammeter to a typical voltage tube tester to add the current test to output tubes? seems it would be a pretty easy mod or just make a separate test socket with a switched ammeter to check current in the different tube sections that plugs into the tester socket... Of course results would still be dependent on the supply V of the tester...
Click to expand...
In short - NO.
A typical tube "tester" don't work with voltages and currents close to the amp it is supposed to work in.
For power tubes they should be compared at 400 V ( or so) using typical currents ( 50mA ?) .
A better test environment is the actual amp, provided that it has means of measuring individual
anode / cathode currents and an adjustable bias.
Not only is current importent when matching, also Gm ( the ability to amplify, or Ia change as function of Vg).
It's measured at a typical working point with a small AC signal.
 
Frank Sol said:
Go with Jim McShane and feel confident with your tubes

Have bought many tubes from him
Click to expand...
I second that. Know your tube vendor. Jim's honest and he stands behind everything he sells. Tubes are a special commodity since it's part hobby and part honesty in selling.

Check out Jim McShane's web page since many of us have been buying tubes from him for over 15 years.
 
knockbill said:
To take this question one step further,,, could it be possible to add an ammeter to a typical voltage tube tester to add the current test to output tubes? seems it would be a pretty easy mod or just make a separate test socket with a switched ammeter to check current in the different tube sections that plugs into the tester socket... Of course results would still be dependent on the supply V of the tester...
Click to expand...

Maybe, but really you'd want something that runs at the voltages the amp would operate at to make it truly useful. Nothing says you can't use a couple of bench supplies to rig up your own test circuit to match things though. Add a little more work and you can have a power output test along with idle current testing.
 
brad44 said:
I am seeing "matching codes" on old stock tubes too... so going on that alone is a crapshoot?
Click to expand...
Codes and silk screened brand names mean nothing. Quad matching is matching of electrical qualities.

As mentioned before know and trust your tube dealer. There's FAR more to matching a set of quad tubes than the name and code stamped on the tube.

For over 15 years Jim has given me excellent advice and recommendations while NEVER over selling me.
 
brad44 said:
I am seeing "matching codes" on old stock tubes too... so going on that alone is a crapshoot?
Click to expand...

That just means the tubes were (maybe) from the same batch. It might not even be a manufacturing code, but a sales and distribution code - i.e., the date wholesaled out to the vendor.

I see those listings from auction vendors who do (allegedly) electrically "match" other tubes. Unless test measurements for each tube are provided (some do), "matched codes" is a red flag to me that they're trying to add value to their auction where there really is none.
 
Thanks Im understanding better now. I should assume that if a quad just states "same matching code" or something to that effect that it is not electrically matched unless more information is provided.

When they provide information like micromhos@ma and then shows what a 100% is on their tester they are referring to strength correct? Not anything to do with matching.

I figured a match quad would all be of equal strength as well.... lots to learn!
 
Tom Bombadil said:
Yes, I have frequently seen sellers on the bay offering "matched" tubes which are no more than matched labels. It is very difficult to find a truly matched quad of NOS tubes. One would need to have many of them and then spend time testing each one to match. Matched new, re-issued tubes are commonplace and easy to find. To find truly matched NOS quads you usually need to go to a respected tube seller, like a Jim Mcshane or Brent Jessee. Even Upscale Audio, a well known tube dealer, doesn't always match NOS. Same goes for many of the sellers here on BT, I once bought a pair of tubes from a highly respected AK member and they were terribly mismatched.

If you have an amp which allows you to individually bias each tube, then you don't need a close match. But if there is just one adjustable bias point, then you need matched tubes.
Click to expand...

This,

Apparently people would have you believe 4 new old stock valves still in the box are matched. It is very difficult to find a set of valves that are matched without the transconductance and idle current numbers they are not "matched" regardless of what the seller has to say about the matter. It doesn't matter if they read a 36 or 38 or whatever and are 95-100% if they're not matched, they're not matched.
 
If you don't know tubes then know your tube vendor. Again - Jim McShane is the go to guy even for many of the tube guys here.
 
You must log in or register to reply here.
Back
Top Bottom