matching tubes

Oldfatdogs

Is it best to buy matching tubes or does it not matter if they are the same tubes 12at7 for example.
While searching tubes on the net I see alot of matched sets.
I think buying used it would make scene, but what about new tubes?

heiney9

Oldfatdogs wrote: »

Is it best to buy matching tubes or does it not matter if they are the same tubes 12at7 for example.
While searching tubes on the net I see alot of matched sets.
I think buying used it would make scene, but what about new tubes?

It's really not necessary to "pay extra" for matched tubes. Many times when you buy current production tubes they are matched by the dealer because the quality from batch to batch can vary greatly. This is not the case for old stock tubes. A match within 20% is inaudible to most. I wouldn't worry too much about it for SIGNAL TUBES if you are buying old stock tubes. Power tubes it can be more of an issue depending on the topology of the amplifier section. Anytime you can adjust the bias, matching is pretty much irrelevant up to a point. Autobias the same thing to a lesser degree, again up to a point. An amp that has no bias adjustment needs matched tubes as far as gain since there is no way to compensate for the mismatch.

Hope this makes sense and others might feel differently but paying a huge premium for closely matched tubes is not necessary. For your Dared as long as they are within 20% you should be fine. Always go for the best pair, but also remember tube testers and the operators vary widely as well so even if they closely match on one tester that maynot be true on another tester or when used in the actual circuit.

H9

doctor r

If the tubes are performing the same function the should be matched. When you start dealing with tubes such as the 12at7 they are dual triodes meaning two seperate triode circuits in one glass container. Some people will speak of matched sections and that is the two inside the one tube. You will see test results like 82/86 and you would try to match this to another one like 84/82. I would also stay in pairs from the same manufacturer. The two numbers for each tube represent the two internal sections. Different testers will give very different types of numbers also. Mine is a range of 0 to 100. Others could be like 1480/1520. Hope this helps.

doctor r

I agree with H9 as far as the "is it critical" question and he obviously is faster on the post.

If you are buying used which can be a better value I still like mine somewhat close if possible.

Rick

heiney9

I disagree slightly with doctor r. I have some tubes that are 70/78 and 82/72 and I can't tell an audible difference. Obviously if you have a pair that measure 105/97 and 66/70, that's probably not a great match. Again 20% max triode to triode and don't pay $150/pr for a perfectly matched pair if you can get a 10-15% matched pair for $50.

This is my approach as I buy used tubes. I have been buying and using hundreds of pairs mostly purchasing in the 10-15% triode matched pairs and have has ZERO issues with all types of signal tubes.

It boils down to how anal you want to be and I suppose really, really expensive tube gear deserves the best tubes, I don't buy into that 100% as I have not heard any detriments when using 10-15% matched tubes.

H9

heiney9

Where I get anal is I like to use the same build series of tubes together as well as similar years (they tend to coincide) and same plate type/getter style, etc.

I would not use an early I61 or I62 (ECC83) tube with a later I65 style. You could be looking at as much as a 10 year span as I61 tubes usually were in 59-60-61 and late I65 types could be 69-70-71. There is a difference in Philips Holland tubes from 1959 to 1970/71/72. The later tubes don't have to same attention to detail or material quality.

Also Blackburn made Mullard tubes sound different than Mitcham made Mullard tubes even if the plate structure and build are the same. Try comparing a Valvo Hamburg tube to a Valvo Holland tube. They look the same, but they sound entirely different. So no mixing and matching there. When I buy tubes all I care about are the codes and or special symbols. A Bugle Boy with a Treble Cleft logo is the best low noise Amperex tube you can buy, but they are very, very rare these days. I have a few pairs of various types.

H9

Oldfatdogs

Thanks for the information,it seems matched sets you pay a premium price.If this is not really necessary why pay extra.Thank you both.Dan

doctor r

I guess I am a little anal but those numbers were actually just made up as an example out of my head. I do have to agree, though my logical side says you should have close numbers, I also have not been able to hear a great audible difference with tubes in a 10 to 15% variation range.

Dawgfish

I too like having tubes that are in the same ballpark(testing wise, as the others have stated, I always run the same manufacturer, location, and construction when it comes to pairs or quads of gain, power tubes, etc), but they don't have to be super closely matched. I like for my pre to have a balance knob for these types of situations if and I mean if a difference is heard. Currently in my listening room at my work apartment, the room is L shaped with a rather large and eneven partition going out on the left hand side of the room. Because of this the right speaker always sounds slightly louder with the balance knob in the dead center position. It's good to have a balance knob to account for any unevenness in tubes, room acoustics, recordings, etc. on an as needed basis.

SCompRacer

Depends on the amp (read the manual), but power tubes are the ones that usually require matching. Pre amps are usually self biasing so you have one camp that says don't bother matching the tubes. The other camp says if your Mu (measure of voltage gain) differs greatly from the right to left channel tube, your gonna have a dB difference between the two. Mu (measure of voltage gain) = Gm (transconductance) x Rp (Plate Resistance Ohms). So with matching, much depends on how the tubes are measured. Some folks don't test for Rp. So maybe this is another reason different tubes sound different?:twisted:

Here is an old web page from my research days that touches upon Rp. (Yeah, it's a guitar amp site, but they use tubes).:cheesygrin:
http://www.guitarstudio.tv/Splawn/explanation_you_must_read.htm

So I like to use closely matched pre amp tubes. As a rule, as the tube ages, they should stay close until you drop below 70% of original cathode emissions.

Oldfatdogs

Dawgfish,thanks for your input.
Scompracer,Thanks for the link I'm going to read that one more than once.

So I like to use closely matched pre amp tubes. As a rule, as the tube ages, they should stay close until you drop below 70% of original cathode emissions.

Is there any way of testing if you don't have a tube tester?Can you guesstamate by the hours you have on the tube?
Or should my next purchase be a tester?
Thanks again for the help.Dan

heiney9

Dan,

I've thought about getting a tester myself but the maintenance can be a bear as well as keeping it properly calibrated is a pain unless you are a true electronics guru. I buy based on the sellers numbers, and again in over 200 tubes I've had one or two issues.

The Amplitrex is the best going but it's really expensive. If you are going to buy and sell very large quantities of untested tubes, then yes, a tube tester is probably necessary. For your own personal use for a couple pieces of tube gear unless you want the novelty and the experience of keeping it running an calibrated, I'd say it's not necessary. I don't have the time ot tinker with stuff like that.

Just my .02c

H9

doctor r

If you buy new, buy from a reputable source and don't look back. You can buy used from high quality tube resellers if you want something specific and it will be well tested. Many people buy of eBay and generally trust the tests done by the sellers to some degree. This usually worksv out Ok. I would not put money into a tester. The only reason I have one is because my father worked for Hickok in the 50's and I bought it to surprise him. If you are truly concerned about testing a tube contact me and we can easily arrange for it to happen. Many small signal tubes expect 5,000 to 10,000 hours as possiblilities. With a used tube it is not really possible to know its previous use, just where it measures today.

Oldfatdogs

I guess I should have put a smiley by the tester question,I don't have a clue how to use one.
There is so many different sellers who use different testers its hard for a tube newbie to know what they all mean.
I guess you have to trust the seller by there feedback ratings.
The cost of tubes isn't that much but I hate getting burned.
Doctor R thanks for the testing offer, Maby if I buy some of the fancy Telefunkens that might be necessary.
I found a shop in town that does work on guitar amps and sells nos tubes I'm sure they could test for me for a small fee.

SCompRacer

Just want to say that I have used some unmatched tubes with no issues. Most of my 5687's came from Tubeworld and he tests for Mu.

If you buy tubes from a good source and they are accurately tested, some say you can get by with a simple emissions tester. I wanted a tester that does it all but they are pretty pricey. I had a good tester from my Uncle but when I was into cars and was moving, I gave it up. When I got back into audio, I regretted it.

Sounds like doc is a tube tester source. IIRC there are other threads here you can do a search for that had some tester suggestions.

mhardy6647 makes a suggestion here.
http://www.polkaudio.com/forums/showthread.php?93425-Tube-testers&