Tube Matching

[kd]

I don't have a tube tester and wouldn't know how to use one anyway but, I do have a homemade thing that works like a bias rite and reads the milliamps of draw through a tube. The question is this, if I hook this thing up to an amp and insert tubes one at a time and get the milliamps of draw for each tube then match them up according to their draw, is this the same thing as getting a matched set of tubes?

Thanks,
Ken

[dartanion]

Tube matching in a guitar amp is not all that necessary. A 10 mA difference in power tubes is about right, perfect matches tend to give a very thin sterile tone. Pre amp tubes I wouldn't bother matching triodes at all. Most of the matching hype has carried over from the HiFi world.

I would say as long as you are around 10 mA difference on the power tubes, then you should be good. I normally match power tubes by ear. Totally non scientific, but some of the mystique of tube guitar amps is pure luck in finding the "right" tube combo. Even more difficult with new production tubes.

[sgtoverdrive]

i am with dart on this 100 percent aspen pittman started this myth so he could become rich .it has worked and put alot of people at hard labor trying to match tubes with useless results and banal mediocre results that in all ways make an amp sterile.i went to vacuum tube alleys little rally last weekend at the embassy .there were the usual bozos with there antiquated hickoks and there idiot attitudes .plus a slew of ho chi mins bidding on anything that fired electrons.i purchased 10 xf2 mullards from these fellows with all the fancy numbers on em.when i got home after hearing them brag about how effecient there machines were .all the ones that had identical michromo numbers were no less then 15 ma apart on my maxi.so never fall for that i matched it on a hickok ..its rubbish .you cannot match a tube with 150 vdc on it then operate it at 340 volts much less 400 plus and expect those numbers to be correct.they regard us guitar players as buffoons and i regard them as audio philes ....aka sound perverts who think they can hear a difference when a triode drops from 105 to 104 ..they are dorks of the highest order and should be classified as they are ....philes and i have not met one ,,and ive met way too many that didnt live in lala land .they regard us guitarists as heathens well they got that right.bottom line dont fall for the bogey stories that get told about matching or youll ...you well i dont like to say sgt audiophile strangler

[zaphod_phil]

I normally match power tubes by ear. Totally non scientific, but some of the mystique of tube guitar amps is pure luck in finding the "right" tube combo.

Yeah, I just look for a pair giving the least hum. That's all you need to do.

i am with dart on this 100 percent aspen pittman started this myth so he could become rich .it has worked and put alot of people at hard labor trying to match tubes with useless results and banal mediocre results that in all ways make an amp sterile....bottom line don't fall for the bogey stories that get told about matching...

Very well said sarge!

[rjgtr]

Well....

There are reasons to match tubes. First, matched tubes generally produce a more clean tone. If you want your amp really clean with pure hi end, then matching power tubes is a good idea. This isn't headroom, also using a graded tubes a can get predictable results in headroom. However, if you are in distortion most of the time then a 10ma difference won't matter.

Matching isn't hype. It allows you to fine tune your power amp response. Using the Groove Tubes or other matching systems lets you optimize your amp for more or less headroom. Fortunately, you don't have to buy GT tubes to get graded tubes. Most vendors will supply tubes in a range of current draws.

But it isn't absolutely necessary either. I've tried it both ways. I prefer matched tubes because IME the high end and low end are clearer and punchier with matched tubes.

[markh]

I think the Sarge is onto something there. Face it, it's all those great *old* recordings that caused us to fall in lust with the old Marshalls and Fenders. When Eric recorded N.S.U. or Jimi recorded Machine Gun or Richie recorded Sweet Child in Time or Jimmy recorded How Many More Times, I guarantee they were using amps with unmatched power tubes, because that (marketing) idea had yet to be invented!

If you're going for a pristine crystal clear jazz sound (or retubing the Dyna Stereo 70 in your hi fi) matching may have merit. But, if you like how these old amp designs synergistically change the sound of your guitar, harmonic distortion is your friend.

Just my 0.02

--mark h

[zaphod_phil]

If you want your amp really clean with pure hi end, then matching power tubes is a good idea....However, if you are in distortion most of the time then a 10ma difference won't matter.

Well you know how it goes, one man's pure high end is another man's sterile tone. And as the sarge pointed out, tubes perfectly matched on a tube tester won't ncessarily be matched when running in a live amp. And are you then also going to mod your PI to be more balanced as well? Personally, I reckon that a slight mismatch makes both clean and distorted tones sound sweeter.

[rjgtr]

I was only pointing out that there are reasons to use matched tubes, not saying anyone has to. At the end of the day, the tubes should still be somewhat matched, even if it is only within 15ma. If you go too far out the amp will hum and sound, well, unbalanced.

There's a reason feneder tried to use values that balanced the PI better instead of just using two 100k plate resistors.

Plus, in the era you are talking about, manufacturing tollerances where much more tight. A run of tubes was generally very close in current draw anyway. That's how Fender got away with not having a bias pot on many amps. And matched tubes have been around for a lot longer than Groove Tubes. It was just that Groove tubes educated the public to what manufacturers and techs alredy knew about.

[zaphod_phil]

There's a reason Fender tried to use values that balanced the PI better instead of just using two 100k plate resistors.

Yes, no one had done guitar amps before, and coming from an audio background, that's what everyone thought you were supposed to do. As my electronics education was all in audio/hi-fi design, that's what I used to think as well. Then I had to unlearn a lot of that when I got into guitar amps.

Plus, in the era you are talking about, manufacturing tollerances where much more tight. A run of tubes was generally very close in current draw anyway. That's how Fender got away with not having a bias pot on many amps.

Quality control on tubes was much better then, but not for resistors and caps, which are also important to maintain balance.

And matched tubes have been around for a lot longer than Groove Tubes. It was just that Groove tubes educated the public to what manufacturers and techs alredy knew about.

That is correct. The old audio electronics books do recommend tube matching for hifi. However, it doesn't appear that amp manufacturers thought of themselves as hifi, so they didn't bother. They just built some very sweet amps - as well as a few noisy ones too. Then Pittman came along and popularized the idea of using closely matched tubes in guitar amps...

[rjgtr]

Phil,

No argument, but some amp makers did care about a hi-fi sound. Ampeg being the biggest example. They were definitely striving for a full balanced clean tone. It was well known that Hull hated distortion of any kind and sought to eliminate is as much as possible. So was Fender, to the point of making the senselessly clean later silver face amps (talk about clueless).

In many ways the amp makers (with maybe Marshall and Vox the exception) were pretty clueless to what rock players wanted. Nobody expected us to really turn up an amp into distortion. Fortunately we got lucky and many amps sound great cranked!

[zaphod_phil]

Yes, that's a very good assessment of what happened. I often think of it as story of lucky accidents, and some half-baked engineering too. Apart from Ampeg, Hiwatt also had very hifi-ish designs and beautifully built. They had such things as fixed biased LTP PIs, with a regulated bias supply! For anyone who wanted to get all their guitar tone from pedals those things were perfect.

And Hiwatt is back in action again - now owned by a certain infamous music shop in Leeds UK!

[rjgtr]

Also, as for parts a tollerance, only a few very high end HiFi builders even bothered to test and match parts for closer tollerance. I'm sure my Dad's old tube based Zenith hifi was slapped together from whatever the cheapest parts they could buy, just like Fender amps. Things are much more accurately built now in every way. That's why some old amps sound great and some sound like crap, even when restored to new specs.

Lets look at strings as another example. We can now buy all kinds if strings built to extremely tight tollerances with all kinds of variations. Back in the early 60s, you had a choice of a couple brands. No lights or heavies. Then Rotosound came along with roundwound guitar strings. Ernie Ball came along with .09s and .10s with unwound 3rds in an actual set of strings.

We won't even talk about neck shapes...

So the evolution has been toward a much more accurate set of tools. Matched tubes being part of this whole thing.

Back to matched tubes...in the 70s I knew a lot of guys who just bought tubes from Rat Shack. They didn't even care about what brand it was. So things really have changed...

[zaphod_phil]

..in the 70s I knew a lot of guys who just bought tubes from Rat Shack... So things really have changed...

Tubes being sold at Rat Shack. Things sure have changed!

[Foxhound]

Matching your output tubes within a moderate margin will help to lengthen the life of your tubes though. Being sure to check your bias on all tubes is most important to keep from running any of them too hot.

Jon

[KT77]

i find it interesting that Fender had more bias 'balance' circuits than actual bias voltage adj circuits

and that old SC's had individual bias adj on each side...and that didn't carry over to DR's HiWatt designs....

markh....any thoughts?

[markh]

I'm not sure why Dave Reeves never put any bias adjustment into the DR504 and DR103 amps. That and the awful screen resistor setup are the only two flaws in an otherwise wonderful design, IMO.

Of course, Hiwatts used Mullards exclusively, and I guess in the 70s they were consistent enough that he didn't feel the need to provide an adjustment. I think DR would be quite surprised to see how popular these amps have remained 25 years later.

--mark h

[sgtoverdrive]

mark is correct in my view, i cannot even begin to count the number of people that come to me almost daily for the ....evh tone.as i grew up with him and watched him incinerate that 68 plexi .tubes were changed out if they went bad.bias? not a chance.on one occasion his starboard engines flamed out and i ran back to my garage and yanked two of my amperexs ..you know the ones in the green and yellow box. lent them he popped em in and off to the races .whenever a tube went south one was bought ,not a whole compliment.that would have cost beer and cig money.and thats out.l...why those tubes were almost 7 dollars ...a huge sum of money in those days.and then we had to walk to school in the snow 8 miles up hill.and then we had to go home 11 miles up hill.the world has changed since then.how did it change >? they put a dow radio and ratshack between our houses and school.lol sgt

[sgtoverdrive]

back in the deeps of time whenever a hiwatt was encountered fear and panic spread! a guitarist that used one was either two things .or both. deaf or very wealthy.i went to west la music in 73 with my father in tow for a co sign,so i could become a bond servant.i went after the hiwatt .2000 dollars was a bit more in those days.like a considerable down payment on a 3 bedroom house.so i ended up with and orange 120 .with a little luck the bass player i worked with, only had a 72 50 marshall we swapped.thank the lord. orange may have not been a great overdrive amp,but it was the loudest pa in northern san gabriel ! if you ever get a chance to snag an early biacrown lead 100 i will wrestle you for it.

[sgtoverdrive]

everett hull was indeed a sage inventor but bare in mind this man thought the guitar was on its way out and accordian was coming back to be the premier instrument.this can be seen on any old ampeg all have accordian inputs.lol gibson also strived to get linear amplifiers .a misrable failure due to non linear woodman shumacher transformers .there are at least 6 smoothing caps and the like, in every gibson in the early days.one of mine had original 047s across the output sockets it had about 6 watts .removed it produced a tad more output.like 30 watts.well i predict the zither will make a comeback.