Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: tubeswell on February 09, 2012, 11:49:12 am
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http://www.amplifiedparts.com/tech_corner/12ax7_comparison_of_current_made_tubes (http://www.amplifiedparts.com/tech_corner/12ax7_comparison_of_current_made_tubes)
How the hell did they come up with a 10-point scale for gain? and noise?
And how did they measure 'noise'?
No info on the actual sample size of tubes they 'tested' to get their results, nor any data on the batches they took their samples from. Tubes of the same type made in the same factory on the same production line can exhibit differences. So how are we supposed to know whether the differences are attributable to the different brands/models, or to the tubes they tested?
Plate characteristics charts for each tested tube would've been more interesting.
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Hrm, they probably are not talking to builders/OEMs, they are targeting consumers, who for some reason like to see graphs and not think about things like "gee is that a sample size of one?" or "hey, even tubes from the same line from the same factory from the same day can sound different, so did you average that out"...
I agree with you though... what is "noise". I have had NOS stuff that was as noiseless as you can get. OTOH I have a GE in my desk that puts out so much noise some would call it a white noise generator. Same goes for new stuff. Gain? What is gain here? Is it like "this one seems louder in this amp?" Or "this one makes my amp break up sooner?" Very odd choice of words without enough definition.
However... I do like the fact that at the bottom there is a nice little diagram of what the plate and getter look like for each one, although that should not impact your purchasing decision.
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I take those sort of "findings" with the grain of salt.
I love to roll tubes in and out of an amp and do think they make a BIG difference.
My personal observation is that the results are most often unpredictable. That is to say what I expect to hear is often different than what actually happens.
BUT! I can't say that chart doesn't have merit, It may be helpful in choosing tube brands to get desired results.
Now that I've bookmarked it, I'll probably peruse it before I purchase new tubes.
It is neat too, to see some of the physical properties of a group of tubes all in one place, long plate, short plate, filament structure etc.
Thanks for the link!
Ray
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An audio store that i do repairs for has a really cool digital tube tester that runs the plate voltage up to 250v and you can actually 'listen' to the tube with a set of earphones.
It's so rediculously cool and gucci that I want one!
I get to use it to test my tubes.I'm in heaven! it cost 3500.00 bucks so it's on my christmas list.
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An audio store that i do repairs for has a really cool digital tube tester that runs the plate voltage up to 250v and you can actually 'listen' to the tube with a set of earphones. ... it cost 3500.00 bucks so it's on my christmas list.
Most Hickok tube testers run about the same plate voltage (maybe a bit more), and also have jacks for old-style headphones so you can listen for noise/microphonics.
And if you have the money to pay $3500 for a Hickok, I've got a lot of cool old stuff that should be right in your budget (I'll only charge you $2k for a $400 item)! :icon_biggrin:
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I've got a wealth of "rubbish" tubes that I actually really like in the right application...I've got plenty of brand new ones I find better than many NOS. Ei EL84s for example...much better than a lot of the NOS ones I've tried. Basically it's all subjective...and such a shame that your basic guitarist can often fall for swanky claims of testing and grading the finest tubes for their amps. Same's true of speakers too...I have some great sounding cheap rubbish speakers.
Or maybe my ears are duff?!?! :laugh:
It is a shame digital tube testers are so expensive though...lowly people like me have to make do with a basic Sencore Mighty Mite to give me vague tube data!
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I used to think that NOS 6V6's were the only 6V6's worth using. Now I have new-found love for the Tung-Sol re-issues. Quite a nice sounding tube IMO. How long they last is yet to be determined, but the sound is good.
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> runs the plate voltage up to 250v and you can actually 'listen' to the tube with a set of earphones.
For $3,500 you can do that AND listen on an actual speaker (headphones lack any relative reference). Just find a Champ amp that's way over-priced.
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Alright I'll get a nice Hickock and a nice champ and be done with it.
But....a Gucci tube tester lets you overcharge for /chinese tubes./never thought of that i bet!
Champ tester says "sounds good" Gucci tube tester gives mutual tranconductance,gain,current draw per triode,and lots of cool digital readouts.And cool lights too.
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Champ tester says "sounds good" Gucci tube tester gives mutual tranconductance,gain,current draw per triode,and lots of cool digital readouts.And cool lights too.
Okay, you probably have a point with the "overcharge for chinese" stuff! :l2:
But PRR's point is that a Champ and a meter (maybe an analog meter with a dB scale) will provide all that info as well. Minus the digital readouts, but you ju8st print up a "test results sheet." That's gotta be worth an extra 25% charge!
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I put them in an amp and use the best tool there is, your ears
Well, actually fingers are the best tool there is, but ears are way up there on the best tools scale.
Nice thing about it is, you already own an amp and it did not cost $3500 ( I hope it didn't )