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Dirty-South Blues Harp forum: wail on! >
Tube tech 101
Tube tech 101
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rbeetsme
1397 posts
Oct 19, 2013
7:53 AM
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I have a pretty good understanding regarding the tone of tube amps and what works well for harp. I've certainly owned enough of them. I am technically challenged however, and would like some input regarding tubes. There seems to be a lot of opinions about the quality of vintage American, Military, Asian and Russian tubes and how they affect the overall tone and character of tube amps. I've tried to buy RCA clear tops whenever I can find them and they seem to work well enough. But what about power tubes, etc., what should we be looking for? Case in point, I have had tube amps that were just killers, great tone, great cut and could just bite through the mix. And then another same brand, same chassis design that was much cleaner, less bite, fine amps but didn't sound the sound. Assuming that both were in pretty original condition without extensive mods, could tubes contribute to the tone of each?
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Frank
3039 posts
Oct 19, 2013
8:00 AM
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When messin with tubes I have noticed a change in amp tone characteristics - particularly when the tube change is drastic :)
Last Edited by Frank on Oct 19, 2013 8:01 AM
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shbamac
384 posts
Oct 19, 2013
8:02 AM
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Yes, tubes contribute to the tone. Tubes of the same brand can differ from tube to tube. Most all the componets contribute to the tone of the amp to some degree.
Last year I attended an amp building workshop where five or six of us built the same chassis. Each one was built using the same components. The tone of each amp was very similar but there were subtle variations to each one. Some so slight to be hardly noticeable. A difference in the speaker, caps and resistors (variations in build, off spec), OT and tubes can all contribute. With vintage amps a lot of the variations in the tone from amp to amp (same build, model, year) has a lot to do with components and how far off spec they have drifted. And the tubes and so on...
As far as what you should be looking for in a tube... Different people have different tubes that they swear by. You can buy 100's of the same tube and might get some great ones and you will get some duds...
Last Edited by shbamac on Oct 19, 2013 8:42 AM
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Barley Nectar
140 posts
Oct 20, 2013
11:39 AM
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I build tube type harp amps and my take on tubes is to buy the best you can afford from a reputable seller. Unfortunatly, this is no gaurentee that the tubes will sound good in the circuit they are in. As stated above, there are a million variables. Unlike many of the tube snobs out there, I usally cannot tell the difference between power tubes, tone wise. I still buy good ones though, bassed on durabuility. Most NOS tubes will last a long time. JJ 6V6s, JJ EL84, Winged "C" 6L6's and Sovtek 6L6 WXT are all tough tubes IMO. The big change in tone is in the preamp tubes, these I can definatly hear. Funny thing is, although I have lots of noval base tubes, I'm not really into tube rolling. I usually stick um in there and if they work and are not noisy, they stay. To me, tube rolling means loose tube sockets that will soon cause problems. I do adjust for gain by changing tubes if the amp is unruelly. BUT, I also tend to let the amp be itself and learn how to set it up for best tone. Sometimes your better off just getting another amp. That is one thing I am really good at...(<:...BN
Last Edited by Barley Nectar on Oct 20, 2013 11:40 AM
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528hemi
411 posts
Oct 20, 2013
11:53 AM
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I've had 2 amps the same and even substituting the tubes and even swaping speakers they sounded different. I guess there are more variables....Cap/resister drift?
Maybe transformer differences? Probably would have to do alot of testing and take measurements to figure out why they sound so different??
528hemi
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Greg Heumann
2422 posts
Oct 20, 2013
6:13 PM
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@528 -Well beyond the known differences from tube to tube, an amp has potentiometers, resistors, capacitors, transformers, speakers... Sometimes a very few other components as well - but the ones I listed are the vast majority. ANY can have an impact on tone. The tolerance on these components is often +/- 10% of their stated value. Some were held within +/- 5%. When you add up these variances over dozens or even hundreds of components, those differences can add up to a good deal of variation from amp to amp. Anything with a coil (speakers, transformers, chokes) will vary as well - especially if those coils were hand-wound.
A modern amp with all surface mounted components on a printed circuit board and robotically wound coils will sound very consistent from one to the next off the assembly line. But older amps - no two sound exactly alike.
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BlowsMeAway Productions
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Last Edited by Greg Heumann on Oct 20, 2013 6:14 PM
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