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Guitar Discussions -> stupid tube questions
There are 9 messages in this thread.
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stupid tube questions - Grant W. Petty - 00:47 07-12-05
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1. Besides microphonics, what are the other common ways in which it
becomes clear that tubes are due for replacement? Are the symptoms
different for power tubes (e.g,. EL-84s) vs preamp tubes (12AX7s)?
2. Are there replacements for 12AX7s that are harder to push into
clipping? I'd ideally like to be able to hit the input of my Gibson
GA-15RV (Class A, single volume control) fairly hard and know that any
clipping is only occuring in the power stage, as I don't like preamp
clipping. Maybe this is already the case; I don't know. Without a
separate preamp and master volume, it's hard to tell.
3. How important is tube brand? My main music store offers GT and Mesa.
I usually buy Mesa. Should I look at other brands elsewhere?
4. By reputation, my amp "eats power tubes like popcorn". This is
presumably because of the Class A thing .. large plate current even when
silent. What does this mean in practical terms? For how many hours of use
should I normally expect my tubes to last? I've retubed twice in about two
years (a few hours per week of use, on average) just for fun, but haven't
really noticed any difference between the old and new tubes. I don't want
to be excessively paranoid about my tubes giving out on me, but I don't
want to miss the symptoms either. I'm already chronically concerned about
whether my amp "sounds right", but I'm pretty sure most of that is, well,
paranoia. Or hypochondria. Or something.
- Grant
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Re: stupid tube questions - DeeAa - 01:49 07-12-05
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"Grant W. Petty" <gpetty@aos.wisc.edu> wrote in message
news:Pine.LNX.4.60.0512062333070.3915@cloud.aos.wisc.edu...
>
> 1. Besides microphonics, what are the other common ways in which it
> becomes clear that tubes are due for replacement? Are the symptoms
> different for power tubes (e.g,. EL-84s) vs preamp tubes (12AX7s)?
>
There will be more knowing people answering, but what the hell, here's my
take:
I have never had to replace power tubes, as I've never owned a tube amp long
enough to burn 'em - never really found an all-tube amp I'd be really happy
with, never had the money to buy the biggest badass Marshalls I _think_ I'd
like a lot - my friend has this blue special Marshall stack from the early
90's or so and that thing surely rules. Or a modded Plexi I guess I'd like.
The longest I owned a tube amp was a BluesDeVille I had for about 2 years,
maybe 45-50 gigs and a lot of playing. Never worried about them much, I
always kept a few spares to pop in if need be.
But I've often had to replace the very first preamp tube as I've usually
driven the input real hard (I don't much care for excessive tube power stage
distortion, it's usually way too mushy and round, I want most of it to
happen in the pre). It was really easy to tell when to change too; started
making noises and squeals and random slight variations in level and tone in
the last stages.
> 2. Are there replacements for 12AX7s that are harder to push into
> clipping? I'd ideally like to be able to hit the input of my Gibson
Sure, AU7, AT7 I think, and also some others...they should be able to tell
in the store.
Mind you, I don't know if the amp can handle different tubes easily...might
have to adjust something.
Also the 'cleaner' preamp tubes are often much colder-sounding it seems,
perhaps because they need more juice and don't really function that well
with the AX7 levels.
> 3. How important is tube brand? My main music store offers GT and Mesa.
> I usually buy Mesa. Should I look at other brands elsewhere?
>
Truthfully, I haven't noticed that much of a difference, except that the
Russian mil-spec tubes do sound cold and harsh compared to audio-targeted
tubes. But they're supposed to last forever :-) I keep a few as spares, but
yep, JJ's and Mesas do sound better.
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Re: stupid tube questions - William Black - 03:57 07-12-05
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"Grant W. Petty" <gpetty@aos.wisc.edu> wrote in message
news:Pine.LNX.4.60.0512062333070.3915@cloud.aos.wisc.edu...
>
>
> 1. Besides microphonics, what are the other common ways in which it
> becomes clear that tubes are due for replacement? Are the symptoms
> different for power tubes (e.g,. EL-84s) vs preamp tubes (12AX7s)?
In the days when I worked with valve equipment professionally we'd use a
thing called a 'valve tester'.
All the tubes on all the equipment would get pulled every service interval
and tested for a drop in performance (usually gain).
Valves are usually run at slightly below their maximum design performance so
when you tested them and they didn't make the design spec they were on the
way out and could be changed before they started to affect equipment
performance.
You used to be able to pick up an old valve tester for a few quid when they
all went out of service many years ago, these days I imagine most of them
are museum pieces...
--
William Black
I've seen things you people wouldn't believe.
Barbeques on fire by the chalets past the castle headland
I watched the gift shops glitter in the darkness off the Newborough gate
All these moments will be lost in time, like icecream on the beach
Time for tea.
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Re: stupid tube questions - Keith Adams - 04:10 07-12-05
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I personally dont care for the sound of a 12AX7 or 12AD7. Both have an
amplification factor of 100. Too harsh.
Much prefer a 12AZ7---V7---T7----U7----Y7 which range from 70 to 20 in
their amplification factors. These tubes give a smoother less grainy
sound than the AX7 tubes. I dont care for preamp distortion either
Just because an amp is single ended (class A) doesnt mean it should eat
power tubes. I've never had one go bad in mine and it gets used quite
often. The original tubes were in it when I bought it in about 97 and
it was made in 65. They worked fine still. GT and Mesa dont make
tubes. They buy them from whoever they can,run them through a bogus
performance test,rebrand them with their logo,stick em in a pretty box
and charge double for what they're worth.
"Grant W. Petty" <gpetty@aos.wisc.edu> wrote in message
news:Pine.LNX.4.60.0512062333070.3915@cloud.aos.wisc.edu...
1. Besides microphonics, what are the other common ways in which it
becomes clear that tubes are due for replacement? Are the symptoms
different for power tubes (e.g,. EL-84s) vs preamp tubes (12AX7s)?
2. Are there replacements for 12AX7s that are harder to push into
clipping? I'd ideally like to be able to hit the input of my Gibson
GA-15RV (Class A, single volume control) fairly hard and know that any
clipping is only occuring in the power stage, as I don't like preamp
clipping. Maybe this is already the case; I don't know. Without a
separate preamp and master volume, it's hard to tell.
3. How important is tube brand? My main music store offers GT and
Mesa.
I usually buy Mesa. Should I look at other brands elsewhere?
4. By reputation, my amp "eats power tubes like popcorn". This is
presumably because of the Class A thing .. large plate current even
when
silent. What does this mean in practical terms? For how many hours of
use
should I normally expect my tubes to last? I've retubed twice in about
two
years (a few hours per week of use, on average) just for fun, but haven
't
really noticed any difference between the old and new tubes. I don't
want
to be excessively paranoid about my tubes giving out on me, but I don't
want to miss the symptoms either. I'm already chronically concerned
about
whether my amp "sounds right", but I'm pretty sure most of that is,
well,
paranoia. Or hypochondria. Or something.
- Grant
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Re: stupid tube questions - RD Jones - 08:18 07-12-05
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Grant W. Petty wrote:
> 1. Besides microphonics, what are the other common ways in which it
> becomes clear that tubes are due for replacement? Are the symptoms
> different for power tubes (e.g,. EL-84s) vs preamp tubes (12AX7s)?
If the filament doesn't glow, it's a dead giveaway ;o{/
If the silvery deposit on the inside of the glass starts to fade
away, the tube may be getting "gassy" and should be replaced.
If the output(s) are run real hot (as is possible with a classA)
the plate may glow red and eventually melt or sag and short
internally, taking other components with it before a fuse blows.
(I've never seen this with a preamp, though)
If a plates been run that hot for a period of time it will become
discolored, and that's a indication of the need for a bias adjustment.
> 2. Are there replacements for 12AX7s that are harder to push into
> clipping? I'd ideally like to be able to hit the input of my Gibson
> GA-15RV (Class A, single volume control) fairly hard and know that any
> clipping is only occuring in the power stage, as I don't like preamp
> clipping. Maybe this is already the case; I don't know. Without a
> separate preamp and master volume, it's hard to tell.
12AT7, 12AU7, 12AV7, etc types have less gain and therefore
will be harder to clip, but when they do it will at near the same
signal level as the 12AX7. This is determined by the circuit
and supply voltage more than the tube type itself.
> 3. How important is tube brand? My main music store offers GT and Mesa.
> I usually buy Mesa. Should I look at other brands elsewhere?
Depending on the quality control of a particular 'brand' there may
as much variation among individual tubes within a brand as there
are among brands. Some of the better sounding preamp tubes
I have are Radio Shack brand from the '70s. (No, not for sale)
> 4. By reputation, my amp "eats power tubes like popcorn". This is
> presumably because of the Class A thing .. large plate current even when
> silent. What does this mean in practical terms? For how many hours of use
> should I normally expect my tubes to last? I've retubed twice in about two
> years (a few hours per week of use, on average) just for fun, but haven't
> really noticed any difference between the old and new tubes. I don't want
> to be excessively paranoid about my tubes giving out on me, but I don't
> want to miss the symptoms either. I'm already chronically concerned about
> whether my amp "sounds right", but I'm pretty sure most of that is, well,
> paranoia. Or hypochondria. Or something.
Or something ... I'd just have spares available (fuses too) and just
look for obvious physical signs (noted above) a couple times a year.
ClassA has it's own sound in contrast to pushpull (which I prefer)
and part of that comes from the tubes running hot.
You should be able to get better life from the tubes than you seem
to think.
rd
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Re: stupid tube questions - Ron Thompson - 08:21 07-12-05
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Grant W. Petty wrote:
> 1. Besides microphonics, what are the other common ways in which it
> becomes clear that tubes are due for replacement? Are the symptoms
> different for power tubes (e.g,. EL-84s) vs preamp tubes (12AX7s)?
Humming, cyclical(sp?) noise, loud hissing, scratching sounds, random pops,
changes in sound as it heats up.
Power tubes can make really bad howling/humming sounds once they heat up,
then it can just go away. It is time to change them if they get that far.
Basically, if you fire up a t00b amp and you want to play with a band,
you'll know when something is wrong. You may not know exactly what is
wrong, but you'll know it needs looking at.
> 2. Are there replacements for 12AX7s that are harder to push into
> clipping? I'd ideally like to be able to hit the input of my Gibson
> GA-15RV (Class A, single volume control) fairly hard and know that any
> clipping is only occuring in the power stage, as I don't like preamp
> clipping. Maybe this is already the case; I don't know. Without a
> separate preamp and master volume, it's hard to tell.
Well, no offense, but if you don't know, then why would you bother chasing
tubes around? Does it sound good? Yes? Ok. No? Ok, maybe change tubes
if you can determine it is this clipping problem you suspect. That's a
great amp to turn all the way up and thrash at like yer in a car wreck.
It'll sound good pretty much no matter what when it is turned up. Stop
reading things on the 1nt4rw3b and LISTEN to it.
> 3. How important is tube brand? My main music store offers GT and Mesa.
> I usually buy Mesa. Should I look at other brands elsewhere?
I don't know man, I really don't. A reliable, reputable seller is all I
require for tubes for my amps, and I don't care what is written on them.
The guy that works on my amps gets them or tells me where to get them or
more importantly, tells me where NOT to get them. It's what it sounds like
after, that's what matters.
> 4. By reputation, my amp "eats power tubes like popcorn". This is
> presumably because of the Class A thing .. large plate current even when
> silent. What does this mean in practical terms? For how many hours of
> use should I normally expect my tubes to last? I've retubed twice in
> about two years (a few hours per week of use, on average) just for fun,
> but haven't really noticed any difference between the old and new tubes.
Then you didn't need to retube. In my experience, a few hours per week
won't need really any attention for quite a few years unless it starts to
get all skwawky on you.
> I don't want to be excessively paranoid about my tubes giving out on me,
Too late.
> but I don't want to miss the symptoms either.
You can't. It isn't rocket surgery at all. The average non guitar playing
civilian can hear a shot tube amp, you should have no trouble. STOP READING
THIS STUFF and LISTEN.
> I'm already chronically concerned about whether my amp "sounds right", but
> I'm pretty sure most of that is, well, paranoia. Or hypochondria. Or
> something.
I'll take "Or something". You can't be concerned about that because it
does, or it doesn't. If it does, stop. If it doesn't, try to quantify and
qualify what it is that is wrong with it, and go from there. If you don't
know, take it to an amp type fixer in yer area. And don't overlook the
local small TeeVee repair shop. They know how to align an amp too, they can
usually help in a pinch.
--
rct
The opinions above are mine and mine alone.
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Re: stupid tube questions - Keith Adams - 09:59 07-12-05
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They're just your opinions Ron but they're good ones that he should pay
attention to.
"Grant W. Petty" <gpetty@aos.wisc.edu> wrote in message
news:Pine.LNX.4.60.0512062333070.3915@cloud.aos.wisc.edu...
1. Besides microphonics, what are the other common ways in which it
becomes clear that tubes are due for replacement? Are the symptoms
different for power tubes (e.g,. EL-84s) vs preamp tubes (12AX7s)?
2. Are there replacements for 12AX7s that are harder to push into
clipping? I'd ideally like to be able to hit the input of my Gibson
GA-15RV (Class A, single volume control) fairly hard and know that any
clipping is only occuring in the power stage, as I don't like preamp
clipping. Maybe this is already the case; I don't know. Without a
separate preamp and master volume, it's hard to tell.
3. How important is tube brand? My main music store offers GT and
Mesa.
I usually buy Mesa. Should I look at other brands elsewhere?
4. By reputation, my amp "eats power tubes like popcorn". This is
presumably because of the Class A thing .. large plate current even
when
silent. What does this mean in practical terms? For how many hours of
use
should I normally expect my tubes to last? I've retubed twice in about
two
years (a few hours per week of use, on average) just for fun, but
haven't
really noticed any difference between the old and new tubes. I don't
want
to be excessively paranoid about my tubes giving out on me, but I don't
want to miss the symptoms either. I'm already chronically concerned
about
whether my amp "sounds right", but I'm pretty sure most of that is,
well,
paranoia. Or hypochondria. Or something.
- Grant
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Re: stupid tube questions - Grant W. Petty - 11:34 07-12-05
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On Wed, 7 Dec 2005, Keith Adams wrote:
> They're just your opinions Ron but they're good ones that he should pay
> attention to.
And I am -- thanks for all the responses.
Probably the only reason I fret about this stuff is that I have a tendency
hear (or imagine) "problems" with the tone. One day I'll be playing, and
it sounds like ice picks are coming out of the amp. Another day, I'll
think I'm hearing some kind of brittle crackly distortion on top of the
"normal" crunch. Yet another day, I'll think it lacks clarity. And then
there are days when the amp sounds heavenly. And sometimes I go through
all of these phases in one session. I increasingly suspect that it's
variations in my ears, not the amp itself, that's giving me fits.
- Grant
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Re: stupid tube questions - M.J.P. - 12:22 07-12-05
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"Grant W. Petty" <gpetty@aos.wisc.edu> wrote in message
news:Pine.LNX.4.60.0512071026350.4999@cloud.aos.wisc.edu...
> On Wed, 7 Dec 2005, Keith Adams wrote:
>
> > They're just your opinions Ron but they're good ones that he should pay
> > attention to.
>
>
> And I am -- thanks for all the responses.
>
> Probably the only reason I fret about this stuff is that I have a tendency
> hear (or imagine) "problems" with the tone. One day I'll be playing, and
> it sounds like ice picks are coming out of the amp. Another day, I'll
> think I'm hearing some kind of brittle crackly distortion on top of the
> "normal" crunch. Yet another day, I'll think it lacks clarity. And then
> there are days when the amp sounds heavenly. And sometimes I go through
> all of these phases in one session. I increasingly suspect that it's
> variations in my ears, not the amp itself, that's giving me fits.
>
> - Grant
>
>
Some amps are just plain inconsistent. For example i owned a
mesa mk2 that "shifted" from day to day, always a different
tone, always spinning knobs etc. I changed caps, everything
no avail. This one had me, i couldn't figure it out, considering
there was no logical reason for the shift. MJP
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