https://guitarnoise.forum/live-sound/what-do-the-tubes-do-in-each-position/ Guitar Noise Discussion Board en-US Thu, 04 Jun 2026 04:13:13 +0000 wpForo 60 https://guitarnoise.forum/live-sound/what-do-the-tubes-do-in-each-position/#post-198903 Fri, 15 Sep 2006 21:02:53 +0000 https://www.guitarnoise.com/forums/viewtopic.php?t=25026
:D]]> Live Sound Ricochet https://guitarnoise.forum/live-sound/what-do-the-tubes-do-in-each-position/#post-198903 https://guitarnoise.forum/live-sound/what-do-the-tubes-do-in-each-position/#post-198884 Fri, 15 Sep 2006 20:29:20 +0000
Try and give him another shot. Maybe he's on vacation or something. Email's not 100% reliable either, there's any number of reasons why he might not be getting them...]]> Live Sound Misanthrope https://guitarnoise.forum/live-sound/what-do-the-tubes-do-in-each-position/#post-198884 https://guitarnoise.forum/live-sound/what-do-the-tubes-do-in-each-position/#post-198883 Fri, 15 Sep 2006 20:28:33 +0000
8)]]> Live Sound slejhamer https://guitarnoise.forum/live-sound/what-do-the-tubes-do-in-each-position/#post-198883 https://guitarnoise.forum/live-sound/what-do-the-tubes-do-in-each-position/#post-198874 Fri, 15 Sep 2006 19:58:43 +0000
Try and give him another shot. Maybe he's on vacation or something.]]> Live Sound Mike https://guitarnoise.forum/live-sound/what-do-the-tubes-do-in-each-position/#post-198874 https://guitarnoise.forum/live-sound/what-do-the-tubes-do-in-each-position/#post-198828 Fri, 15 Sep 2006 17:26:55 +0000 they drive too easy
True, but if I can tame the preamp I'll be satisfied. Not looking for jazz clean, more of a power-pop chimey clean. With the 12ax7s I can get that if I keep the preamp gain under 3. With the 12AT7 in V1 I can goose it up to 5-1/2 before it gets a bit of hair. Very slight volume loss, but not significant.

Interesting about the 12dw7 - hadn't heard of that before. On Tube Depot they say "You can think of it as 1/2 a 12AU7 and 1/2 a 12AX7." Might be worth a shot! I'm also curious about 5751s and might give one of those a try.

Thanks for the info, and welcome to GN!

Oh, by the way Wes, the Eurotubes guy has completely ignored my emails, though he claims on the site that he encourages questions from potential buyers. He won't be getting my business.]]> Live Sound slejhamer https://guitarnoise.forum/live-sound/what-do-the-tubes-do-in-each-position/#post-198828 https://guitarnoise.forum/live-sound/what-do-the-tubes-do-in-each-position/#post-198800 Fri, 15 Sep 2006 10:01:31 +0000 the second tube has the job of driving the power tubes (phase inverter)

You can replace either one with a 12at7 , there are some rules but generally it just "works"
tubes are forgiving..

however to be technically correct the plate resistance and amplification factor
is different, I have noticed on occasion there is a fatter (more bass) clean tone
with a 12at7, if you go down to 12ay7 or 12au7 you may get the amp to the point
where it actually loses power (but its finally clean!) el84 amps are not known for clean tones
they drive too easy
also a neato tube to try is the 12dw7 or the 7247 but only for V1 (preamp)

ok I will go back to my tubes..]]> Live Sound uglyamps https://guitarnoise.forum/live-sound/what-do-the-tubes-do-in-each-position/#post-198800 https://guitarnoise.forum/live-sound/what-do-the-tubes-do-in-each-position/#post-194872 Tue, 22 Aug 2006 22:50:57 +0000
What we're talking about here is voltage amplification. Power amplification is a different matter, and power amplifiers have a rather low amplification factor. All that's needed from the voltage amplifiers is enough voltage to drive the power amplifiers to full output.

We guitar players are weird, though. We want to be able to overdrive amplifier stages into distortion. None of the designers of the classic amps expected that, it was a happy accident that they sounded good that way.
:D]]> Live Sound Ricochet https://guitarnoise.forum/live-sound/what-do-the-tubes-do-in-each-position/#post-194872 https://guitarnoise.forum/live-sound/what-do-the-tubes-do-in-each-position/#post-194756 Tue, 22 Aug 2006 08:19:53 +0000
Often in schematics you'll see the stages labelled as (ferinstance) Pre-amp, Driver, Power Amp (and possibly an IPA - intermediate power amp- or 2).
Basically, the first stage is set up to expect a very low input level, and amplifies it by (say for arguement) 20 times. Then the signal may go thru a level control (the volume knob to most of us) and onto the next stage of amplification, and so on.

Each stage may be one or more tubes (at the lower levels it's usually one tube per stage, or even half a tube for some of the dual types), at the highest power levels it's often 2 tubes per stage. Some designs have 4 tubes in the final power amplifier stage.

There are a few reasons to do it this way, rather than in one big step. The main reason is that you get better stability at lower gain settings.
If you had a gain of (say) 100,000 in one stage, it would take a fair bit of design effort to keep it from having all sorts of noise and probably spontaneous oscillations going on.]]> Live Sound kent_eh https://guitarnoise.forum/live-sound/what-do-the-tubes-do-in-each-position/#post-194756 https://guitarnoise.forum/live-sound/what-do-the-tubes-do-in-each-position/#post-194733 Tue, 22 Aug 2006 05:23:14 +0000 Live Sound Ricochet https://guitarnoise.forum/live-sound/what-do-the-tubes-do-in-each-position/#post-194733 https://guitarnoise.forum/live-sound/what-do-the-tubes-do-in-each-position/#post-194725 Tue, 22 Aug 2006 04:31:52 +0000
I am no expert on amps, but I would assume you have a tube (at least) for each stage.

I don't think you have to replace all tubes at once. I bought preamp tubes for my HRD from Eurotubes, got the power tubes about 6 months later. Just didn't have the money at the time. I still have all the old tubes as spares just in case.]]> Live Sound Wes Inman https://guitarnoise.forum/live-sound/what-do-the-tubes-do-in-each-position/#post-194725