How Tube Amps Work

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How Tube Amps Work

Post by jeremyb »

I'm sure many of you know Uncle Doug, well I'm trying to educate myself on tube amps and how they work and I've found these two videos explain so many things in plain and simple language, really dig it!



Slowy wrote: That's the problem; everything rewarding is just such hard work. Regret takes much less effort.

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Re: How Tube Amps Work

Post by MikeC »

jeremyb wrote: Wed Aug 04, 2021 3:12 pm I'm sure many of you know Uncle Doug, well I'm trying to educate myself on tube amps and how they work and I've found these two videos explain so many things in plain and simple language, really dig it!



Uncle Doug is great :thumbup:
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Re: How Tube Amps Work

Post by jeremyb »

This is a cool deep dive into the AC10 and trying to improve it.

Slowy wrote: That's the problem; everything rewarding is just such hard work. Regret takes much less effort.

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Re: How Tube Amps Work

Post by MikeC »

Just being pedantic but you'd swear after watching this that current flows from positive to negative. Guess what...
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Re: How Tube Amps Work

Post by RectifiedAmps »

MikeC wrote: Thu Aug 05, 2021 4:21 pm Just being pedantic but you'd swear after watching this that current flows from positive to negative. Guess what...
They had a 50% chance of getting it right... and got it wrong. And while we're at it, there's no such things as 'holes' when talking about transistors!

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Re: How Tube Amps Work

Post by Anvil Amps Alan »

MikeC wrote: Thu Aug 05, 2021 4:21 pm Just being pedantic but you'd swear after watching this that current flows from positive to negative. Guess what...
Chinese valves have retrothermionic cathodes which suck up electrons?
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Re: How Tube Amps Work

Post by MikeC »

Anvil Amps Alan wrote: Thu Aug 05, 2021 4:41 pm
MikeC wrote: Thu Aug 05, 2021 4:21 pm Just being pedantic but you'd swear after watching this that current flows from positive to negative. Guess what...
Chinese valves have retrothermionic cathodes which suck up electrons?
Ahhh, of course...
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Re: How Tube Amps Work

Post by RectifiedAmps »

jeremyb wrote: Thu Aug 05, 2021 3:53 pm This is a cool deep dive into the AC10 and trying to improve it.

That video title opens a whole can o' worms in itself: http://www.aikenamps.com/index.php/is-t ... ly-class-a (not the AC10 but equally applicable). Hot cathode biasing does not mean class A, but it doesn't really matter because all the qualities we love with (what we misconstrue as) class A are provided by a cathode biased (class AB) amps.

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Re: How Tube Amps Work

Post by Conway »

I think JB is probably interested in rectum-friers...
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Re: How Tube Amps Work

Post by sizzlingbadger »

Changing the cathode bias resistor wasn't a bad move (Its even more Class AB now ;-) ), but the other volume mod was a bit pointless, you just have less overdrive now at higher volume settings. It doesn't have any more clean headroom than before, its just the volume control is at a higher position for the same actual volume.
Tube amp and guitar tones straight from 1958… amazing how believable the sounds were back then, even without the modellers...

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Re: How Tube Amps Work

Post by jeremyb »

sizzlingbadger wrote: Fri Aug 06, 2021 10:29 am Changing the cathode bias resistor wasn't a bad move, but the other volume mod was a bit pointless, you just have less overdrive now at higher volume settings. It doesn't have any more clean headroom than before, its just the volume control is at a higher position for the same actual volume.
Putting a 5751 into mine to see how that goes, SRV was a fan of them :lol: will measure the tube voltage while I'm at it, don't want to nuke the new power tubes I'm putting in either... isn't the theory of the lower preamp tube to give more of the flavour of the power amp tubes?
Slowy wrote: That's the problem; everything rewarding is just such hard work. Regret takes much less effort.

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Re: How Tube Amps Work

Post by sizzlingbadger »

jeremyb wrote: Fri Aug 06, 2021 10:37 am
sizzlingbadger wrote: Fri Aug 06, 2021 10:29 am Changing the cathode bias resistor wasn't a bad move, but the other volume mod was a bit pointless, you just have less overdrive now at higher volume settings. It doesn't have any more clean headroom than before, its just the volume control is at a higher position for the same actual volume.
Putting a 5751 into mine to see how that goes, SRV was a fan of them :lol: will measure the tube voltage while I'm at it, don't want to nuke the new power tubes I'm putting in either... isn't the theory of the lower preamp tube to give more of the flavour of the power amp tubes?
V1 on this amp is transistor so you can't reduce the gain of it by changing a tube, that is where you would normally use a 5751 to maintain headroom in the pre-amp stages.

In that circuit I expect just turning the Gain down one notch would have the same effect as trying a 5751 in the second stage. The second triode of that tube is a DC coupled cathode follower which is appx unity gain anyway. Its a low impedance output design to drive the EQ circuit. I would stick with the Chinese tubes in that position, I have had the Russian tubes (TungSol specifically) fail due to the raised grid-to-cathode voltage.
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Tube amp and guitar tones straight from 1958… amazing how believable the sounds were back then, even without the modellers...

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Re: How Tube Amps Work

Post by RectifiedAmps »

sizzlingbadger wrote: Fri Aug 06, 2021 10:40 am I would stick with the Chinese tubes in that position, I have had the Russian tubes (TungSol specifically) fail due to the raised grid-to-cathode voltage.
This is about the only case where a standby switch actually does prevent stress on valves. There's a fairly simple mod to protect against this - just a resistor and a diode from grid to cathode. See towards the bottom here: http://www.valvewizard.co.uk/dccf.html

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Re: How Tube Amps Work

Post by jeremyb »

Put the new tubes in today from Tone Lounge, man, the amp is quite a bit louder, the stock tubes must have been seriously pants :lol: the tone is quite lovely too, and even with the 5751 in it the gain fully maxed is way more than I need :rofl:
Slowy wrote: That's the problem; everything rewarding is just such hard work. Regret takes much less effort.

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Re: How Tube Amps Work

Post by jeremyb »

Looks like one of our (ex? maybe just a lurker now?) forum members has still been making cool stuff!

Slowy wrote: That's the problem; everything rewarding is just such hard work. Regret takes much less effort.

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