Scaling an AC30CCH...

[Hellhammer]

Hi,

Would you scale the whole amp, PI+power tubes or just the power tubes?

I'm thinking just the power tubes as it has a post PI MV. But I would need another choke for that right? Or leave either screens or preamp without choke and maybe up the filtering instead.

So how would/did you do it?

Schematic

Cheers,
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[10thTx]

There is some useful VVR information here:

http://www.el34world.com/Forum/index.php?topic=6899.0

With respect, 10thtx

[Masco]

Buy an SB2 kit from London Power and read the directions.

You'll want to scale the trem oscillator as well in the AC-30CC, since it is the output modulated type.

[renshen1957]

Buy an SB2 kit from London Power and read the directions.

You'll want to scale the trem oscillator as well in the AC-30CC, since it is the output modulated type.

Hi,

I agree with Masco, and will add my 2 cents, power scaling the power amp and and not the PI will require a MV volume or compensation pot, however you should be able to dial in any level of power amp distortion (or not). Power Scale the power amp and PI requires only one pot for PS, but is less versatile at lower volumes for power amp distortion. I don't see any advantage to power scaling the entire amp.

Best Regards,

Steve

[Masco]

The AC-30CC already has a cross fade type MV in place, but I agree not to scale the whole amp.
Additional choke is not needed, nor do you have to split the DC after the rectifier as with VVR examples I've seen on the net. The SB2 comes w/ 2 regulators; one for plates and one for screens. They simply go in-line w/ their feeds from the PI filter nodes, the gates tie together for a single scale control. The trem oscillator's supply will come from the regulated(scaled) screen supply.

[Hellhammer]

Thanks for the heads up on the trem, hadn't thought about that. A PS-kit would be the easiest probably, but I was going to DIY this. Haven't found any schematics of the newer PS-kits so I don't know how they work... but if I was to use a VVR type of circuit, I'd need some additional filtering on either the Screens or PI+Pre node right? Depending on which node I use the existing choke in.

[d95err]

My guess is that since tremolo oscillators are rather sensitive, the ocillation would stop once the voltage reduction is significant (e.g at around half the normal voltage).

[Hellhammer]

Tjena Erik!

So should I leave the trem fixed voltage? Damn I have no idea how the tremolo works, need to study some.

My guess is that since tremolo oscillators are rather sensitive, the ocillation would stop once the voltage reduction is significant (e.g at around half the normal voltage).

[Masco]

My guess is that since tremolo oscillators are rather sensitive, the ocillation would stop once the voltage reduction is significant (e.g at around half the normal voltage).

It's not a tube oscillator, it uses a FET. The oscillator does cut off at really low scale settings, probably below 1/4 w/ stock rail R. The trem is not useable w/o scaling, it must track w/ output. There are ways around this if you scale that low, but I don't usually scale below 1/4.

[Hellhammer]

Ok, did some reading on oscillators and tremolo and i sortof understand the circuit now. I will scale it and see how i like it. Thank you all.