Clean headroom

Scarey · Post by **Scarey** » Sun 08/03/08 4:33 am

Can I replace the 12ax7s with 12ay7s in my 1974x without any modification?

kleuck · Post by **kleuck** » Sun 08/03/08 4:48 am

Yes, but i wouldn't use one in the Pi.

1950 · Post by **1950** » Sun 08/03/08 11:33 am

Can I do the same with a 5751.
Not sure just asking for second opinion

kleuck · Post by **kleuck** » Sun 08/03/08 11:52 am

Héhé, yes you can.

1950 · Post by **1950** » Sun 08/03/08 1:45 pm

Thanks for that one Kleuck
Whats with the froggy thing? are we not all humans

kleuck · Post by **kleuck** » Sun 08/03/08 5:19 pm

I'm french.

1950 · Post by **1950** » Mon 08/04/08 4:40 am

What are yout taste of amp and guitar Kleuck, is there French manufacturers of this sorta gear. S'pose you guys have all Europe to pick from so probably tons more options than us in Ireland and more sensible prices too!

kleuck · Post by **kleuck** » Mon 08/04/08 5:36 am

Not sure of that !
I have a Jonshon Loredo (cheap), heavily modded, in wich i tried 5751 12AT7 and 12AY7 (12AY7 are best). ; and a Home Made (except the edge) ash "Albert Collins-like" guitar (dp103 paf57 and alnico2 telecaster bridge PU).

I'm working (planning in fact) to build, with transformer and chassis i own for a long time, a "Little 18 watts" (The OT is an ultrea-linear hi-fi transformer rated 10watts, so i will rate the amp 12-15 watts max).
Not really a 18 watt though, my chassis has two pots, so i will go for a lite, add a little more gain to the preamp (220k/2k7) with 12AT7/ECC81 (have a bunch of them), a cathodyne direct coupled 12AU7/ECC82 dephazer (not a PI), and a "bright" switch.

You're right, the low dollar change allow low prices on amps.
But when i see the second hand market in usa...tons of cool amps we just cannot find, whatever the price...
There is one or two manufacturers, NOS for example.

1950 · Post by **1950** » Mon 08/04/08 8:13 am

Checked yer websites Kleuck, learned French at school, but not too good. I did some messing with solid state before this. There was no transistors when I began, full circle, back to reality (valves)!
My favourite at this moment a black LP shaped Cort EVL Z4, EMG pu's with all the graveyard hardware swapped off - 18 watt homebuild, plenty loud (beware the drummer) "but the sound is !!!!!£$ <", & an EVJ for fun!
Good to have you here Kleuck

Post by **zaphod_phil** » Mon 08/04/08 8:33 am

Why spoil an 18W by making it have more clean headroom? 18W amps are, like most typical Marshall amps, all about breaking-up tones and distortion.

Alexo · Post by **Alexo** » Mon 08/04/08 8:47 am

I built a variant with a 6DJ8 feeding a 12AU7/cathodyne pi, I've been meaning to switch it over to a 12AX7 because it is just toooo clean, especially with single coils.

kleuck · Post by **kleuck** » Mon 08/04/08 8:57 am

zaphod_phil wrote:Why spoil an 18W by making it have more clean headroom? 18W amps are, like most typical Marshall amps, all about breaking-up tones and distortion.

Because il love "just on the edge" crunch for my amps.
Spent a lot of time modding my Loredo for that (stock, it has an awfull power stage distortion)
Because i want to use it with my Loredo (preamp out) without too much crunch.
Because, i love my home-made boosters and distortions.
Because, the best part of the 18 watts (to me), is the first stage.
I make a booster/buffer/mixer/splitter using only a pair of Fets, wich in fact derives directly from the 18 watts first stage.

1950 wrote:Checked yer websites Kleuck, learned French at school, but not too good. I did some messing with solid state before this. There was no transistors when I began, full circle, back to reality (valves)!

Here, i am describing the mods to make this cheap but good amp become a really f***ing good vintage sounding single channel amp.

Post by **rjgtr** » Mon 08/04/08 9:39 am

If you aren't afraid of a soldering iron, you can change the power tube grid leaks from 470k to 220k. This will give you a little more range before power amp distortion kicks in.

Leave the grid leaks alone but put in a post phase inverter master volume. This will let you dial in your headroom.

If you don't want to chagne the amp too much, then try a 12at7 in the PI position. This will make the amp break up a little later.

kleuck · Post by **kleuck** » Mon 08/04/08 9:50 am

(If you are talking to me)
I know there is other ways to deal with the break-up level (used 12AT7 in my Loredo, before i get a ECC803S, and by the way, with a 100k anode resistor, a 12AT7 gives same gain as a 12AX7)
But as i said, i have only two knobs (little chassis) so a post Pi master is not an option.

And i have a couple ideas in mind : make the simplest design possible ; use as many old components i have as possible, for example.
A 12AU7 direct coupled cathodyne dephazer needs less parts, and i have a bunch of nos 12AU7.
Added to that, the lower driving impedance for the power stage.

boboso · Post by **boboso** » Tue 08/26/08 10:14 am

seems like a cool plan

Post by **zaphod_phil** » Tue 08/26/08 5:05 pm

kleuck wrote:Because il love "just on the edge" crunch for my amps.

So do I. So I simply reduce the guitar volume (by means of a passive volume pedal) and the 18W does a beautiful clean just breaking up tone

I also ended up putting away my pedals because the distortion tones of an 18W are just so good!

kleuck wrote:Here, i am describing the mods to make this cheap but good amp become a really f***ing good vintage sounding single channel amp.

But it already is that - an ultimate vintage guitar amp.

Still, as long as you're enjoying what you're doing, that's what counts.

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