Spare Triode

[megawhat]

Hello!

Let me open by saying hi! I'm new!
I've been trawling the interwebnerd for inspiration for an amp I want to build for myself (I'm into amps and the guitarist from my old band is into cabinets, so we're joining forces on a one-off project for ourselves)

I've tried searching the forum, but i wanted to ask straight up about mods using the spare triode in trainwreck preamp. I don't want to clone a wreck but i'd be interested in hearing about circuit variations using parallel stage or cathode followers etc...

I do have a schematic of something wreck-eqsue with a cathode follower right after V1 driving the early tone stack.
I have also heard of later stages being made into cathode followers or parallel stages, but I can't find any notes or schematics on the sounds created.

Im just after some opinions on this.

I also need to have a think about this circuit with master volume controls... oh well.

cheers!
Bob

[sliberty]

If memory serves me correctly, the Matchless Spitfire and Lightening amps both use paralleled triodes at the preamplifier stage. Nice amps, with an interesting combination of fatness and chimeyness. Simple circuits too.

[megawhat]

yep. that is true.
I liked that idea and I own/owned amps with a parallel triode input stage also. High gain beast though, not matchless.

In the wreck, Ive seen some notes about making V2 a parallel stage.

The matchless amps with 3x12AX7's are mostly parallel triode input, then cathode follower.

I did think about doing something like that (parallel plates and grids with varying cathode resistors for mixed bias) but thought I might want more gain and that drew me to not using a parallel triode. The chassis I have is limited to 3x9pin preamp tubes, I also didn't want to stretch to 4.

[paulster]

The Wreck circuit isn't a good one to use as a basis to try to do something with the unused triode IMO as there's already gain out the wazoo with it in stock form that borders on the uncontrollable.

I'd really consider a different topology or at least gain staging if you wanted to incorporate the additional triode.

A JCM800 preamp is a really nice basis to tweak around as it can be modded in all sorts of ways for voicing/gain without having to add any additional tubes, or you could lose the cathode follower and put an extra stage in like the Roccaforte HG100, for example.

[megawhat]

and have a plate driven TS.
the JCM800 way seems more natural to me... all the amps I love are part of that marshall heritage.

Maybe you're right... i keep flip flopping on my plans.

I think the schems ive seen with the extra triode used in a wreck preamp either use it as a cathode follower, which isn't really increasing gain, parallel stage would, but i think in that preamp the over gain had been lowered.

The Komet Concorde (from what notes ive dig out) uses the spare triode for a CF.

I think you might be right though. I might go back to something more marshall based.

[PlinytheWelder]

You can use the spare triode to run an effects loop....


Blasphemy!!

[megawhat]

hahaha.

yeah, im not into FX loops.
the one amp i had that had one in, I sold.

right at this second im thinking... moving away from the wreck' style pre.
parallel input stage > gain ctrl > cathode follower > TMB stack > Master Vol > PI (maybe F.Paraphase/LTP switchable)

maybe with a k*met type power supply and slo NFB controls.
maybe bootstrap the CF

[M Fowler]

If you go to search option above type in spare triode check trainwreck discussion tab to the left of the screen you will come up with some similiar discussion plus a whole history of great old posts about TW amps lots of good info in these old threads.

Mark

[megawhat]

dont worry. ive been working my way through it!

[statorvane]

You can use the spare triode for a tremolo - LFO.

[megawhat]

is anyone going to suggest turning it into a bong?

paulster has convinced me to move away from the wreck

[RJ Guitars]

I agree with Paulster concerning the Express and Liverpool amps... they are finicky enough. However with the Rocket amp there is one cool thing you can do... use the extra triode for "Rocket Booster".

https://tubeamparchive.com/viewtopic.php?t=11401

The Rocket is simple to build, enormously stable, and a great sounding amp. The extra triode boost doesn't take this over the top and it's nothing like an Express. It's not necessarily a better sounding amp this way but it is totally harmless to your circuit otherwise.

rj

[paulster]

RJ's suggestion is a good one.

The other thing you could consider would be the Concorde preamp that you've already mentioned since this is already a killer Marshall-esque amp and that's the kind of sound you said you're interested in.

[PCollen]

Hello!
(snip)...
I've tried searching the forum, but i wanted to ask straight up about mods using the spare triode in trainwreck preamp. I don't want to clone a wreck but i'd be interested in hearing about circuit variations using parallel stage or cathode followers etc...
(snip)...
cheers!
Bob

Each stage of the TW Express has little if any more "gain" than a typical Marshall or Fender triode stage, and the 3rd stage has much less but more than the V2b cathode follower stage of the Marshall. It's the cascading of the three 'plate follower' stages that creates the much larger signal level , and therefore results in a pre-amp with a much higher total gain , at the input to the phase inverter. If you parallel the first 12AX7, and use the second 12AX7 for the 2nd and 3rd stages, you can increase or decrease first stage ( and thus overall pre-amp) gain and noise (hiss) level by manupulating the shared plate and shared cathode resistor values.