A Trainwreck-Style two-knobs amp (just in the cradle)

[roberto]

Hi all,
I'm working on my 2+2 channel amp, but meanwhile I keep on projecting the next amp: a Trainwreck based minimalist two knobs head.
The idea is born while I was figuring out the scoop mod for the clean channel of the current head: adjust the scoop with a single pot (clean versatility gains but I can have less knob on the panel).
So the idea migrate to a Trainwreck-style amp (I like plug&play amps, not plug&pray).
R1 is used cause this is a guitar amp, not a radio receiver
TU1 polarization is more midrangey than usual, I've used also in other amps this configuration.
C35 fixes bass frequency cutoff (you can raise mids adding a res to ground)
R45 fixes the maximum sweep of pot R47
R47 is a bass-scoop-treble balance, heart of the equalization. It must be log, because of the way it works.
TU2 is standard, but I'll try out some 2k2 or 1k8 cathode resistors.
I've used a little less bass cutoff after TU2, because the cold stage is more hard-rock style (supports lows better than 10k), with a little cutoff on harmonycs (C39's work).

Obviously R25 won't be used in the real amp, but after C14 there will be the PI (470 and 10k tail resistors) and a fixed presence.

Has anyone ever used a similar EQ for amps? Or worked on TW cold stage? Any suggestion about this work?

Thanks all!

[roberto]

Well, 160 views of the thread in 24h, alot of downloadas and no idea..
Quite strange!

[El_Martin]

Ciao Roberto!

I'm currently fiddling with a similar styled TW. It has got no full tonestack either. Thought about a RC combination to ground after first stage to tame the highs followed by a volume pot.
I did not care to simulate the schematic. It will be tuned by ear and scope.

I still expect some troubles with too much highs in my design, but I'm ready to implement a cut control before the power stage/across the OT.

If I get to it, the amp only needs a few hours of work. But there are always other things to do.

Another idea was to use some kind of reduced (think tweed treble bass TS inside, kind of mini HRM)

Ciao
Martin

[roberto]

Ciao Martin,

thanks for the answer. In this post I've attached some frequency simulations of the modified "tonestack". Name of file is related to knob position (12 o'clock is half way vertical knob). These simulations fits quite well a regular stack. Please note the mid-band raise as you add a resistence from C35 to ground and raise its value.

[rfgordon]

Here's my version of that simplified approach--the TNT or Two Nob Trainwreck. I've built one, and another forum member has, too. Great sounding amp. But then, how can you go wrong when Ken's work is your foundation?

[roberto]

Hi Gordon,
Great work! Do you have any sample or layout?

Thanks!

Robi

[Amwatts]

Here's my version of that simplified approach--the TNT or Two Nob Trainwreck. I've built one, and another forum member has, too. Great sounding amp. But then, how can you go wrong when Ken's work is your foundation?

Hi Rich, I've decided to build this as a Christmas project , I have an Express Clone and was looking for something not as loud , As the 5E3 uses the Cathodyne Phase inverter, Which is less efficient than the earlier Deluxes 5B3/5C3/5D3 Paraphase PI , I was wondering what your thoughts would be in modding your design to run the Paraphase.

an extra triode will be needed to accommodate the twin triode paraphase so I was going to add a 6AV6 socket to the chassis to cover that .

Any thoughts or is the Cathodyne PI a big part of the formula here

Regards
Watto

[Littlewyan]

There is a Trainwreck Express with a single tone control. It also has a volume control.

https://m.facebook.com/story.php?story_ ... 3072194215

I’ve no idea on what volume control it uses, but I wondered if the tonestack could be replaced with a simple voltage divider bypassed by a capacitor. Same as the first stage of a JCM800 or SLO100.

[Mark]

Here's my version of that simplified approach--the TNT or Two Nob Trainwreck. I've built one, and another forum member has, too. Great sounding amp. But then, how can you go wrong when Ken's work is your foundation?

Hi Rich, I've decided to build this as a Christmas project , I have an Express Clone and was looking for something not as loud , As the 5E3 uses the Cathodyne Phase inverter, Which is less efficient than the earlier Deluxes 5B3/5C3/5D3 Paraphase PI , I was wondering what your thoughts would be in modding your design to run the Paraphase.

an extra triode will be needed to accommodate the twin triode paraphase so I was going to add a 6AV6 socket to the chassis to cover that .

Any thoughts or is the Cathodyne PI a big part of the formula here

Regards
Watto

How did the build go Watto?

[Amwatts]

I haven't completed it yet, I'm still waiting for the transformers to arrive ... I've built the chassis minus transformers ... I ended up going with the 5E3 Phase Inverter , I'm thinking the TV front cab would be nice as I have a small stash of the original 1940's Luggage cloth used on the first Dual Professionals in 47 ...

Living in Australia means parts take SO long to arrive .... I'll post an update when I get the transformers , until then I'm in a holding pattern

[Mark]

In the meantime you have a Barwatt Express.

Keen to hear how the project turns out.

[Amwatts]

Finished the amp yesterday, sounds fantastic straight outta the box, I went with the 5E3 Cathodyne PI , I think it adds to the gain structure , I added a 470k resistor to balance the PI as well and a VVR . Went with the pot in the gain section instead of the resistor, it's subtle but definitely there , might have to play around with that section .
I think the Paraphase version will be nice as well , but the Gain section may need to be increased to , any thoughts .

I ended up using a Vintage 1957 Jensen P12Q speaker as it's all I had , But I feel it will suit an Ceramic much better , The Jupiter 25w is on order , Also ended up using the larger BF Deluxe Reverb output transformer , I had an NOS one here , I think that's part of the tightness in the crunch stage .... lots more tweaking

Very happy with the results as is , but I think there's more to be gotten out of it , Thanks for the design initial design rfgordon

Watto

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[xtian]

Cab is beautiful! And I like the "TV" front.

[Mark]

Great looking amp Watto. You will have to post a clip of it when it’s finished.

[Amwatts]

Screen Shot 2023-04-17 at 9.40.57 am.png

Hi all, I'm curious as to how much this resistor and its value changes the gain/saturation feeding the phase inverter . I've noticed Gordon has it at 47k (I did the pot adjustment version)

Looking at Francesca and Kelly , Ken used 150k , in some recommended mods I've seen as much as 330k ...
Roberto's schematic above has it labelled as R10 68k

I'm thinking of changing out the 50 pot to maybe 150k or there abouts and see what the results are , any thoughts on this

I also found after jamming with the amp yesterday that the top end gets cut slightly when winding back the guitars volume , My Francesca copy is crystal clear in comparison . I'm experimenting to try and reduce this , I know the single tone pot is different to the TMB and has an effect too, Any thoughts from those who have played with these circuits more than me would be appreciate , I'm new to the KF rabbit hole .

regards
Watto