Has anyone heard of this old mod? Some Marshall/ Vox bark?

[Dandrix]

Can someone please explain what I should be gaining (hopefully gain?)by performing this mod? Should I be shocked by the amount of British gain I would be receiving? I have wrote down my voltages and made a schematic ( sorry for the hand drawing). Tell me what you think. Should I be getting more gain? What was the reason for using V5? Thanks

[Chuck H]

1) How many Kendrick amps do you see around or even hear about?

2) Gerald Weber has a long history selling snake oil.

3) Anyone who promotes their mod by explaining it to you rather than providing a proper schematic (not a modified layout) believes that the only people they can sell this to don't know anything about electronics. That is, "amp mod paint by numbers for dummies".

4) Marshall amps sound different from Fender amps for a lot of reasons not even related to the preamp. Adding a gain stage to a Fender amp, no matter how it's voiced, will not make it sound like a Marshall. Or even Marshall-y.

The mod should indeed provide more gain though. If that's all you're interested in. But I see no reason to rape the trem circuit. Torres has a slightly better reputation than Weber in the amp nerd circles and he pretty much specializes in hot rodding Fender circuits. Whatever else anybody says about Dan Torres, his circuits typically sound good. And he has several mods for increasing gain using the normal channel that don't include defuncting the trem circuit. I'd look into those before I'd implement this mod.

JM2C

[The Dude]

^^^^^^That. Plus,...... it would help to know what amp we're modding. And FWIW, if I were adding a gain stage for the purpose of overdrive, I'd want a gain control. At a quick glance, I don't see that there.

[Dandrix]

Yes to all, it’s super reverb kit from mojo. I don’t use the Trem. I thought it would worth modding seeing that I do not use normal channel? I was curious. It’s a more of experiment. I even changed the load plate resistor of v1a to 220k. Not really getting that wow experience yet?
Any ideas to spice this up?

[g1]

There is also the cascaded inputs idea, you have an unused channel that you can put to use.
Like Boogie MKI or 2203 JCM800.

[The Dude]

Yep. The old "One Wire" cascade mod.

[Chuck H]

Ken Fischer (a guy that's generally considered to have an ear for tone ) has said that the best place to put an extra gain stage in a Marshall type amp (which would include a Bassman type amp?) is in front of the preamp. While the best place to put an extra gain stage in a BF Fender type amp is at the end of the preamp (this considering the "normal" channel). And if you look at a Trainwreck amp you'll see that the extra gain stage follows the preamp and is placed behind the phase inverter. Most players don't have a problem with the tone of Trainwreck amps. That said...

My own amp designs include one that's very similar to the TW/BF Fender with the extra stage ideology. I designed this amp long before anyone knew the TW circuit though and I make it a point to say so every chance I get for fear of being accused of copying the TW circuit. Anyway, I have some experience with this topography. Gain isn't a problem. You can have pretty much all you want. Even bordering on metal tones for harmonics and gain level. But your EQ is rendered useless as an EQ and becomes a 'distortion character' circuit instead. You see, with the BF Fender topology the EQ is set early in the preamp before any overdriven gain stages. By the time the overdriven signal gets to the speaker any adjustment to TMB has been frappe'd to mush. So the only EQ control in the system becomes your OT, speaker/s and the cabinet. This actually works out remarkably well if you are using decent speakers and cabinets because we generally want a flatter, more balanced EQ for overdriven tones.

And incidentally, crunchy, hard rock tones are eminently achievable with this topography. I dare not say "Marshall". But way more so than stacking a gain stage with the ubiquitous .68 cathode bypass cap into a BF Fender preamp.

And, incidentally, this Weber mod seems to ignore the loading of the shared cathode resistor by two triodes. In order to achieve the actual frequency response of the Marshall 2.7k/.68uf cathode bypass circuit in a shared stage you would have to use a 1.35k cathode resistor and a 1.36uf capacitor. And this would seriously foul the tone of the "vibrato" channel. This Weber mod is an uneducated hack that tries to insert Marshall tone into a Fender amp by implementing Marshall amp circuit values arbitrarily. I wouldn't even consider it. The "right" circuit values for a given frequency response always have to be calculated based on circuit specifics. You can't just cut and paste component values into a design based on their provenance from a completely different circuit.

[Zouto]

You could also use this old school 80´s mod without butchering your precious amp https://www.premierguitar.com/articl...a-super-reverb

[Dandrix]

That’s the spirit I am looking for. Thanks Zouto
I guess, I was looking for an explanation of this Brit mod. It seemed to be a lot of work to get little bark. Lol
Your mod would get results with a lot less hassle.

[g1]

Yep. The old "One Wire" cascade mod.