Marshall 18watt Reverb

18watt-specific Tech Talk - Building, Fixing, Parts, Mods...

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JMPGuitars
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Re: Marshall 18watt Reverb

Post by JMPGuitars »

fiat_cc wrote:
Thu 10/19/17 4:27 am
This is what I've come up with. I have tweaked the schematic a little bit (and the layout a bit more) since my first prototype, but only due to tremolo thump. The reverb worked nicely straight out of the box (well once I moved all things tremolo away from all things reverb).

18 watt reverb - 6v6 schematic v1-4.pdf
18 watt reverb - 6v6 layout v1-4.pdf
You should have read a little more. ;)

We were discussing removing some of the reverb circuit's tone-sucking resistors and sending the return through the unused triode of the PI on single-channel, non-NFB amps (especially our 18 watters)... Your signal origin point is 1 option, but it's nice to experiment with the signal before and after the tone stack to see how that affects the reverb tone. I've already done all this (including removing the extra resistors), now it's his turn...and maybe yours too, if you want to improve the reverb tone even more.
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fiat_cc
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Re: Marshall 18watt Reverb

Post by fiat_cc »

Well, since I’m here now...
If I wanted to bring the reverb return directly into V3b in my schematic (spare triode of phase inverter), do I change (or delete) any of my resistor values?
Also, is there a benefit in tapping the reverb signal before the tone stack? I imagine that would leave you with less possibilities in terms of reverb sound.
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geoff 1965
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Re: Marshall 18watt Reverb

Post by geoff 1965 »

hello pilgrim's
this might be useful/interesting to the topic? it's the hoffman 18watt lite reverb which i saved for the V1 cathode biasing "has anyone tried this?"
note how the reverb circuit uses both halves of the phase inverter mentioned earlier in the post.
18w lite reverb.GIF
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SkilpaddaN287
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Re: Marshall 18watt Reverb

Post by SkilpaddaN287 »

Yes exactly hurray
And reverb circuit look much easier to do than the blackface reverb cicuit :wink:
Is there any info somewhere about what reverb tank(pan) to use and other stuff...? Read
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Re: Marshall 18watt Reverb

Post by fiat_cc »

It looks, at a quick glance, to be the same reverb circuit I used (and posted a few posts ago). The main difference being I fed it in on the other side of the phase inverter. Tank model is on my schematic, and the transformer is the same as the standard Fender reverb transformer. Also, I don’t see it using both sides if the phase inverter. ‘C’ refers to a power node. R2 feeds back into 1 side of the phase inverter (the opposite side to the rest of the amp).
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Re: Marshall 18watt Reverb

Post by geoff 1965 »

SkilpaddaN
glad the schematic was of good use for you! i have'nt built an amp with reverb but i'm sure the rest of the guys will help you out. if you go to the "EL34 world" website there are schematics,layouts and parts lists for the hoffman reverb amps.
good luck
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Re: Marshall 18watt Reverb

Post by SkilpaddaN287 »

But i some wonder if this reverb will have some weak signal compared to the fender...?
Fender have two triodes in paralell for extra current before the transformer and an extra triode after the recovery triode....
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Re: Marshall 18watt Reverb

Post by fiat_cc »

SkilpaddaN287 wrote:
Mon 10/23/17 9:37 am
But i some wonder if this reverb will have some weak signal compared to the fender...?
Fender have two triodes in paralell for extra current before the transformer and an extra triode after the recovery triode....
It is not as strong as the Fender blackface reverb. I find that there’s plenty available for my personal taste, but if you’re wanting Fender amounts, this circuit won’t get you all the way there.
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Re: Marshall 18watt Reverb

Post by SkilpaddaN287 »

Image
Did some old fashioned drawing...
Have to tune the power supply to get good voltages but on my view it should work...
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Re: Marshall 18watt Reverb

Post by Banker »

I have an original 18w "Master Reverb", a 1958 in 2x10 format. It's an interesting amp, single channel with both reverb and trem. Interesting layout too. A friend knocked up a schematic for me, which I'll do my best to find and post here in due course.

In the meantime, a couple of pictures.....

Image

Image

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Image

Image
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Re: Marshall 18watt Reverb

Post by JMPGuitars »

Banker wrote:
Wed 03/07/18 9:43 am
I have an original 18w "Master Reverb", a 1958 in 2x10 format. It's an interesting amp, single channel with both reverb and trem. Interesting layout too. A friend knocked up a schematic for me, which I'll do my best to find and post here in due course.
I'd love to see the schematic when you get it. Can you post some sound samples? I'd love to hear the reverb half way, and fully cranked.

Thanks!
Josh
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Re: Marshall 18watt Reverb

Post by sreiter »

I havent been on here in a longggg time.

My buddy has a orginal 18w w/reverb.

If my gallery is still on here, there's pics, including chassis
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Re: Marshall 18watt Reverb

Post by JMPGuitars »

sreiter wrote:
Fri 04/06/18 4:47 pm
I havent been on here in a longggg time.

My buddy has a orginal 18w w/reverb.

If my gallery is still on here, there's pics, including chassis
Do you remember what your album was called? The old archive galleries are here: gallery/

Thanks,
Josh
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Re: Marshall 18watt Reverb

Post by Malibu2006Vride »

Hello I just joined this site and am planning to build an 18W amp. I'd like to add reverb and found this thread. It looks like it went stale back in 2018.

Does anyone have a schematic for the original Marshall design with the reverb option?
I'd like to stay as close to the original as possible as opposed to kluging in something.
I'd appreciate any help from you all.
Regards
Dave
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Re: Marshall 18watt Reverb

Post by Daviedawg »

I do not recall any approved or tested circuits while I have been on the Forum. But even so there may be one buried somewhere. Unfortunately some early material in threads was not recoverable after a hack several years ago.

Having said that it would be a useful circuit to have. What form of 18 watt were you considering? If it is an 18 watt lite then all the standard iron should work fine. But if a trem or TMB then you would have to consider the power transformer needs first since you are adding at least one twin triode and possibly also a triode pentode depending on how good a reverb you would like.

I have a vague recollection of someone on PPWatt discussing a form where the reverb went in place of the trem channel (a big loss in my view) so I will go have a look there. This is a feasible build so it is worth pursuing even if some of our elder members disapproved of 18 watt with reverb.

Dd
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