What's so bad about plexi amps ?

paulphoenix

I've recently felt very drawn towards this style of amp.

I've heard a lot to like on various youtube demos and have also read good things...

But what's not to like? 

ICBM

They are massively loud and will need an attenuator to get natural overdrive at anything like a usable modern gig volume, unless you play with a *very* loud band in huge spaces... even the 50W models.

They also have surprisingly little gain by modern standards, even fully cranked - you will not get effortless smooth sustain without either using feedback (ie high volume) or a boost or overdrive pedal of some sort in front.

That said, the clean sound at lower volume is also wonderful - much richer and more vibrant than the typical Fender clean sound, and yet almost totally overlooked - and they take pedals very well.

You need a fairly big cabinet for them to sound right - anything smaller than a large 2x12" won't.

If you can deal with the size, weight, volume and the need to use a couple of other bits of kit to get them to work at lower volume, go for it... there's nothing else like one.

p90fool

I'd agree with all that, but they also work amazingly well as a clean pedal platform, even down to home volume levels. 

For some, NOT pushing the power section into brain-numbingly loud overdrive is "missing the point" but it really isn't, they're a high-quality, rich and complex clean amp too. 

Put a deep, spacious reverb in front of one, put the master on about 2 and be lost to the world for hours. 

paulphoenix

Thanks chaps, my bad -  I should've said I'd been looking at mainly lower wattage modern non Marshall plexi-esque amps. 

Is a PPIMV mod the way to go? Or is a plexi with a MV just not a plexi ? 

hywelg

I put 6V6's in mine (Russian 6Π6S) and it was plenty loud enough to gig and much better volume wise. It is a circuit that works very well as a pedal platform but for that the amp needs to be run with the output section still with plenty of headroom. 

As ever, attenuators will only reduce volume by about half before losing character, same with Powerscaling . Speaker choice can help keep.colune under control but unfortunately you do need Celestions for a vintage vibe and they don't tend to be as inefficient as some Jensens for example. 

paulphoenix

ICBM said:

"They are massively loud and will need an attenuator to get natural overdrive at anything like a usable modern gig volume, unless you play with a *very* loud band in huge spaces... even the 50W models."

I mic up every gig and play using a low stage volume - so attenuator or PPMIV would be the go even at 18W to get a little natural overdrive? 


"They also have surprisingly little gain by modern standards, even fully cranked - you will not get effortless smooth sustain without either using feedback (ie high volume) or a boost or overdrive pedal of some sort in front."

Wouldn't leave home without my pedalboard so not worried about this one. 


"That said, the clean sound at lower volume is also wonderful - much richer and more vibrant than the typical Fender clean sound, and yet almost totally overlooked - and they take pedals very well."

So not a one trick pony? I heard Plexi's mainly described as "but what a trick" amps? 

"You need a fairly big cabinet for them to sound right - anything smaller than a large 2x12" won't."

How would a compact 1x12" or 1x10" contribute to the detriment of the plexi tone? How does one define "boxy sounding"?  

"If you can deal with the size, weight, volume and the need to use a couple of other bits of kit to get them to work at lower volume, go for it... there's nothing else like one"


This is the one factor that entices me in, but not if i need a 50W with 2x12" 

Hoof

MY favourite amp is my 50 watt 1987x but I just can't use it because it's just too loud. At a reasonable pub/rehearsal volume it just sounds terrible. You don't have to drive the output into submission but you do need a bit of warmth on the clean sound to unlock any sort of decent tone. 

Oddly, mine does have some serious gain available as the clean volume tops out at about 9 o clock, the rest of the dial is added filth.

ICBM

paulphoenix said:

I mic up every gig and play using a low stage volume - so attenuator or PPMIV would be the go even at 18W to get a little natural overdrive?

How would a compact 1x12" or 1x10" contribute to the detriment of the plexi tone? How does one define "boxy sounding"?

In my opinion the typical 18W (EL84) power section and/or a 1x12" does not sound like a Plexi - it doesn't have the depth and authority. 20W - with 6V6s in a Plexi circuit - and an inefficient 2x12" is about the lowest you can go and still get the 'roar'.

A PPIMV works better than power scaling but not as well as an attenuator, to me.

If you're trying to keep the volume down, the old G12S-20 speakers are worth looking for - they didn't used to be popular, and aren't very valuable, but they have the nice vintage Celestion tone, although with less bass and lower sensitivity.

Hoof said:

MY favourite amp is my 50 watt 1987x but I just can't use it because it's just too loud. At a reasonable pub/rehearsal volume it just sounds terrible. You don't have to drive the output into submission but you do need a bit of warmth on the clean sound to unlock any sort of decent tone. 

Oddly, mine does have some serious gain available as the clean volume tops out at about 9 o clock, the rest of the dial is added filth.

That's largely due to the oversized bright cap, which is really a 'metal panel' feature - I don't know why they did that. If you replace the 4n7 cap with a 470pF it will get a lot more controllable, better-sounding at lower volume and with a more usable volume taper.

samzadgan

nothing else sounds like a plexi for sure. I use to have a 1974 Superbass...and whether i played it with a band at close to full volume, or at home at low volumes, it sounded amazing. I agree with the cab suggestion that ICBM mentions, you need something that can project the sound well, otherwise the amp is wasted a bit. 

The biggest issue i can see with a plexi is the size and weight of a 100 or 50w head and large cab if you taking to gigs and rehearsals...but that's never bothered me that much...but each to their own.

for the record my Superbass had a PPIMV mod done to it...i rarely used it, but then again i never went for the amp overdrive. I ran mine clean and used pedals, and it took everything i threw at it better than any amp (except the two i own now) 

57Deluxe

if you watch any of Johan Segeborn's vids you will see he makes anything sound like a Plexi - study his channel!

Jalapeno

I have the 2061X  - JMP "Lead and Bass" reissue.  All of the good stuff applies to this too.   I love it.

robinbowes

For the avoidance of all doubt, what specific amp do we mean by "plexi"?

R.

paulphoenix

robinbowes said:

For the avoidance of all doubt, what specific amp do we mean by "plexi"?

R.

Holy can of worms batman. The Marshall historians and aficionados amongst us will soon be out to state the model numbers and production years of the  plexi amp. 

But for the purpose of my OP and as a jumping off point into the abyss of the plexi sound (right or wrong - as I love a good learning curve), I had basically been looking at anything lower wattage/lower gain with plexi in it's name or with the words "plexi" contained within the marketing hype that sounded great in demo's.

 

ICBM

For me it specifically means a 1967-1969 50W or 100W JMP. JTM45s do also have ‘plexi’ panels but sound different. 18/20W amps are a totally different circuit even if from the same era. Early metal-panel amps from 1969-1971 or so do sound basically the same, but then became progressively brighter-sounding - but Bass, PA and Organ models weren’t changed as much and are a good way to get a vintage Plexi without spending as much, and can easily be modded to Lead specs.

TTBZ

I love the 1987x and 1959 but yeah they're bloody loud! I guess if you want something in that vein but more modern/manageable I'd have to suggest an Origin - 50w would be my choice as the power scaling is good and it goes down to about half a watt. I'm not saying it'll sound the same as the "proper" ones but through greenbacks they sound great. Take pedals really nicely too and have a nice chimey clean sound.

paulphoenix

..So as long as the control panel is of a plexi material it will be called a plexi amp regardless of circuit topology? 

So maybe I am not drawn towards plexi amps after all?... especially as I have been looking and listening to review of amps <18w ?

paulphoenix

TTBZ said:

I love the 1987x and 1959 but yeah they're bloody loud! I guess if you want something in that vein but more modern/manageable I'd have to suggest an Origin - 50w would be my choice as the power scaling is good and it goes down to about half a watt. I'm not saying it'll sound the same as the "proper" ones but through greenbacks they sound great. Take pedals really nicely too and have a nice chimey clean sound.

The new Origin amps are the only modern Marshall offerings that I have given any kind of second look in the last 20 years, and I keenly await the reviews on TFB from those whose pre-order waiting times are very nearly over. 

robinbowes

paulphoenix said:

The new Origin amps are the only modern Marshall offerings that I have given any kind of second look in the last 20 years, and I keenly await the reviews on TFB from those whose pre-order waiting times are very nearly over. 

R.

TTBZ

I'd recommend trying one out through a good cab with H30 or Greenbacks in, the combo speakers aren't really to my taste and don't show it off to its full potential imo.

Fwiw someone on TGP is saying he prefers it to his HRDx as a clean pedal platform as well. 

John_A

Jalapeno said:

I have the 2061X  - JMP "Lead and Bass" reissue.  All of the good stuff applies to this too.   I love it.

Very different circuit and sound to a 'Plexi' often called a mini-plexi because they look like one.  Great amps but very little in common with a 1987 or 1959

Winny_Pooh

I have one. Extremely simple amp. When played loud it is a dream. Downsides are size and power. Attenuation is like a nicotine patch. If you do get one, get a smallbox 50 watt clone with a decent master volume.