Hey everyone, and T. Ballz.
I've been looking into the current crop of 20w Marshalls, mainly out of personal curiosity. These can be broken into two categories: the Studio series which is assembled in the U.K. (mini plexi, jtm, jcm, and jubilee), and the Vietnam amps (DSL20 and Origin 20).
The aspect that really stands out is that the amps is that they still use EL34 power tubes. I believe this is the case for all of them. They get the wattage down to 20 by using a lower B+, and with cathode biasing. I like this idea because I am almost always not fond of EL84 amps. I also prefer power amps with negative feedback, and most EL84 amps eliminate that out of tradition.
I see a lot of Youtube techs using these as a platform for classic Marshall mods. They mod the plexi with some cascading stage or diode clipping/Jose mod. Or, they completely rebuild the Origin preamp into a known hard-rock circuit. On Youtube, they always sound pretty great. And, of course, the mini Plexi and JTM look super classy and cute.
Has anyone messed with any of these? Balls, have you built any amps with big tubes but a lower B+ and cathode biased?
Should I get one and mess with it? Should I just build one? Should I just commission something from T.Ballz since I'm lazy?
Re: The Current 20 watt Marshalls (paging Dr. Balls)
2You're not a fan of most of the amps that get built around EL84 power sections, but that doesnt mean you dislike EL84s or the amps that *could* be built with them. About 5 years ago I learned that (at the time) you could get the transformer set that Fender uses in the Blues Jr for dirt cheap. So I started building a lot of 2xEL84 amps because of that (some for members of this forum). Many of them were just a basic blackface approach I labeled as BF-15. Its a normal channel of a Super Reverb with 2xEL84 in cathode bias for the back end and it sounds great and very much like a BF amp, not an AC-15. I'm still doing that sort of thing (one on the bench right now) and I think EL84s are very versatile tubes that can sound like a lot of different things. They're small, 15W for a pair is a perfect power level, lower plate voltage keeps filter caps smaller, I think they're great. You can of course use negative feedback with them and even run them fixed bias if you choose....Hiwatt did this and so did the Blues Jr. /rant but EL84s are awesome, imo.benadrian wrote: Thu Sep 04, 2025 10:46 am I like this idea because I am almost always not fond of EL84 amps.
yes/no/yes. I've built some big tube/cathode biased amps (Neal Markowski has one) but the B+ isnt that far shy of normal. Neal's is 2xEL34 for ~40 watts.benadrian wrote: Thu Sep 04, 2025 10:46 am Balls, have you built any amps with big tubes but a lower B+ and cathode biased?
IMO.....Marshall is using "the sound of EL34s" as their bait for these and i'm not biting. I dont really believe in the sonic differences between power tube types, at least to the extent that they are preached/expected to make a difference. Marshall could have easily done these amps with 6V6s but they wouldnt be 1) "british" and 2) following in the Marshall lineage of using EL34s.
Re: The Current 20 watt Marshalls (paging Dr. Balls)
3I for one have not heard a thing different in Marshalls with factory EL34s, 6L6, or 6550 regardless of what the internet says. I think %90 of the time people are just hearing bias setting variance / same bias with a different tube.Dr Tony Balls wrote: Thu Sep 04, 2025 11:24 amYou're not a fan of most of the amps that get built around EL84 power sections, but that doesnt mean you dislike EL84s or the amps that *could* be built with them. About 5 years ago I learned that (at the time) you could get the transformer set that Fender uses in the Blues Jr for dirt cheap. So I started building a lot of 2xEL84 amps because of that (some for members of this forum). Many of them were just a basic blackface approach I labeled as BF-15. Its a normal channel of a Super Reverb with 2xEL84 in cathode bias for the back end and it sounds great and very much like a BF amp, not an AC-15. I'm still doing that sort of thing (one on the bench right now) and I think EL84s are very versatile tubes that can sound like a lot of different things. They're small, 15W for a pair is a perfect power level, lower plate voltage keeps filter caps smaller, I think they're great. You can of course use negative feedback with them and even run them fixed bias if you choose....Hiwatt did this and so did the Blues Jr. /rant but EL84s are awesome, imo.benadrian wrote: Thu Sep 04, 2025 10:46 am I like this idea because I am almost always not fond of EL84 amps.
yes/no/yes. I've built some big tube/cathode biased amps (Neal Markowski has one) but the B+ isnt that far shy of normal. Neal's is 2xEL34 for ~40 watts.benadrian wrote: Thu Sep 04, 2025 10:46 am Balls, have you built any amps with big tubes but a lower B+ and cathode biased?
IMO.....Marshall is using "the sound of EL34s" as their bait for these and i'm not biting. I dont really believe in the sonic differences between power tube types, at least to the extent that they are preached/expected to make a difference. Marshall could have easily done these amps with 6V6s but they wouldnt be 1) "british" and 2) following in the Marshall lineage of using EL34s.
Same tube with different plate voltage is far more interesting of a difference
Re: The Current 20 watt Marshalls (paging Dr. Balls)
4Are any of you familiar with the Line 6 DT25 amps? They came out 14 years ago, right when I started there. It was a hybrid amp with a tube power amp and digital models of preamps. The 25 had two EL84 tubes. They could be run in fixed or cathode biased mode. There was also pentode/triode switching. And, there were four setting for NFB: tight, medium, resonant, and none.
So, if a mesa recto model was loaded, then a resonant NFB and class A/B fixed bias was selected. If a vox model was loaded, the power amp would configure to cathode biased and no NFB.
This (and playing blues Jr. amps) really allowed me to realize that I don't hate EL84s. I just prefer lots of NFB and fixed bias, in general. Still, I could never get a sound with that amp which was truly satisfying. I have not, however, spent time building/designing amps with EL84 power tubes. I don't know if I could push it more into something I'd dig. Conversely, I DO enjoy 6V6, 6L6, and EL34/6CA7 tube in almost all of their configurations; cathode and fixed, with and without NFB , etc. About the only thing I don't like is too much resonance from blocking low frequencies in an amp with negative feedback.
But yeah, I've never played with B+ power scaling.
So, if a mesa recto model was loaded, then a resonant NFB and class A/B fixed bias was selected. If a vox model was loaded, the power amp would configure to cathode biased and no NFB.
This (and playing blues Jr. amps) really allowed me to realize that I don't hate EL84s. I just prefer lots of NFB and fixed bias, in general. Still, I could never get a sound with that amp which was truly satisfying. I have not, however, spent time building/designing amps with EL84 power tubes. I don't know if I could push it more into something I'd dig. Conversely, I DO enjoy 6V6, 6L6, and EL34/6CA7 tube in almost all of their configurations; cathode and fixed, with and without NFB , etc. About the only thing I don't like is too much resonance from blocking low frequencies in an amp with negative feedback.
But yeah, I've never played with B+ power scaling.
Re: The Current 20 watt Marshalls (paging Dr. Balls)
5I suppose I have *a bit* but only because I bought the wrong power transformer and needed to drop B+ so I used a little Mosfet dropping circuit, which worked great. But it wasnt for the point of power scaling.
Anyway I feel some initial shade on the EL84 sent me into defense mode and we got derailed. To the original post, I have not messed with one of those amps BUT i'm sure they sound fine. I checked out the one schematic that I could find and at least this one looks perfectly reasonable to me. Just a plexi circuit with ~340V plates. They did away with the choke (I wouldnt care about this) and IMO they should have added a LarMar MV but whatever.
Now to the question of should you get one AND MESS WITH IT? Nah, imo. They're PCB amps that will be a drag to swap components on unless you have a concrete game plan from the start. And for what point?? The EL34s running with a low plate? The SV20H is $1350 new, which is about what it would cost for a 20 watt 2x6V6 plexi from me and you could easily mod that. Also you could build one for much less than that (laziness aside).
Re: The Current 20 watt Marshalls (paging Dr. Balls)
6Ben have you tried the canonical 18W marshall?
Re: The Current 20 watt Marshalls (paging Dr. Balls)
7Barely. I didn't give them much of a chance. They are cathode biased, and i believe no negative feedback, so I steered clear for a while. The people I know who have them seem to use them as an occasional recording/overdub amp, but I never seem to see them as a "main amp."
I have a kooky idea. Plexi style amp head with traditional bright and normal channels. Power amp yoinked from the Carr Slant 6v, which is 4 6V6; two cathode biased and 2 fixed bias, with selections for either, or all four. Then, a switchable boost stage in front of that.
The more I think about it, the more I realize that I should just build something.
Re: The Current 20 watt Marshalls (paging Dr. Balls)
9Mixing fixed and cathode pairs is so simple and brilliant I wish I had thought of that