Improve the Marshall SV20H with $5 of parts? BENCH DEEP DIVE!! 

I assume the bass channel is bypassed by something like a 330uf cap?

@@BlakeC27 yes, the Bass channel (Input 2) has a 330uF cap in parallel with the 820R resistor on the cathode. For the Normal channel (Input 1), there is a .68uF cap in parallel with that 820R resistor on the cathode!

@@RozsaAmplificationLLC I imagine with the right tools and technical nouse you could mod the amp to the classic Plexi circuit. The preamp section at least.

@@BlakeC27 sure. Very simply. It's all there except for the power transformer, even in HI voltage mode, it's quite low, so lower headroom! 😩

@@RozsaAmplificationLLC It's a fantastic concept in terms of reducing the size, weight and unneeded volume of 2x EL34 but despite all the means Marshall has available they overlooked one of the most basic details of power-scaling; providing a separate HT supply for the preamp! They get their transformers custom made for them anyways, why not add a separate 300vDC tap so the half-power switch doesn't half-starve the preamp?

Not me, it's all swahili if you're not a tech ;-)

Glad to hear it!

Thanks Ed!

Jose mod vid for the SV20 coming soon!

Leon! Yeah, this is Ed’s amp man. It rounds off the complete set from all the Roland guys in Australia!

Those $5 in parts made a world difference to my ear. A little sweeter and definitely more organic. I can’t wait to see the final mods that you do. Thank you.

@@HeadfirstAmps haha Roland Australia bingo!

@@HeadfirstAmpsJason, what were the settings on the amp? It sounds like it has more gain than my sv20h

You should definitely learn Transdermal Celebration by Ween as well 😂

Tnx brother, you rock too!

I’ll convert you over to real amps one day…!

It has to do with playing the amp and not the sound. Digital does not provide that. I imagine you haven’t spent time on a real tube amp. You can’t hear it over a video neither can you feel it… but when you plug in and the tubes are warming with every note it’s like you are starting a fire and building intensity in ten cities. The depth of each note starts to mess with your head instantly illuminating fresh awareness bands that provide deep new instant inspiration of every facet of your playing. Get a real good one. When you plug and realize 6 hours goes by with a blink that means you’ve finally been experienced.

Agree, both sounded the same to me aswell...

Me netiher. But it is improved…

It’s subtle but I hear the highs are a little less harsh and there is a bit of a low mid shift. A bit less cut on the lower notes which to me sounds more plexi like

The SV20 might have enough gain, but you'd have to turn it up pretty loud in order to get it. The SC20 can get more gain at a lower volume level, but the tone characteristics will be different. For me, nothing beats a Plexi driven hard. I'd get the SV20 and have a PPIMV installed.

Or different speaker/cab choice

Thornbuckers!

That's interesting! I have a 1989 2210 that I have a love-hate relationship with. No amounts of EQ tweaking seem to make it sound right to me. The bass sounds bloated, the midrange is just wrong and the high end is spikey. I've always blamed it on the clipping diodes, but maybe your PI tube suggestion would improve it. What do you think?

@@markn4526 you only have to try it and see. Tone and overall dynamics are in the ear of the observer, and many have said these amps are too dark and muddy, but I always thought they sounded way better than the overly bright JCM 900's that followed. But this is up to the individual ear, and not for me to pontificate on; anyway you could always try it out for yourself and see how it sounds to you. To me they sounded a little softer and probably quieter,( nit a problem for a 100 watter), but the overdriven sound was a bit tighter, almost as if tge amp had EL84's instead of EL34's at output. One of my amps always sounded better than tge other anyway, so they must vary a bit ( although the one I liked less was originally the combo version which I had rebuilt into a top unit) so maybe some variation in componentry happens deprnding on whether they are made for open backed ttwin combo or top and speaker. I just tried this splitter tube change on a whim( can't remember where I got the idea- back in the 80's, so probably Guitar Player mag) and the amps seemed to like it. I'd say give it a try tubes are not that expensive.

@@chrisgmurray3622 Vintage Marshall amps often varied from piece to piece which is why Marshall amps frustrate a lot of people. Changing the PI tube with one of lower gain would decrease the signal coming from the preamp to the power amp section. My thought is that would make the amp sound less hard and soften up the tone a bit. Surely that would attenuate the spikey high end, but it might make the bass even worse. But who knows? I guess I just have to give it a try! I wonder if it's possible to bypass the clipping diodes.

Would you buy an 1987x over a SV20h?

@@Chillnote well I did :) I honestly prefer the 50/100w over the 20. I found one for 700£ with the flycase while a sv20 was 550-600....so it was a no brainer for me. if I have to go for these mods I would maybe go trough a Origin directly (I made a 800-SIR34 out of it and I like it) because it is a lot cheaper (at least in the UK it is 200-250 vs 550-600) but it is a lot more work to do. Jason in a video shows also how to do a plexi conversion out of an origin too :). btw: if you have to play around, the sv20 or a 20w modified, is a good solution: really small and light, if you just want to have the amp for the sound and you do not mind to lift it...1987x :) ....differences are not incredibles, the bigger amps just sound with a wider spectrum in the low freq. where I find the marshall 20w squished :)

@@Valerio_VDF Thank you for your insight, the fuzziness and harshness of the SV20H is driving me crazy. I am in the process of upgrading from the SV20H to a 1987x

@@Chillnote if you are UK based I can try to have a go with it and improve it a bit :)

@@Chillnote I've got both - the circuitry is literally identical but they sound and feel different - the 87x has a far fuller but tight low end and the highs are not as fizzy: a result of its massive power and output transformers I presume.

Hi Blake. The stock amp has a 4n7 bright cap. 3n3 coupler for the treble channel and 22nF for the bass channel

@@HeadfirstAmps Thanks for that Jason. It is interesting that V2 didn't have a bypass cap either. I've been tempted by one of these since they were released but I could never pull the trigger for some reason. Having someone like yourself take a look inside helps. Keep up the good work!

demeter+vht to be more technical

Good idea. Next one that comes in…

Legend!

While point to point is in a way kinda nice for collectors it's not the be all and end all many circut board perform admirably there is enough Amps out there to prove this point I like the point to point stuff too but I have realised it is a big selling point for companies who need to sell amps and need a sprinkle off good ole fashioned voodoo dust to sell their product and I'am not saying their Amps are bad but we all have been sold up years ago myself included that point to point is the only way your listening to your own sv,20 I have one too along with all the old classics too and you like the sound off your sv20 and it ain't no turret boarded bumble bee capped ge or Telefunken tube powered amp it runs tubes but nothing vintage in it I get the vintage thing I'm in it too but these compromises within the sv20 are pretty incredible and proof enough you can still do it essp with 75 hz g12m or g12h maybe ev speakers 12l anyway enjoy ya tones

Hey Chris, the end game with this amp is the high gain José but it occurred to me I could get two for one value by doing these first stage changes as a video! I’d probably still do them for the treble channel if it was my amp and I was keeping it as a Plexi.

@@HeadfirstAmps I'm looking forward to part 2 with the José mod.

The Origin 50 delivers 50watts. Thet amp is not worth spending money on replacing the PT imho. The output section is fine the way it is.

It’s because there are dropping resistors in the B+ line, normally 10k. As current flows through you get a voltage drop across those resistors.

@@HeadfirstAmps I understand that, thank you. But why not just supply them with the same voltage to each plate through a voltage bus?

The purpose of the dropping resistor is to work with its adjacent filter cap to act as a low pass filter, with a cutoff at close to 0Hz. Ie DC If you didn’t have that, you amp would motor boat and oscillate. Plus you get sag and feel through the B+ string.

@@HeadfirstAmps Thank you for explaining. I've built a few tube amps from kits, studied schematics, and even done modifications to amps. It's always something I've been curious about.

Hammond is fine. 3hy

See my other videos on high gain mods for the SC20

I tested one in a SC20 and thought it was workable, I’ve heard worse. Not as good as the zeroloss loop we have but workable

@@HeadfirstAmps Would it be difficult to add yours and bypass the marshall effects loop?

Yes - it's a quality board

@@HeadfirstAmps Thanks, your opinion means a lot. I'm quite sceptical and was reading up on the subject "hand-wired vs. PCB".

@hammondvoodoo9555 PCB can be handwired, for example how I build my amps. All hand soldered and wired, and with a PCB backbone. Then there is PCB machine stuffed and wave soldered, that’s different. People should look past PCB to understand the actual construction method. PCB done right is superior, especially for high gain.

@@HeadfirstAmps My concerns are not about function, but about longevity and how often you can replace electronic components that are soldered to a circuit board before the board is broken. For me, hand-wired means that there is no circuit board and you can overhaul the amplifier as often as you like. Defective electronic components may sometimes even burn out and damage the circuit board permanently to such an extent that the affected area must be bypassed.

After

No they don’t

💯. Search the channel

Interstate Love Song

I think the only mods Page had done to his SLP is to have them run KT88 power tubes instead of the EL34

Yes, it’s a ‘for marketing’ choice only