Improve the Marshall SV20H with $5 of parts? BENCH DEEP DIVE!!
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- Опубліковано 27 лип 2024
- Can a handful of low cost parts improve a stock SV20H? Well, let's find out.
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0:00 Intro
1:42 A/B Test
2:48 Overview of the stock amp
16:02 The mods
18:09 Stock play though
19:14 Mod play through
20:18 Parts list
Guys, worth mentioning that you don’t need to change the 820r cathode for the bass channel for this. I did both cathodes for v1 to 2k7 in prep for the phase 2 Jose style mod. There, I just saved another dollar!
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?
STOCK sounds pretty KILLER already !👍😁
All of us SV20H owners have been waiting for this video and especially part two... Cant wait.
Not me, it's all swahili if you're not a tech ;-)
Thank you Jason, I've waited an eternity for SV20H mods 😊
oww yeah. Been waiting as well for a series on the SV! Already quite an amizing little amp! thx so much!
Liked the stock, less lower mids more open. You can always bump mids with an overdrive. Definitely a good choice to have. Switchable would be cool.
Great video, changes are subtle like you say but the mod is definitiely an improvement to my ears. Looking forward to the José mod video too!
Your videos are gold Jason! Thanks so much for making them and you channel overall. I've learned a ton.
Glad to hear it!
Nice sounding little amp, both stock and with the mod. 👌
Love your videos Jason. Cant wait for the Jose mod
Thanks for showing this reachable mod💜🎸🤘
Another awesome video Jason. Been missing you man !! - I have to say, .... initially I thought the stock amp sounded really pretty good. I was quite surprised how nice this SV20 sounded, straight out of the box. However, ..... the modded tone just brought the core tone right where it needed to be. A very pleasant compliment of gain indeed, set this amp onto the next level. The enhanced Mid, ..... fuller and articulate - Bravo. As always, ... the work you do, NEVER disappoints. I can't wait for Part 2 !!! - hope you are well brother - Cheers
Sounded fantastic, great though walk through of the circuit and the mods you incorporated. They definitely improved the stock sound similar to what you described. Also, thank you for going over your parts list used in the mod.
the mods sounds amagazing, seems like the mods add the sort of sack feeling in the tone cheers
You are a legend Jason, you made the sound much better, such a talent.
Your a master Jase, can’t wait to hear it after the Jose mod…
Definitely a change , thanks for posting that.
Great stuff Jason, love this kind of video. Excellent tweaks to the circuit 👌
Thanks Ed!
Really cool and interesting! To my ear, there's a definite change to the mids. I guess it all comes down to taste for some people, but if that's your ideal "in my head" tone, then this is cool! Even though I don't own a Plexi, I find all the info really useful to apply to my own DSL20 that I've altered to add an extra gain stage to the Green Channel. Knowledge is power, right? Thanks for what you share
Definitely preferred your mod - tamed the harshness.
The changes are definitely better, I would like to have that done.
You did a great job walking through it as well.
I was able to follow even with my limited knowledge of circuitry.
Thanks for this, off now to watch the Jose style mod.
Jose mod vid for the SV20 coming soon!
Jason the Mad Brilliant Scientist ! Love from Quebec !
It will be interesting to hear the final product, at this stage i preferred the stock sound
Sounds great, the mod sounds "fuller" to my ears.
Thanks Jason - yeah I heard it - with the mod a bit more clear and a bit less raw sounding for lack of a better term and a bump in the low end from the fat cap came through as well. I can see liking the stock for some sounds too but if I had to pick its the mod for sure
Really great video Jason, it’s like “to put at point” a f1 car… really great amp and “desirable” mod…
Absolutely brilliant!
Sounds a little bit harsher post-mod but definitely clearer. Overall post-mod is the better sound. I've been finding lately sometimes tones have trade offs and compromises you have to select from! It's bloody amazing that you know (and remember) so much about what was done and when in the lineage of these amps and what the effect is!
Definily like the stock, nice an open sounding, the mod seem to muddy up the sound, thanks for sharing! : )
plexi amp I want wicked bad, awesome accent , wicked good STP riff that I need to learn asap .....DEF DIGGING THIS SO FAR
LOVING the Explorer with the body binding.
Nice. Subtle but its definitely less harsh listening on decent speakers. It would be interesting to hear the same A/B test with OT upgrades and whether its worth the expense.
Also I've always meant to learn that STP song. Got it down in 10 mins after watching this. Cheers dude.
You should definitely learn Transdermal Celebration by Ween as well 😂
In my country, this amp is double the price of an Origin20. Seeing this... the Origin 20 is the deal of the century if you like to mod. Sure, the studio 20 Watt series have better head shells and some other bits. But to me, that doesn't defend it being twice the price. Great vids though, keep it up. Looking forward to part 2.
You rock Jason!
Tnx brother, you rock too!
So this is the amp you were telling me about! The mod sounded a little thicker and more "mature" in the overall tonal balance. Can't wait to hear it once it's had some more Headfirst fairy dust applied.
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
Hilarious choice of STP. It’s nice to see the algorithm at work…lol
I like that sound stock better. Modded sounded compressed with the blanket over the speakers
Very subtle result.
Thanks for the suggestions. I actually prefer the stock sound. But sometimes the "feel" of the amp in the room can be something else than what is captured, so it may still be an improvement.
Im torn between the two versions, both had qualities the other didnt IMO. Stock for me was the over all better tone, it just needed taming in the top end. Mod had great top end but then to me had a little extra wooliness to the tone. Keen to see the high gain mod!
I love my SV20 and the idea of improving it is tantalising. But even with my hifi headphones I can't hear any difference. Did it feel different?
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
Sweet Jesus that Friedman JEL100 sitting in the background😮💨👌
I've grown to really love your channel. I"ve never owned( Well, I actually owned a 5150 and a Diezel VH4 with matching 4x12 cabs for about 20 days) nor would I ever own a tube amp in my 30+years of playing. Digital is superior in every facet. Just my opinion. I own over 100 amps (Line 6 Helix) and find them to sound as good as the real things.
That being said, IF I ever owned a Tube amp for longer than 20 days, I would employ you to modify it. I think your style, attention to detail and work ethic are top notch.
I love learning about tube amps. They are far to inconsistent for me to consider owning one but I sure do get the magic surrounding them. Thanks for the videos.
Best wishes,
Ben
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.
Hey Jason, post ALL of the voltages in BOTH 5W and 20W modes please.
It looks like there is the following taps on this Power Transformer...0, 110, 220, 230V inputs, with 108V and 147V secondary, 13.7V for loop, DI, relay, and filament, and balanced 6.3V for heaters.
The preamp is 4-input 2 gain stage +CF normal and bass Hi and LO input plexi.
I lot more versatility could be added, but in Marshall and other amp manufacturer fashion, they wouldn't want that, so you have to keep buying more product and perpetuity!
One MOD would be a one-wire MOD on a switch, so can switch between Plexi or re-route the signal to to turn the amp into a JCM800! I would do that with one of the volumes and put on a push-pull.
Likewise, one could add an NFB or number of MODs to this amp!
Seems like a good modding platform, just need to take care of the B+ line and for both modes, 5W and 20W, then take it from there!!
Immediately when you switched to the modded amp,it had less gain,and filled out in the low mids..that scratchy high end went away…it definitely sounded smoother…I thought the mods were a definite improvement..Can’t wait to hear it breathe fire!!…Any mods for the Mini Jubilee?
I like the idea of these amps, but the El34’s are almost a gimmick at that plate voltage.
For what these cost, you should get more than a different circuit using Origin parts and construction.
Thank GOD there’s guys like you that work their magic on these things.
Excited to hear how this turns out! I have been on the fence on whether to get the SV20 or the SC20. The concern being the SV20 may not have enough gain, whereas the general concensus seems to be that the SV20 is the better sounding of the two. Wonder how the end result will compare to the SC20
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.
Nice video. Would changing the V1 tube have a bigger impact on the sound? I have had mine for two years and I am amazed on what it can deliver.
The mod is subtle, but sounds great!
Regarding the cold biasing of the power tubes. Does the cold bias result in crossover distortion?
Wow. Almost a no brainer
Subtle but sweet.
Well hello there Jake E Lee just chilling in the background there
I don’t have any Marshal amp but this give me an idea on how they’re supposed to sound 😅
Nice mod but having the high end bite available is awesome.
It can be tamed with volume/tone controls.
Or different speaker/cab choice
In a cathode biased EL34 amp with fully variable power scaling going from say 30W or so max downwards you would expect the dissipation to drop proportionally and the bias appear to be cold at 20W and 5W etc. The cold bias of some of Marshall's 20W cathode bias amps has been criticised for causing crossover distortion but I haven't seen this tested and this would imply power scaling causes crossover distortion which it doesn't seem to. If you considered this to be permanently scaled down to 20W then maybe 65% isn't unexpected? It may have been the Origin 20 specifically rather than this one but I'd be really interested to see more of an analysis! Thanks for the great videos!!
Interesting video! As you've pointed out, I hear the differences in the tone after the modifications that you performed...adding both warmth and clarity at the same time, which is sort of contradictory, but you can certainly hear it. Although it is subtle unless you know what you're listening for. There also seems to be a slight amount of added sag. I think the amp sounds great both before and after the mod, but better after. What speakers were your using for the demo?
On a related subject regarding the SV20H, some techs are saying that this line of amps is way over-priced for the level of components and build quality you're getting for the price they're being sold at. Also, that the fact that the power tubes are biased so cold from the factory is a big factor regarding the amp's potential. What are your thoughts on this?
Great stuff! Have you ever modded a DSL 15 or 20? Would love to see one of those if they ever come through.
Cool mod, sounds more balanced to my ears! What pup`s are in that gold top Les Paul? Cheers!
Thornbuckers!
It seemed to take away a bit of the high end sizzle and bring the mids a bit forward. I imagine the Jose' mod will provide extra sizzle so the combination should complement each other.
Hi, great video, many thanks! Do you know if the pots are sealed or cleanable? My mid pot developed a bit of scratchiness and intermittent contacts.
The tightening up of the stock low-end flub is worth doing it alone
I wish you would have done the demo with the channels jumped as well to show the difference in that configuration.
I Like
can you do a cathode follower vs plate driven tone stack video with clips?
Hey Jason, have you ever looked at a JMP-1? Just curious of any thoughts?
I think the mod made the sound a little smoother to my ear, not a great deal different,though.
Could you make a video on output transformers. What specs you think are important and does a paper bobbin make any difference
Can you explain a little more about the biasing? Seemed really low according in your calculations. What should be done about that for this amp?
👍👍
Hi
What IR are you using here? Or is it a micked cab?
Hey, you have got a Friedman JEL! Top Amp. I would like to know the schematic of the JEL.
Awww yeah.
Honestly I couldn’t hear a difference at first. I listened a couple more times and yes it’s a subtle difference the cringy ear piercing highs are calmed down I think. I have a Carvin bel air combo amp that I made some mods to. It was like a weighted blanket was lifted off of the front of the amp. So much better than the stock dark sounding amp it originally was.
Would love to see a similar vid on a 1987x
Good idea. Next one that comes in…
Legend!
Really interesting Jason. I have been waiting for someone to do take a technical look inside of one of these amps. I assume it has a bright cap on the high treble channel? What value are the coupling caps on the normal and high treble channels?
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!
I bought an SV20H when they first came out. I was an ex-owner about a year later. I found the amp unusably bright and harsh with the Teles that I favour. Wish I'd seen this vid back then. Thanks for putting it up!
Cool video but once the drummer kicks in what’s the difference! Rock on my brothers!
interstate love maybe was played w/vox at steroids… i wouldn t this particular point mess you around… it s tricky .. anyway good job mod man!
demeter+vht to be more technical
I feel like you can or should be able to get similar differences and even waaaaaay more with just moving knobs around both on the amp and the guitar.
Ive got a 68' plexi 1987. Best mod i ever did was plate load 4 stage it and install 6550s 😭😭😭😂🤘
I once had two 2210's(JCM 800) and both of them sounded so much better when I simply replace the phase inverter pre/tube with a 12AU7. Both amps sounded less boomy and noisy, and had a more balanced overdrive tone, with a more balanced high to low, whereas the original 12AX7 was as your amp here pre-mod was, a bit too strident and out of control... with a lot of mud and noise.
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.
I did the same mods on my 1987x and I can confirm that they really improve the amp: replaced the two 820ohm with 2.7k cathodes and left 0.68u on the cathode of the third stage...a lot better...also the channel 1 had 22n coupling I reduced to 2.2n ... a lot better and less fuzzy sound (then I used the 2 channel to configure it as a optional additional be100/cali stage) + diodes... I can go now from classical sounds up to metal.Added pre MV (was already there tbh) and post PI MV and now I have a really flexible amp.
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.
Honestly, if I didn't know about the mod, I wouldn't have noticed at all and I'm usually very critical about tone. The differences are very subtle. IMHO, it's not worth doing. When I tried this amp out two days ago my impression was that with bridged channels one primarily adjusts the normal and bright volume - like with any Plexi. This has by far the biggest impact on the overall tone. The 3-band EQ as well as the presence control are set afterwards for fine-tuning - that's it. Very simple and straight-forward like it should be if the sound is right. I'm actually astonished what Marshall achieved with the Studio Series but as soon as I saw the circuit board I was a little disappointed. Point-to-point-wiring is so much better in the long run. But then the amp would be much more expensive, especially with that mentioned choke transformer added ...
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
Is it possible to do a Bradshaw/Crunch/Dookie mod (or same sound) on a SV20H ?
Hi, could you list the parts for this mod and where to purchase?
Hi Jason, I've also seen the other video comparison between this and the Origin. A friend of mine told me that these little bests have a 50w rated output transformer but the power tansformer are not rated for that. So, I have both trafo that I bought months ago for a project. Couold you tell me if it's possible to make this amp a 50w amp? And if yes, if I send you my e-mail, could you tell me what to do?
Thanks a lot.
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.
Sounded a bit darker with the mod. It’s like you took some of the gain out or what you say is harshness. Isn’t the Jose mod gonna put that harshness right back in with the high gain? I’m not a huge fan of modifying amplifiers. I mean, I use a bone stock SC 20 stealth. To me it’s like you’re changing the original or trying to make something that you’ve purchased different but you’re brand loyal and don’t want to change.
how different would be trying this in a SC20H?
I really love the sound of my SC20H but I need it to have more gain for hi gain modern metal would you be able to asist here ? Please
See my other videos on high gain mods for the SC20
Would it be possible to bias the EL34's hotter by just plugging in a lower value cathode resistor, like 120r? Sorry if this is a silly question, new to all this :')
The PT almost certainly won’t be rated to cope with it.
One thing I've been curious about is, regarding the B+ line cascading down from power tube to preamp tube, why does it get less and less as it goes? Does it have something to do with the gain structure of the preamp?
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.
Both sound great. Subtle difference. I reckon it's subjective as to whether or not the mod sounded "better" (whatever that means). Horses for courses. I reckon using different speakers (or IRs) would make more difference. You're chasing the last little bit though so why not go for it?
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.
which pickups has the explorer?
What value and brand choke would you use if you were to change out the resister?
Hammond is fine. 3hy
Mod sounds good, but doesnt sound as Plexi as the stock
@HeadfirstAmplification Is the PCB of the amp of high quality in your opinion (i.e., so that it would last)?
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.
Do the transformers on these have internal taps to switch from 220V to 120V?
No they don’t
What is your opinion on the effects loop of this amp? Is your effects loop better or are they comparable?
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?
For the love of Pete I cannot place that STP song. Someone help me out! Which is it?
Interstate Love Song
At 12:45 275V is before the PI dropping resistor right?
After
Don’t you think using el34 tubes was ill advised at only 20w? A pair can easily deliver 80w and 20 just seems like expecting peak performance from a v12 engine in a car limited to 25mph.
Yes, it’s a ‘for marketing’ choice only