Santiago Alvarez (electronics engineer, JVM, YJM, AFD...)

[KingsXJJ]

I do have a question for you Sir if I may. I have a 2024 standard JVM410H that is mint and very low mileage. While I’d like it to be the best it can be, I’d prefer not to mod it all to heck. By that I mean MAJOR surgery. I do have a tech who is super talented though and services/mods for a lot of “big” names as well as full time gigging pros so that’s in my favor. Hello from Austin, Texas!

So, a couple of approaches in mind.

1) Move it toward the JS model. I like that it might be smoother overall and that OD2 is closer to OD1. Is the first just a simple cap mod? Is the second, OD2 mod complicated?

2) maybe in combo with approach one, what would be YOUR personal choices or recommendations that you might do with a stock version 410 to get it closer to what you would do for your own or if there were no cost or production volume considerations when designing it? A choke, different component values, etc. again hopefully not major surgery.

My overall goal? To get my dream amp to sound the best it can while moving it as close as possible on the appropriate channels and modes to not just authentic Plexi, JCM800 and Modern Marshall high gain tones but if possible to killer modded ones as well.

It’s a big ask, I know. I won’t think any less of you if you’d rather not. But it certainly would be mind-blowingly appreciated if you did.

WWSD? What Would Santiago Do? Thank you for reading! -Jason

 

[santiall]

You designed the Studio series? If so, wow.

no, I designed the power amp that is used in all those 20W amps and also the full mini-Jubilee, which was an idea that I proposed after launching the Jubilee reissue at NAMM. I had to do it on my own as the product people didn't think it was a good idea...

 

[KingsXJJ]

no, I designed the power amp that is used in all those 20W amps and also the full mini-Jubilee, which was an idea that I proposed after launching the Jubilee reissue at NAMM. I had to do it on my own as the product people didn't think it was a good idea...

Ouch! Well my Studio JCM is awesome! Thank you for the great power amp in it!

 

[santiall]

I do have a question for you Sir if I may. I have a 2024 standard JVM410H that is mint and very low mileage. While I’d like it to be the best it can be, I’d prefer not to mod it all to heck. By that I mean MAJOR surgery. I do have a tech who is super talented though and services/mods for a lot of “big” names as well as full time gigging pros so that’s in my favor. Hello from Austin, Texas!

So, a couple of approaches in mind.

1) Move it toward the JS model. I like that it might be smoother overall and that OD2 is closer to OD1. Is the first just a simple cap mod? Is the second, OD2 mod complicated?

2) maybe in combo with approach one, what would be YOUR personal choices or recommendations that you might do with a stock version 410 to get it closer to what you would do for your own or if there were no cost or production volume considerations when designing it? A choke, different component values, etc. again hopefully not major surgery.

My overall goal? To get my dream amp to sound the best it can while moving it as close as possible on the appropriate channels and modes to not just authentic Plexi, JCM800 and Modern Marshall high gain tones but if possible to killer modded ones as well.

It’s a big ask, I know. I won’t think any less of you if you’d rather not. But it certainly would be mind-blowingly appreciated if you did.

WWSD? What Would Santiago Do? Thank you for reading! -Jason

Hi Sir,

hmm, lots of what would you do if I could do what I think you may consider that could be done
ok, first thing is that there are tons of JVMs out there, it is not that you have the one and only amp that is worth thousands. So feel free to mod it or find a cheap one out there to experiment.

Now as for the approaches:
1- the standard JVM and the HJS are completely different amplifiers. Maybe they look the same but they are not the same at all, the circuits are completely different so it is not that you can change a cap and transform the standard JVM into the HJS.
What you refer with changing 'one' cap is converting the standard OD2 into OD1 but that won't give you the HJS sound. You could extensively mod the standard JVM to be similar to the HJS but you will have to decide which modes you want, because the HJS has a different switching inside. What I mean is that if you choose to get OD1 RED from the HJS most likely all the rest of the modes won't work nicely...

2- my approach... I don't know, I designed the JVM so I'd say it is the amp I wanted when I designed it, so I wouldn't change anything. A different question is what if I design the JVM now and I don't know what to answer. Probably a blend of the standard JVM and the HJS, something like clean from the standard, crunch from the HJS, OD1 from the standard, OD2 from the HJS, loop from the HJS, reverb and gate, but modifying a JVM to do that is quite impractical

It is not that I wouldn't do it but modifying the amp, while retaining the 12 modes usability, without writing new firmware to control it isn't possible in my opinion. YOu may modify here and there and optimize some of the modes but you will have to give up other modes.

WWSD, I'd just play the amp and try to improve my guitar technique!

 

[KingsXJJ]

Hi Sir,

hmm, lots of what would you do if I could do what I think you may consider that could be done
ok, first thing is that there are tons of JVMs out there, it is not that you have the one and only amp that is worth thousands. So feel free to mod it or find a cheap one out there to experiment.

Now as for the approaches:
1- the standard JVM and the HJS are completely different amplifiers. Maybe they look the same but they are not the same at all, the circuits are completely different so it is not that you can change a cap and transform the standard JVM into the HJS.
What you refer with changing 'one' cap is converting the standard OD2 into OD1 but that won't give you the HJS sound. You could extensively mod the standard JVM to be similar to the HJS but you will have to decide which modes you want, because the HJS has a different switching inside. What I mean is that if you choose to get OD1 RED from the HJS most likely all the rest of the modes won't work nicely...

2- my approach... I don't know, I designed the JVM so I'd say it is the amp I wanted when I designed it, so I wouldn't change anything. A different question is what if I design the JVM now and I don't know what to answer. Probably a blend of the standard JVM and the HJS, something like clean from the standard, crunch from the HJS, OD1 from the standard, OD2 from the HJS, loop from the HJS, reverb and gate, but modifying a JVM to do that is quite impractical

It is not that I wouldn't do it but modifying the amp, while retaining the 12 modes usability, without writing new firmware to control it isn't possible in my opinion. YOu may modify here and there and optimize some of the modes but you will have to give up other modes.

WWSD, I'd just play the amp and try to improve my guitar technique!

Great advice Sir! And I thank you for it! It was truly awesome to read from the man himself such open advice!

I’m unsure how to express it well enough, so a full on THANK YOU will have to do.

Final question and I promise! Add a choke to reduce some types of noise or no? I don’t have the JS co I don’t have the nice built in noise gates. Would that compromise your design across the modes? It reduces noise and perhaps the only side effect is a slightly tighter low end is what I’ve been told. But you would know best. I fully believe that. Thank you again for your kindness.

Please don’t answer if I’m being too persistent!

 

[santiall]

Great advice Sir! And I thank you for it! It was truly awesome to read from the man himself such open advice!

I’m unsure how to express it well enough, so a full on THANK YOU will have to do.

Final question and I promise! Add a choke to reduce some types of noise or no? I don’t have the JS co I don’t have the nice built in noise gates. Would that compromise your design across the modes? It reduces noise and perhaps the only side effect is a slightly tighter low end is what I’ve been told. But you would know best. I fully believe that. Thank you again for your kindness.

Please don’t answer if I’m being too persistent!

I don't think the choke will reduce any noise, perhaps, and this a big stretch, some hum but the JVM doesn't have much hum. The hiss you hear is preamp noise (thermal noise that gets amplified). Th eonly reason why the HJS has a choke is because I was so tired of people asking me that I put it in

 

[KingsXJJ]

I don't think the choke will reduce any noise, perhaps, and this a big stretch, some hum but the JVM doesn't have much hum. The hiss you hear is preamp noise (thermal noise that gets amplified). Th eonly reason why the HJS has a choke is because I was so tired of people asking me that I put it in

Great to know and a bit of history thrown in! You are such a gem and very very kind to share your knowledge and time.

I will always remember this conversation when I turn it on to play!

 

[santiall]

Great to know and a bit of history thrown in! You are such a gem and very very kind to share your knowledge and time.

I will always remember this conversation when I turn it on to play!

hey, if knowing that having a choke installed will make you play better then go for it!

 

[Szlast]

I calculated and specified those back in the day. They were properly interleaved, not just pri-sec-pri but I forgot the exact details (and couldn't reveal them anyway). They were not as extreme as a hi-fi transformer but more sophisticated than the simpler guitar ones

Thanks! If I could ask two more questions (for now)

1. Why there is no chokes in lower wattage amps like this studio series? It is cost reduction decision or there is no difference in tone? Also was surprised recently that DSL100 has no choke.
2. I noticed that all modern amps has transformers on opposite sides of the chassis also in ADF100. It is just for weight distribution? I was forced when built two my amps to do like that but I was worried about influence of the HT and plate wires on effects loop and signal path that will produce oscillations and noise.

 

[santiall]

Thanks! If I could ask two more questions (for now)

1. Why there is no chokes in lower wattage amps like this studio series? It is cost reduction decision or there is no difference in tone? Also was surprised recently that DSL100 has no choke.
2. I noticed that all modern amps has transformers on opposite sides of the chassis also in ADF100. It is just for weight distribution? I was forced when built two my amps to do like that but I was worried about influence of the HT and plate wires on effects loop and signal path that will produce oscillations and noise.

1-, well the mini jubilee has one, and I think the origin 20 also had one, unles they removed it, but it is a valid point... those amps were designed with a choke, just because people expect one, and when they see one they think it is "a better design" but I can't really tell if there is any difference. without testing it. I wouldn't expect much difference though, something subtle.
There are quite a few 100W amps there wihtout choke, starting from the Marshall 30th Anniversary, the 900s, the 2000s, the JVMs, the Vintage modern, the JTM60, the Peavey 5150, etc. Probably cost has a lot to do with this, although in the case of the JVM and Vintage Modern was more of a "none of the older Marshall amps had one", rather than the cost of the component. Probably if Steve and I weren't quite new in the company by then, we would have put a choke

2- yes, it is for weight and it is a PIA. You need to be extremelly careful and know what you do when wiring the amp as you have a 100W output trasnformer right where the input tube is... In the case of the JVM it was a design requirement, the amp had to be balanced when being carried by the handle. I'd rather offset the handle, put two handles on the sides or something like that

 

[HomespunEffects]

At one time I had two Vintage Modern 2466s. One was original and the other was modified by the previous owner with a choke. There was absolutely no tonal difference between them.

Adding a choke or “upgrading” a power transformer are dubious mods, in my opinion.

 

[santiall]

Adding a choke or “upgrading” a power transformer are dubious mods, in my opinion.

yes, and in most cases even the output transformer as well but if people like to do it and that makes them feel happier, I am nobody to stop them.
For example, I used to like changing the suspension of my car to a stiffer and a bit lower one and usually the car handled worse than with the original, but it looked better to my eyes so who cares haha

 

[HomespunEffects]

yes, and in most cases even the output transformer as well but if people like to do it and that makes them feel happier, I am nobody to stop them.
For example, I used to like changing the suspension of my car to a stiffer and a bit lower one and usually the car handled worse than with the original, but it looked better to my eyes so who cares haha

It’s a good point.

 

[Szlast]

yes, and in most cases even the output transformer as well but if people like to do it and that makes them feel happier, I am nobody to stop them.
For example, I used to like changing the suspension of my car to a stiffer and a bit lower one and usually the car handled worse than with the original, but it looked better to my eyes so who cares haha

Thanks for the info. Yeah I'm in couple of DIY facebook groups for amp mods or builders and there is very popular opinion that when your replace 20W output transformer with 50W your amp will be 50W

Santiago in your opinion are there any arguments to build 100W amp instead of 50W? From my point of view there is no sense to invest more into bigger transformers and additional two power tubes but maybe I'm missing something.

 

[KHAAAAAAANNNNNNN!!!!!!!!]

WWSD, I'd just play the amp and try to improve my guitar technique!

Wrong forum.

 

[la szum]

yes, and in most cases even the output transformer as well but if people like to do it and that makes them feel happier, I am nobody to stop them.
For example, I used to like changing the suspension of my car to a stiffer and a bit lower one and usually the car handled worse than with the original, but it looked better to my eyes so who cares haha

I think with so many options out there it is kind of nonsense to "Mod" an amp. You could literally find
one that has what you need already existing out there.

"Leave the poor Amp alone and work on you," I say!

Giving them a facelift sometimes turns out worse in the end, as you suggest. Pretty sure we have seen
that outcome on actual faces, too, and not just with Tube Amps. One step forward, 2 steps back.

 

[santiall]

I think with so many options out there it is kind of nonsense to "Mod" an amp. You could literally find
one that has what you need already existing out there.

"Leave the poor Amp alone and work on you," I say!

Giving them a facelift sometimes turns out worse in the end, as you suggest. Pretty sure we have seen
that outcome on actual faces, too, and not just with Tube Amps. One step forward, 2 steps back.

I guess there is always the excitement part of having something "new", like when updating Windows just to find new bugs

 

[la szum]

I guess there is always the excitement part of having something "new", like when updating Windows just to find new bugs

Have you heard of the German word Verschlimmbesserung ?

No direct translation to other languages, but it is a cool word meant to call out progress and improvement
that actually makes things worse.

​

 

[santiall]

Thanks for the info. Yeah I'm in couple of DIY facebook groups for amp mods or builders and there is very popular opinion that when your replace 20W output transformer with 50W your amp will be 50W

Santiago in your opinion are there any arguments to build 100W amp instead of 50W? From my point of view there is no sense to invest more into bigger transformers and additional two power tubes but maybe I'm missing something.

there are few arguments to make them different. The phase splitter needs to drive 4 tubes instead of two, the output impdance of two tubes is ~half (you approx. double the transconductance), the output transformer, most likely, has lower resistance. Then the output votlage, for the same impedance is 1.4 times so you would need to compensate with the feedback. etc. On top of that, many 50W marshall power amps run at a relatively low voltage (the voltage that was in the datasheet btw) so the tubes are not even operating in the same point.

so yeah, there are a few arguments that points to potential differences. That doesn't mean that you couldn't design a 50W that is indistinguisable from a 100W, I guess Hi-Fi guys do this (or try to) all the time, but for a guitar amp one may want those two to be different.

 

[santiall]

Have you heard of the German word Verschlimmbesserung ?

No direct translation to other languages, but it is a cool word meant to call out progress and improvement
that actually makes things worse.

View attachment 47410

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yeah, I knew that one, I had forgotten it!, I lived in Germany for a short while many years ago and one of my colleagues was always using that word (feah-slim-besegung when I say it haha). I guess it is the perfect word to many of the classic albums being remastered nowadays...

It is also interesting how those words relate to the different cultures ahaha, traditionally in Spain probably we would just "bodge" things, English would start properly to end "bodging through politics" before they reach the "verschlimmbesserung" stage, hence none of us have that word . Germans end overengineering everything so much that yeah, they make things worse. Then Japanese would try to perfect things so much that they don't evolve, although things tend to work (although this doesn't apply to a Japanese web which is packed with so much info that you end dizzy by just looking at it, all written in HTML 2 with courier fonts, but hey, it works!), etc.

Disclaimer: the above paragraph is ironic-cynical-joking, just in case I hurt any sensibilities out there...