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

santiall said:
Hmmm, interesting question... I may actually know a thing or two about the jvm pedal. Perhaps it's somehow related to a circuit that I had prototyped years ago and brought with me when I rejoined Marshall while all these pedals were under development..

My opinion about any of these (any brand), that claim to sound like an amp is that pretty much they are a distortion pedal that you somehow shape to "sound like" but I don't think they are any sort of real amp models. At the end you depend on what amp you are using and how you set it up. Mind you, back in the day, pedals like the boss DS-1 and SD-1 were already described as pedals that replicate your "cranked full stack" in a box...

Doing myself that?, well, not really, not claiming specific amp models but I do understand why they are doing it. Every brand has their - insert brand name here - pedal, Marshall can of course do it too. I also can imagine that they want to present some new products in various market segments.

That "jvm" pedal started just as a high gain pedal experiment back in the day, I'm curious what they have changed in 3 years. I have improved it since then and I use it with clean amps from time to time, hopefully it can see the light sooner rather than later ;)
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Awesome answer and I really appreciate your insights.

I can absolutely see the value in Marshall offering these seeing as everyone else seems to make them (and it’s almost always because people want a JCM800/plexi/jtm45 sound).
 
santiall said:
The one I designed had a FET input stage, roughly based on an Echoplex input. I developed that one almost 10 years ago and was used in the Teisco Booster pedal. Then the rest of the pedal is op-amp based.
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The thorpy gunshot is like that. It's a fet based gain section (SHO) into the front of a tubescreamer with led clipping.
 
SillyOctpuss said:
The thorpy gunshot is like that. It's a fet based gain section (SHO) into the front of a tubescreamer with led clipping.
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FETs can be interesting because certain characteristics, specially high impedance inputs with low noise. People tend to see them like "solid state tubes", because the curves may look like a pentode, although the input load is completely different to a tube grid input.
 
When I first saw the pictures of the new Marshall amp pedals I assumed they were digital models.
I can’t see how you can do a decent high gain distortion pedal without providing proper eq control. What is going on in the JVM pedal?
 
Eagle said:
When I first saw the pictures of the new Marshall amp pedals I assumed they were digital models.
I can’t see how you can do a decent high gain distortion pedal without providing proper eq control. What is going on in the JVM pedal?
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At the end you design it expecting some sort of clean amp after the pedal. There is some fixed filtering and in this case also a simple tone control, a variable low pass filter.
You still rely on the amplifier you are using with its speaker, etc. The pedal isn't intended to be a stand alone amp simulator.
 
santiall said:
Hi all, it is my pleasure to have been invited to have my own thread here in The Gear Forum.

I'm electronics engineer mostly known for my woks for the 'big M' company including several signature amps, JVM, MG, CODE series, etc. I've also been employed by Behringer and I've been running my own consultancy firm for a few years. My works include companies like Softube, Blackstar, Harmony and Teisco, Acoustic, Harbinger, Sterling Audio, Darkglass, and Neural among others.

Happy to chat about anything, learn something and hopefully help others as well :)

As a disclaimer, any views or opinions represented here in the forum belong solely to myself and do not represent those of other people, institutions or organizations that I may or may not be associated with in professional or personal capacity, unless explicitly stated.
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I just joined this forum after posting numerous comments on youtube how to get a hold of Santiago. I have both a JVM and a YJM100. My YJM100 is on the fritz and my tech (who is Big M authorized repair ) can't figure out the problem. When I wrote the Big M company of who he was in contact with about repairing it....all I got from the Big M company was "were sorry". I need help getting this amp repaired so please Santiago if you read this, I really would be greatful for any help....thanks !
 
JimGuitar86 said:
I just joined this forum after posting numerous comments on youtube how to get a hold of Santiago. I have both a JVM and a YJM100. My YJM100 is on the fritz and my tech (who is Big M authorized repair ) can't figure out the problem. When I wrote the Big M company of who he was in contact with about repairing it....all I got from the Big M company was "were sorry". I need help getting this amp repaired so please Santiago if you read this, I really would be greatful for any help....thanks !
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Hi Jim, thanks for reaching out. Noted about Youtube but I wouldn't get notified unless someone sees the comments, anyway, here we are.
I've heard a few similar stories to yours, started after Marshall was acquired last year or whenever it was and they took all th eservice to themselves. The YJM and AFD also have been an special case as many people didn't know how to repair them and Marshall resorted to keep sending control boards even when the fault was usually a power tube and a resistor. The outcome is that they run out of spares and binned plenty of perfectly working boards...
Anyway, ranting over, how may I help you :)
 
santiall said:
Hi Jim, thanks for reaching out. Noted about Youtube but I wouldn't get notified unless someone sees the comments, anyway, here we are.
I've heard a few similar stories to yours, started after Marshall was acquired last year or whenever it was and they took all th eservice to themselves. The YJM and AFD also have been an special case as many people didn't know how to repair them and Marshall resorted to keep sending control boards even when the fault was usually a power tube and a resistor. The outcome is that they run out of spares and binned plenty of perfectly working boards...
Anyway, ranting over, how may I help you :)
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Thank you so much for reaching out Santiago ! My YJM100 worked perfectly until about a month or so ago. When I turn it on, everything comes on as usual, but 3 of the 4 LED lights saying the tubes failed in the back lit up, so there is no sound at all. The footswitch still functions and all buttons still work. I took it to my tech who is Marshall authorized and he thinks its the chip. Of course Marshall doesn't support the amp and when I contacted Marshall directly, all I got was a were sorry....so I am on my own on this. My tech tested the tubes and other components , sockets, and everything checked out. He also said there could be other points of failure and tracking them down could do more harm then good if that proves to be the case. Any idea what this could be? I even asked my tech if I heard from you, would he be willing to communicate with him directly and he was good with that.....that is if you would be willing as well? I am not an amp tech so pretty much everything he explained to me went right over my head LOL. Looking forward to hearing from you...thank you !!!
 
Hi, understood. I don't think it is "the chip" because the amp works and that controller manages the full amp, everything.
If several LEDs are ON it is, most likely, because there is no HT so the amp can't bias itself, or that the control of the screen voltage has some issues. All those are on the main board.

Anyway, please feel free to send me a private message, or ask you tech to send it, and we can follow the details in there. Otherwise I think we will be banned if we have 400 posts online haha
 
Hey @santiall ,

I'm a big fan of your work and was fascinated by your episode of the tone talk podcast!

I've read through most of the thread so forgive me if this has been covered before, but can you speak to how to go about safelty pulling two tubes from the 410h? Which pair, need to rebias, whether you use a different speaker jack, etc.

I would like to experiment with diming my JVM into my Two Notes load box. It's rated for 100 watts but lately I've heard a few horror stories of 100 watt amps putting out more than rated power into load boxes and blowing up.

Thanks a ton!
 
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vanhendrix said:
Hey @santiall ,

I'm a big fan of your work and was fascinated by your episode of the tone talk podcast!

I've read through most of the thread so forgive me if this has been covered before, but can you speak to how to go about safelty pulling two tubes from the 410h? Which pair, need to rebias, whether you use a different speaker jack, etc.

I would like to experiment with diming my JVM into my Two Notes load box. It's rated for 100 watts but lately I've heard a few horror stories of 100 watt amps putting out more than rated power into load boxes and blowing up.

Thanks a ton!
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Hi, thanks for the compliments!
you can remove either tube from either side. If you number them 1-2-3-4, you can keep 1-3, 1-4, 2-3, 2-4, it doesn't matter. Ideally you should connect the load to the "next lower output", so if you are using a 16Ω load, you should connect it to the 8Ω output. If your load is 8Ω, connect it to the 4Ω output.

Btw, this works in any amp, nothing special about the JVM

cheers
 
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