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

[gearJunkie]

Hell Santi, I hope you’re doing good over there in Japan,
Tell Marty Friedman “You Rip!!
if you run into him.

Question,

The footswitch is a masterpiece in the JVM 410H
I started researching & investigating how you designed & implemented the functions,
-would you say there’s literally tiny camera’s taking “snapshots” of the pots to remember your settings/adjustments?
The wires and connections on the pots is VERY interesting.
Do tell!!

From the manual...

Preset store mode: Each switch can be programmed to instantly call up a combination of JVM button options to form a preset. This allows you to recall complete channel setups in any order and combination.

I believe only the channel (clean, crunch, OD1, OD2) + voicing (green, orange, red) + fx loop (on/off) + reverb (on/off) + master volume (1 or 2) button selections are saved. The channel volume, BMT, gain, and reverb pot values are not saved.

 

[santiall]

Hell Santi, I hope you’re doing good over there in Japan,
Tell Marty Friedman “You Rip!!
if you run into him.

Question,

The footswitch is a masterpiece in the JVM 410H
I started researching & investigating how you designed & implemented the functions,
-would you say there’s literally tiny camera’s taking “snapshots” of the pots to remember your settings/adjustments?
The wires and connections on the pots is VERY interesting.
Do tell!!

From the manual...



I believe only the channel (clean, crunch, OD1, OD2) + voicing (green, orange, red) + fx loop (on/off) + reverb (on/off) + master volume (1 or 2) button selections are saved. The channel volume, BMT, gain, and reverb pot values are not saved.

hi, yeah, the JVM doesn't store the potentiometer settings, just the switch positions.
On the other hand, the MG series do store the potentiometer positions using digital potentiometers. The whole signal path is analog and the digital pots are replacing the usual analog ones in the circuits. A CPU 'reads' the pots on the front and translates that into the actual pots in the circuit.

In a tube amp that's much more challenging to do because the signal levels are very high. In a solid state amp one can keep the signal levels quite low so no issues

 

[Jonttu]

let me know how it goes, good luck!

Hello again Santiago!
I finally got new mainboard for my JVM410 and i replaced it, biased the amp (around 76mV both) and it worked flawlessy at thome.
Just came back from rehearsals and the same old problems came back again.... Amp went mute after about 15min of playing and changing the channel brought it back alive again, few times.. until it didn't work anymore.

Any guesses? Faulty main transformer?

 

[PLX]

What amp(s) did Joe Satriani use to record "Not Of This Earth" ?

 

[santiall]

Hello again Santiago!
I finally got new mainboard for my JVM410 and i replaced it, biased the amp (around 76mV both) and it worked flawlessy at thome.
Just came back from rehearsals and the same old problems came back again.... Amp went mute after about 15min of playing and changing the channel brought it back alive again, few times.. until it didn't work anymore.

Any guesses? Faulty main transformer?

hmmm, since most of the switching is happening on the front pcbs, I'd think that the problem is still there. It can be many things but it seems temperature/mechanical related. If the amplifier has been disassebled many times, it is not uncommon that he wire harness become loose and make bad contact. Those are rated for only a handful of insertions.
Otherwise it could be a relay or something but I don't think the mains transformer would be the problem.
I'd also change all the fuses if you haven't changed them yet. Sometimes the thin wire breaks internally but still make contact till it warms up or moves a bit

 

[santiall]

What amp(s) did Joe Satriani use to record "Not Of This Earth" ?

ok, just asked and he kindly told me:
he used a Rockman and whatever was in the closets at Hyde Street studios which turned out to be a drip edge era Fender Pro Reverb.
That plus DS-1 and CE-2 pedals. No wah wah pedal on the album. Outboard gear: EMT 250 reverb, Lexicon Primetime, Eventide 949, Publison Infernal Machine units and the TC 2290. Along with LA-2A and 1176 limiters and a few great microphones and mic pres

 

[PLX]

ok, just asked and he kindly told me:
he used a Rockman and whatever was in the closets at Hyde Street studios which turned out to be a drip edge era Fender Pro Reverb.
That plus DS-1 and CE-2 pedals. No wah wah pedal on the album. Outboard gear: EMT 250 reverb, Lexicon Primetime, Eventide 949, Publison Infernal Machine units and the TC 2290. Along with LA-2A and 1176 limiters and a few great microphones and mic pres

Wow!

You are the man!

 

[Deadpan]

Hello again Santiago!
I finally got new mainboard for my JVM410 and i replaced it, biased the amp (around 76mV both) and it worked flawlessy at thome.
Just came back from rehearsals and the same old problems came back again.... Amp went mute after about 15min of playing and changing the channel brought it back alive again, few times.. until it didn't work anymore.

Any guesses? Faulty main transformer?

I don't have a JVM but a few amps I have had issues with the effects loop connection causing some odd issues.

Are you using the effects loop? If not does putting a patch chord in help? Just a thought.

 

[Jonttu]

hmmm, since most of the switching is happening on the front pcbs, I'd think that the problem is still there. It can be many things but it seems temperature/mechanical related. If the amplifier has been disassebled many times, it is not uncommon that he wire harness become loose and make bad contact. Those are rated for only a handful of insertions.
Otherwise it could be a relay or something but I don't think the mains transformer would be the problem.
I'd also change all the fuses if you haven't changed them yet. Sometimes the thin wire breaks internally but still make contact till it warms up or moves a bit

Thanks once again! Yes, problem is definitely temperature related, since amp starts acting weird allmost immediately when i crank it up! I did some measurements and you're absolutely right! Main transformer works as it should, there are no voltage drop nowhere when amp goes mute... i checked the min/max levels from the main transformer outputs, only 0.2VAC differences and few volts from the "high voltage" side.

i'll check the front board and ask if there's a spare part (another new circuit board ) for the amp

Problems started before amp had been disassembled so i'll put my money on the front circuit board.
Oh yeah, and all fuses has been replaced :)

Thanks!!! You are the man!!!

EDIT: oh.. and it seems that there's not only one circuit board in the front panel? i'll check the wirings between boards!

 

[Jonttu]

I don't have a JVM but a few amps I have had issues with the effects loop connection causing some odd issues.

Are you using the effects loop? If not does putting a patch chord in help? Just a thought.

Yeah, that's known problem :)

But believe me, this has nothing to do with it

 

[Sorxes]

¡Hola Santiall! ( vivo en Alemania pero mi madre es de Sevilla . :))

…but Let’s keep it english for the Rest here :)


Its been a while ive asked you about some Mods for the jvm and your answers really helped me to find my way with the jvm ! So thanks again for that.

Now i got another question:

As the DI Out of the JvM410h has no IR. I thought: what if Theres a way to Mod that di out. And maybe Plug it in an IR Loader Pedal or something Like that.i think it Would be awesome.

I have thought about using the fx Loop but the fx Loop only catches the preamp section so you wont get the real feeling of the amp.

Is the Sound of the stock DI out influenced by the poweramp ?

Is There maybe a Mod or something to Plug the di into an IR loader to get more Flexibilit out of it ?


Thanks again !

Y hasta luego

 

[JiveTurkey]

ok, just asked and he kindly told me:
he used a Rockman and whatever was in the closets at Hyde Street studios which turned out to be a drip edge era Fender Pro Reverb.
That plus DS-1 and CE-2 pedals. No wah wah pedal on the album. Outboard gear: EMT 250 reverb, Lexicon Primetime, Eventide 949, Publison Infernal Machine units and the TC 2290. Along with LA-2A and 1176 limiters and a few great microphones and mic pres

Crosses fingers in Joe Satriani TGF cameo that would obviously never happen but baby can dream

 

[santiall]

Thanks once again! Yes, problem is definitely temperature related, since amp starts acting weird allmost immediately when i crank it up! I did some measurements and you're absolutely right! Main transformer works as it should, there are no voltage drop nowhere when amp goes mute... i checked the min/max levels from the main transformer outputs, only 0.2VAC differences and few volts from the "high voltage" side.

i'll check the front board and ask if there's a spare part (another new circuit board ) for the amp

Problems started before amp had been disassembled so i'll put my money on the front circuit board.
Oh yeah, and all fuses has been replaced :)

Thanks!!! You are the man!!!

EDIT: oh.. and it seems that there's not only one circuit board in the front panel? i'll check the wirings between boards!

you are welcome!
don't forget to check the ribbon cable from main board to the front pcb too

 

[santiall]

¡Hola Santiall! ( vivo en Alemania pero mi madre es de Sevilla . :))

…but Let’s keep it english for the Rest here :)


Its been a while ive asked you about some Mods for the jvm and your answers really helped me to find my way with the jvm ! So thanks again for that.

Now i got another question:

As the DI Out of the JvM410h has no IR. I thought: what if Theres a way to Mod that di out. And maybe Plug it in an IR Loader Pedal or something Like that.i think it Would be awesome.

I have thought about using the fx Loop but the fx Loop only catches the preamp section so you wont get the real feeling of the amp.

Is the Sound of the stock DI out influenced by the poweramp ?

Is There maybe a Mod or something to Plug the di into an IR loader to get more Flexibilit out of it ?


Thanks again !

Y hasta luego

hey, hola, gutten Morgen!
the IRs are a relatively modern thing, I mean, the theory is known for many many years but implementing it in real time at the speed we want requires certain computational power that wasn't possible, at least at 'payable' prices .

The JVM XLR output has a fixed analog speaker emulation and the signal is taken before the Master volumes.

If you want to use the amp in the 'silent recording mode' you could do two things, one is to get the signal from the PREAMP SEND jack on the back and pass that thorugh your IR, or if you want to use the XLR output, you'll need to bypass the speaker emulation by removing some parts... but none of these options will give you power amp response.

If you really want to use the power amp signal then you need some external load and then you have to tap the signal somewhere to send it to your IR processor. There are some products out there that will do that for you like some Two Notes stuff, the UAD Ox, etc

 

[santiall]

Crosses fingers in Joe Satriani TGF cameo that would obviously never happen but baby can dream

I just asked him, hey Joseph, there is this forum out there... but don't worry, in this particular one they haven't been too harsh with Mean Street, how badly you screwed it up and how ashamed you should be of yourself for even attempting to play it in front of the world wide online guitar community. I mean you even made me feel ashamed of myself and I am considering to stop playing guitar and putting all your CDs in ebay.




I'm still waiting for his reply...

 

[texhex]

I just asked him, hey Joseph, there is this forum out there... but don't worry, in this particular one they haven't been too harsh with Mean Street, how badly you screwed it up and how ashamed you should be of yourself for even attempting to play it in front of the world wide online guitar community. I mean you even made me feel ashamed of myself and I am considering to stop playing guitar and putting all your CDs in ebay.




I'm still waiting for his reply...

Nailed it! LOL

 

[JiveTurkey]

I just asked him, hey Joseph, there is this forum out there... but don't worry, in this particular one they haven't been too harsh with Mean Street, how badly you screwed it up and how ashamed you should be of yourself for even attempting to play it in front of the world wide online guitar community. I mean you even made me feel ashamed of myself and I am considering to stop playing guitar and putting all your CDs in ebay.




I'm still waiting for his reply...

 

[PLX]

I saw Joe live on the "Surfing" tour in Houston, TX with Jonathan Mover on drums and Stu Hamm on bass.

Never forget it !

 

[JiveTurkey]

I saw Joe live on the "Surfing" tour in Houston, TX with Jonathan Mover on drums and Stu Hamm on bass.

Never forget it !

As an old fart; I got to see a LOT of killer concerts of great artists at their peak. I missed Joe on this tour on a stop nearby in the midwest when I was like 16 and I still kick myself

 

[Jonttu]

you are welcome!
don't forget to check the ribbon cable from main board to the front pcb too

Yes i did it when i changed the main circuit board. I measured every pin and wobbled the cable but there were no differences in continuity readings.