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

Many dudes put their JVM’s back to stock after crittering around in there adding/switching out components.
A lot going on in there.
There is a night & day difference after switching out power/output/choke to everything to MM.
Even after that, due to the ample additional headroom added,
-ya gotta find the right power tubes & bias.
JJ EL34L’s rule it.

I’ve been obsessively reading this book and memorizing definitions of all common words in amplifier repair -I’m my own Google.
-followed by taking it to the streets.
Working around live primary power lines learned me good about electricity,
so I respect the machines.
This is the book I’m studying and living.
 

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Hey Santiago, do you happen to know make and type of the plugs/connectors Marshall uses in their amps now, for example the newer Studio series?
Also which grey coaxial cable to run from PCB to PCB? Right now I'm using Teflon RG174 (?) i.o. to not melt anything when soldering it to the boards. But it's PITA to work with, and the inner conductor is veeery thin. So I want to try something the pros use 😁
Seems like Fryette also uses some grey coaxial cable and similar connectors.

I also really like the look of the black cable and connectors used in the 2555x and 2525 Mini Jubilee's. But this looks way more expensive..
 

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Hi, those shielded cables are most likely UL1691, UL1185 or the likes. Generic shielded audio cable. Actually if you happen to have one of those amps with you, you can read the spec printed on the cable, they usually have the manufacturer and some numbers/letter. Some of those numbers, like 1691, are the UL specification for them. Then they should have the thinckness, AWG24, AWG26 probably for those thin ones.

The RG174 is more intended to radio, it can have just a single conductor in the center and the shield may not be 100% plus yeah, on top of that they are a pain to work with so don't use that :D

Connectors... maybe JST XP for 2.5mm and PH for 2mm pitch. They also used some other types in some amps but if you search in the JST page you should be able to find them. They are popular and different manufacturers make complatible types.

The "cloth" cables that were used in the Jubilees are High Temperature fiberglass covered wire. I'm not sure the exact type but if you search for 200°C fiberglass cable you'll find them. The connectors probably were Molex 55932 if I remember correctly.

hope it helps!
 
Hey Santiago, thanks a lot for you answer. I don't own any amps you would buy, since I have been building amps since like 15+ years or so.

I started using that Teflon RG174 just a few years ago, because all those years I was unable to find some generic coaxial audio cable, that would NOT get its dielectric or outer insulation melted under my soldering efforts :p
I even started to make some support for the RG174, because it is quite stiff, and it puts a lot of stress on that thin inner conductor. I bent some silver wire around the outer insulation, folded the shield around it, soldered the little strands to it with a decent dollop of solder, and soldered the end of the wire to the gnd solder pad. This kinda worked, but it's still a lot of work, and still quite some stress on that thin inner conductor.

So I want to try using PCB mount pots on a separate PCB for one of my next builds, and connecting the PCBs using those connectors, and by this, I can go back to some standard audio cable. Plus, I then don't need to solder the many small wires from the pots to the PCB

So again, thanks a lot, I will go and make my homework now ;)
 
If someone else is interested: As far as the connectors goes, Marshall seems to use the JST EH series, at least in the SC20 amps. Pics are from the Reichelt.de webshop.
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headcrash said:
Hey Santiago, thanks a lot for you answer. I don't own any amps you would buy, since I have been building amps since like 15+ years or so.

I started using that Teflon RG174 just a few years ago, because all those years I was unable to find some generic coaxial audio cable, that would NOT get its dielectric or outer insulation melted under my soldering efforts :p
I even started to make some support for the RG174, because it is quite stiff, and it puts a lot of stress on that thin inner conductor. I bent some silver wire around the outer insulation, folded the shield around it, soldered the little strands to it with a decent dollop of solder, and soldered the end of the wire to the gnd solder pad. This kinda worked, but it's still a lot of work, and still quite some stress on that thin inner conductor.

So I want to try using PCB mount pots on a separate PCB for one of my next builds, and connecting the PCBs using those connectors, and by this, I can go back to some standard audio cable. Plus, I then don't need to solder the many small wires from the pots to the PCB

So again, thanks a lot, I will go and make my homework now ;)
Click to expand...
yeah, but crimping all those tiny connectors is also a PITA haha. You should be able to solder the shielded wire without melting it, perhaps you just need to pre-tin the wire, pre-tin the hole and then solder everything together, it'll be much easier and won't melt.
 
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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Welcome : I wonder if you can do a direct preamp with two channels two tubes but a third tube which can add output harmonics / OR faux phase inverter type harmonics / padded back down to line level AND mixed back into the two preamp tubes in PARALLEL so add to taste for player - then it goes into Cab IRs and EFX ...The standard two tube pres always seem to have something missing except maybe the CAE3+ old style .

Can you make this work easily ?
 
robertkoa said:
Welcome : I wonder if you can do a direct preamp with two channels two tubes but a third tube which can add output harmonics / OR faux phase inverter type harmonics / padded back down to line level AND mixed back into the two preamp tubes in PARALLEL so add to taste for player - then it goes into Cab IRs and EFX ...The standard two tube pres always seem to have something missing except maybe the CAE3+ old style .

Can you make this work easily ?
Click to expand...
it could be tested, sure, but my experience is that the phase splitter distortion tends to sound quite fizzy. It is like an amp with post phase inverter master volume set at very low volumes. You'll hear the splitter fizziness rather than the output tube distortion athough the IRs will help smoothing all that out... you got me thinking now :unsure:
 
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!!
 
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