Who Designed the JVM 410 Mods on this Forum? Electronics Engineers? Professional Amp Builders?

[Rocker Ray]

I am considering modding my JVM 410h with some mods listed elsewhere on this forum Specifically I want the Negative Feedback mod, The Plexi mod, the choke mod, and clipping the c83. Before I do that I would like to know who came up with these mods. Are these legit mods, designed by qualified professionals like amp builders engineers or ? Any input would be appreciated! thanks!

 

[Tatzmann]

Him.












No, it wasn't him ofcourse. It was the Marshall
designer Hugh Jorgan. Great guy!

 

[Jon Snell]

Not wishing to sound off or anything but if they were legitamate, they would be listed in the Appropriate Marshall Service Bullitins and they are not.

I think some are guesswork and glue. Some are good ideas but non I would put my name against, as a professional qualified Electronics Engineer.

 

[PelliX]

No, it wasn't him ofcourse. It was the Marshall
designer Hugh Jorgan. Great guy!

I'm pretty sure the choke mod was Haywood Jablome.

 

[Spanngitter]

The majority of JVM Mods are something which brewed in the JVM Forum (R.I.P.) and there even the designer of the JVM was involved.
There is reasonable mods and there is funky mods, I consider the NFB, Plexi and Choke Mod reasonable, clipping C83 not, but your mileage may vary.
BTW: the Plexi Mod and the Choke Mod had been approved by Santiago Alvarez and as per his statement they had been involved in the first draw up but had been crossed out by cost cutting measures. Also, a fact what is/was never mentioned is that the older series (where the pots are not mounted to the front fascia) has some issues which are critical (like underrated Ceramic Caps C7/8 between Screen and GND, underrated Coupling Caps (400Vdc instead of 630Vdc) which have to be fixed to retain reliability.

 

[twilt1973]

Greetings!
I'm relatively new here but just recently landed a JVM410H and did a few mods.

Before doing any other mod, I would suggest starting with the NFB Mod (Chatlotte Method) using a 1 meg audio pot.

This alone, may give you everything you need.

I did this mod along with the Plexi and Compression Reduction mods.

Also running a JJ ECC823 in V1 (V6 according to Marshall) and a JJ 5751 in V2 ( V7 according to Marshall).

With these minor adjustments the amp does anything and everything I could hope for.


Hope this helps!

~Troy

 

[santiall]

The majority of JVM Mods are something which brewed in the JVM Forum (R.I.P.) and there even the designer of the JVM was involved.
There is reasonable mods and there is funky mods, I consider the NFB, Plexi and Choke Mod reasonable, clipping C83 not, but your mileage may vary.
BTW: the Plexi Mod and the Choke Mod had been approved by Santiago Alvarez and as per his statement they had been involved in the first draw up but had been crossed out by cost cutting measures. Also, a fact what is/was never mentioned is that the older series (where the pots are not mounted to the front fascia) has some issues which are critical (like underrated Ceramic Caps C7/8 between Screen and GND, underrated Coupling Caps (400Vdc instead of 630Vdc) which have to be fixed to retain reliability.

Hi, for the sake of clarification I haven't approved any of those modifications. The only one I was involved was the "c83 mod" that I privately discussed with some person and later on saw the light. The rest were done mostly by a very knowledgeable engineer in that forum but I never "approved" any of them. In fact, I think that my only comment was that playing with the feedback could be risky and lead to oscillations.
As for the rest of comments, sorry to be blunt but they are false, all anode coupling caps in the jvm are 630V, c7 and c8 are 500V and only subject to the bias voltage, around 40-45V. You can see them in the schematics... Nothing was changed when the pots were fixed to the front panel either.
The choke was not removed for cost reasons, as I explained in multiple occasions, it was never there simply because the jvm power amp was designed to be relatively clean and "stiff", with quite a lot of feedback and big reservoir caps.
Cheers.

 

[Rocker Ray]

Thank you all SOOOOOOOOOOOOOOOOOOOOOOOO much! Great information!

I guess it makes logical sense that whoever came up with these mods would need to have quite a bit of understanding of how these amps work to even come up with the mods! Plus the mods I am considering have been successfully done by a lot of folks with great results. I guess the proof is in the pudding.

 

[Rocker Ray]

Hi, for the sake of clarification I haven't approved any of those modifications. The only one I was involved was the "c83 mod" that I privately discussed with some person and later on saw the light. The rest were done mostly by a very knowledgeable engineer in that forum but I never "approved" any of them. In fact, I think that my only comment was that playing with the feedback could be risky and lead to oscillations.
As for the rest of comments, sorry to be blunt but they are false, all anode coupling caps in the jvm are 630V, c7 and c8 are 500V and only subject to the bias voltage, around 40-45V. You can see them in the schematics... Nothing was changed when the pots were fixed to the front panel either.
The choke was not removed for cost reasons, as I explained in multiple occasions, it was never there simply because the jvm power amp was designed to be relatively clean and "stiff", with quite a lot of feedback and big reservoir caps.
Cheers.

Are you the amps designer?

 

[Rocker Ray]

The majority of JVM Mods are something which brewed in the JVM Forum (R.I.P.) and there even the designer of the JVM was involved.
There is reasonable mods and there is funky mods, I consider the NFB, Plexi and Choke Mod reasonable, clipping C83 not, but your mileage may vary.
BTW: the Plexi Mod and the Choke Mod had been approved by Santiago Alvarez and as per his statement they had been involved in the first draw up but had been crossed out by cost cutting measures. Also, a fact what is/was never mentioned is that the older series (where the pots are not mounted to the front fascia) has some issues which are critical (like underrated Ceramic Caps C7/8 between Screen and GND, underrated Coupling Caps (400Vdc instead of 630Vdc) which have to be fixed to retain reliability.

Thank you Soo much for this info!

 

[Rocker Ray]

Greetings!
I'm relatively new here but just recently landed a JVM410H and did a few mods.

Before doing any other mod, I would suggest starting with the NFB Mod (Chatlotte Method) using a 1 meg audio pot.

This alone, may give you everything you need.

I did this mod along with the Plexi and Compression Reduction mods.

Also running a JJ ECC823 in V1 (V6 according to Marshall) and a JJ 5751 in V2 ( V7 according to Marshall).

With these minor adjustments the amp does anything and everything I could hope for.


Hope this helps!

~Troy

Thank you for that info!

 

[Rocker Ray]

Not wishing to sound off or anything but if they were legitamate, they would be listed in the Appropriate Marshall Service Bullitins and they are not.

I think some are guesswork and glue. Some are good ideas but non I would put my name against, as a professional qualified Electronics Engineer.

Words to live by. Thanks!

 

[Dogs of Doom]

Are you the amps designer?

yes, he is....

 

[Rocker Ray]

Hi, for the sake of clarification I haven't approved any of those modifications. The only one I was involved was the "c83 mod" that I privately discussed with some person and later on saw the light. The rest were done mostly by a very knowledgeable engineer in that forum but I never "approved" any of them. In fact, I think that my only comment was that playing with the feedback could be risky and lead to oscillations.
As for the rest of comments, sorry to be blunt but they are false, all anode coupling caps in the jvm are 630V, c7 and c8 are 500V and only subject to the bias voltage, around 40-45V. You can see them in the schematics... Nothing was changed when the pots were fixed to the front panel either.
The choke was not removed for cost reasons, as I explained in multiple occasions, it was never there simply because the jvm power amp was designed to be relatively clean and "stiff", with quite a lot of feedback and big reservoir caps.
Cheers.

Thank you so much for that info! Very helpful. Great amp BTW. Mine was biased very cold form the factory so the only usable channel for me was OD1. After retubing with early break up, matched tubes and bias at 70% all channels really came alive. I just need less compression for my style, so I am interested in the mods. Do you approve of these mods? I just don't want to do anything to harm my amp.
Thanks for responding!

 

[santiall]

Thank you so much for that info! Very helpful. Great amp BTW. Mine was biased very cold form the factory so the only usable channel for me was OD1. After retubing with early break up, matched tubes and bias at 70% all channels really came alive. I just need less compression for my style, so I am interested in the mods. Do you approve of these mods? I just don't want to do anything to harm my amp.
Thanks for responding!

Hi, no, I can't approve nor disapprove those mods, I have no "authority" for that, those are the works/experiments of people in their amps. I also don't work for nor represent Marshall at all and I can not approve modifications to their products.

What I can say is that most of the mods that I have seen were pretty much value changes or minor circuit changes and won't harm anything if implemented correctly but if something goes wrong, the amp behaves funny, you don't like the results, etc. you can't come back to me with a "but you approved the mods"

 

[Rocker Ray]

Thanks so much for your input. I didn't mean to put you: "on the spot", in any way. I am not looking for a guarantee and would never look to hold anyone responsible if things went wrong. I totally get how you have to be careful not to open yourself to any liability in your situation.....

..........."Heavy is the head who wears the crown" ha ha

Anyway, again I appreciate your input. It really is a great amp. Very versatile, I just want to fine tune it to match my style.

 

[santiall]

Thanks so much for your input. I didn't mean to put you: "on the spot", in any way. I am not looking for a guarantee and would never look to hold anyone responsible if things went wrong. I totally get how you have to be careful not to open yourself to any liability in your situation.....

..........."Heavy is the head who wears the crown" ha ha

Anyway, again I appreciate your input. It really is a great amp. Very versatile, I just want to fine tune it to match my style.

Hi, I always sound harsher than intended but yeah, you can read between the lines... the mods are mostly safe to implement but you'll invalidate the warranty (if still any left) and maybe some service centers may even refuse to work in the amp, most likely it'll lose resale value etc etc. Saying "mods approved by Santiago" won't work either plus I haven't even implemented the mods myself to support them in any way.

There are some YouTube videos with modified JVM amps, you can also search for those and see if that's what you are after.

 

[Spanngitter]

As for the rest of comments, sorry to be blunt but they are false, all anode coupling caps in the jvm are 630V, c7 and c8 are 500V and only subject to the bias voltage, around 40-45V. You can see them in the schematics... Nothing was changed when the pots were fixed to the front panel either.

With the uppermost respect but I disagree from my practical experience.
From >20 JVMs coming thru here in the past I had 3 (including mine, a 2007 Model) where either C7 or C8 failed, causing the Powertubes go havoc since the bias shorted to GND. These ceramics might be spec'd ok in Voltage but are no durable versions, nothing like a good Vishay or TDK single layer CC. These caps have been omitted in the HJS Model (which also has the the main stage coupling caps reduced to .022nF) and if I recall also in most recent standard 410.
Also I found .047/400V (instead of the spec'd 630V) C12/14 coupling caps in 2 of them (the usual grey box), none of these had been serviced before so somehow there was a booboo made somewhere.

 

[Pete Farrington]

To be fair, the design team may well be ignorant of sins committed by procurement / production.

 

[santiall]

With the uppermost respect but I disagree from my practical experience.
From >20 JVMs coming thru here in the past I had 3 (including mine, a 2007 Model) where either C7 or C8 failed, causing the Powertubes go havoc since the bias shorted to GND. These ceramics might be spec'd ok in Voltage but are no durable versions, nothing like a good Vishay or TDK single layer CC. These caps have been omitted in the HJS Model (which also has the the main stage coupling caps reduced to .022nF) and if I recall also in most recent standard 410.
Also I found .047/400V (instead of the spec'd 630V) C12/14 coupling caps in 2 of them (the usual grey box), none of these had been serviced before so somehow there was a booboo made somewhere.

I am not aware of any of that...

Anyway, those C7/C8 are only there for stability reasons in all the standard JVMs. Those amps have higher feedback and, by its own nature, the stability is worse than in amps with lower feedback. The HJS doesn't need them as that power amp is different, just a standard 100W Marshall power amp.