Marshall JVM series

[Jackie]

I noticed there are a few users here.

It was my first tube amp and I still love it. I did some mods to adjust the feel but it was more of a curiosity thing than a "mod of need".

I like the myriad of features and tones you can get with it, and it's a great companion to my Mesa rig.

I think most people treat this amp wrong... for example I don't think turning the Gain past noon on the Red channel and 6 on the Orange channel yields anything but feedback and mush, most people are used to boosting and diming gains on a Marshall - resulting in mushy and over compressed tone.

Anyway once you get into the logic it's simple to dial and it sounds great
Also cool to use it as a power section - just one resistor change and it's identical to the JCM800.

Anyone else feel the same :?:

 

[coupie666]

I used to have a JVM combo and i really liked it. I used it for the covers band i play in. The orange mode on channel 1 was just awesome with a tubescreamer and was more or less all I needed. I agree with the mushy sound when u turn the gain much further than one oclock on the amp. I ended up selling it because i got the roadking and had a stiletto and i couldnt justify having all 3 at the time. Miss it for the marshall crunch sound though... Although I know the guy I sold it to so i know it went to a good home... Even if it has ended up in Austraila with him!!! lol :lol:

 

[Assumer]

I was thinking of looking at the JVM. Have always liked the marshall sound and love the versatility of the amp. What mods did you make and what did they do for the amp?

 

[Jackie]

Well, I think any amp with adjustable bias benefits from it being higher than stock. Let Randall Smith talk all he want and I know it's consistency he's after but to my ears upping the bias was the best thing to do. I set it from a chilly 46% plate dissipation to 60%.

I fiddled around with preamp tubes a little (something still awaiting my Mesa rig), Ended up with EH 12AX7 in V1 and V5, Chinese 12AX7s the rest. The amp isn't very finnicky when it comes to preamp tubes but it's something I wanted to experiment with so it's a slight adjustment from stock.

I did the mods out of curiosity to see what can be achieved by modding rather than a necessary measure for the tone I wanted.

I added a switchable choke, but I keep it on all the time so I could just say "I added a choke". It made it feel a little more spongy and it sounded a bit "nicer", more polished.

I also put a 1uF cap across a certain resistor to slightly boost the high mids to make it more oldschool sounding, it made it a little more "throaty".

Both these tweaks are very very small but noticeable if A/B'd with a stock JVM.

I also lowered the negative feedback (made the poweramp less clean) - all you have to do is change one resistor - to introduce some extra harmonics and powertube dirt. This was the more dramatic tonal/feel mod (yet it's still not a very big change), and it basically changes the JVM's powersection into that of a JCM800 (except for the Resonance knob, if you turn that to 0, it's almost a clone). What it does tonally is make the amp more responsive since the powertubes are working harder and there is also more midrange clipping because of that. I made a switch to go from stock to "JCM800" value, but most go for a pot to make it on the fly adjustable.
There is a myriad of mods over at the JVM forum and lots of info on them too. One user (also the one who contributed most of the mods) turned his JVM into a Blackface+1959SLP+JCM800+Dual Rectifier clone, each amp topology=one amp.

All that said, I think the amp sounds kickass even stock. To my ears it has the best crunch of any hi-gain four channel head out there. I just did the mods out of curiosity and it turned it more towards a genuine oldschool Marshall tone, which is what I like and therefore I usually play with the mods on.

Yeah this amp is crazy versatile and I have become so spoiled by it's features I instantly miss something if I'm playing another amp. It also makes a great companion for a Mesa like the TriAxis/2:90 rig or Mark V, perhaps Dual Recto. They both cover a lot of tonal territory and there isn't a lot you can't do with either separately or mixing preamps/poweramps together. For example, I run the JVM's preamp (OD2 channel) into the Mesa poweramp to get something like an ENGL-ish tone

 

[talltxguy]

Thanks for the information on this amp. Gotta admit that the digital reverb scares me a bit. How's it sound? And more importantly, does it mess with the feel and dynamics while playing through it? Can you hard bypass it with a mod?

 

[Jackie]

No problem. I think a lot of people don't understand that this ain't 4 of your granpa's Marshalls crammed into one and given some extra gain. It's a hard rock/metal machine all of it's own.

Well the reverb is a very good one. I like it, unlike the Vintage Modern's which I think is too dark. It's nice and airy and even when set to "bathroom levels" it's not muddy. Most people are satisfied with it (I know of one person that has outboard reverb pedal on the whole 1000 user JVM forum). I don't see any tone/feel being affected by it, and when it's off, it's off so there's no need to mod it for bypass. I don't think it's anything to be scared of. :mrgreen:

 

[KH Guitar Freak]

The OD channels are too noisy for me IMO. However, the new Satch head is intriguing to me...

 

[Assumer]

Well, I think any amp with adjustable bias benefits from it being higher than stock. Let Randall Smith talk all he want and I know it's consistency he's after but to my ears upping the bias was the best thing to do. I set it from a chilly 46% plate dissipation to 60%.

I fiddled around with preamp tubes a little (something still awaiting my Mesa rig), Ended up with EH 12AX7 in V1 and V5, Chinese 12AX7s the rest. The amp isn't very finnicky when it comes to preamp tubes but it's something I wanted to experiment with so it's a slight adjustment from stock.

I did the mods out of curiosity to see what can be achieved by modding rather than a necessary measure for the tone I wanted.

I added a switchable choke, but I keep it on all the time so I could just say "I added a choke". It made it feel a little more spongy and it sounded a bit "nicer", more polished.

I also put a 1uF cap across a certain resistor to slightly boost the high mids to make it more oldschool sounding, it made it a little more "throaty".

Both these tweaks are very very small but noticeable if A/B'd with a stock JVM.

I also lowered the negative feedback (made the poweramp less clean) - all you have to do is change one resistor - to introduce some extra harmonics and powertube dirt. This was the more dramatic tonal/feel mod (yet it's still not a very big change), and it basically changes the JVM's powersection into that of a JCM800 (except for the Resonance knob, if you turn that to 0, it's almost a clone). What it does tonally is make the amp more responsive since the powertubes are working harder and there is also more midrange clipping because of that. I made a switch to go from stock to "JCM800" value, but most go for a pot to make it on the fly adjustable.
There is a myriad of mods over at the JVM forum and lots of info on them too. One user (also the one who contributed most of the mods) turned his JVM into a Blackface+1959SLP+JCM800+Dual Rectifier clone, each amp topology=one amp.

All that said, I think the amp sounds kickass even stock. To my ears it has the best crunch of any hi-gain four channel head out there. I just did the mods out of curiosity and it turned it more towards a genuine oldschool Marshall tone, which is what I like and therefore I usually play with the mods on.

Yeah this amp is crazy versatile and I have become so spoiled by it's features I instantly miss something if I'm playing another amp. It also makes a great companion for a Mesa like the TriAxis/2:90 rig or Mark V, perhaps Dual Recto. They both cover a lot of tonal territory and there isn't a lot you can't do with either separately or mixing preamps/poweramps together. For example, I run the JVM's preamp (OD2 channel) into the Mesa poweramp to get something like an ENGL-ish tone

Thanks

 

[Jackie]

No prob

Yeah I hear you on the noise, but this amp has gain to spare anyway, I usually play with around 5-6 on Orange modes and never go over 4.5 on the Red modes, most people overgain it since Marshall isn't really known for having a lot of gain and then they moan about noise. With potted PUs and good cables it's controllable.

 

[rjsc5]

I own the 410c, 4 channel 100watt combo, and must admit the clean channel is really great. Different from my lonestars, but very useable. You could easily play jazz with this amp, and it has decent tone at low volume. No issues with the reverb quality either. If you think it sounds fizzy, just turn the resonance knob. I am a Mesa lover, but really enjoy this amp as well.

 

[J.J]

I really like the JVMs. You do get a lot of great tones in the one box. The only reason I didn't get one is because Mesa made the Royal Atlantic.