Marshall JVM 410 choke mod
Marshall JVM 410 choke mod
So in this installment of fucking up an expensive amp, I'm going to add a choke to my Marshall JVM 410. The JVM 410 is a four channel, three modes per channel, all the bells and whistles, tons of features, modern era amp from the blokes at Marshall. It's very complex and sophisticated....but it lacks one simple basic feature found on all of the best classic Marshalls - a choke. What does a choke do, you ask? It's a small little part that looks like a transformer and it goes in the power supply rail to help filter and smooth out the current going to the tubes. Tubes want DC power, but our walls give us AC power. That AC sine wave power comes into the amp and is "rectified" into DC straight line power by the rectifiers, but it's not perfect at that point. It still has ripples. Lots of ripples. Those ripples are further smoothed by the filter caps...and now, an added choke. By design, the choke cleans up and organizes the low frequencies in the power supply and it's inductance filters out the very high frequency leftover AC stuff that we can't hear but it mucks shit up in the tubes anyway. So it's a good thing.
This is where we start. With the chassis removed from the headbox, we gotta get some external stuff off of it. Remove the tubes. This fucker has nine of them. All the jack nuts and two little screws for the DI output need to be removed from the back of the amp. Speaker jacks can stay put, no need to remove them. The power tube retainers also must be removed.
Now we flip the amp and focus on the board. It's gotta come out. It's not as bad as it looks. It's very important (to me) to label the dozen or so wires and connectors that must be removed to get the board out. The board is clearly labeled so by simply marking the wires with a little sharpie you can easily put it all back together.
Now you remove about 6 screws and the board comes right out.
With the board out, we can now mark, drill, and fit the choke. This is the choke. Note - gotta use a rubber grommet where the wires pass through the chassis. We don't want those things rubbing. I just kind of eyeballed it's location because I want it close to where the wires have to go and as you can see there is plenty of real estate available.
This is the resistor that the choke will replace. R106. Gotta go bye-bye.
And buh-bye!
Now the wires from the choke will penetrate the delicate holes left behind where the resistor was. I stood the board up inside the chassis and stuck the wires. The choke is non-polarized and does nothing else, so it doesn't matter which wire goes to which hole. Just stick em in and solder. I made an executive decision here to leave the leads as long as possible instead of cutting them just long enough to reach straight to the soldering spot. The choke's location is pretty much exactly adjacent to where the leads have to go, so sure, a short straight shot is probably better - as I learned from my last modding adventure - but in this case the longer wires leave me with two benefits 1) I can twist them so they self-cancel any noise they may make, and 2) since this thing is permanently wired to the board, the longer leads will give me some flexibility if I have to remove the board again. I can now flip the board if necessary with the choke leads still attached.
Now it's just a matter of putting it all back together, and hot damn alakazam. Done!
One thing I majorly fucked up on....I recorded some before-mod sound clips....and didn't save them.
I know.....fucking n00b.
I'm sorry, I really wanted to show the difference, but I goofed that part and it's too late to go back now!
I'll just try to describe it. The tone differences aren't as significant as the "feel" differences. Even if I hadn't fucked up the recordings, sound clips might not do it justice anyway. It definitely feels and responds punchier and more ballsy. The low end is definitely tighter and more percussive without being muddy or mushy. I really like the low end improvement. It's more noticeable on the higher gain channels, but the cleanish stuff gets benefit too. The fizz is also significantly reduced. This amp can squeal like a pig at stupid gain levels if you're too close to it. That part is much better. It could go into oscillation at high gain levels...but not so much anymore. I have to chalk that up to the high frequency filtering being done by the choke. That's a good thing.
So all in all...the choke was free for me, but it's only like 30-40 bucks US dollars. An hour and a half of pretty easy work and roughly 50 bucks in parts including nuts and bolts and grommets, it really improved the performance of this amp.
This is where we start. With the chassis removed from the headbox, we gotta get some external stuff off of it. Remove the tubes. This fucker has nine of them. All the jack nuts and two little screws for the DI output need to be removed from the back of the amp. Speaker jacks can stay put, no need to remove them. The power tube retainers also must be removed.
Now we flip the amp and focus on the board. It's gotta come out. It's not as bad as it looks. It's very important (to me) to label the dozen or so wires and connectors that must be removed to get the board out. The board is clearly labeled so by simply marking the wires with a little sharpie you can easily put it all back together.
Now you remove about 6 screws and the board comes right out.
With the board out, we can now mark, drill, and fit the choke. This is the choke. Note - gotta use a rubber grommet where the wires pass through the chassis. We don't want those things rubbing. I just kind of eyeballed it's location because I want it close to where the wires have to go and as you can see there is plenty of real estate available.
This is the resistor that the choke will replace. R106. Gotta go bye-bye.
And buh-bye!
Now the wires from the choke will penetrate the delicate holes left behind where the resistor was. I stood the board up inside the chassis and stuck the wires. The choke is non-polarized and does nothing else, so it doesn't matter which wire goes to which hole. Just stick em in and solder. I made an executive decision here to leave the leads as long as possible instead of cutting them just long enough to reach straight to the soldering spot. The choke's location is pretty much exactly adjacent to where the leads have to go, so sure, a short straight shot is probably better - as I learned from my last modding adventure - but in this case the longer wires leave me with two benefits 1) I can twist them so they self-cancel any noise they may make, and 2) since this thing is permanently wired to the board, the longer leads will give me some flexibility if I have to remove the board again. I can now flip the board if necessary with the choke leads still attached.
Now it's just a matter of putting it all back together, and hot damn alakazam. Done!
One thing I majorly fucked up on....I recorded some before-mod sound clips....and didn't save them.
I know.....fucking n00b.
I'm sorry, I really wanted to show the difference, but I goofed that part and it's too late to go back now!
I'll just try to describe it. The tone differences aren't as significant as the "feel" differences. Even if I hadn't fucked up the recordings, sound clips might not do it justice anyway. It definitely feels and responds punchier and more ballsy. The low end is definitely tighter and more percussive without being muddy or mushy. I really like the low end improvement. It's more noticeable on the higher gain channels, but the cleanish stuff gets benefit too. The fizz is also significantly reduced. This amp can squeal like a pig at stupid gain levels if you're too close to it. That part is much better. It could go into oscillation at high gain levels...but not so much anymore. I have to chalk that up to the high frequency filtering being done by the choke. That's a good thing.
So all in all...the choke was free for me, but it's only like 30-40 bucks US dollars. An hour and a half of pretty easy work and roughly 50 bucks in parts including nuts and bolts and grommets, it really improved the performance of this amp.
Rebel Yell
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Re: Marshall JVM 410 choke mod
I'm more in awe of anyone being able to use an amp with 28+ knobs.
The mod is just icing on the cake. Good work Greg. Sucks you didn't get tones. you could try this piece of software https://www.ccleaner.com/recuva
If you wrote the files to a hard disk i am sure it is there if you felt so inclined.
What inspired you to do this one alteration
The mod is just icing on the cake. Good work Greg. Sucks you didn't get tones. you could try this piece of software https://www.ccleaner.com/recuva
If you wrote the files to a hard disk i am sure it is there if you felt so inclined.
What inspired you to do this one alteration
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Re: Marshall JVM 410 choke mod
You sir, are a fucking hero. Amazing pics and walkthrough. I have the JVM set up in the dining room just now and I realised earlier tonight that I have the OD channel gains up a bit too high. Unusual for me, I must have knocked them in transit, but a small reduction in gain got rid of a large amount of noise. This has to be a major design fault.
I think I will get this mod done, but I'm still not sure about doing it myself!.
I think I will get this mod done, but I'm still not sure about doing it myself!.
Haggard Musician
Re: Marshall JVM 410 choke mod
Dude that thing spazzed my antivirus!WhiskeyJack wrote: ↑Thu Mar 29, 2018 8:23 pm I'm more in awe of anyone being able to use an amp with 28+ knobs.
The mod is just icing on the cake. Good work Greg. Sucks you didn't get tones. you could try this piece of software https://www.ccleaner.com/recuva
If you wrote the files to a hard disk i am sure it is there if you felt so inclined.
What inspired you to do this one alteration
I clear my Reaper folders as a habit, so I just looked and nothing's there. It's gone. No big deal.
What inspired this mod....um...my buddy Chris. I've known about the chokes for a long time. I didn't know how much or what kind of difference it would make. He also has a JVM exactly like mine and he wanted to add a choke. So he asked me to do it for his amp and in return he'd also buy a choke for mine. I said sure. So i did his and liked it so much I just did mine too.
Rebel Yell
Re: Marshall JVM 410 choke mod
You can definitely do it, man. Seriously, if you can work a drill and a screwdriver and a soldering iron, you can do this. If you can fucking carve a dinosaur head out of a block of wood, you can do this.Bubba wrote: ↑Thu Mar 29, 2018 8:44 pm You sir, are a fucking hero. Amazing pics and walkthrough. I have the JVM set up in the dining room just now and I realised earlier tonight that I have the OD channel gains up a bit too high. Unusual for me, I must have knocked them in transit, but a small reduction in gain got rid of a large amount of noise. This has to be a major design fault.
I think I will get this mod done, but I'm still not sure about doing it myself!.
I just laid it all out for you. It's really surprisingly easy....and worth it IMO.
I never run my gains past noon on any of the JVM's channels. I don't know if that's a design fault, but not having a choke sure is!
If I need more gain, I prefer to go up a mode and keep the gain low. Hotter mode/less gain is better than milder mode/more gain.
Rebel Yell
Re: Marshall JVM 410 choke mod
Nice job dude! Nicely executed, and very nicely documented. Those pics are great, and the verbal detail is top notch. I'll have to catch the sound clips later.
And yeah, ccleaner has gone rogue and included a silently installed version of Avast antivirus in its recent versions. I stopped using it because of that bullshit.
And yeah, ccleaner has gone rogue and included a silently installed version of Avast antivirus in its recent versions. I stopped using it because of that bullshit.
Re: Marshall JVM 410 choke mod
I've hung onto an ancient version of ccleaner and it works a treat but I noted a year or so ago that when I began the update process there were freebies I didn't want & I lost trust.
Greg,
You continue to amaze - not just the technical skill to do the work and do it NEATLY but the ability to think the process and through as well as the implications of each step.
I agree - an MP3 isn't going to demonstrate the difference well enough - a .wav probably wouldn't either unless the ears and grey stuff between had been tuned to the level of detail and comparisons needed.
Greg,
You continue to amaze - not just the technical skill to do the work and do it NEATLY but the ability to think the process and through as well as the implications of each step.
I agree - an MP3 isn't going to demonstrate the difference well enough - a .wav probably wouldn't either unless the ears and grey stuff between had been tuned to the level of detail and comparisons needed.
Cheers
rayc
rayc
Re: Marshall JVM 410 choke mod
Tadpui wrote: ↑Fri Mar 30, 2018 2:51 am Nice job dude! Nicely executed, and very nicely documented. Those pics are great, and the verbal detail is top notch. I'll have to catch the sound clips later.
And yeah, ccleaner has gone rogue and included a silently installed version of Avast antivirus in its recent versions. I stopped using it because of that bullshit.
Thanks guys. I really enjoy tinkering on my amps. It's like working on a car without the grease, dirt, and heavy lifting.rayc wrote: ↑Fri Mar 30, 2018 6:21 am I've hung onto an ancient version of ccleaner and it works a treat but I noted a year or so ago that when I began the update process there were freebies I didn't want & I lost trust.
Greg,
You continue to amaze - not just the technical skill to do the work and do it NEATLY but the ability to think the process and through as well as the implications of each step.
I agree - an MP3 isn't going to demonstrate the difference well enough - a .wav probably wouldn't either unless the ears and grey stuff between had been tuned to the level of detail and comparisons needed.
Rebel Yell
Re: Marshall JVM 410 choke mod
Fucking hell, this is witchcraft.
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Re: Marshall JVM 410 choke mod
Very nicely done Monsieur LeBloodshit! Props!
- Bubba
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Re: Marshall JVM 410 choke mod
Just looked up the part based on your Classic Tone spec, Greg - 100W JCM800-style amps. The Dagnall version comes out at £30.00 including shipping. I'm going to wait till next month to order it.
Haggard Musician
Re: Marshall JVM 410 choke mod
Awesome. I'm pretty sure any choke will do....provided it can handle around 120-150ma. The Henry value is flexible. We went with 5H because it's kind of middle-of-the-road. Anything between say like 3H and 10H should be good for the JVM.
Rebel Yell
- WhiskeyJack
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Re: Marshall JVM 410 choke mod
Apologies to all who may have downloaded that piriform software. i had no idea they put antivirus stuff in their software now i am so very sorry!!!! I rarely update my ccleaner defraggler or recova softwares so i haven't noticed any of that crap.!!!
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Re: Marshall JVM 410 choke mod
Brilliant. The actual figures for this part are not given on the Modulus website, just that it's a suitable replacement for a JCM800 choke. I find that a little odd.
Haggard Musician
Re: Marshall JVM 410 choke mod
Man, I'd suggest you get the actual specs for that part. Some of those "800" chokes are like 40Henries and only 50ma.
Rebel Yell
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Re: Marshall JVM 410 choke mod
Yes, I think I will need to.
Haggard Musician
Re: Marshall JVM 410 choke mod
Hey, my buddy Chris used his JVM with the new choke at practice tonight. It is definitely punchier and chunkier, but not mushy at all. The lows are ballsy but tight. The top end is much less fizzy. And it's significantly quieter at idle. That was the most shocking. Normally it sits there and hisses. Not tonight. You couldn't even tell it was on over the ambient noise of people talking and fans running and stuff.
So yeah, do the choke.
Rebel Yell