Possible Issue With Jvm 410h?

[Rockraver]

Hi folks. Been a few years. Anyway, I recently purchased a used JVM 410H and I have some concerns. I've read how loud and how much gain this amp has but, it's doesn't seem to be living up to that claim.

For starters, I have to max out the volume on OD2 (Red Channel) and set my Master 2 volume up to 70% - 75% to match the stage volume I use on my old TSL100 head, which rarely ever has to go past 12 o'clock.

Second, the tone of OD2 is great but, still just a hair short of the gain I have on my TSL100. Even at full Gain and volumes set so high.

Lastly, and this is difficult to believe but, even at Max Gain and Max Volume on OD2 (Red Channel), with the Master2 Volume set to 75% (with Master Switch Engaged), the amp barely makes any hissing noise and..., my guitars only then start to get unruly and squeal and stuff. I'm so used to high gain amps hissing and squealing at such high gain and volume settings that I can't believe that this is right! Something has to be wrong! Normally, I HAVE to use a Noise Gate on my TSL and Mesa Boogie Dual Rec or else, it's just too noisy and out of control when I play live. Now, with this JVM410H, I didn't even need a noise gate!

I love the lack of noise of this amp and, can make the best of the gain being a hair under satisfactory gain levels but, i'm having a hard time believing that there isn't something wrong with this amp. Lol!

Primarily, my biggest concern is the lack of volume output and secondly, the uncharacteristic quietness / noiselessness of this amp. If anyone out there can tell me if this is on par with these amps or, if there is an issue I should look into, let me know. Like I said, my TSL100 (which does have an excessive amount of noise as of late) and Dual Rec are both such beast-like characters, that I just can't believe that a High Gain amp can be so quite and sound great at the same time. Help!

 

[ampmadscientist]

Hi folks. Been a few years. Anyway, I recently purchased a used JVM 410H and I have some concerns. I've read how loud and how much gain this amp has but, it's doesn't seem to be living up to that claim.

For starters, I have to max out the volume on OD2 (Red Channel) and set my Master 2 volume up to 70% - 75% to match the stage volume I use on my old TSL100 head, which rarely ever has to go past 12 o'clock.

Second, the tone of OD2 is great but, still just a hair short of the gain I have on my TSL100. Even at full Gain and volumes set so high.

Lastly, and this is difficult to believe but, even at Max Gain and Max Volume on OD2 (Red Channel), with the Master2 Volume set to 75% (with Master Switch Engaged), the amp barely makes any hissing noise and..., my guitars only then start to get unruly and squeal and stuff. I'm so used to high gain amps hissing and squealing at such high gain and volume settings that I can't believe that this is right! Something has to be wrong! Normally, I HAVE to use a Noise Gate on my TSL and Mesa Boogie Dual Rec or else, it's just too noisy and out of control when I play live. Now, with this JVM410H, I didn't even need a noise gate!

I love the lack of noise of this amp and, can make the best of the gain being a hair under satisfactory gain levels but, i'm having a hard time believing that there isn't something wrong with this amp. Lol!

Primarily, my biggest concern is the lack of volume output and secondly, the uncharacteristic quietness / noiselessness of this amp. If anyone out there can tell me if this is on par with these amps or, if there is an issue I should look into, let me know. Like I said, my TSL100 (which does have an excessive amount of noise as of late) and Dual Rec are both such beast-like characters, that I just can't believe that a High Gain amp can be so quite and sound great at the same time. Help!

Bench test w/ oscilloscope. No reason to be guessing about it.
There is no substitute for test equipment.

 

[MonstersOfTheMidway]

Hello @Rockraver

Congratulations on owing a JVM410H. The 410H are incredible amps that have served me well.

What you are describing is not typical of JVM4 amps. For example, with the settings you are using on OD2/red mode ("max gain and max volume"), you should be experiencing a significant amount of "noise" in the form of hiss and/or feedback.

The problem might be tube related (my best guess is that it's a power tube). If the tubes that are currently in the amp are the same tubes at the time you purchased the amp, then it might be a good idea to change all your tubes (or at least the power tubes) because the hours and wear and tear might be high.

But because you said you purchased the amp used, I think that forum member @ampmadscientist recommendation to test the amp is a reasonable and good idea. If you have the equipment and knowledge (or have a good friend), I'd suggest having it tested. You might even catch a potential problem in the making that will save you money in the future.

Good luck with your amp.

 

[Jethro Rocker]

Or at minimum, at least change out power tubes with spares. Might be that simple, cheap and hurts nothing. Pre amp tubes too. It's even easier and cheaper. If it doesn't fix it, tech time.

 

[Dogs of Doom]

have you looked at the tubes?

I bought a hot rodded Ampeg (Lee Jackson) & the guy I bought it off, replaced all the 12AX7s w/ 12AU7s. It sounded like shit. I plopped in a bunch of old Philips 7025s & it breathes fire. It could be something like that, or the tubes are simply worn. Always check that 1st. If that doesn't seem to do it, then start looking further...

 

[dslman]

My DSL50 went half volume quiet like you're describing.
Turned out to be V3 preamp tube.

 

[GuitarIV]

This is definitely not normal behaviour. I only tested the 410 a couple of times, but everytime I did it had ridiculous amounts of gain and it was noisy. Not noisy in the sense of being overwhelming, but you could tell for sure that the more gain you dialed in the more hiss you'd get.

I had the amp with the gain knob on 3 or 4 on the orange channel (ch 2 or 3 don't remember anymore) and that was plenty. Enough for 80ies hard rock and metal. Also loud. So yeah sounds like yours has some flaws. I'd do what the others suggested and replace tubes and if that doesn't make the thing tear down some walls I'd give it to a tech to check it out.

 

[Jethro Rocker]

Seems ro me ro be suspiciously like a preamp tube given the lack of gain. Easy fix, if that is indeed the case.

 

[mulletmule]

I have have owned a couple JVM's. I agree it's probably a tube issue. Start with the pre amp tubes first. Stupid question but your plugging straight in right? Nothing in the loop?

 

[Deep Purple fan]

If you’re using the fx loop check how you have that set. Check the knob on the back. But that does not address the lack of gain.

 

[Rockraver]

Yeah, I have an Oscope and other stuff but, since i've moved a little over a year ago, I haven't had a chance to set up a new work bench. Still a lot of work to do before I can set aside a permanent spot for my work bench. In the meantime, I do have a shit load of spare tubes that should still be good. Gonna check 'em all with my tube tester (Orange VT1000). Once I get a quad of decently matched EL34's and a handful of choice 12AX7's, I will start swapping tubes. I'll let you know what happens and thanks for the input.

 

[Rockraver]

So I changed the power tubes, and it looks like the volume issue has been resolved. Oddly, the tubes did test out good on my Orange tester. Whatever. Still have to bias them but, at least the volume levels leveled out to where you would expect them to be. Where should I bias them btw? Usual 45/90 per side? Gonna swap out the preamp tubes next to see if I can’t get the gain up a bit. Let you know what happens.

 

[Dogs of Doom]

try 39/78

 

[Iwanarock]

What you had experienced was absolutely not normal.

I have owned a JVM410H since late 2007. Glad you figured it out with the Power tubes, but i also suspected the V3 as well as mentioned above as that has definitely caused volume issues in the past. So no harm in trying different per amp tubes (not sure what is in there now) since you now have figured out the power tubes were a issue, who knows what pre-amp tubes are in there and how old. They will definitely effect your overall sound.

As far as bias most JVM owners and the designer Santiago recommended 35 per side so 35/70. That is what my 410H bias is set at. Some owner went a little hotter but not sure i recall anyone doing higher the 39/78. TSL was 45/90 per side but not the same with the JVM.

 

[Rockraver]

The power tubes were the original Marshall tubes so, very likely that the preamp tubes are old too. I have some tung-sol and jj’s to put in there so, I’ll start with them. Thanks for all the help. Let you know what happens tonight or tomorrow.

 

[Rockraver]

I’ll stick with the 35/70 settings as well. I’m assuming the bias pins are right there on the back panel, no? Like on the TSL’s, yes? I didn’t notice. Find out when I get home I guess.

 

[MonstersOfTheMidway]

Hello @Rockraver

I have my 410H bised at 34mA per tube/70mA per side. I've almost always ran it this way, but for awhile I took it down to 30mA per tubes/60mA per side with very little different in terms of tone, responsiveness, etc. From the factory, though, it came at 35mA per tube/70mA per side.

The bias test prongs and the bias trim pots are on the inside of the chassis and both are mounted to the pcb. Therefore, you will need to take the chassis out of the box to check and/or adjust the bias.

Here are some pics of the bias trim pots and bias test prongs:

The test prongs are labeled "1CON1"

Good luck with your amp.

 

[Rockraver]

That's a pain in the ass! Oh well. In the meantime, can anyone tell me what the layout is of the pre-amp tubes from left to right when looking at the amp from behind? Thanks.

 

[Jethro Rocker]

 

[RickyLee]

Make sure you have a speaker cab/load hooked up if you pull the chassis to bias it.