JVM Sound/Valves

All about tube choices for the JVM series. See workbench for biasing and tube problems you may have.

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JVM Sound/Valves

Post by Bailz » Mon Sep 02, 2019 9:00 am

Hi guys,

So I recently changed the bridge of my main Les Paul to a Tonepros as the original Gibson one was collapsing (buzzing on the D and G strings). It sounded pretty good at practice last Wednesday and had buckets more sustain than it did with the old bridge. It also used to get a bit ice picky up the top strings so I'd usually run my JVM with the presence at 5, treble at one or off to dial it out. This seemed to be gone now. Happy days.

Fast forward to gig on Saturday and the JVM felt pretty lifeless, felt like there was less gain and my sound was disappearing whenever the drummer kicked in. This is the first time for a while we've gigged on a carpeted floor rather than wood so I guess it could be down to that. I ended up compromising with the presence on 10, mids on 10 and treble on 5, but still wasn't really "satisfied" with the sound.

My concern is that this could be power valves going bad, just unfortunate that it's happening at the same time as I swapped out the bridge. I'm currently using JJ's, which I know are a bit darker than other valves, but this was never an issue with the old bridge. I also used to think that the sound got thinner when the valves were failing so I'm a bit confused.

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2008 Gibson Les Paul Custom :: 2004 Gibson Les Paul Standard :: 2009 Gibson Les Paul Junior ::1992 Epiphone Les Paul Standard
Marshall JVM 205H :: Marshall Vintage Modern 226 :: Marshall Code 50

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Re: JVM Sound/Valves

Post by MonstersOfTheMidway » Sun Sep 08, 2019 7:07 pm

@OP: Lots of things could be at play regarding your situation.

If your "gain"/distortion/overdrive/dirt is starting to lessen, you could look at the preamp tubes, bad cable, power tubes, etc. Easiest and cheapest is to check cables and speaker connection to make sure everything is in good condition. Next, I'd try different preamp tubes to see if the sound improves (stick with ECC83/12AX7 since those will give you the highest gain factor). Next, check your power tube bias. If the bias is off, perhaps a small adjustment might improve the sound quality. Also, give your tubes a visual inspection to make sure nothing obvious is affecting the functioning of the tubes.

I, too, use JJ power tubes. The JJ type I'm running is E34L quad biased at 35mA per tube. I'm not really noticing any specific frequency changes with the JJ E34L, but I do like how the low end is tight and not "loose" and "boomy."

Previously, I ran SED Winged =C= EL34 quad also biased at 35mA per tube. When those power tubes began to die, the first symptom I noticed was a loss of volume. I was having to push the volume much higher than normal, but then the volume would suddenly jump back to the levels I expected. Then, I noticed that the sound quality was kinda distorted, but in a bad way. I never experienced any unusual sound qualities with respect to gain/distortion/overdrive/dirt.

Good luck with your amp. Let us know if your situation improves and what you did to make it better.

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