Gainfreak
New member
The JVM is quickly becoming one of my favorite amps of all time and I haven't said that since 1992. I even like the powerball but the JVM smokes it in features.
kannibul
New member
:|::QBB:
I've noticed that as well (orange/red)...
Have you tried rolling the volume on your guitar? It takes to it surprisingly well, IMO.
SgtThump":66f28 said:Sounded even better this time around. I imagine it's a combination of the following:
- Bogner cab breaking in more
- New pickup in bridge of LP (Duncan '59 Model)
- We turned up louder at this gig
Also, I biased the JVM up to 80mV (or mA, whatever it is) per side. I suppose that's around 40 per tube. On the www.jvm410.com forum, Santiall said that a good balance of tone vs tube life was something like 30-35 per tube. He also suggested going no higher than 45 per tube. I decided to go for 40 and I think that may be why the amp sounded better to me (but it could be one of the above things too.)
It was smoother and the distortion seemed to be more under control? I don't know if I'm just getting used to it or if there indeed was a wider sweep on the preamp gain knob for the OD1/Orange channel/mode. But dialing in the preamp distortion at 10:00 o'clock just seemed better to me at this past gig than before.
Also, I don't remember what the amp was biased at from the factory, but it was colder than 80 per side. Maybe it was at 60 per side or something? I think so...
So anyway, it won me over even more this past weekend. I used the "Crunch/Red" and "OD1/Orange" channels/modes 99% of the time with an occassional jump over to the "Clean/Green" channel/mode.
At one point, I was confused, because the distortion seemed waaaaay too high and the guitar was feeding back and stuff. I then realized I switched it to "OD1/Red" by accident. The Orange and Red lights on the footswitch look similar at times and I didn't realize the mistake. Once I figured that out, I was back to rocking good.
Great amp for sure!
I've noticed that as well (orange/red)...
Have you tried rolling the volume on your guitar? It takes to it surprisingly well, IMO.
Digital Jams
New member
Thanks for the bias info, sounds like something I will look at as well.
PeteLaramee
Well-known member
You sunbitches keep talking about these and I keep drooling. I'm on vacation in a few days. When I get back I'm going to have to bite the bullet.
kannibul
New member
I've not touched mine yet, but I'll likely set mine to 60% and see.
With Marshall's "recommendation" for the TSL/DSL being 90% idle dissipation, I take anything they say with regards for bias with a grain of salt!
With Marshall's "recommendation" for the TSL/DSL being 90% idle dissipation, I take anything they say with regards for bias with a grain of salt!
C
chobley
Member
Nice...
chris did you change the tubes also ?
I just ordered some winged C and tung sol preamp tubes . I love the amp . I also use a Duncan '59 in the bridge , probably my favorite pup to date .
JB
chris did you change the tubes also ?
I just ordered some winged C and tung sol preamp tubes . I love the amp . I also use a Duncan '59 in the bridge , probably my favorite pup to date .
JB
Gainfreak
New member
:|::QBB:
Well there is a differance in taking what marshall says with a grain of salt vs what the actual amp designer says! That's the HUGE plus side of having Santiall post here and on the JVM site
kannibul":95c65 said:I've not touched mine yet, but I'll likely set mine to 60% and see.
With Marshall's "recommendation" for the TSL/DSL being 90% idle dissipation, I take anything they say with regards for bias with a grain of salt!
Well there is a differance in taking what marshall says with a grain of salt vs what the actual amp designer says! That's the HUGE plus side of having Santiall post here and on the JVM site
duesentrieb
Well-known member
:|::QBB:
It is/was less. Those amps are running at lower plate voltages like 440V (at least those I've biased - DSL100s), which then calculates to 75% or so.kannibul":00d07 said:I've not touched mine yet, but I'll likely set mine to 60% and see.
With Marshall's "recommendation" for the TSL/DSL being 90% idle dissipation, I take anything they say with regards for bias with a grain of salt!
kannibul
New member
kannibul
New member
:|::QBB:
I remember doing the calculations having measured my plate voltage, and it coming out to something like 90% idle.
Then again, this was before I knew that the plate voltage would shift when you change the bias - I don't know why I didn't think of that at the time...
wattage = current x voltage, you have the same power (wattage) being consumed, but you're changing the amount of current, therefore the voltage will flux.
duesentrieb":c9e9b said:
I remember doing the calculations having measured my plate voltage, and it coming out to something like 90% idle.
Then again, this was before I knew that the plate voltage would shift when you change the bias - I don't know why I didn't think of that at the time...
wattage = current x voltage, you have the same power (wattage) being consumed, but you're changing the amount of current, therefore the voltage will flux.
duesentrieb
Well-known member
Since my guess is that it has the same transformers as the DSL - sounds good to me, but in the end it depends on the plate voltage (PIN 3).
25W*x/440V = 0.04A
x = 0.04 x 440V/25W => 70%
if the plate volatage should be higher --> safe
if it should be lower (I don't think so) --> too hot
I've also set the DSL to 40mA (80 per pair) per tube btw
25W*x/440V = 0.04A
x = 0.04 x 440V/25W => 70%
if the plate volatage should be higher --> safe
if it should be lower (I don't think so) --> too hot
I've also set the DSL to 40mA (80 per pair) per tube btw
kannibul
New member
:|::QBB:
I guess it depends on the plate voltage. I'd take a measurement of the plate voltage with it at 80, and see what it works out to be.
I think (if I remember correctly from last night) you can easily read the plate voltage from the white wire leading to the OT (and ground the other lead)
I will likely make a pop-noise when doing so...
SgtThump":0ad25 said:
I guess it depends on the plate voltage. I'd take a measurement of the plate voltage with it at 80, and see what it works out to be.
I think (if I remember correctly from last night) you can easily read the plate voltage from the white wire leading to the OT (and ground the other lead)
I will likely make a pop-noise when doing so...
kannibul
New member
:|::QBB:
I know the transformers are different than what's in the TSL.
duesentrieb":c3a0a said:Since my guess is that it has the same transformers as the DSL - sounds good to me, but in the end it depends on the plate voltage (PIN 3).
25W*x/440V = 0.04A
x = 0.04 x 440V/25W => 70%
if the plate volatage should be higher --> safe
if it should be lower (I don't think so) --> too hot
I've also set the DSL to 40mA (80 per pair) per tube btw
I know the transformers are different than what's in the TSL.
duesentrieb
Well-known member
I've never opened a TSL - but some DSLs and from the pics I've seen from the JVM . . . but as I've said: I'm just guessing here . . .
Chris needs to read the plate voltage - and he owns a bias rite with the VI option, so its not a hard thing to do for him - with tubes installed.
Btw to avoid the pop by measuring the PV or even shunt-bias it: just hook the wires with croco leads to the OT and THEN switch on
Chris needs to read the plate voltage - and he owns a bias rite with the VI option, so its not a hard thing to do for him - with tubes installed.
Btw to avoid the pop by measuring the PV or even shunt-bias it: just hook the wires with croco leads to the OT and THEN switch on
B
Buckeyedog
Active member
I played a JVM at George's shop on Saturday and I was real impressed with it. Even played through a cab with new 75's it still sounded great! Now I want one as well. Gotta love the "no boost pedals needed" thing too. Wow.......think it has enough gain???......holy cow! I really liked OD1 orange. Neat amp.
kannibul
New member
:|::QBB:
All I got is the standard probes that came with mine - but some clips would be nice - just I use my meter so rarely outside of building amps, and really I doubt I'll be doing it much any more.
duesentrieb":bfeb0 said:I've never opened a TSL - but some DSLs and from the pics I've seen from the JVM . . . but as I've said: I'm just guessing here . . .
Chris needs to read the plate voltage - and he owns a bias rite with the VI option, so its not a hard thing to do for him - with tubes installed.
Btw to avoid the pop by measuring the PV or even shunt-bias it: just hook the wires with croco leads to the OT and THEN switch on
All I got is the standard probes that came with mine - but some clips would be nice - just I use my meter so rarely outside of building amps, and really I doubt I'll be doing it much any more.
SkyhighRocks
New member
Glad to hear its working out well Chris. I was supposed to gig with mine last friday but we got snowed out. Now I have to wait until this friday to gig test it.