4 CM - reduced max volume, is using the serial loop the problem?

PolarityMan

I currently use a boss gt-10 in 4CM with my marshall JVM. The parallel loop has signal bleed on this amp so I'm using the serial loop instead.

The only problem with this is that I think output of the GT-10 is limiting the total volume i can get out of the amp. Im consistently having to run the master pretty high. While there is plent of room on the output volume of the GT-10 (it's only at a quarter) pushing it any further clips the meters on the GT-10.

So what I'm wondering is, the output of the GT-10 simply not sufficient for the poweramp stage of the amp? Would I benefit from giving it a lift with a transparent preamp of some kind before the power stage? Is it possibly an impedance type issue or something like that?

Alternatively should I just go back to the parallel loop and live with the bleed?

John_P

I might be way off and should probably leave it for people who own a jvm and a gt10...  but you need to run in series mode for 4cm to work, are the meters on GT measuring the signal going in or out?  It could be that the signal going in is a bit hot, meaning you aren't turning the output up enough.

If you ignore the meter can you hear any clipping if you turn up the GT output?  That should sort your volume level,  then you need to deal with any clipping in the GT - can you adjust the input level or the send/return level on the JVM?

ICBM

Sounds like the GT is just operating at too low a signal level for the amp's loop, so it's limiting the overall volume - boosting it afterwards might help. This is a fairly common problem with guitar-level FX and preamp-out/power-amp-in loops, which is what many series loops are.

Drew_TNBD

It's gonna be the GT. JVM's are insanely loud. Have you compared it with and without? Maybe something else going on, like a tube failure?

PolarityMan

ICBM said:

Sounds like the GT is just operating at too low a signal level for the amp's loop, so it's limiting the overall volume - boosting it afterwards might help. This is a fairly common problem with guitar-level FX and preamp-out/power-amp-in loops, which is what many series loops are.

@ICBM This is exactly what I'm thinking. I'm fairly sure the series loop on the JVM is exactly that. Is there any reason I couldnt use one of these http://www.juno.co.uk/products/art-tube-mp-studio-v3-preamp/250316-01/?currency=GBP&flt=1&gclid=CNaI_q_Uo7oCFXMRtAode1EAJw (which i have kicking around already) to boost the signal back again? 

@John_P You can meter anywhere in the chain but I'm using the output meter, therefore tweaking the S/R levels is just going to modify where the sweet spot is on the output pot of the GT-10. ie/ i put a slightly less hot signal in but i turn the output meter up to 50% instead of 25% but the total juice coming out of the pedal is going to be the same.

Cranking the output meter does produce clipping if you go much higher than the sweet spot.

@Drew_fx Haven't run it without fx for a while and last time was when balancing my S/R levels in the house so at low volume. Only noticed it recently as we got a new PA in our rehearsal space and now we've ended up practicing a little louder and im almost diming the master. My feeling is that I should still have some more volume in there. Mind you I havent checked if its a speaker sensitivity issue, Im running neo's at the moment so it's possible theyre just not as loud speakers.

ICBM

PolarityMan said:

@ICBM This is exactly what I'm thinking. I'm fairly sure the series loop on the JVM is exactly that. Is there any reason I couldnt use one of these http://www.juno.co.uk/products/art-tube-mp-studio-v3-preamp/250316-01/?currency=GBP&flt=1&gclid=CNaI_q_Uo7oCFXMRtAode1EAJw (which i have kicking around already) to boost the signal back again? 

Try it, it can't hurt.

Drew_TNBD

Hmmm. With my clean channel I almost dime the clean channel volume, and master at noon. With my gain channels, everything at noon, and master 2 at noon also. It is supremely loud when I do this, I never have to dime either of the masters!

PolarityMan

I'm running all channel vol's at noon at the moment (only use master 1 and providing vol boost by balancing patches currently), running clean higher would just mean dropping the patch level I would expect.

What I might do (since i can do it without getting an ASBO) is run serial out from the raw JVM into my sound card, set so it comes to a fixed point on the meter and then do the same thing with the GT-10 output with the rest wired as per 4-cm

That should tell me if the GT-10 is outputting significantly less level I think.

Are you still using a 2x12 or did you go back to a 4?

Van_Hayden

Is it not loud enough with the effects in place? If you can get buy if live with it.

Make sure your running all your patches at the highest lever possible.

Drew_TNBD

PolarityMan said:

I'm running all channel vol's at noon at the moment (only use master 1 and providing vol boost by balancing patches currently), running clean higher would just mean dropping the patch level I would expect.

What I might do (since i can do it without getting an ASBO) is run serial out from the raw JVM into my sound card, set so it comes to a fixed point on the meter and then do the same thing with the GT-10 output with the rest wired as per 4-cm

That should tell me if the GT-10 is outputting significantly less level I think.

Are you still using a 2x12 or did you go back to a 4?

My ENGL 2x12 at home and my Egnater 4x12 for live - both with V30's. Currently I am not doing any 4-cable method stuff, but when I did with the Boss GT-100 it didn't affect my volumes. But my switchable loop is a series loop, whereas I think you're using the Line level preamp out and poweramp in, right??

Grumpyrocker

If it's anything like my POD HD500 you should run the GT10 master volume all the way up to allow the whole signal through.

PolarityMan

Grumpyrocker said:

If it's anything like my POD HD500 you should run the GT10 master volume all the way up to allow the whole signal through.

I'm pretty sure the output meter is before the DAC. Running the volume all the way up will result in a little extra volume perhaps, but I think it will result in a ridiculous amount of clipping.

dhaywood67

i used to run a gt10 and a jvm and had no problems with volume. have you got the effects mix nob turned 100% full serial? another option but possibly not viable, backup ypur gt10 and try a factory reset. it might be a parameter somewhere is wrong?

Danny1969

Is your GT10 set to line level rather than instrument?  I use mine on Line in a serial loop and theres plenty of output

PolarityMan

dhaywood67 said:

i used to run a gt10 and a jvm and had no problems with volume. have you got the effects mix nob turned 100% full serial? another option but possibly not viable, backup ypur gt10 and try a factory reset. it might be a parameter somewhere is wrong?

No the serial loop on the JVM doesnt have a "mix" facility. It's a preamp/power amp insert loop.

dhaywood67

that might be part of the issue, but yes it should run fine there also. I ran it in the parallel/serial inserts with the mix nob on the back on 100%. It might be worth trying the other loop and 100% wet which makes it a serial loop, at least it does on a 100w head. 

Can you give us your signal path e.g.

guitar -> GT10 input

etc 

and how you've got the GT10 configured for output to the JVM input

Should give us a bit more to go on.

PolarityMan

dhaywood67;62015" said:

that might be part of the issue, but yes it should run fine there also. I ran it in the parallel/serial inserts with the mix nob on the back on 100%. It might be worth trying the other loop and 100% wet which makes it a serial loop, at least it does on a 100w head. 

Can you give us your signal path e.g.guitar -> GT10 inputetc 

and how you've got the GT10 configured for output to the JVM input

Should give us a bit more to go on.

No offense but Im not a muppet, if it was that simple I'd have fixed it already

Its in the title I'm using 4cm for those who dont know that is:

Guitar -> Boss gt-10 input -> Boss Gt-10 send -> JVM Input -> JVM Serial loop send -> Boss Gt-10 return -> Boss GT-10 out -> JVM Serial Loop Return.

As I already mentioned using the parallel loop even at 100% wet introduces phasing issue due to signal bleed in the JVM.

Im pretty sure ICBM hits the nail on the head here and the issue is that the "serial loop" is expecting a lot more level than is capable of being delivered by the GT-10 because it isn't either a line level or instrument level loop but actually significantly hotter than both.

Drew_TNBD

The GT-10 is a line level -10dBU output. It's possible the JVM expects +4dBU, hence the quiet signal. I don't know for certain that this is the issue, but it would explain it.

1nten5e

This helped me dial my GT10 for 4CM

http://www.bossgtcentral.com/showthread.php?24755-Copy-of-my-previous-tutorial-about-4CM-(adapted-to-the-GT10)

PolarityMan

Drew_fx said:

The GT-10 is a line level -10dBU output. It's possible the JVM expects +4dBU, hence the quiet signal. I don't know for certain that this is the issue, but it would explain it.

You can switch between -10 and +4, the +4 is even quieter. Im going to bring my preamp to practice tonight and see what i can determine.

PolarityMan

Ok so, I took my art mic preamp to practice with me. I calibrated the preamp by runnging the guitar straight into the JVM and putting the preamp in the serial loop then setting the preamp so the input gain didn't clip and the output meter was a fraction below unity.

I then left the preamp setting as they were and put the preamp in between the OUT of the GT-10 and the return of the JVM serial loop with everything else wired for 4CM

The art registered an 8-9db drop in output level, so it looks like the GT-10 simply doesnt kick out enough juice. 

I tried running with the preamp in the loop, it gives you more volume but it compresses the signal and changes the tone quite considerable so I dont think that's a valid solution.

I did on a whim try wiring into the parallell loop instead of the series one (set 100% wet of course) and the headroom is all back. Some of my patches sound a bit arse in the loop but the only serious issues are with chorus and flange in the loop which sounds a little odd, im hoping i can fix this with tweaking on the GT-10 side to an acceptable level.

I REALLY want a satriani JVM though...proper series loop and no switching gap would be awesome.