JCM 900 help with FX Loop

[johnnyg]

I have the 100w dual reverb head with EL34 tubes and love the tone it gives me when cranked thru a 2x12 cab with G12-65 heritage celestions.

 

I have never used the FX loop until I tried for the first time last night to run my new Small Clone analog chorus and digital delay.. it didn't work for some strange reason.. all i could hear was a very faint saturated tone barely audible.. so i put the chorus through the front of the amp and if sounded great with high gain.

 

Maybe i need to play around a bit to get it working.. anyone else use the FX loop/had issues with it .... and if so what pedals you put through it for what sounds etc Also how do you use the level control on the back of the head ?

[The Idiot]

 

I have the 100w dual reverb head with EL34 tubes and love the tone it gives me when cranked thru a 2x12 cab with G12-65 heritage celestions. I have never used the FX loop until I tried for the first time last night to run my new Small Clone analog chorus and digital delay.. it didn't work for some strange reason.. all i could hear was a very faint saturated tone barely audible.. so i put the chorus through the front of the amp and if sounded great with high gain. Maybe i need to play around a bit to get it working.. anyone else use the FX loop/had issues with it .... and if so what pedals you put through it for what sounds etc Also how do you use the level control on the back of the head ?

 

 

Did you try turning that little screw thingy in the back?

[guitargod0dmw]

I don't think this is your problem...but

 

Pedals don't belong in the effects loop...rack gear does.

 

Pedals use an instrument level signal...like a front end of an amp

FX loops use a line level signal...Rack gear uses a line level signal

 

It's a mismatch that usually results in a {censored}ty tone.

[Mr Roboto]

Yes, that little screw thingy adjust the effects loop level. If it's turned all the way down, you won't get much, if anything out of it.

 

I run an EQ, gate, and delay in the loop of my 4500, and it works perfectly. Sounds great.

[Mr Roboto]

 

I don't think this is your problem...but Pedals don't belong in the effects loop...rack gear does. Pedals use an instrument level signal...like a front end of an amp FX loops use a line level signal...Rack gear uses a line level signal It's a mismatch that usually results in a {censored}ty tone.

 

 

Not true at all. It depends on the loop for a start. Please don't give people incorrect advice. Most amps have an effects loop set up for pedals. Very few are set up for rack gear only.

[MetalHeadd]

Yeah, you have the screw that adjusts the loop level turned the wrong way. Turn it all the other way and it'll be at pedal level and should sound great. The loop on my mkIII 2500 head works great with pedals.

[guitargod0dmw]

 

Not true at all. It depends on the loop for a start. Please don't give people incorrect advice. Most amps have an effects loop set up for pedals. Very few are set up for rack gear only.

 

 

That's not correct at all. Of course it depends on the loop, which is why I said...most FX loops are set up for a line level signal. I never said they all are.

 

Very few? I'd say it's the other way around. Read some manuals...

 

EDIT: A lot of companies have now started using adjustable loops...like the JCM900.

[johnnyg]

what about analog chorus in the Loop used with the amps own distortion ? Better than thru the front end ?

[guitargod0dmw]

 

what about analog chorus in the Loop used with the amps own distortion ? Better than thru the front end ?

 

 

That's totally up to your ears...

 

Just make sure that you've dialed in that loop level pot on the back to match the signals.

[Mr Roboto]

That's not correct at all. Of course it depends on the loop, which is why I said...most FX loops are set up for a line level signal. I never said they all are. Very few? I'd say it's the other way around. Read some manuals... EDIT: A lot of companies have now started using adjustable loops...like the JCM900.

 

You show me a list of amps with line level only loops.

 

Oh, and the JCM 900 was introduced back in 1990. That's 19 years ago.

[guitargod0dmw]

You show me a list of amps with line level only loops.

 

Mesa Boogie...all of them

[Mr Roboto]

 

what about analog chorus in the Loop used with the amps own distortion ? Better than thru the front end ?

 

 

It's generally accepted that time based effects (delay, reverb, chorus, etc.) work best in the loop.

[Mr Roboto]

Mesa Boogie...all of them

 

 

 

This doesn't show the dB range, but normally it should go from -20dB to 0dB. If Mesa doesn't allow for this, then I'd say that's short sighted on their part.

[Alex W]

I don't think this is your problem...but Pedals don't belong in the effects loop...rack gear does. Pedals use an instrument level signal...like a front end of an amp FX loops use a line level signal...Rack gear uses a line level signal It's a mismatch that usually results in a shitty tone.

 

x 1000

[guitargod0dmw]

 

Maybe I shouldn't have said all Mesa...

 

I give up...you're right, I'm wrong. I don't have time to search away to find multiple sources...so here are a few...

 

http://www.guitarsite.com/guitar_FAQ.htm#LOOP

 

http://www.thegearpage.net/board/showthread.php?p=5277270

 

http://acapella.harmony-central.com/archive/index.php/t-1044106.html

[Invader.CC]

I tried the same thing when i first got a JCM 900 i was told that effects pedals will not work in the FX loop they don't have enough power that the fx loop on the JCM series is for rack mount effects.That s what i was told not sure if its true but they would never work on mine either so i just ran them in line from my guitar input

[Invader.CC]

Not sure who said it but they said there was a knob i could turn and run my pedals through the fx loop were is this knob located i just went down stairs and i don't have a knob by my fx loop.I f i could i would much rather run my effects through the loop then in the input line from the guitar.We are still talking about JCM series amps?

[Mr Roboto]

 

Not sure who said it but they said there was a knob i could turn and run my pedals through the fx loop were is this knob located i just went down stairs and i don't have a knob by my fx loop.I f i could i would much rather run my effects through the loop then in the input line from the guitar.We are still talking about JCM series amps?

 

 

No it's not a knob. It's a recessed pot, and you need to use a screwdriver to turn it. If you're looking at the back of your amp, it is directly to the left of your send jack.

 

You would still have to run any gain based effects (OD, wah) in front of your amp.

 

EDIT: Your sig doesn't say anything about a 900.

[potaetoes]

two things:

 

1 - most pedals work FINE in a JCM900 fx loop, as long as the level is set appropriately on the recessed trimpot. anyone who says otherwise is simply full of {censored}.

 

2 - the contacts on the jacks of JCM900 fx loops are notorious for getting contaminated. usually the problem is a muffled sound when the loop isn't being used, caused by dirty switch contacts in the jack, but it can also cause muffled sound when using the loop. squirt them with a spray contact cleaner and plug the cord in and out several times to make sure they're clean. many JCM900 fx loop problems can be solved just by cleaning the jacks.

[knucklefux]

if there's something wrong the loop in your JCM900, the amp won't work. all signal from the preamp goes through the SS FX loop. could be part of the reason they don't sound so good:idk:

[potaetoes]

 

if there's something wrong the loop in your JCM900, the amp won't work. all signal from the preamp goes through the SS FX loop. could be part of the reason they don't sound so good:idk:

 

 

that's what happens if the switching contacts are crappy. when nothing is plugged in the loop, the switch contacts are in closed position and signal passes through. if the loop is seldom/never used, the switch contacts can remain fine while the unused plug contacts get crappy, in which case the amp would be fine with nothing in the loop but quiet when the loop is used.

 

quick way to test is to plug a cable directly from send to return. if the amp gets quiet, the jack contacts are crappy. if the amp gets louder, the switch contacts are crappy.

 

edit: n/m, looks like you're talking about if the loop's circuitry was screwed up the amp wouldn't work, which is true.

[soundguruman]

The effects loop is a bit of a mistake. There are about 5 basic mistakes in design of JCM 900...

The level control turns the send up, and the return down at the same time.(counterclockwise)

turn it the other way (clockwise), and the return is going up, and the send going down.

which explains why it is very confusing to operate, and most give up altogether...besides being mislabled.

besides the fact that it is probably the wrong level, and over-loads the input of your effects pedal, with too much signal...yes it was designed and built that way, there is no malfunction.

Besides the malfunction of the designer.

 

So to make it work right...it can't.

You have to modify it to make it work with a standard effects pedal (guitar level input of pedal, 1V PP maximum, 1V PP output of pedal, approximately). Or the levels in/out are completely fubar.

 

There is certain effects units which match the original levels, but not standard in this country, USA.

 

 I have modified the effects loops, and it is possible to make it right for a standard effects pedal.

In fact it sounds pretty sweet.

The MOD ("The Yerzy Mod") Involves taking the effects send jack off the circuit board, and turning it upside down, so you can re-program the effects send jack wiring. Inserting whatever parts in-between there, to obtain the correct effects send level. Then, your effects pedal has a nice clean input signal...