First Show With JCM 900 Yesterday - Thoughts and Questions for the Experts!11!!

[Amp360]

A couple of weeks ago, I posted that I picked up a JCM 900 at a pawn shop for $300. It's a 4102 100-watt High Gain Dual Reverb.

When I took it home, the pots were very noisy. I cleaned them and used them for a couple of hours, then it blew a fuse. I narrowed the problem down to a bad output tube and decided to retube everything. Once that was done, it lit up but didn't sound. The issue was a dirty contact in the impedance switch.

Then, the reverb didn't work. This isn't the type of amp I would use the reverb on, but I pulled the tank out, and a couple of the wires were unsoldered. All fixed now. Next, I tried using a Marshall footswitch I have. It has LEDs. The channels switch, but the reverb is dead. Apparently, this is the wrong one, but I found the OEM on GC used for $30.

I have to say I love this amp with a Les Paul or SG. It sounds wonderful. It does what it does, and for more rock-oriented music, it's way better than I expected. It seems to be built well. The sockets are mounted to the chassis, the cabinet is wood, and the speakers are fantasic - the same ones from the 1960, which I love.

I used it last night, and it sounded exceptional. A freind of mine had the head/cab of this back in the 1990s and neither of us loved it. Now, I do. I am going to hav him come check it out soon.

So anyway, the problem I'm having is that it is too harsh with p90s. I just can't get it to sound good. It's almost there, but I'm just fighting it. I saw a bunch of mods online, but in my experience, mods aren't usually worth it, and since I like the amp so much, I don't want to change it.

I've read about people using an EQ in the effects loop. Has anyone done this? I never use effect loops, but thought if I could put something there that would smooth out the P-90 when engaged it would be awesome.

Also, I'm thinking Boss (my fav) or MXR (used to be good, not sure if they still are?) if this will help. Any suggestions?

Thanks!

 

[MBSC]

common sense would make me think P90s were never going to match with that high gain amp set up

 

[Amp360]

common sense would make me think P90s were never going to match with that high gain amp set up

I’m running it low gain.

 

[mdubya]

Turn down the treble and middle?

Dial the volume and tone down on the P-90s?

 

[Jethro Rocker]

If the built in EQ doesn't seem to dial it out, an EQ in the loop is extremely effective.
BTW, I dial up fairly high gain and tried my 53 with P90s a week ago at a show. It sounded spectacular! Good low end thump, some high end bite but not excessive. I did reduce mid and treble a bit with that guitar.
Synergy amp witn Peavey 6505 preamp module. I have no issue using that in a higher gain setup. Use a noise gate.

 

[corpse]

As you don’t use the hi gain channel what about making it lower gain with a 12AT7?
Complete speculation.

 

[Offshore Angler]

I would try adding a closed-back extension. Open-back with Celestions have IME a tendency to be a tad on the brittle side. The closed back will give it some "womp" on the bottom and smooth things out. Actually, I've never been a fan of Marshalls with open backs but to each their own. The 4102 is a very polarizing amp. Some love it, some hate it. I suspect the haters are those looking for a more traditional Marshall sound.

I also suspect that at 100W maybe you're not pushing it to where it wants to live and that is making the P90's sound a tad strident.
I would run the EQ before the amp. This allows you to change the input EQ when switching guitars and eliminates 2 cables. Run the EQ after your input buffer on your effects board and before any compression or OD/Distortion so you can push past unity gain where you need it and see if you like it.

Chuck

 

[GreenBurst]

Another option is to use an attenuator to get to the sweet spot. Well worth the effort IME.

 

[Amp360]

Turn down the treble and middle?

Dial the volume and tone down on the P-90s?

Yeah that doesn't work.

 

[Amp360]

Another option is to use an attenuator to get to the sweet spot. Well worth the effort IME.

I don't want to drop the volume. I'm running the amp at about 1 o'clock

 

[Amp360]

I would try adding a closed-back extension. Open-back with Celestions have IME a tendency to be a tad on the brittle side. The closed back will give it some "womp" on the bottom and smooth things out. Actually, I've never been a fan of Marshalls with open backs but to each their own. The 4102 is a very polarizing amp. Some love it, some hate it. I suspect the haters are those looking for a more traditional Marshall sound.

I also suspect that at 100W maybe you're not pushing it to where it wants to live and that is making the P90's sound a tad strident.
I would run the EQ before the amp. This allows you to change the input EQ when switching guitars and eliminates 2 cables. Run the EQ after your input buffer on your effects board and before any compression or OD/Distortion so you can push past unity gain where you need it and see if you like it.

Chuck

I have the amp probably 3/4 of the way up. I'm running it loud on 100-watt mode. In the past I've had open back Marshall amps (Bluesbreaker) and liked it.

With humbuckers it's great. The guitar knobs and tone controls just aren't cutting it with the P-90s.

 

[Amp360]

If the built in EQ doesn't seem to dial it out, an EQ in the loop is extremely effective.
BTW, I dial up fairly high gain and tried my 53 with P90s a week ago at a show. It sounded spectacular! Good low end thump, some high end bite but not excessive. I did reduce mid and treble a bit with that guitar.
Synergy amp witn Peavey 6505 preamp module. I have no issue using that in a higher gain setup. Use a noise gate.

Thanks! What eq are you using? I'm thinking a little 150hz would do the trick,.

 

[Offshore Angler]

What wattage are the speakers? If you're not driving them hard enough that can be an issue too. That's why attenuators aren't the same. You don't get the speaker breakup or cone-cry, which is a major part of making the amp smooth.

 

[Offshore Angler]

Just out of curiosity, how does a Strat sound through it?

 

[Jethro Rocker]

Thanks! What eq are you using? I'm thinking a little 150hz would do the trick,.

I have several but have never compensated strictly for P90s.
I like a parametric EQ. Empress is mine.
Try it in front as mentioned and in loop, see what you like better. Up front it can add more saturation depending on settings. Whether you want that or not is subjective.

 

[Amp360]

What wattage are the speakers? If you're not driving them hard enough that can be an issue too. That's why attenuators aren't the same. You don't get the speaker breakup or cone-cry, which is a major part of making the amp smooth.

OK, like I said before, the amp is turned up 3/4 of the way up (i.e. prettyloud). I'm not using it at small shows. It has the stock Celestions, two of them.

 

[Amp360]

I have several but have never compensated strictly for P90s.
I like a parametric EQ. Empress is mine.
Try it in front as mentioned and in loop, see what you like better. Up front it can add more saturation depending on settings. Whether you want that or not is subjective.

Thanks!

 

[Offshore Angler]

OK, like I said before, the amp is turned up 3/4 of the way up (i.e. prettyloud). I'm not using it at small shows. It has the stock Celestions, two of them.

OK, but what wattage are they? If the speakers are too highly rated you won't get a smooth breakup. I've run into this several times with supplied backlines. The speakers get blown and then replaced by the sound company with higher Wattage versions for durability and then sound not-so-good. Justy trying' to help and throwing it out there.

Chuck

 

[Amp360]

OK, but what wattage are they? If the speakers are too highly rated you won't get a smooth breakup. I've run into this several times with supplied backlines. The speakers get blown and then replaced by the sound company with higher Wattage versions for durability and then sound not-so-good. Justy trying' to help and throwing it out there.

Chuck

It's the stock 75-watt Celestions, which I actually really like. Like I said, it's more of a voicing problem because the amp sounds great with humbuckers.

 

[garagemonkey]

Not sure exactly what you're after but when an amp sounds good with a couple guitars but not another, just me but I don't mod the amp. Personally speaking, I'll use a GE-7 or an Xotic RC Booster (bass and treble controls do quite a bit) in front of the amp and tweak those to help even things out. That lets me adjust sound and level for just that one guitar, especially if I'm only playing it for a couple of songs per night.

(also, I don't own one, but an Empress ParaEq Mk II would do the same thing with more range/scope)