Taming a REALLY bright JCM800

[B2D]

Re: Taming a REALLY bright JCM800

Sounds like you won't have to play with that amp anyway.

Sorry, I should have mentioned that there's a possibility of having to play a gig with this thing.

 

[Burkwieser]

Re: Taming a REALLY bright JCM800

Can you return the 800 for another amp that's not so trebley? If not, just plug your guitar into an EQ pedal then into the amps input. That's what I'm doing with my DSL 50. The treble is rather "over the top" to put it mildly. I took the far right sliders on the EQ down considerabley and took it from there. Such a simple thing and it made such a HUGE differance. No more "ice-pick treble."

+1

Adding a EQ is probably the easiest thing to do. I am sure you can rent one of those also. It beats pi$$ing around with the amp and getting yourself into an unwanted bill. It should be enough to get you by.

 

[Burkwieser]

Re: Taming a REALLY bright JCM800

Is it a vertical input or side by side input JCM-800? The earlier version with the vertical inputs has a better tone and is a slightly differant curcuit than the side by side version. The side by side input version also has higher plate voltage on the tubes and that makes it brighter and more shrill, IMO. I tried darn near everything I could think of to make my '86 JCM-800 sound as nice as my '82 and never could. The differences in the circuit and are subtle but, IMO, the differences in the trannies and voltages made it impossible to really warm mine up enough to satisfy me.

Good info to know.

 

[tone4days]

Re: Taming a REALLY bright JCM800

yeah, a graphic eq in the effets loop could be about your only change with a rental

are the speakers broken in? ... maybe they could stand a buncha hours of rap music blastin through them with the cab facing the floor

good luck
t4d

 

[V!N]

Re: Taming a REALLY bright JCM800

Sorry, I should have mentioned that there's a possibility of having to play a gig with this thing.

I see. In that case, the soundman is your best friend.

 

[B2D]

Re: Taming a REALLY bright JCM800

yeah, a graphic eq in the effets loop could be about your only change with a rental

are the speakers broken in? ... maybe they could stand a buncha hours of rap music blastin through them with the cab facing the floor

good luck
t4d

The cab is probably about 20 year old... I would assume someone has broken it in by now, hahaha. :laugh2:

And Marshall 2204s do not have effects loops. :blackeye:

Is it a vertical input or side by side input JCM-800? The earlier version with the vertical inputs has a better tone and is a slightly differant curcuit than the side by side version. The side by side input version also has higher plate voltage on the tubes and that makes it brighter and more shrill, IMO. I tried darn near everything I could think of to make my '86 JCM-800 sound as nice as my '82 and never could. The differences in the circuit and are subtle but, IMO, the differences in the trannies and voltages made it impossible to really warm mine up enough to satisfy me.

It's a vertical input model. I do not know what year it is.

I will not put up with tone this bad!! I will win!

 

[Luke Duke]

Re: Taming a REALLY bright JCM800

The cab is probably about 20 year old... I would assume someone has broken it in by now, hahaha. :laugh2:

And Marshall 2204s do not have effects loops. :blackeye:



It's a vertical input model. I do not know what year it is.

I will not put up with tone this bad!! I will win!

WOW that bright/bad of a tone from a stacked input 800? It MUST have some cold 6550s in it......probably bad ones at that.

Kill the presence knob.

Luke

 

[B2D]

Re: Taming a REALLY bright JCM800

WOW that bright/bad of a tone from a stacked input 800? It MUST have some cold 6550s in it......probably bad ones at that.

Kill the presence knob.

Luke

They're Electro Harmonix EL34s and they looks like they're pretty healthy judging by thw glow.

You mean kill as in turn it to zero? I did. Same with the treble. Still REAL bright.

Good to see you here again, btw.

 

[B2D]

Re: Taming a REALLY bright JCM800

I'm with Luke Duke on this one. But you might not like the tone of those 6550's...I redid mine to take EL-34's. I think 6550's sound to clean and do not have the classic Marshall Plexi style tone. Your amp needs some work...I'd start by having a tech reconfigure it to take EL-34's. Lew

*sigh*

Take a closer look at post 29, mang.

 

[OlinMusic]

Re: Taming a REALLY bright JCM800

It could be the speakers. Also consider a creamy pedal to smooth it out like a Rat with the tone set low, or a modded SD1.

I never had a JCM piss me off like you describe.

 

[B2D]

Re: Taming a REALLY bright JCM800

It could be the speakers. Also consider a creamy pedal to smooth it out like a Rat with the tone set low, or a modded SD1.

I never had a JCM piss me off like you describe.

Yeah my OCD with the tone set low helps some but not a whole lot.

Maybe I just got a bad one? I'll try the biasing by ear tonight and see whats in the cab.

 

[ErikH]

Re: Taming a REALLY bright JCM800

I've watched this one for a while and there's one thing that nobody has mentioned at all.......

"TAKE IT BACK!" Ask them to check it out and see what they'll do for you since you're renting it while yours is in the shop.

Look at the serial number on the back and then look up the code. Marshall Arts: How Old is My Marshall?

 

[J Moose]

Re: Taming a REALLY bright JCM800

When you open up the cab check & make sure it's wired right. I've seen ALL kinds of whacky stuff on rental gear...speakers that are either blown or wired out of phase are the biggies.

 

[Lewguitar]

Re: Taming a REALLY bright JCM800

If it's a rental there's not much you can do. Maybe check the bias and make sure it's not biased to cold...

 

[V!N]

Re: Taming a REALLY bright JCM800

Always look on the bright side of life ! :smokin:

 

[PoorMan]

Re: Taming a REALLY bright JCM800

Try a loooooooong cable...a coil one if you can find one. That'll cut some of the highs.

 

[B2D]

Re: Taming a REALLY bright JCM800

Try a loooooooong cable...a coil one if you can find one. That'll cut some of the highs.

:chairfall

 

[DeadSkinSlayer3]

Re: Taming a REALLY bright JCM800

Make sure the speakers are wired in phase with one another, too! Trusty old 9V battery test.

 

[B2D]

Re: Taming a REALLY bright JCM800

Ok here's a quickie Paint mock-up of the wiring I found inside the cab. All the cable colors are true to life, and I made sure to copy the wiring exactly. The red stars are positive terminals. The speakers say "Celestion G12 Vintage 16 ohms" with a black and gold label and thats it... no wattage markings or anything else.

Something about that wiring scheme doesn't look right to me... It looks like someone tried to wire it up in parallel but added two wires and plugged in the terminals wrong.

 

[ErikH]

Re: Taming a REALLY bright JCM800

That cab is wired series/parallel which is correct. All 4 speakers are rated at 16 ohms and all of them wired series/parallel makes 16 ohms.

See post #32 for actual solution to the problem.