JCM 900 50 watt Dual Reverb Model 4500 - Slash amp setting

[GrayFox14048]

Hi everybody!
I have a gibson LesPaul sunburst and a valve JCM 900 50 watt Dual Reverb Model 4500.
I would like to try to have the "Slash sound" so I followed this setting:
but I not able to convert this setting for my amp:

The amp settings for Slash’s dirty tone are:

• Presence: 5
• Bass: 7
• Middle: 5.5
• Treble: 5
• Output Master: 6
• Lead Master: 10
• Input Gain: 3

On my amp (JCM 900) I have only:
- "Volume Master" for channel A and B
- "Lead gain" for channel B
- "Gain" for channel A

Can somebody convert it or know me the correct Slash settings for my amp?
Here's a picture of my amp for details!

Thanks for anyone can help me!!

 

[paul-e-mann]

Hi everybody!
I have a gibson LesPaul sunburst and a valve JCM 900 50 watt Dual Reverb Model 4500.
I would like to try to have the "Slash sound" so I followed this setting:
but I not able to convert this setting for my amp:



On my amp (JCM 900) I have only:
- "Volume Master" for channel A and B
- "Lead gain" for channel B
- "Gain" for channel A

Can somebody convert it or know me the correct Slash settings for my amp?
Here's a picture of my amp for details!

Thanks for anyone can help me!!

Theres no "Slash" settings for that amp or any amp, use your ear and dial it in!

 

[GrayFox14048]

Theres no "Slash" settings for that amp or any amp, use your ear and dial it in!

That's a beautiful reply but useless, can you tell me what does Output Master, Lead Master and Input Gain correspond to my amp?
Thanks

 

[Deftone]

I have a 4500, not sure you can dial in that tone with it as it is designed differently than the 2555SL.

 

[cjs42079]

That's a beautiful reply but useless, can you tell me what does Output Master, Lead Master and Input Gain correspond to my amp?
Thanks

You won’t get the same sound, but you can get close. The 900 has two channels with two independent gain knobs. The SJ shares a gain across both channels (Input Gain). Output Master on the SJ is your master volume, and Lead Master is your lead channel volume.

Personally, I set the gain on channel A around 1-2 o’clock just past edge of breakup. And channel B I keep the gain lower (below 11 o’clock) and slam it with an SD-1 for my dirtier sound. Also gotta watch your treble and presence on this amp, it can be ice picky especially compared to the warmer and darker SJ. Don’t try to use Slash’s EQ settings from his Joob on your 900.

Good luck

 

[Mitchell Pearrow]

To The Forum
The best thing you can do is as
@paul-e-mann said
I have very little experience with your amp

 

[Deftone]

There was pretty simple mod for the DR on this site: http://sgravenmade.nl/ I think the guy is a member here as well. You might try searching for the mod, I've seen it on here and on the Gear Page

Otherwise, people seem to prefer the EL34 version of this amp, might be a good candidate for a conversion?

 

[Tatzmann]

The volume/gain recommendations dont really
correspond to the preamp layout of the 900DR.

Consider the settings mean Channel B, Channel B Mastervolume at 10 (17 oclock, full up) and
Channel B LeadGain at 3 (8.30 oclock, very low).

This setting wont give you GNR guitartone at all.

You can try Ch.B Master at 14 oclock and CH.B.
Leadgain at 12 to 14 oclock.

That atleast will get you in the ballpark.

The 900DR thicken up about 14 oclock on the
master, but it will be rather loud with high preamp settings, but thats the road to slashcity.

 

[paul-e-mann]

That's a beautiful reply but useless, can you tell me what does Output Master, Lead Master and Input Gain correspond to my amp?
Thanks

Experiment, turn some dials and see what they do! You gotta use your ear, theres too many variables in the tone chain nobody can tell you how to dial in YOUR amp with YOUR guitar. Start with all knobs at noon, listen to your reference Slash song, dial away to copy the tone, thats all you can do! Good luck with it!

 

[tschrama]

Get a Boss GE-7 infront, and gradually boost from 1kHz upwards.

 

[GrayFox14048]

There was pretty simple mod for the DR on this site think the guy is a member here as well. You might try searching for the mod, I've seen it on here and on the Gear Page

Otherwise, people seem to prefer the EL34 version of this amp, might be a good candidate for a conversion?

Sorry but there's nothing on the link, I'm looking for the MOD tutorial but there isn't there, can you help me please?

 

[Deftone]

@tschrama is the man to talk to but I found the mod elsewhere and saved it....

1] C27, (4n7)snipe one leg off
disables the nasal sounding tone stack that it feeds into..good mod

2] C35, (220pF) to 100pF
lowers the bright cap on lead channel for less shrill tone..good mod

3] R42, (10k) piggy back another 10K over it.
increases gain in lead channel..if too much try 15k, 22k, 47k..good mod, to taste

4] D10, (diode) snipe one leg off
this disables the diode bridge clipper..little more organic tone, will need to turn gain pot up to compensate

R60, (470k) Pickybag 47K over it
increases the signal pad, necessary because you will get a big boost from losing the voltage drop across the diode bridge you clipped
R13, (220k) snipe one leg off
this one I don't know

you might try snipping a leg of c8 if things get muddy..that's a low end boost that makes it harder to get the sound to clean up with guitar volume in lead channel

edit: checked out R13..it's a negative feedback resistor ..snipping it will give a big gain boost..might try going from 220k to 330k for a more moderate boost.

Disclaimer: I'm not an amp tech. Amplifiers can kill you if you don't know what you are doing. Consult a professional. I have never tried this mod myself.

 

[Wildeman]

Set it clean and loud, get this pedal.i have this pedal, it's good.

 

[Deftone]

Set it clean and loud, get this pedal.View attachment 123200i have this pedal, it's good.

900 DR's have a really nice clean channel.

 

[GrayFox14048]

@tschrama is the man to talk to but I found the mod elsewhere and saved it....

1] C27, (4n7)snipe one leg off
disables the nasal sounding tone stack that it feeds into..good mod

2] C35, (220pF) to 100pF
lowers the bright cap on lead channel for less shrill tone..good mod

3] R42, (10k) piggy back another 10K over it.
increases gain in lead channel..if too much try 15k, 22k, 47k..good mod, to taste

4] D10, (diode) snipe one leg off
this disables the diode bridge clipper..little more organic tone, will need to turn gain pot up to compensate

R60, (470k) Pickybag 47K over it
increases the signal pad, necessary because you will get a big boost from losing the voltage drop across the diode bridge you clipped
R13, (220k) snipe one leg off
this one I don't know

you might try snipping a leg of c8 if things get muddy..that's a low end boost that makes it harder to get the sound to clean up with guitar volume in lead channel

edit: checked out R13..it's a negative feedback resistor ..snipping it will give a big gain boost..might try going from 220k to 330k for a more moderate boost.

Disclaimer: I'm not an amp tech. Amplifiers can kill you if you don't know what you are doing. Consult a professional. I have never tried this mod myself.

this is gold! thanks!!

 

[Wildeman]

900 DR's have a really nice clean channel.

Yeah man, I used to have a 4500, really good amps, I wish I still had it. I mean it about the pedal, I would totally try that before I started modding the amp, it's $100.00 and easy, then you could retain the nice clean tone, just a pedal stomp away.

 

[Deftone]

Yeah man, I used to have a 4500, really good amps, I wish I still had it. I mean it about the pedal, I would totally try that before I started modding the amp, it's $100.00 and easy, then you could retain the nice clean tone, just a pedal stomp away.

I use a pedal in front of mine...maybe an EQ in the loop sometimes and sounds awesome.

 

[GrayFox14048]

@tschrama is the man to talk to but I found the mod elsewhere and saved it....

1] C27, (4n7)snipe one leg off
disables the nasal sounding tone stack that it feeds into..good mod

2] C35, (220pF) to 100pF
lowers the bright cap on lead channel for less shrill tone..good mod

3] R42, (10k) piggy back another 10K over it.
increases gain in lead channel..if too much try 15k, 22k, 47k..good mod, to taste

4] D10, (diode) snipe one leg off
this disables the diode bridge clipper..little more organic tone, will need to turn gain pot up to compensate

R60, (470k) Pickybag 47K over it
increases the signal pad, necessary because you will get a big boost from losing the voltage drop across the diode bridge you clipped
R13, (220k) snipe one leg off
this one I don't know

you might try snipping a leg of c8 if things get muddy..that's a low end boost that makes it harder to get the sound to clean up with guitar volume in lead channel

edit: checked out R13..it's a negative feedback resistor ..snipping it will give a big gain boost..might try going from 220k to 330k for a more moderate boost.

Disclaimer: I'm not an amp tech. Amplifiers can kill you if you don't know what you are doing. Consult a professional. I have never tried this mod myself.

Anyway just few questions:
- I must do all the steps or just someone (like only the leg off for example)
- If I have undestood, I need to cut sum legs from some capacitor or replace something else, right?
Thanks again!

 

[Deftone]

Anyway just few questions:
- I must do all the steps or just someone (like only the leg off for example)
- If I have undestood, I need to cut sum legs from some capacitor or replace something else, right?
Thanks again!

These questions are for the real amp techs in the workbench forum. Please don't work on your amp if you aren't absolutely certain you know what you are doing. There is stored energy in there that can easily kill you.

 

[cozmacozmy]

I got my 4500 900 sounding really good with a GE-7 eq pedal in the loop and replacing the V1 preamp tube with a GT-7025 tube. It sounds amazing now! It was a major improvement from what it was at before! I originally had Sovtek 12ax7 WXT in there before.

I would of modded mine, but it is in such great condition I decided on not doing it.