opinion needed - what second channel for JCM800?

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kiira

Well-known member
Joined
Aug 2, 2004
Messages
536
Location
Baltimore - Blobsville USA
Hi all!

I'm about half done with my JCM800 and I'm just looking for opinions and ideas from you guys about what type of 2nd channel i should build into it. The first channel will be of course a regular JCM800 and my first impulse was to make the other channel something closer to a JTM45, but I'm looking for other ideas... what do you think would be cool? I also am putting in an effects send/return on the non-JCM channel (I want to minimize any sonic effect on the JCM800 pre section)- the full featured tube circuit from Kevin O'Conners Ultimate Tone book. So, my amp has 5 pre-amp tubes IOW, 2 stages for the lower gain, 2 stages for the effects loop, 4 stages for the JCM and then the P.I.

The other amps I own are a real Deluxe Reverb and Ampeg V4 and a homemade Matchless Lightning clone, so those sounds are covered.

Also...does anyone have any opinion on having a switchable gz34 rectifier, like to use with the lower gain channel? Or is the difference between a gz34 and SS rectifiers negligible in a Marshall? I do have room for one more octal socket if it would be a really valuable feature. I really like the sound of a stock JCM800 though.

Edited to add: or just any interesting ideas for things to do on a two channel amp. Like I would like to be able to swap in 6V6s with a bias change, stuff like that. Thi si smy most ambitious guitar amp yet. BTW, it is using remote channel switching with a relay board powered off the rectified heater current.

thank you,

Kiira
 
The relay heater [ is it d.c. ? ] was an early boogie thing , might
have hum probs if a.c. , but a convenient idea . add some decoupling

How about a soldano channel , if you want overdrive ,

but even the Marshall dsl had fender ttype tone stacks on the clean channel , and Cathode as normal on the crunch , so one of each may be an option , or how about a pentode stage ?

way to go , Madame Amp factory , one should always have as many amps as guitars !
 
[quote author="okgb"]

How about a soldano channel , if you want overdrive ,
[/quote]

Kiira:"mmmmmmm... Soldano SLO"

I only have one tube for it though,,, I'd need two for an SLO. Are those things as buzzy as Boogies? The only way I could ever get my mkIIB to sound good was to use the clean channel. Nah... I like JCM800 for high gain.

The relay current is rectified ... DC!

thanks!

Kiira
 
The tone stacks on most tube amps really suck, genrally very broad Q fixed frequency tone controls. I've been playing around with a Pultec EQP-1A3 on my guitar and it I'm getting sounds I've never heard before, it's fantastic. So I'm now working on building a Pultec style eq into a tube amp, not quite there yet but on the drawing board at present- it needs lots of panel space for pots and swicthes, but I think it will be very unique.

Michael
 
If you only got one tubes and want something different go for something like an Ampeg B15 with its baxandall (not real baxandall) tone stack. Or by one tube do you mean the standard 9pin 12AX7, the Silvertone 1484 Is pretty much the same as a B15 with a 12AX7 instead of a 6SL7. Frequency response is abit different as well, the Silvertone was not intended for bass duties like the Ampeg. Both sound great though.

adam
 
well one tube is either an ultra clean stage direct to the inverter
or infront of the others for drive

I agree about the boogies , saved my ass in the eighties with channel switching but only way i can use it now is with el84 adaptors

the SLO is smooth , you could switch & insert a tube into the circuit
search out the x-88 is floating around the net .

Wait i have a few things i'll dig em up & send them tomorrow

Speaking of that anyone got some of the various Marshall mods when
everyone was trying them ?

have fun , regards Greg
 
Maybe heresy, but how about a solid state front end on channel 2? I really like the SS/Tube hybrids like the Music Man and SG Systems. Worlds apart from the "wrong" type of hybrid with a 12AX7 feeding a solid state amp. I have a Dean Markley practice amp that sounds absolutely amazing fed directly into the PI of a 50 watt Marshall (2204 rev). It gives a chunkier clean sound than the Marshall is capable of. It even sounds good with the solid state overdrive, giving a tighter and punchier crunch than the Marshall's pre. It doesn't sound unnatural at all, and IMHO, better than a good stomp box feeding a Fender.

I actually started reverse engineering this amp for a Laney to Marshall conversion I just finished for a friend. I was going to give him a "Glass/Sand" switch on the front but couldn't fit the DM board inside the amp. If you interested, maybe I can pick up on it again. I am thinking about making a foot pedal version of the preamp for myself anyway.

-Chris
 
I really like the SS/Tube hybrids like the Music Man and SG Systems

Those really good sounding amps. I had an SG but it went suicidal shortly after I got it. But I did get a pair of preamp board and a maestro phaser out of it, and a good power transformer. In the end, I find the preamps to be much more useful as stand alone units then part of an amp.

I should scan those schematics, people need to make those preamps and use them, they are fairly simple and great sounding. They would be useful tool.
 
I'd be interested in a scan of the SG amp schematics. I used to have a copy but never got it back from a tech who worked on mine.

-Chris
 
[quote author="Emperor-TK"]It even sounds good with the solid state overdrive, giving a tighter and punchier crunch than the Marshall's pre. It doesn't sound unnatural at all, and IMHO, better than a good stomp box feeding a Fender.[/quote]
Hmm, sounds interesting ! Would indeed be nice to see scans :thumb:
 
Gibson is full of sneaky bastards. They Copy onto blue tinted paper, and it is tinted that great blue that scanners and photocopiers can not see.

I got the main schematic scanned, but I probably will not do the phaser or the rest of the service manual unless someone really needs it. The phaser is just the Oberheim/Maestro phaser with a few minor tweaks, and the service manual is pretty much useless, more of a large sales brochure.

Here you go, managed to get it down to 1Meg and still have it legible.
http://www.sdiy.org/oid/ersatz/CMI-SG_Amplifiers.jpg

The notch shift on the second channel is really slick, great sounds in it.
 
From a guitarists point of view and not a engineering - I have owned a 1960s JTM45 head (sold it for £200 -what a muppet I was !)
The best rhythm guitar sound I ever had in my life was a cheap squire tele with the pickup on the mid of bass and treble - into a crap £10 overdrive pedal into the JTM45 - the presence tamed - into a closed back 2 x 12
Without the pedal and the presence backed off it was so trebly it took my head off
Instant Open G crunch.. keef, rich r - brilliant sound
Now what would I give for that sound again BUT without using a o/d pedal
Over to you Kiira
 
How, pray tell, did my thread about tube guitar amp channels get turned into a thread about SS effects or whatever? Hmmmm? ::taps foot::

[quote author="uk03878"]From a guitarists point of view and not a engineering - I have owned a 1960s JTM45 head (sold it for £200 -what a muppet I was !)
[/quote]

Let it go. We've all been there. :sad:

The best rhythm guitar sound I ever had in my life was a cheap squire tele with the pickup on the mid of bass and treble - into a crap £10 overdrive pedal into the JTM45 - the presence tamed - into a closed back 2 x 12
Without the pedal and the presence backed off it was so trebly it took my head off
Instant Open G crunch.. keef, rich r - brilliant sound
Now what would I give for that sound again BUT without using a o/d pedal
Over to you Kiira

You talked me into it... JTM45 it is. I've always been interested in Soldano but I've never had a chance to play through one (the um... $2500 price tag is a deterent) but I know I love the jtm45 and jcm800. If U get them both sounding good I would be really happy.

thanky you!

Kiira
 
Personally, I would pair the JCM800 lead with a Hiwatt clean. These are very complimentary sounds in my opinion.

I'm not sure just how you would blend the channels, but I've a seen a schematic a while back for a "Marwatt", 18 watt hybrid.

Cheers
 
[quote author="kiira"]How, pray tell, did my thread about tube guitar amp channels get turned into a thread about SS effects or whatever? Hmmmm? ::taps foot::[/quote]

...what type of 2nd channel i should build into it...

...looking for other ideas...

...just any interesting ideas for things to do on a two channel amp...

:razz: :grin:

-Chris
 
Yeah if you wanted s.s [ Nazi ? ] just get an overdrive box

But things to consider for the extra tube

Fender type clean W / tone ?

one tube switchable overdrive , many variations from mild boost

buffered fx loop

alternate switchable tone w/ boost

of course some of these could use a switchable master as well

and i never soiled your thread with the word tube screamer
[ but i have a good mod for them ]

regards Greg
 
[quote author="okgb"]Yeah if you wanted s.s [ Nazi ? ] just get an overdrive box
[/quote]

It just doesn't sound the same. The same Dean Markley preamp driving the instrument input versus the phase inverter has a completely different feel. The tight bark and immediacy are lost when going through the Marshall's preamp. It sounds, well, more Marshally. That isn't bad in itself, but it is when the goal is to get a different sound.

-Chris
 
Fair enough , suppose one can always switch from the fxs loop
though and have both , i do appreciate s.s. distortion for some
dryer , tighter dirty rythms and there are those super pickers
who need a good transient response , but that could be tube or s.s.

regards Greg
 

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