Marshall JCM 800 Questions

[VanWhalen]

Hey...

I recently bought a 1983 JCM 800 (with Cab, 50W, Master Volume 2204) and have some questions. Please excuse my ignorance as I am new to this kind of rig.

1) I have read that the use of a Hotplate or Attenuator will allow you to run this gear at full tilt but pull back on the volume. Since this has a master volume, do I really need a Hotplate, or does the master volume work the same?

2) I have read that in your effects chain, the best setup is something along the lines of: guitar => Tube OD => Head => effects chain => Cabinet. Would you guys agree with that basic structure for best sound practices?

3) Have read differing opinions on the use of a Variac to get a better tone. True? Your experiences?

4) I have a Digitech GNX4 and over the years have used that in a solid state amp and would like to know if this would fit in the effects chain position in my diagram above, or in front of the head? What changes will I need to make to make it work best?

Any other advice, tips, tricks, and recomendations are appreciated.

[Fast Castle]

Wish some of the guitar amp wizards would respond to this. I'm curious too.

I can tell you that I've owned that amp for almost 20 years. It's hard rock. It's all meat. It's not a house pet. Not domestic at all. It bites and snarls in a house, or in any small place, and you might make the mistake of thinking it sounds too harsh... then, you get it miked up with a 57 on a decent sized stage and you hear it in its element. It simply kicks ass. It translates over the PA system with authority. I keep it simple, putting an AnalogMan moded tubescreamer in front of it. I don't have attenuators. I try to turn it up loud enough to get the actual wood of the cabinet involved and resonating a little. Then it sounds glorious.

[orange]

here's answers to some of your questions (which probably would have been better posted in the geekslutz forum).

a hotplate is not the same as the master volume - the hotplate allows the output and preamp valves to run hot whilst master volume just allows the preamp valves to run hot (if that makes sense). Be aware that a hotplate doesn't replicate a cabinet exactly - all kinds of impedance/speaker compression issues to consider.

I think it unlikely (impossible !!) that you could put your effects chain after the head/before the cabinet (i.e. at speaker level) You will risk damaging the FX and the output transformer of the amp.

stay away from using a variac - you will risk doing damage to your amp, especially as you seem to be asking 'inexperienced' type questions.

hope this helps.

[redddog]

In my experience with the exact same amp, I found that it's completely dependant on where the master is wired. On mine, which was modified with a global master, it did allow you to drive the amp as hard as you could and just turn down the output level - just like a hotplate. It really isn't that simple though. Amps simply don't act the same way at low volumes as they do at loud volumes. You can get a great, driven sound with the master modification but it's just not gonna sound the same as an amp that's as loud as it can go. Dynamics respond differently, more air is being moved and feedback reponse will all be affected by volume alone.

That's just my impression, which may not be considered expert.

[allencollins]

Originally Posted by VanWhalen

Hey...

I recently bought a 1983 JCM 800 (with Cab, 50W, Master Volume 2204) and have some questions. Please excuse my ignorance as I am new to this kind of rig.

1) I have read that the use of a Hotplate or Attenuator will allow you to run this gear at full tilt but pull back on the volume. Since this has a master volume, do I really need a Hotplate, or does the master volume work the same?

2) I have read that in your effects chain, the best setup is something along the lines of: guitar => Tube OD => Head => effects chain => Cabinet. Would you guys agree with that basic structure for best sound practices?

3) Have read differing opinions on the use of a Variac to get a better tone. True? Your experiences?

4) I have a Digitech GNX4 and over the years have used that in a solid state amp and would like to know if this would fit in the effects chain position in my diagram above, or in front of the head? What changes will I need to make to make it work best?

Any other advice, tips, tricks, and recomendations are appreciated.

1. Do you have a reissue 2203 with the fx loop? I don't think the originals had one. If you have an fx loop an attenuator would be a waste of money. You can simply patch a pot to the io of your fx loop to add a second "master volume" which in reality would act as an attenuator.

Even though you have a master volume an attenuator will greatly increase (overdrive)distortion and natural harmonix of the tubes by turning the amp all the way to 10.


2. You need to experiment. This works well but you need to have a true bypass fx loop.

3. Don't use a variac youll fry your output transformer. If you know how to bias an amp you can obtain similar results without damaging the amp


4. Running an effect via the input can create lot of noise. You need to experiment

[stevennn]

I use a hotplate with my 800 and my fender amps, and they work well to a point. You can crank the amp if you set the Hotplate reduction to extreme levels. However, the hotplate does affect the overall sound, and the more attenuated, the more you move away from a natural sound. I usually set the reduction to about -4 to -12db. After that, your sound become much more affected.

With that, a Hotplate is a useful tool and I use them all the time. It just wont make a loud amp quiet.

steve

[chetatkinsdiet]

Originally Posted by VanWhalen

Hey...

I recently bought a 1983 JCM 800 (with Cab, 50W, Master Volume 2204) and have some questions. Please excuse my ignorance as I am new to this kind of rig.

1) I have read that the use of a Hotplate or Attenuator will allow you to run this gear at full tilt but pull back on the volume. Since this has a master volume, do I really need a Hotplate, or does the master volume work the same?

I wouldn't use a hotplate...they absolutely change the tone. You have a master vol...you don't really need it. True w/ an attenuator, you can pump the amp tubes as opposed to the pre-tubes, but it still changes the tone of the amp. I've also read that it's a tad harder on the tubes and such.

2) I have read that in your effects chain, the best setup is something along the lines of: guitar => Tube OD => Head => effects chain => Cabinet. Would you guys agree with that basic structure for best sound practices?

Gtr-OD-delay, etc-head. I typically skip the OD as I LOVE the marshall sound by itself. I always use an old delay pedal, volume pedal and tuner though.

3) Have read differing opinions on the use of a Variac to get a better tone. True? Your experiences?

Don't bother. You can really shorten the life of the tubes by using one. The gain isn't that much anyway.

4) I have a Digitech GNX4 and over the years have used that in a solid state amp and would like to know if this would fit in the effects chain position in my diagram above, or in front of the head? What changes will I need to make to make it work best?

Do you need the effects? If so, use it. If not, just wallow in Marshall tone and skip all the gimmicks.

Any other advice, tips, tricks, and recomendations are appreciated.

Later,
m

[Musiclab]

Originally Posted by VanWhalen

Hey...

I recently bought a 1983 JCM 800 (with Cab, 50W, Master Volume 2204) and have some questions. Please excuse my ignorance as I am new to this kind of rig.

1) I have read that the use of a Hotplate or Attenuator will allow you to run this gear at full tilt but pull back on the volume. Since this has a master volume, do I really need a Hotplate, or does the master volume work the same?

2) I have read that in your effects chain, the best setup is something along the lines of: guitar => Tube OD => Head => effects chain => Cabinet. Would you guys agree with that basic structure for best sound practices?

3) Have read differing opinions on the use of a Variac to get a better tone. True? Your experiences?

4) I have a Digitech GNX4 and over the years have used that in a solid state amp and would like to know if this would fit in the effects chain position in my diagram above, or in front of the head? What changes will I need to make to make it work best?

Any other advice, tips, tricks, and recomendations are appreciated.

Is this for recording or live playing? I have an old 80's 2204. The thing with this amp is the pre amp needs to be driven abit, it completely interacts with the tone controls.
There is a point where these suckers start sounding good, and thats is usually when you've got the power amp section and the speakers moving . You can't just do this with the pre. For live if it's too loud I'd get a hotplate and not attenuate more than a few db, more than that and the presence goes away and it starts sounding like crapola. In general I havent really liked an attenuator on a 50 watt amp. For recording just play it loud and maybe read slipperman's article about recording a distorted electric guitar.

[VanWhalen]

Its the 2204 model from 1983, without the fx loop. Based on the comments here, I guess I dont have much choice, I would have to run any fx before the head.

[Farview]

No matter what, never hook anything other than a speaker (or speaker simulator, hotplate, etc...) to your speaker output.

[Jim Williams]

Originally Posted by VanWhalen

Its the 2204 model from 1983, without the fx loop. Based on the comments here, I guess I dont have much choice, I would have to run any fx before the head.

Other than a fuzz tone or a wah pedal, all your effects will be distorted by the amp and sound like crap. Just try it with a digital reverb and you will understand.

Back in the 80's I used to install a tube loop into these. Add an extra tube socket, a small perf board and a couple of 250k pots and an adjustable, switchable loop can be installed. Then those digital reverbs sound pretty good as they occur post distortion, not pre. Any qualified amp man can do this for you.

Jim Williams
Audio Upgrades

[VanWhalen]

So, how do people use Phaser or Flanger or Chorus with these amps if they all get outta wack if they are setup pre head? I guess this is why people have put in effects loops into their amps. I hate to muck with it though... :( but I do want to use some of the pedals mentiond above...

[Farview]

Originally Posted by VanWhalen

So, how do people use Phaser or Flanger or Chorus with these amps if they all get outta wack if they are setup pre head? I guess this is why people have put in effects loops into their amps. I hate to muck with it though... :( but I do want to use some of the pedals mentiond above...

Chorus, phasers and flangers were normally done with pedals between the guitar and the input of the head. Delay is a pain because of the compression effect of the distortion. Also, with delay, the repeats get less distorted as they get quieter.

In 1983, guitar effects were just pedals. These all in one units didn't really start poping up until the 90's.

[max cooper]

The coolest thing about using a variac, to me, is to turn down the power, not up.

Kind of softens the midrange; mushes it up a bit. I like it.

I've been told on more than one occasion by amp techs that power attenuators like Altair, Scholz, etc. can fry the output tranny. I don't know enough about what's going on in there to know first hand, though.

The effect of a master volume is different than the effect of a power attenuator; the master volume allows you to overdrive the preamp stage; the power attenuator allows you to overdrive the amp stage. They're different sounds. I really like to overdrive the amp stage.

JCM800 sounds good pretty much however you set the controls. I used to wonder if all the tone controls were even connected to anything in there.

So, does anyone know about JCM800's overdriving an LED? I heard about this back in the day.

[Jay Kahrs]

Originally Posted by VanWhalen

So, how do people use Phaser or Flanger or Chorus with these amps if they all get outta wack if they are setup pre head? I guess this is why people have put in effects loops into their amps. I hate to muck with it though... :( but I do want to use some of the pedals mentiond above...

I run all that stuff before the head & generally any kind of fuzz or booster too.

Sounds kooler that way IMO.

Running 'em through the FX loop nets a different kind of sound. Try 'em both but have no fear...guitar > stompboxes > amp is a time proven method for many a plankster.

Don't burn the house down.

Stay away from the Variac!

Get a Hot Plate or Power Break. THD makes a great one. So does Dr. Z. Marshall makes an 'ok to good' one but it can work at more then one ohmage. That matters to me...might not to you.

Anyway...put one those between the heads speaker out & the cab & you'll be able to run the power tubes hard & not pull a reenactment of Back to the Future...

Ponder that for a minute...

LOL

Make sure that the is ALWAYS connected to a speaker cabinet with a proper 'speaker cable' and NOT an 'instrument cable' unlesse 'ya wanna blow up the head.

If you just gotta use your digidoo FX box then I'd use it for delays & verbs through the FX loop but do what 'ya gotta. Try it both ways & see what you like better but honestly man...just plug into the amp with no pedals or nothing, go full tilt...most knobs on 7 (or 11) and make some noise.

Build the rest of your rig from there.

[VanWhalen]

Which HOTPLATE is appropriate for a JCM800 50W with 1960A Cab? Does the OHM rating for the HOTPLATE coorespond to the OHM rating of the speaker cabinet? Does the hotplate handle stereo input and stereo output? What is the proper procedure to slave using the hotplate? Should the second head (power amp) be PA style power amp so as to not add any more distortion or gain to the signal?

[softwareguy]

The Hotplate should be the same impedance ast the speaker cab that it will be driving (e.g., 16 ohm). It should also be the same as the output of your amp (e.g., also 16 ohms). Hotplates are mono, but can output to multiple cabs. If used in this way you must treat the cabs as being in parallel, e.g., two 16 ohm cabs equal 8 ohms. The conventional use for Hotplates is to reduce the power going to the cabs.
The Hotplate also has a line out that can be used as a line level feed. This can go direct, or (where it can be useful for you) it can be turned down (built-in attenuator) and fed to effects which can then be reamped and run through a separate cabinet. This way you can control your conventional volume and your effects volume separately, and changes in your gain structure won't screw up your time-based effects.

Best of luck.

[VanWhalen]

so, based on what your saying, if I have a single cab, I want a 16 OHM hotplate, if I have two cabs, I need a 8 OHM hotplate. Am I understanding you correctly? Do they make a Hotplate that is variable resistance, so I can set it to 4, 8, 16, etc...?

[softwareguy]

Hotplates come in specific impedances. They need to match both the impedance of your output transformer as well as the impedance of your cab.

There is a lot more info on these at amptone.com, including a great article on running post-amplifier effects at http://www.amptone.com/thdhotplate.htm#_Toc30648412.

This has a better more information than I could give you and covers a lot more ground.

[Jay Kahrs]

Originally Posted by VanWhalen

so, based on what your saying, if I have a single cab, I want a 16 OHM hotplate, if I have two cabs, I need a 8 OHM hotplate. Am I understanding you correctly? Do they make a Hotplate that is variable resistance, so I can set it to 4, 8, 16, etc...?

You need whatever ohmage 'yer amp is running at.

If you've got a 4 ohm rig & buy a 16 ohm box & it all melts...well...that isn't our fault! LOL


No, they don't make a variable ohmage Hotplate. That's kinda why I bought a Powerbreak instead...well, that & I found a used one. But really, I needed a 16 ohm load for my AC30 & 8-ohms for the old Fenders which pretty much steers me away from Hot Plates unless I want two of 'em.

[KrisNY]

Originally Posted by allencollins

You can simply patch a pot to the io of your fx loop to add a second "master volume" which in reality would act as an attenuator.

I tried this on my 800. Sounded awful - made the tone all muddy and lifeless.

[marchhare]

via Max-"So, does anyone know about JCM800's overdriving an LED? I heard about this back in the day."

I think that was just the channel switching 800's that had solid state clipping in
them, not the single channel amps. That's probably why the single channel
ones sound so much larger & more open. I remember thinking they didn't have
enough gain when they came out. Now that I'm older and so much more sophisticated, I appreciate them.

[Sqye]

just watch the variac with your tubes - it can blow them out a lot more
frequently than you might be used to.

sorry, if i'm repeating what's already been said. i didn't comb this thread that carefully.


there's a guy, Kevin O'Connor, at London Power in Ontario who builds his custom amps and pres
with a custom plate voltage input powerscale regulator type thing. his amps sound pretty
awesome. he does an 800 emulation pre, as well. i know some tone purists who really dig his thing.

Kevin's also written all the Ultimate Tone books - i think he's up to volume 6 or 7, maybe later.

he's built several amps and pre/ amp combos for me, and for some fellow tone freaks.

his main website seems to be down - wtf, Kevin?

check this out.

http://www.amptone.com/londonpowerstudio.htm