JCM 800 2205 - Clean Channel way too much break-up

JCM 800 2205 - Clean Channel way too much break-up

I have a 1989 JCM 800 2205. The overdrive channel rocks, but the
"clean channel" starts to break up if I get the volume knob anywhere
past 9:00 position. As you can guess, that means it is barely on (off
being at about 7:00).

The problem, of course, is matching the volume between my clean sound
to my high-gain channel. I have to turn down the volume knob on the
overdrive channel which (you already know) changes the sound of the
channel drastically.

Do I have the wrong tube in my pre-amp stages (what is recommended?) -
or does anyone know of another way match the two channels output so I
can get more gain on my clean channel without it breaking up?

Re: JCM 800 2205 - Clean Channel way too much break-up

"cruisemates" <editor@cruisemates,com > wrote in message
news:4153a9de-f4a8-4b60-b8d2-d99ba4dd1c36@k1g2000prb.googlegroups,com ...
>I have a 1989 JCM 800 2205. The overdrive channel rocks, but the
> "clean channel" starts to break up if I get the volume knob anywhere
> past 9:00 position. As you can guess, that means it is barely on (off
> being at about 7:00).
>
> The problem, of course, is matching the volume between my clean sound
> to my high-gain channel. I have to turn down the volume knob on the
> overdrive channel which (you already know) changes the sound of the
> channel drastically.
>
> Do I have the wrong tube in my pre-amp stages (what is recommended?) -
> or does anyone know of another way match the two channels output so I
> can get more gain on my clean channel without it breaking up?

I thought the best thing about them JCM's was exactly that you would get a
great driven clean sound outta them very easily...,fr ankly, IMO if you dial
them all clean the sound totally sucks. They're sort of one trick ponys,
what you get is insanely good 'cleanish' rock sound and then even more drive
but if you want 'clean' go Fender. My JCM went ballistic even on clean
channel already at '2' position of gain because I run it with hot EMG's.

Re: JCM 800 2205 - Clean Channel way too much break-up


"DeeAa" <deeaaREMOVE_THIS@dnainternet,net > wrote in message
news:4819572f$0$2663$9b536df3@news.fv.fi...
> "cruisemates" <editor@cruisemates,com > wrote in message
> news:4153a9de-f4a8-4b60-b8d2-d99ba4dd1c36@k1g2000prb.googlegroups,com ...
>>I have a 1989 JCM 800 2205. The overdrive channel rocks, but the
>> "clean channel" starts to break up if I get the volume knob anywhere
>> past 9:00 position. As you can guess, that means it is barely on (off
>> being at about 7:00).
>>
>> The problem, of course, is matching the volume between my clean sound
>> to my high-gain channel. I have to turn down the volume knob on the
>> overdrive channel which (you already know) changes the sound of the
>> channel drastically.
>>
>> Do I have the wrong tube in my pre-amp stages (what is recommended?) -
>> or does anyone know of another way match the two channels output so I
>> can get more gain on my clean channel without it breaking up?
>
> I thought the best thing about them JCM's was exactly that you would get a
> great driven clean sound outta them very easily...,fr ankly, IMO if you
> dial them all clean the sound totally sucks. They're sort of one trick
> ponys, what you get is insanely good 'cleanish' rock sound and then even
> more drive but if you want 'clean' go Fender. My JCM went ballistic even
> on clean channel already at '2' position of gain because I run it with hot
> EMG's.

Perhaps OP can have a dual-master volume added? Not for
the squeamish... there's sand in there (CA3047?).
__
Steve
.

Re: JCM 800 2205 - Clean Channel way too much break-up

Steve...

I had a reliable guitar/amp tech tell me he does master volumes on
these amps. I am thinking about it. Can you give me details on what
you mean by "not for the squeamish, there's sand in there?"

I hear what you are saying about the "overdriven" clean sound, if that
is what you want or need it does it very well. I need both. I like the
overdrive sound on my amp, but the clean channel on these (2205) is
very bare bones, and as you said, breaks up at a very low level.

I play in a Beatles band, and I need to have nice, clean sound for the
ballads. You can't play the chords to "Something" with a distorted
sound.

I am starting to think I may have to go dual amps and an A/B switch as
I have not found the amp that does both well, yet.

More about the clean channel: three knobs; bass, treble, volume. I
can't get enough clarity out of it with no midrange knob. Not too
happy about that either, but I think it would work well enough if only
I could get more volume without the breaking up.

Re: JCM 800 2205 - Clean Channel way too much break-up


"cruisemates" <editor@cruisemates,com > wrote in message
news:5e29b503-d482-4579-9471-ca5bb3aef5e7@t12g2000prg.googlegroups,com ...
> Steve...
>
> I had a reliable guitar/amp tech tell me he does master volumes on
> these amps. I am thinking about it. Can you give me details on what
> you mean by "not for the squeamish, there's sand in there?"

1.) Your amp already has a master volume... you would be adding another,
just like the Boogie has. This is the most flexible way... pre and post
for
both channels.

2.) There is a chip in there with a bunch of transistors, some of these are
used for switching channels. This is more complicated than a relay.

3.) You might need some gain structure work in order to get more
clean throw on the clean pre control... or it may be that some
leakage from the dirt channel is causing your problem. You might
not need a second master, or it might not help much... someone
very familiar with this amp should perform the mods. Make sure that
they understand what you're asking for. It's much easier to tune
one sound... when you try to get *two* good sounds out of an
amp, you're looking at compromises. Dirt leakage is one... relays
leak much less, but bring their own set of problems (vibration,
contact bounce, pop noise, etc.).

> I hear what you are saying about the "overdriven" clean sound, if that
> is what you want or need it does it very well. I need both. I like the
> overdrive sound on my amp, but the clean channel on these (2205) is
> very bare bones, and as you said, breaks up at a very low level.

Probably DeeAa's comments... I'm not that familiar with the amp.
I *have* looked at the schematic, though... you might print a copy and
take it when you talk to your tech, it's at Schematic Heaven.

> I play in a Beatles band, and I need to have nice, clean sound for the
> ballads. You can't play the chords to "Something" with a distorted
> sound.

One reason many folks start with a clean amp and use a dirty pedal!

> I am starting to think I may have to go dual amps and an A/B switch as
> I have not found the amp that does both well, yet.

Plenty of folks do that, too.

> More about the clean channel: three knobs; bass, treble, volume. I
> can't get enough clarity out of it with no midrange knob. Not too
> happy about that either, but I think it would work well enough if only
> I could get more volume without the breaking up.

If you can get more clean drive you can turn down B/T and mids will
come up. Your tech can also voice the channel... there's a mid resistor,
it's just not a knob you can tweak without a soldering iron.
__
Steve
.

Re: JCM 800 2205 - Clean Channel way too much break-up

Thank you for all the input - greatly appreciated.

From playing around with different settings - not being an electronics
pro, I am guessing the thing about leakage between channels is very
true.

Here is an interesting compromise I found that works better than
expected. I started with turning down the tone controls for the clean
channel - much less grit and overdrive and more volume available, so a
better match when I switched to the clean channel. I could add just a
hint of treble and with no bass it sounds pretty good.

Then I found when I switch to the overdrive channel I also have to
turn down the tone pots or else I can't get the volume loud enough to
get that combination of overdrive you get from turning the channel up
(the gain control mostly adds the diode grit, not beef).

So, I thought I would try the effects loop. I patched in a 31-band
Yamaha Graphic, and lo & behold, it seems to give me total control of
the amps overall volume. In fact, it makes the master volume 90%
irrelevent as all my overall volume control is now in the Yamaha. I no
longer have to worry about blasting out the neighbors (unplugged the
power-soak). And I can get clean, clean, clean on the clean channel at
any volume I want. The graphic EQ also gives me back the tone control
I lost by turning all the tone pots down. It actually is a very sweet
and full sound

On the clean channel bass if OFF, treble is at 9:00, volume is at
9:00.

Gain channel - gain and volume can be wherever I want them - all the
loudness control issues seem to be in the tone ciruitry. By turning
those nearly off the channels match up much better. I have gain at
3:00 (that would about 75% ON), volume at 4:00 (ABOUT 85% ON), treble
at 9:00 (BARELY ON), mid at 8:30 (BARELY ON) and bass at 7:00 (ALMOST
OFF). Strangely, the treble & mid controls do not change the tone or
gain much, but if I turn up the bass volume the amp ROARS.

All a very strange design - but it works. BTW: the master gain pot is
almost irrelevent once you get it to 9:00, from there up it just adds
a little more beef (moreso on the overdrive than the clean channel).
The oddest thing is this, I have tone knobs almost off on both
channels, and the clean channel volume at 9:00 matches the overdrive
volume placed at 4:00. Why? I don't know, but it's working.

based on all this, I am guessing there are a lot of things about this
circuit that I never would have guessed being a layman - things go
places you wouldn't ever expect. I know what I am saying doesn't even
make sense logically, but it works and I guess you have to see it to
believe it.

being a layman, I have noticed that different parts of circuits on
most amps interact in ways you would never expect - like especially
the tone controls on a Mesa Boogie. If you turn up the mids full, the
treble pot makes no difference for example. One reason I prefer
Marshalls, but I guess there is a fair amount of "voodoo" in these
Marshall circuits as well.