Help on my jcm 800 mods

[wizard333]

Most of the complaints about diode clipping are in regards to the 900 series Marshalls, which sounded like thin annoying crap. People assume this was due to do the diode clipping; it wasnt. IT was due to bad design.

[trem]

Alex
Steve
Wizard
Thanks for hangin' in there with me on this one. Each of your last posts were very helpful. This should be a "sticky" for the forum. As somebody involved in backline/recording rentals, I can tell you that I hear this "complaint" all the time (and we do not even rent PCB Marshall's). Wizard makes a good point. The jump from 800 to 900 may have done more damage to the reputation of the earlier amps than it did to the latter.
Thanks Again

[walkman]

Can we make this a sticky thread The diode clipping Marshalls are designed as a system, and ripping out the diodes just unbalances other things. In particular, the diodes clip symmetrically, so they generate no blocking distortion, so they can drive them far harder than you can drive a tube, and get real heavy grind with fewer tube stages.

If you take them out, I think the amp would get less metal, not more. If it couldn't cut it at a metal gig, would it have got out of the door at Marshall?

Old thread yes but I'm looking again at 4210 that I modified back in 2007.

My intention was not to make a higher gain amp rather something more blues rock than heavy metal.
The clean channel is intact only the gain channel modded.

I removed to clipping diodes and rerouted the signal flow to have the tonestack after the cathode follower.
To me it sounds better for what I want.

It does however get a bit to wooly with the volume and gain up high in the gain channel. I'm considering doing the mods to the power section that Merlin details to reduce blocking distortion.
The one I have is the earlier model from 83 not the one linked in this post from 87.

Without trying to tip over any apple carts surely diode clipping in an amp will affect the touch sensitivity of the amp.

Just my 2c and inexperience talking here ( yes there may have been no need to mod it at all)

Very interesting to read what Merlin has written here regarding going for more gain. For me I guess that I'm really not interested in super high gain sounds at all, heavy rock yes but no metal please.

[soundguruman]

If you want the amp to have more clean headroom, then the diodes must go.
The diodes cause clipping distortion. Personally, I can't stand the way they sound.
If it were my amp, I would nuke the diodes, first thing.

I would rather get tube overdrive, than diode clipping. I think the clipping sounds awful.