4100 diode clipping. When?

[Kutt]

Not another nauseating JCM 900 debate thread. Just one question.

I've read conflicting info on when, exactly, the clipping diodes kick in when turning up the gain controls on a 4100 Dual Reverb. Is it immediately at 1? Half way? Other?

 

[Tatzmann]

Everything bullshit.

The 900DR is a Hybrid Amp.

The Preamp is all ICs and Diode
clipping on top of that.

The Poweramp is standard Tube PA.

The 12AX7s add nothing to the
Distortion. Even the 12AX7 in
the cathode follower can be taken
out and the preamp still works, just
quieter. Because its partially bypassed.

Most stupid design masterpiece award
goes to 900DR.

 

[Kutt]

Anyone have a non-idiotic reply that actually relates to the question? Notably, it helps to read and comprehend what's being asked.

 

[Tatzmann]

Why are you asking when the clipping
diodes kick in? Its all Transistordistortion
anyways.

Butthurt because you now realize that
you got a bogus Marshall?

 

[Kutt]

Why are you asking when the clipping
diodes kick in? Its all Transistordistortion
anyways.

Here's some great life advice I learned when I was about 7 years old- If you don't have anything useful to add to a conversation, stay out of it.

 

[Tatzmann]

You should get your impedance checked
Dude.

 

[Tatzmann]

I dont like to be called an Idiot for giving
an realistic answer to your problem.

So here i tell you again very slooowly when
your Diodes "kick" in...

As soon as you hear distortion from
the preamp then your Diodes "kicked"
in...

Get it?

 

[South Park]

Diode clipping is full time on the gain . It is the same circuit as the pedals use .

 

[scozz]

Diode clipping is full time on the gain . It is the same circuit as the pedals use .

Nice, calm, concise, lucid answer.


Thanks for that SP!

 

[gregr]

Here's some great life advice I learned when I was about 7 years old- If you don't have anything useful to add to a conversation, stay out of it.

I kinda like “If I wanted your opinion I would have beaten it out of you.”

 

[iron broadsword]

Clipping diodes are always on, in fact the first preamp tube has handcuffs on it so that it cannot clip. If you want to swap a few resitors/caps you can turn it into a beast though, check out this thread:

https://www.marshallforum.com/threads/modding-my-900-all-tube-with-clips.77639/

 

[gregr]

More precisely:
JCM 900 4100 mod

 

[jeffb]

Clipping diodes are always on, in fact the first preamp tube has handcuffs on it so that it cannot clip.

I'm not a tech guy and had no idea of the particulars, but no wonder I hated that amp with a passion.

Does the MKIII have the same "issue"? (I use quotes because for me it is, for some it's not)

 

[Tatzmann]

Nice, calm, concise, lucid answer.


Thanks for that SP!

Nice calm and totally wrong and unprecise
answer.

If they were always "on" you could not
have a clean sound or could you?
Hogwash...as i said
5000 posts before...as soon as you hear
distortion from the preamp the diodes cut
the highs and lows of the sinewave which
results in distortion or better limiting.

But he has a fan i guess. Lmfao.

 

[gregr]

I'm not a tech guy and had no idea of the particulars, but no wonder I hated that amp with a passion.

Does the MKIII have the same "issue"? (I use quotes because for me it is, for some it's not)

It sounds to me like the OP is mistaking the DR for the Mk III since there is a direct answer to that question.

In the Mk III, the preamp control gets the tubes clipping, whereas the sensitivity control drives the diode/bridge rectifier into clipping. Your ears will tell you when (for the most part). I’m not entirely sure what’s going on with the gain stage before the cathode follower when the sensitivity is set low. I believe it should already be clipping.

The two amps sound different from one another, as does the SL-X for that matter.

 

[Tatzmann]

The original post stated 4100DR.

 

[jeffb]

I thought he was mistaking the DR for the Mk III.

In the Mk III, the preamp control gets the tubes clipping, whereas the sensitivity control drives the diode/bridge rectifier into clipping. Your ears will tell you when (for the most part).

Thanks. I need to go find a MKIII to give another whirl. Good bud of mine had the 50W head for many years, and finally had to move it- He gave me first dibs at a great price . I wanted to give it a whirl but I just couldn't fund it- he hit me up right as I was between jobs after a layoff.

 

[gregr]

It’s a good amp but it’s not legendary. I have the 9th 2500 off the line, but I’m pretty sure Kelia has me beat.

I like to run it in triode. It makes it smooth and creamy and gives it some squish. The amp has its own character this way. Kinda like how a VM is a Marshall but has its own sound.

You can get all sorts of places using the controls on your guitar with the amp up loud. I don’t know that is has a lot of that treble bloom that you like, however.

I like to push it with a TS to get it into saturation for high gain shredding, but I think the wheelhouse of this amp is mid-gain. An SD-1 can add aggression, otherwise I don’t consider it an aggressive amp.

 

[Kutt]

Thanks to nearly all of you for the useful input.

No desire to mod the amp. There is no problem with the amp. It is not my only amp. I look forward to keeping it for decades to come.

Fact is, the thing sounds really really fkucking good dimed through my BOSS Tube Amp Expander with the output section cooking and I had a simple technical curiosity about this one aspect of the diodes. I have zero curiosity about diatribes.

TTFN