Carvin's diode-clipping stuff. Introduced by the JCM900?

[jon the art guy]

I've never been a Marshall fan, to be honest. I never really cared for the middle of the road rock tone, so I've never did much research on the breed until just recently.

When the JCM900 was introduced as a meaner JCM800 that didn't need modding for moar gainz, the trick was a diode clipping circuit, correct?

The reason I ask is now I'm all obsessed with Carvin amps. I'm reading about the Vintage and MTS amps having a...similar? same? diode clipper that folks go in, cut out and bridge with a resistor.

Anyone in the know about both know if this is a clipping circuit derived from the Marshall version, or is it a different creature? Sounds like it was conceived as a good idea, but really ended up not being useful.

 

[Rich_S]

Re: Carvin's diode-clipping stuff. Introduced by the JCM900?

JCM800s had diode clipping before the 900s. On the JCM800 channel-switching models, the dirt channel had a pair of LED clippers, similar to a modded DS-1. In contrast, the "modded JCM" tones that defined the '80s were more about tweaking single-channel, all-tube 800s for more gain, often adding an extra preamp tube stage to accomplish it. The trick to getting lots of good-sounding overdrive out of tubes is to use a lot of moderately-overdriven stages. The SLO is probably the pinnacle of this design.

Unfortunately, lots of tubes => lots of money. Adding a diode clipping stage (basically, building a Tube Screamer or DS-1 into your amp) is a lot cheaper. Lots of amps have diode clippers, one really popular one is the the little Vox Pathfinder 15. And yes, lots of people think it sounds better with the diodes removed. It turns the distortion circuit into more of a "boost" circuit.

 

[jon the art guy]

Re: Carvin's diode-clipping stuff. Introduced by the JCM900?

Sounds like Ibanez's little Tube Screamer amp is the ultimate evolution of that breed.

 

[saladin]

Re: Carvin's diode-clipping stuff. Introduced by the JCM900?

Your right, the Vintage series and The MTS both use diode clipping. I've had both and didn't like either!
I've also had the JCM900 and it sounded equally bad.

If it's a Carvin your looking for then find a grey fuzzy EL-34 loaded X-100B and then you'll be happy!

 

[Gearjoneser]

Re: Carvin's diode-clipping stuff. Introduced by the JCM900?

I've found that preamps with diode clipping have two big negatives. They don't clean up by rolling off your volume as well as an all tube preamp. Single coils sound harsh and buzzy through them.

Where diode clipping isn't an issue is highgain tones with humbuckers. It's basically like putting an OD in front of a tube amp.

 

[JeffB]

Re: Carvin's diode-clipping stuff. Introduced by the JCM900?

Yup..2210/2205s...introduced 1982? 1983?

Then the Jooby, then 900s.

my first Marshall was a diode clipper...4010 I eventually ran through a 4x12. I never really cared for any of the diode clippers There is a certain sterile/fake nature to them that drives me nuts. Just like low end Blackstars do today.

 

[misterwhizzy]

Re: Carvin's diode-clipping stuff. Introduced by the JCM900?

There are some amps that sound decent with that type of overdrive. Blackstar's HT-5 is one of them. It doesn't sound GREAT, but it's definitely got some gain on tap. And of course, it is like building a TubeScreamer into your amp. But honestly, in most of the amps I've tried with that method, it's not a good thing. I'd rather have lower gain, because there seems to be more character to an amp built that way. It just sounds better.

 

[jon the art guy]

Re: Carvin's diode-clipping stuff. Introduced by the JCM900?

Hasserl (apparently who lurks around these forums) has posted the diode cutout mod on a site that works for both of dem amps, along with a bunch of other mods to make them sound better (or best).

 

[Brow]

Re: Carvin's diode-clipping stuff. Introduced by the JCM900?

Didn't Silver Jubilees use diode clipping too?

I have 1 of the 100w diode clipping JCM800s and it's a decent sounding amp.

Some of the Friedman amps use diode clipping too and they sound great.

 

[Rich_S]

Re: Carvin's diode-clipping stuff. Introduced by the JCM900?

my first Marshall was a diode clipper...4010 I eventually ran through a 4x12. I never really cared for any of the diode clippers There is a certain sterile/fake nature to them that drives me nuts. Just like low end Blackstars do today.

The 4010 was NOT a diode clipper, is was a plain single-channel master volume 2204 chassis. Best amp Marshall ever made, IMO, and I'd kill to have mine back again.

 

[Lake Placid Blues]

Re: Carvin's diode-clipping stuff. Introduced by the JCM900?

Didn't Silver Jubilees use diode clipping too?

I have 1 of the 100w diode clipping JCM800s and it's a decent sounding amp.

Some of the Friedman amps use diode clipping too and they sound great.

The Jubilee's do use diodes but they are used very differently than the JCM800 2205 design. First, the Jubilee uses LEDs (light emitting diodes) while the 2210-2205 does not. The LEDs produce a soft clip, or really more of a compression instead of a hard clip of conventional diodes. Secondly, the pre-amp design also is very different between the two amps. On the Jubilee dirt channel, the voice is established by driving the output from the first triode hard into the second triode of the 1st pre-amp tube. The signal then goes to the LEDs for further compression and then on to the 2nd preamp tube. They are just using the LEDs to accomplish the same thing an extra preamp tube would do, but LEDs add less noise to the high gain signal than an extra tube would.

On the JCM 800 diode clip design the 2nd triode in the 1st preamp tube isn't even used.

On the JCM900s it is more like the Jubilee for the MKIII (single channel) except the diodes are not LEDS. On the SL-X version the diodes are replaced by an extra tube.

Now the JCM900 dual reverb is waaaayy different from any of the other Marshalls discussed here. The signal see's 6 op- amps (Solid state preamp chips) and a hard dide clip before it reaches tube number 1! It's really a hybrid design.

 

[Lake Placid Blues]

Re: Carvin's diode-clipping stuff. Introduced by the JCM900?

On the JCM 800 diode clip design the 2nd triode in the 1st preamp tube isn't even used.
.

Looking further at the design, the JCM800 channel switching amp is rather unique. After the signal is amplified by the first triode of the number 1 tube, it goes right to the tone stack, from there it (the dirt channel signal) passes in series through both triodes of the number two tube and then on to a single diode clipp before the mater volume.

This is quite different from the Fender Tweed/Plexi Marshall design. In that design the signal for either dark or bright channel sees one triode each in the first tube before being mixed and through the second tube and then to the tone stack.

The single channel JCM800 follows the plexi design but the signal goes from the first triode cascading into the second triode of the first tube before on to the second tube and then the tone stack. Jubilees and JCM900 MKIII/SL-X are modified versions of the single channel JCM800.

 

[Lake Placid Blues]

Re: Carvin's diode-clipping stuff. Introduced by the JCM900?

Jubilees and JCM900 MKIII/SL-X are modified versions of the single channel JCM800.

The same can be said of the Soldano SLO-100

 

[jon the art guy]

Re: Carvin's diode-clipping stuff. Introduced by the JCM900?

The Jubilee's do use diodes but they are used very differently than the JCM800 2205 design. First, the Jubilee uses LEDs (light emitting diodes) while the 2210-2205 does not. The LEDs produce a soft clip, or really more of a compression instead of a hard clip of conventional diodes. Secondly, the pre-amp design also is very different between the two amps. On the Jubilee dirt channel, the voice is established by driving the output from the first triode hard into the second triode of the 1st pre-amp tube. The signal then goes to the LEDs for further compression and then on to the 2nd preamp tube. They are just using the LEDs to accomplish the same thing an extra preamp tube would do, but LEDs add less noise to the high gain signal than an extra tube would.

On the JCM 800 diode clip design the 2nd triode in the 1st preamp tube isn't even used.

On the JCM900s it is more like the Jubilee for the MKIII (single channel) except the diodes are not LEDS. On the SL-X version the diodes are replaced by an extra tube.

Now the JCM900 dual reverb is waaaayy different from any of the other Marshalls discussed here. The signal see's 6 op- amps (Solid state preamp chips) and a hard dide clip before it reaches tube number 1! It's really a hybrid design.

Fascinating. I know one thing, that the Silver Jubilee is one of the most sought after modern Marshalls you can ask about. LED clipping has been a staple of dirt pedals, many times with switchable options between LEDs, Germanium and Silicon diodes.

So, this begs the question; modifying the diode clipping of a Carvin or Marshall to Silver Jubilee specs. If a JCM800 can have it's clippers modded to Jubilee style, I would also assume that the cheapo Carvins could too. Nothing like a $250 MTS3200 head going for the gold, so to speak. Heck, I wonder if one could add clipping options to it and stick a bunch of switches on the front. It's not like it'll kill the resale value; Carvins are a losing proposition on resale.

I was also going to ask about if there's am op amp clipped amp out there, and you answered that pretty fast too.

 

[Lake Placid Blues]

Re: Carvin's diode-clipping stuff. Introduced by the JCM900?

So, this begs the question; modifying the diode clipping of a Carvin or Marshall to Silver Jubilee specs. If a JCM800 can have it's clippers modded to Jubilee style, I would also assume that the cheapo Carvins could too. Nothing like a $250 MTS3200 head going for the gold, so to speak. Heck, I wonder if one could add clipping options to it and stick a bunch of switches on the front. It's not like it'll kill the resale value; Carvins are a losing proposition on resale.

I think that would be a complicated mess. A simple alternative is to just plug in your favorite LED driven dirt box into the FX loop and use the clean channel.

 

[jon the art guy]

Re: Carvin's diode-clipping stuff. Introduced by the JCM900?

I think that would be a complicated mess. A simple alternative is to just plug in your favorite LED driven dirt box into the FX loop and use the clean channel.

I dunno, most of it can be done on the back of a 3 way switch, or two if you wanted to mix and match clippers. Or it could all be on a daughterboard.

Or yea...you could just either run a pedal into the front or fx loop. I gueeeeeeeeeeeeeeeeeeeeeeeeess.

 

[xxxplorer]

Re: Carvin's diode-clipping stuff. Introduced by the JCM900?

Just take a pair of 12 volt zeners, attatch them with the stripes facing out, and attatch one end to lug 2 on your master, and the other end to ground. A quick way to see if you like it... Then if you do, put it after your cathode follower with a 10K resistor and a .2U cap. Boom... Basically a jose mod. The 'proper' Jose mod puts the eq after the master volume though.

I didn't like it fwiw... I just upped my plate resistors and tweaked my tone stack and gain stage values.

 

[JeffB]

Re: Carvin's diode-clipping stuff. Introduced by the JCM900?

The 4010 was NOT a diode clipper, is was a plain single-channel master volume 2204 chassis. Best amp Marshall ever made, IMO, and I'd kill to have mine back again.

Whatever model the 2205 1x12 combo was then, sorry.