Marshall vs. Mesa/Symmetrical vs. Asymmetrical (clipping)???

[JakeAC5253]

Quite a loaded observation here, but I think that this makes sense in some way. I've got a Maxon OD808 and a BOSS SD-1 here and there isn't much of a difference in the filtering of the pedals but the gain on the 808 is Symmetrical and the gain on the SD-1 is Asymmetrical. I have found that if you play these pedals on the clean channel with the gain turned up the SD-1 is reminiscent of a Marshall style of gain sound while the 808 much more closely resembles the tone and feel of a Mesa amp minus the mid scoop.

This got me thinking. Is this transferrable to the amps themselves? Does a Marshall sound like a Marshall because it has Asymmetrical clipping? And does a Mesa sound like a Mesa because it has Symmetrical clipping?

 

[Sixtonoize]

No...if anything, a Marshall has more symmetrical clipping than a Mesa (assuming that you're talking about a Dual Rec) because a Dual Rec gets most of its distortion from a cold clipping stage which only clips one side of the waveform.

Again, assuming that you're comparing a Recto to a JCM-style amp, I'm willing to bet that the tonal difference that you're noticing is more caused by the voicing of the gain stages - the Mesa will push a lot of bass through the gain stages whereas the Marshall is more mid-focused. Clipping different frequency ranges causes a significant difference in the tone and feel of the amp.

 

[JakeAC5253]

No...if anything, a Marshall has more symmetrical clipping than a Mesa (assuming that you're talking about a Dual Rec) because a Dual Rec gets most of its distortion from a cold clipping stage which only clips one side of the waveform.

Again, assuming that you're comparing a Recto to a JCM-style amp, I'm willing to bet that the tonal difference that you're noticing is more caused by the voicing of the gain stages - the Mesa will push a lot of bass through the gain stages whereas the Marshall is more mid-focused. Clipping different frequency ranges causes a significant difference in the tone and feel of the amp.

Interesting bit, especially about the cold clipping, did not know that. Yes I think I am comparing a JCM style amp with a Recto.

You can 'hear' the gain in the Marshall while the Mesa's gain is more something that is felt than heard. Then there are two different feels that I've noticed. The typical Marshall amp has a certain grind to the gain that seems to span the entire frequency range. I find Mesa amps to feel like a Fender style clean with more bass and the gain turned up to 30. It's like the guitar's personality and dry sound is still there buried under a top layer of fat saturation. It's like two tones going at once playing through a Recto. Your analysis on the half clipped-half dry wave seems to go along with this observation.

At what stage in the amplifier is this cold clipping stage? And does it have anything to do with the rectifier switch (spongy/bold)?

 

[Sixtonoize]

In a Recto (and a 5150, and any other amp that's lifted the idea from an SLO) the cold clipping stage is the 3rd gain stage.
All it is is a 12AX7 gain stage with a 39k cathode resistor so that the tube is biased so cold that it can't help but to clip the absolute crap out of the signal (hence, "cold clipping").

It has nothing to do with the rectifier, other than that changing the rectifier method can possibly lower the supply voltages, which in turn can slightly alter the characteristics of the cold clipping stage.

 

[Shask]

In a Recto (and a 5150, and any other amp that's lifted the idea from an SLO) the cold clipping stage is the 3rd gain stage.
All it is is a 12AX7 gain stage with a 39k cathode resistor so that the tube is biased so cold that it can't help but to clip the absolute crap out of the signal (hence, "cold clipping").

It has nothing to do with the rectifier, other than that changing the rectifier method can possibly lower the supply voltages, which in turn can slightly alter the characteristics of the cold clipping stage.

You know, this is an interesting topic. I was thinking about this last night after reading this thread. I knew that 39K resistor was a key component in the more modern, saturated sounding amps. But, I never really thought of it in comparison of symmetrical/asymmetrical clipping before.

I am really considering installing a pot in my JCM800 based high gain clone I built, to vary this value from the stock 10K to about 39K, so I can hear the direct difference. I wonder if this is what some amps do that have a "saturation" control...

 

[JakeAC5253]

I am really considering installing a pot in my JCM800 based high gain clone I built, to vary this value from the stock 10K to about 39K, so I can hear the direct difference. I wonder if this is what some amps do that have a "saturation" control...

Let me know how that goes

 

[Shask]

I am really considering installing a pot in my JCM800 based high gain clone I built, to vary this value from the stock 10K to about 39K, so I can hear the direct difference. I wonder if this is what some amps do that have a "saturation" control...

Let me know how that goes

I did it earlier. I have also been wanting to change some other stuff in there, so I spent an hour or so messing around. I gotta get back in there, because I don't think I like one of the changes I made, lol. I can never decide, keep it fat sounding so a Tubescreamer sounds nicer with it, or make it nice and tight on its own...

Anyways, I just added a 25K pot in series with it, so it only goes to about 35K, but I figure that is close enough for an experiment. It is kind of strange alright. I figured I would love it since I love amps based with that design (Recto, 5150, etc...) But I am not so sure in the 2203/JCM800 based preamp. Turning it up kind of reminds me of a Big Muff, lol. More bassy, More highs, and just thick everywhere. Strange though that it adds gain. I thought it would sound less gainy for some reason (Sound more clipped, but not actually have more gain). I have to turn my gain knob back a few notches when I crank it.

I am thinking about adding it as a knob, or maybe just a switch to go from stock to saturated.

I will have to play with it more, and give it more time though. I didn't spend a ton of time messing with it.

 

[Shask]

Oh, and with this control, and my depth control dimed, it actually sounds more in the neighborhood of my Recto. I mean, it still sounds Marshall based, but its quite a difference...

 

[JakeAC5253]

Oh, and with this control, and my depth control dimed, it actually sounds more in the neighborhood of my Recto. I mean, it still sounds Marshall based, but its quite a difference...

I'd love to hear a clip demo of this. Sounds very neat.

 

[Sixtonoize]

Very cool write-up.
I'd definitely like to hear your continued thoughts as you mess more with the concept.

 

[FIREBALL]

great thread

 

[Nigel Tufnel]

I am really considering installing a pot in my JCM800 based high gain clone I built, to vary this value from the stock 10K to about 39K, so I can hear the direct difference. I wonder if this is what some amps do that have a "saturation" control...

Let me know how that goes

I did it earlier. I have also been wanting to change some other stuff in there, so I spent an hour or so messing around. I gotta get back in there, because I don't think I like one of the changes I made, lol. I can never decide, keep it fat sounding so a Tubescreamer sounds nicer with it, or make it nice and tight on its own...

Anyways, I just added a 25K pot in series with it, so it only goes to about 35K, but I figure that is close enough for an experiment. It is kind of strange alright. I figured I would love it since I love amps based with that design (Recto, 5150, etc...) But I am not so sure in the 2203/JCM800 based preamp. Turning it up kind of reminds me of a Big Muff, lol. More bassy, More highs, and just thick everywhere. Strange though that it adds gain. I thought it would sound less gainy for some reason (Sound more clipped, but not actually have more gain). I have to turn my gain knob back a few notches when I crank it.

I am thinking about adding it as a knob, or maybe just a switch to go from stock to saturated.

I will have to play with it more, and give it more time though. I didn't spend a ton of time messing with it.

That's a bit early in the circuit for a cold biased stage imo. They sound better later on in the circuit, I tend to like a clipper stage biased not quite that cold myself. But if you dig it play the hell out of it and love it, if it sounds good it is good. A clipper stage can work very well in a four stager layed out something like 1-normal, 2-normal/hot, 3-cold, 4-normal---> tonestack. If you ditch the CF and go to a plate fed stack it can be done in an 800. You can bash heads with a setup like that tweaked out properly. That clipper stage is adding "gain" as us guitarists refer to it because is can't do anything but distort, but it's not much of an amplifier in the true meaning of gain. Guitar amps do all kinds of things that would make tube engineers roll over in their grave. Happy soldering.

 

[Shask]

I am really considering installing a pot in my JCM800 based high gain clone I built, to vary this value from the stock 10K to about 39K, so I can hear the direct difference. I wonder if this is what some amps do that have a "saturation" control...

Let me know how that goes

I did it earlier. I have also been wanting to change some other stuff in there, so I spent an hour or so messing around. I gotta get back in there, because I don't think I like one of the changes I made, lol. I can never decide, keep it fat sounding so a Tubescreamer sounds nicer with it, or make it nice and tight on its own...

Anyways, I just added a 25K pot in series with it, so it only goes to about 35K, but I figure that is close enough for an experiment. It is kind of strange alright. I figured I would love it since I love amps based with that design (Recto, 5150, etc...) But I am not so sure in the 2203/JCM800 based preamp. Turning it up kind of reminds me of a Big Muff, lol. More bassy, More highs, and just thick everywhere. Strange though that it adds gain. I thought it would sound less gainy for some reason (Sound more clipped, but not actually have more gain). I have to turn my gain knob back a few notches when I crank it.

I am thinking about adding it as a knob, or maybe just a switch to go from stock to saturated.

I will have to play with it more, and give it more time though. I didn't spend a ton of time messing with it.

That's a bit early in the circuit for a cold biased stage imo. They sound better later on in the circuit, I tend to like a clipper stage biased not quite that cold myself. But if you dig it play the hell out of it and love it, if it sounds good it is good. A clipper stage can work very well in a four stager layed out something like 1-normal, 2-normal/hot, 3-cold, 4-normal---> tonestack. If you ditch the CF and go to a plate fed stack it can be done in an 800. You can bash heads with a setup like that tweaked out properly. That clipper stage is adding "gain" as us guitarists refer to it because is can't do anything but distort, but it's not much of an amplifier in the true meaning of gain. Guitar amps do all kinds of things that would make tube engineers roll over in their grave. Happy soldering.

Actually, my amp is "2203 based". It already has a stage before the normal 2203 circuit.

I tried to keep the 2203 portion stock, but then I added a stage on the front that is mostly just a "clean boost", but it does cut some highs. (.0047 coupling after, and a 10K/100K divider before hitting the standard 2203 first stage).

So, its like, 2 gain stages, the cold bias stage, another stage, and then the CF, then the Tone Stack.

Actually, I really want to try 6L6's in it, but I am afraid to until I figure out a good way to lower the B+ voltage...

 

[Shask]

Very cool write-up.
I'd definitely like to hear your continued thoughts as you mess more with the concept.

Have you played a Marshall SL-x?

This kind of reminds me of the setup on that amp. It has 2 gain knobs. The first one is brighter, "thinner" and generally good for dialing in tight aggressive sounds. The second one is fatter, thicker, fuzzier, etc....

The setup on my amp kind of reminds me of how that amp was.

 

[Sixtonoize]

Here's another thought - in an SLO (and again, most amps based on the design), there's a pretty significant high-pass filter after the first gain stage (in an SLO, I believe that the cutoff is around 250hz). Varying this resistor/cap combination is a surefire way to tweak the gain response of your amp. All the filter is is a resistor in parallel with a cap that comes between the blocking cap after the first gain stage and the Gain control.

 

[Shask]

Here's another thought - in an SLO (and again, most amps based on the design), there's a pretty significant high-pass filter after the first gain stage (in an SLO, I believe that the cutoff is around 250hz). Varying this resistor/cap combination is a surefire way to tweak the gain response of your amp. All the filter is is a resistor in parallel with a cap that comes between the blocking cap after the first gain stage and the Gain control.

Well, remember that the 2203 has all the 470K/470P filters in between the stages, which, by my math, means it cuts below 720HZ between stages. I think there is 2 sets of those in there.


I have thought about tweaking it more, but if I did that, I would start turning it into a SLO. But, I would rather just build a SLOCLONE at that point, lol. That is something I would like to do, but my checkbook says no at the moment....

 

[jerrydyer]

The Ultimate Tone number one has a really good couple of pages regarding tone shaping using high and low pass filters and cuttoff frequencies etc to really dial in the tone you want. The cold bias on v2a really only works correctly on 4 gain stage plus preamps. I tried an 82k once on a 2204 and it had a great voice but the gain died.

 

[Sixtonoize]

But at that point aren't you getting close to turning the CC stage into a half-wave rectifier?

 

[petejt]

No...if anything, a Marshall has more symmetrical clipping than a Mesa (assuming that you're talking about a Dual Rec) because a Dual Rec gets most of its distortion from a cold clipping stage which only clips one side of the waveform.

Again, assuming that you're comparing a Recto to a JCM-style amp, I'm willing to bet that the tonal difference that you're noticing is more caused by the voicing of the gain stages - the Mesa will push a lot of bass through the gain stages whereas the Marshall is more mid-focused. Clipping different frequency ranges causes a significant difference in the tone and feel of the amp.

Sorry to be possibly detracting from the thread- but would the Mark series Mesa/Boogie amps have more asymmetrical clipping compared to a JCM-style Marshall?

 

[petejt]

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