mesa boogie rectifier

hi guys

im trying to create several types of distortion modules for my dsp modular pack (www.adern.com). as a producer i am well familliar with the mesa boogie rectifier amplifiers and their distortions.

im trying to find out the way they get thier heavy metalish thick distortion. and i have a certain feeling that their rectifier doesnt mean the same thing as us dsp bloaks know it to be (absolute value, aka minus equals plus). information on the web seems to be totaly conflicted by many theories of what it realy is. i heard pople taking about rectifiers as i know them. others talk about several drive stages with filters in between. others talk about bizzar waveshaping.

has anyone here opened a mesa boogies before cna can tell me how it actualy works?

thanks in advance!
Assaf

The rectifier is in the power supply. It changes the AC voltage from the wall into DC that can be filtered and used to power the amplifier. Mesa Boogie Rectifiers have two different kinds of rectifiers, tube and solid state. The solid state is just 4 diodes set up as a bridge, sorta standard. The whole "sound" of the rectifier comes from the tube rectifier acting in a way (different from the solid state) in that the distortion has a more "compressed" sound (or whatever). I think the tube rectifier just gives a little more, I dunno for sure. One of the tube guys could explain it better.

Ian

Mesa Rectifier is also the name of one of their models of guitar amps. I really don't know why they named it thus.

The tube rectifiers in a Mesa dual- or triple-recto amp are there mostly for marketing hype. They only become a sonic factor when the amp is cranked way up.

Tube rectifiers have a higher internal resistance than silicon rectifiers, so when the current demand is great, the output voltage droops. This results in a compression of volume that many guitarists find pleasing. But again, this only really comes into play at high output settings, when the output stage is drawing a lot of current.

Most of the character of a Dual Recto comes from the preamp, which Mesa basically stole from Soldano. Although the design is known mostly for those awful "nu metal" tones, it can also be adjusted to provide some pretty good crunchy and even clean-ish (albeit hissy) tones as well.

Gah! Nevermind my post. I obviously don't know how to read.

thanks a bunch!

so basicaly the distortion stage doesnt have any rectifiers in their path as i thought :>


still compressing a signal befor your distortion will not give a more thick and dense sound.. i wonder how they have created that type of sidtortion what makes it so diferent than others

Make a triangle to sinewave converter, but use a sinewave as input signal and see what you get. Now make this convertion nonsymmetrical on positive vs negative halfsine. Add some time constants to make convertion kick in slowly or act directly on the sienwave from the first half and each period of the sine.
That way you can simulate tube distortion and compression due to sagging of the supply voltage in tube rectifier.
When you've done this send me the royalties to my Cayman account. :grin: :wink:

Alex

what kind of lowpass do they put on the rectified AC?
what order and what frequency?

[quote author="NewYorkDave"]Tube rectifiers have a higher internal resistance than silicon rectifiers, so when the current demand is great, the output voltage droops. This results in a compression of volume that many guitarists find pleasing. But again, this only really comes into play at high output settings, when the output stage is drawing a lot of current.
[/quote]

I wonder if anybody emulates this very effect without driving a power amp at full load. Like this:
Build a preamp, plus an extra tube (or transistor) which will be fed the preamp output signal, and which will simply pull down the Power supply as a shunt. One could probably make the whole mechanism much less power consuming than a real power amp, by choosing a higher series impedance in or after the rectifier. Has this been done?
(I'm aware that there's a lot more going on in a power amp and speaker which forms the sound, but it would be interesting to get this preamp-compression by supply voltage sagging alone, wouldn't it?)

JH.

from Juergen:

I wonder if anybody emulates this very effect without driving a power amp at full load. Like this:
Build a preamp, plus an extra tube (or transistor) which will be fed the preamp output signal, and which will simply pull down the Power supply as a shunt. One could probably make the whole mechanism much less power consuming than a real power amp, by choosing a higher series impedance in or after the rectifier. Has this been done?

Click to expand...

That's a nice idea but don't know of examples. If I'm right, most boxes that are using the mini-poweramp-idea will be using a single tube that'll be more or less in class-A so no sag. I don't know about the SWR Interstellar Overdrive though, it uses 2*EL84 in push-pull but don't know how it is biased. And again, none of them does the extra thing you described (apart from their usual circuit-action).

Peter

I guess preamp compression can easily be achieved even with a small class AB power amp, if the rectifier impedance is chosen high enough to match. (I don't know if this is normally a design goal or not.)

A "big" amp that drives a power soak at full volume should show this effect on the output of its preamp. (But you wouldn't derive the signal there, when you have the power amp and power soak readily available, of course.) In that condition, one could measure at which signal level the supply will start to droop (probably when the power amp leaves class A).
It should be easy to emulate this by rectifying the preamp output with a certain threshold, and controlling a shunt tube / transistor with this.
Nothing gained, yet. (;->). Now scale down the whole thing, by adding a higher resistor in series with the power rectifier and using a smaller shunt device.
Not sure if just using a small power amp will be the better method still. You get away without an output transformer, and without power tubes (shunt can be cheap transistor), but only get the compressed preamp sound.

Only theory, and put up for discussion!

JH.

I would personally just go and model a good sounding amp and then call it a "dual rectifier" in your modeling and sell that to the kids. Those mesa's pretty much sound like a cardboard box which should be easy enough to model. I used to play through one for years and have recorded too many to remember and they are just awful, terrible amps. And what dave said about marketing is very much correct, those amps are very strange when it comes to power. The whole appeal of a guitar amp with a tube refticier is the sag you get from the thing when you run it on ten. If you are familiar with the old fender tremolux design or a tweed deluxe, etc, you know that when you have the amp on 10 and lay into the guitar, the amp responds in a really nice compressed way. Your max volume is usually somewhere around 8 on the volume and the rest is just compression. The idea of that would be easy to put in a modeler. The odd thing about the boogie is that it never responded like that and reached its max volume very much earlier on the dial. The triple recs were even worse like that. You could never HEAR the sag from those amps, at which point the quesiton needs to be raised, why bother with a tube rectifier in the first place... Over the years I began to think that they used two rectifiers to reduce or eliminate the sag, but again, why bother, for most people, thats the whole point... Most guys would come in with the amps set for silicon recitifiers anyway, the amp was louder and sounded more like a cardboard box like that. The very very first year they made those amps, they were ok, but after that they all started to sound exactly the same and not in a good way either.

dave

The MEsa rectifier sound is all about cascaded high gain stages, and massive amounts of filtering in between. Like soudguy says, they sound awful. No need to have used a tube rectifier in there...hell, no real need to have used a tube power section either.

Most modern high gain amps are using the same technique....no wonder modern guitar tone sucks so much.

Cheers.

Kris

Speaking as a metal guitarist, I feel that the Mesa Rectifier series is overhyped overpriced garbage. It takes forever to dial in a good tone, and most of the time that involves disengaging the Tube rectification and enabling the silicon option. Its a bunch of useless bells and whistles.

The problem is that they only really sound "good" with a heavily scooped eq setting, those are most of what these amps are known for.

Thanks for the input, but this an eight year old thread.

(and a rock guitarist/songwriter I'm going to completely disagree with you)

"you have to turn it up to 10 to get a good tone,"

well guess what?  :

ever been to a Deftones concert?

Speaking as a metal guitarist, I feel that the Mesa Rectifier series is overhyped overpriced garbage. It takes forever to dial in a good tone, and most of the time that involves disengaging the Tube rectification and enabling the silicon option. Its a bunch of useless bells and whistles.

The problem is that they only really sound "good" with a heavily scooped eq setting, those are most of what these amps are known for.

Click to expand...

I agree I hate it. I did a visit to Andy LaRocque() last year in his studio at Varbeg and I ask him what he will use for his next album and he said "a rectifier" then I reply, I hate it, I can`t play with it and he said yeah me neither I record with a pod and then I reamp it. ;D ;D ;D

recently I found this video https://www.youtube.com/watch?v=AWja3FkU7rc I think I need that sound for my studio so I bought a grail module, now I have to DIY a rack to use it.

I have tried a dual caliber and it is way better than the rectifier (if you want the metallica sound it have it).