Mc2300 Peak Limiter Theory - REVISITED

[SarnoMusicSolutions]

Jerry's McIntosh Mc2300 Peak Limiter Theory - revisited and revised


Well after having some eye-opening and clarifying discussions with Dan Healy this week, I learned something interesting and a bit humbling regarding the (my) theory around Jerry's tone and how his transient peaks were being smoothed and leveled a bit by the Mc2300's "sentry monitor" peak limiter circuit. Dan describes their batch of Mc2300's, including Jerry's, as NOT having that limiter portion of the circuit in them. From what he described, it sounds like the bulk of the amps they had for the Wall of Sound, from which Jerry's came, may have been of a certain variety or non-commercial version, perhaps military, that did not have those limiter circuit components installed.

Dan went on to describe how he made some very precision component selections and upgrades in Jerry's Mc2300, and by making the upgrades, the improved symmetry made the harmonic content of the amp, when pushed into distortion, have a certain character. He did say that the more common Mc2300's with the limiter installed may also contribute to a similar symmetry and also has the benefit of helping keep the power supply from "flopping around" when subjected to high current demands. By the way, Dan is no fan of the Mac amps nor the JBL's as guitar speakers. I find that kind of funny.

But anyway, this direct info from DH dismisses the theory that part of the smoothing or leveling of Jerry's tone when peaking and clipping was partially created by the limiter circuit. According to Dan, this was caused simply by the transistors clipping/distorting in a very symmetrical fashion, but there was no limiter to clamp the levels down. Pure transistor clipping. The tweaked out Mc2300 was free to distort as much as Jerry wanted to hit it, and the quality of that distortion was refined by the component tweaks.

It never dawned on me that there could have even been some odd versions or variations on the Mc2300 that wouldn't have that limiter circuit installed. All doc's and schematics and all versions of the Mac's I've personally seen and worked on clearly have that circuit in place. So for most any of us using Mac's this way as a Jerry-amp, we are all indeed getting the Sentry Monitor limiter experience if we push the Mac past its limits to obtain some dirt. From what Dan described, this should be just fine, will still provide the transistor clipping, and even have some benefits of power supply stability. I have to admit it's a bit humbling because I've been so personally attached to this theory that I came to thru deduction and experimentation. But not considering the possibility that Jerry didn't even have the limiter circuit in his Mac made it a logical conclusion for me.

What interests me now, is that after re-training my brain to try and understand the nuances of Jerry's tone as I hear it with the recently erased Sentry Monitor limiter theory, I'm more fascinated with this notion of extremely symmetrical transistor clipping in a push/pull circuit. And I have a suspicion that possibly some of the audible smoothing of Jerry's peaks may have actually been the result of Dan peak limiting Jerry's channel at the board instead of being in Jerry's rig itself. Just a thought and a guess, no confirmation on that at all.

Another key part of Dan's explanation of some of the tone we hear out of Jerry is the fact that the JBL's were being hammered, and they would saturate and create their own form of distortion because they simply couldn't deliver what was thrown at them by the amp. That, by nature, is form of clipping or limiting and would naturally generate some harmonic distortion. This would likely be most apparent on the transient peaks or spikes from pick attacks. Dan has stated that the preamp ran very clean, and others have described Jerry's Twin-pre gain setting as generally being fairly low and well below where a Twin pre self-overdrives. This suggests that nearly any or all of his clean-tone-dirt would be from the clipping Mac (with no limiter action). But there is a period in the early '80s where there seems to be an unusually high amount of grunge in his clean tone. I suspect that those were times when he may have also really cranked up his Twin-pre to begin to get it to also clip a little bit along with the Mac. Or, my other take on that is that it could have coincided with his swap to the more rugged E120's and simply allowed him to drive the Mac even harder and grungier without such risk of popping speakers. But for the most part, what I've learned is that Jerry had a fairly pristine tube preamp section into a very tweaked and balanced transistor McIntosh that was simply driven into distortion. It's funny how Jerry was so opposite the convention, that it takes power tubes distorting to get good tone.

Brad

[playingdead]

I remember reading somewhere about the US military freaking out because it needed MC2300s but the Grateful Dead had reserved them all for the Wall of Sound and wouldn't part with any of them.

Interesting info. I'm not so sure about pushing an E120 really hard and getting it to distort, because my own experiments in the studio throwing 800 watts at them and recording them at stupid loud volumes (wearing ear protection but watching the cones really rocking back and forth the way Jerry's used to) didn't yield any noticeable sonic differences from the same setup recorded at a far lower volume.

[rob]

Does this mean you can build us one now, Brad? Brad? Please.....

Rob

[tigerstrat]

You had a similar conversation as I did with DH a few weeks ago! Although much deeper and detailed.

I was pondering how to bring up the "no limiters" factoid on this board, when Real Life + the holidaze struck hard in twain, and it was temporarily forgotten. However DH told me the slight dirt was basically equal parts distorted Mac, distorted speaker, AND distorted preamp. I would pretty much agree that late 70's/early 80's JG kept his gain higher. DH also mentioned not digging any ceramic speakers at all (the E's), and that he loves the newer Neodynium models.

[mkaufman]

Does anyone have the cohones to ask DH about Weir's Ibanez-era sound???

If you do, just be ready for an incoming MC2300..

mk

[SarnoMusicSolutions]

.... However DH told me the slight dirt was basically equal parts distorted Mac, distorted speaker, AND distorted preamp.

That's where I think it'll be interesting for us to explore things a bit on our own and with our ears. I honestly believe that at different times there were varying degrees of each. When I hung with Dan while did DSO sound, there was a discussion going on about where Jerry's "dirt" came from. Dan was not in agreement with the notion of at least one particular means of tube preamp distortion, and that was by means of boosting the signal level by a large amount before it ever reaches the preamp, and thereby clipping the first input stage of a tube preamp. Dan eventually swore fairly adamantly that the preamp was setup to run clean and surely wasn't clipped like that. It robbed the sound of headroom and clarity. But that was in the context of suggestions that there were some "secret magic mojo" methods of creating large amounts of internal preamp overdrive. He was very adamant that the circuit was not messed with like that at all, and while the component selection in Jer's preamp was very precisely chosen and improved, the general circuit design was still true to the original Fender circuit. He said that the dirt would have likely come from the Mac and the saturated JBL's. But I think he was trying to stress the point at the time that the preamp was not hod rodded to become a hot, overdrive circuit. That mixed with numerous comments from those who had talked to Jerry or observed his knob settings that he didn't typically drive the preamp all that hot. As many of us know, if you have the normal Jerry guitar setup and run thru a Twin preamp and really crank the gain and the mids, you can begin to get just a bit of dirt, not much, but a bit of squish. Maybe with the mid and gain both up past 7 or 8. This is where I can see how at times Jerry may have gone for that preamp dirt to a degree. If Dan said preamp dirt was part of the formula, then I believe it.

We know that the clipped mac and JBL's are given the most credit for any dirt, and there are clues and comments even from DH that the preamp may have also contributed at times. I'll tell you though, I've done a lot of experimentation and listening to preamps and Mac power amps and JBL's, and the driven preamp dirt in the Twin circuit just doesn't quite do "THAT" thing. I can see that maybe the preamp pushed to begin to smooth out a bit could be a component, but in my listening experiments, that sound isn't even close to what the pushed Mac sounds like. I just listened to an '89 JFK show, a Healy SBD. Jerry's tone is amazing. To my ears it sounds like a very clean and hi-fi preamp sound, crisp and solid and really not squishy at all. Then as he picks or strums, it just smacks real hard with percussive clarity and a bit of grit. Not warmed over in a tubey way, but with teeth on it and slicing thru the mix with a lot of clarity. I really think that there is the sound of a clean pre into a clipped Mac.

Dig the Scarlet/Fire. This show really has what I think of as the refined Jerry tone. And what's very interesting is at the end of the show, Lovelight has that clean/dirty tone that's so fascinating. It's his clean (no pedals) tone, but he's really diggin in and getting some breakup.

http://www.archive.org/details/gd89-07- ... sbeok.shnf


Brad

[strumminsix]

But there is a period in the early '80s where there seems to be an unusually high amount of grunge in his clean tone. I suspect that those were times when he may have also really cranked up his Twin-pre to begin to get it to also clip a little bit along with the Mac.

Or maybe sent an even lower signal? Was messing around years back and found with the IVP & TubeWorks to get the best headroom I needed a level of X.

X + 3 was too hot and starting sizzling immediately (not good)
X - 3 was too cold and had to crank up the poweramp to near max and it was clipping (musically)

Just another thought as you are rethinking things, dude!

[SarnoMusicSolutions]

All this thinking sent me to the lab (ok the basement) last night to experiment a bit. I used my twin-like preamp and my jerrycaster and my various amp setups, and the more I drove the preamp super hot to get a bit of its internal gush, the less and less it sounded right. It lost that crisp, defined top end and that stiff attack and strum. The cleaner the preamp was set, the more right it sounded. I couldn't crank the power amp because it was late, but it sure reminded me of Jerry's tone, the less I was pushing the preamp. Now all that could change at real high volume, but at low volume, clean and unclipped pre sounded more correct.

Brad

[jdsmodulus]

I was thinking about all that has been said here, so I listened to the JFK show last night, that is a great show, for me its in the top 5 of 89. I was thinking about Jerrys tone and rig and at that time he was really getting in to MIDI gear. Not forgetting gear that was off stage. There was very few times where his tone was "clean". I mean guitar>amp>speakers clean. When we look back at these shows we have to consider when we hear a wah or mutron tone like in "Blow Away" with that distortion and EQ there was also the GR50 and Proteus going on on some level "possibly". This makes me wonder how we will really ever know about the Mac and the JBLs reacting to the preamp or any other combo during this period. Simply because there was so much signal processing going on that was not in Jerrys control. Even Healy had pedals at this time to control delay and verb and well quite honestly anything heard in the house. Im not trying to say this is alyways true or even true in the case of this show, but the midi feeds and the extra signal processing should be considered when what we think we are hearing is Jerry "clean".

[Jon S.]

Don't get me wrong, I enjoy the tone quest as much as the next guy, but to be frank, threads like this one, more than anything else, reinforce to me how chasing after someone else's tone by attempting to copy/clone everything exactly as the other person did it is like grasping for air. There are simply too many variables in play, not the least of which - and I'd argue, the most of which - is the player's thinking process and playing characteristics.

In my old age (so to speak), I've become more a fan of taking the gear you have, or buying new gear with the features you need, that starts out at least generally in the tonal ballpark you're after, and adjusting it to fit your own thoughts, feel, and attack. Whether it be a SF Twin Reverb, an Axe-FX, or anything else, if you really want to sound like Jerry, play like him and adjust your settings accordingly.

We now return you to our regularly-scheduled tone quest.

[SarnoMusicSolutions]

Jon,

I like what you just said. I tend to come to a similar conclusion for myself personally. I play in a band project that's very low volume. I could never pull off the Jerry/Mcintosh thing. I literally fill our smaller gig venues with my home built 12 watt Fender styled amp using a K120. It has the same voicing as the Twin or Deluxe Reverb, real clean "Healy" like components, but it's very low power, and for much of the time, I can ride that little amp right where it wants to break up a bit. For me personally, this is the best way I can achieve my version of a Jerry-like tone.

But this quest for the real deal is a lot of fun, I must say. Plugging into a setup that's very similar or true to Jerry's, and just feeling it and hearing it is at least a thrill. Also, for me, I find myself helping a number of players design and set up a rig and they are playing loud and truly going for that sound, so there is a real world practical side to this as well. But like you said, we have to adapt our rig to suit our playing style. I will never pick as precisely as Jerry did, thus I will never be able to make my music with his amp rig. I can enjoy farting around with it, but when it comes to making music, I have to find my own path, albeit largely inspired by what I've gained from the deep study of the Jerry rig.

Brad

[Jon S.]

Jon,

I like what you just said. ...

But this quest for the real deal is a lot of fun, I must say. Plugging into a setup that's very similar or true to Jerry's, and just feeling it and hearing it is at least a thrill. Also, for me, I find myself helping a number of players design and set up a rig and they are playing loud and truly going for that sound, so there is a real world practical side to this as well. ...

... but when it comes to making music, I have to find my own path, albeit largely inspired by what I've gained from the deep study of the Jerry rig.

Brad

Can't agree more and, to be frank, if you had any idea how much I myself have and am right now questing after rig components similar to JG's you'd laugh at my hypocrisy and I'd be laughing right with you!

[tigerstrat]

SarnoMusicSolutions wrote: But I think he was trying to stress the point at the time that the preamp was not hod rodded to become a hot, overdrive circuit.

That's how I interpreted that assessment- that it was not hot-rodded into its input, but that it was working at a fairly high setting. Did DH say anything about the V2 tube? 12ax7's iirc from other threads, but if they really wanted it cleaner than clean, I'd think they'da thrown a 5751 or other lower gain tube in there.

Ditto about playing/intensity/heart over gear, and that tweakage of gear more important than the gear itself, but still like to learn about Jerry's gear and "htf does he sound like that??"

[Rusty the Scoob]

I used to run a 5751 instead of a 12AX7 in my old SWR head. Really did tame the gain and clean it up a lot. I should try that again, thanks for reminding me!

I like reading about the Jerry quest, and this thread is awesome. To me it's all about the Ballpark. A Strat through a stock twin gets you in the Jerry Ballpark whereas a Les Paul through a Marshall Stack usually does not. An OBEL through clones of Jerry pedals gets you into the next ballpark, running a conventional setup through cheapo pedals usually does not. Brad just discovered a whole new ballpark - the clean preamp, dirty & limiterless Mac ballpark. I love it, I think it's great information!

So when can we expect the SMS Very Balanced 50 watt tube poweramp?

[SarnoMusicSolutions]

....So when can we expect the SMS Very Balanced 50 watt tube poweramp?

That truly is on my drawing table. That and an overdrive pedal are my top projects for 2010. I've had requests from steel guitar players, my largest base, as well as Jerry-heads for a tube amp to complement the SMS Classic pre. This new insight has me considering a number of things, but it does center around a mono push/pull tube amp, not unlike a Fender or Marshall, but with some more precision refinements than you may normally see in a "guitar" amp. Sort of a cross between a guitar mentality and a hi-fi mentality. And a mono block makes sense for us here. It seems that all the commercial offerings today are big, heavy, and stereo, and too loud. I may do a 50 watt amp at first. Personally, I find it hard to use the full power of a Twin, but that's my age showing. That and not wanting to get my ass kicked by any soundmen. So at least for the proto and development, I'll keep it with a pair of power tubes. Then if it all gets rolling, I'll probably have to consider a 4-tube (100-ish watt) amp. I like the lighter weight of a 50w too. Smaller transformers.

Brad