McIntosh Power Guard Peak Limiter

Chat about Equipment Info

Re: McIntosh Power Guard Peak Limiter

Postby mijknahs » Tue Dec 08, 2009 3:36 pm

Mike,

Its a good theory but have you or anyone else you know tried it out yet?

I know what you mean by "hair". You mean a very subtle, smooth clipping (just a tad). I just don't hear that on most recordings (on some recordings -yes). I certainly don't hear it in the late 70's (same amp setup). Can you give an "archive" example of the sound you're talking about? Or what year? By what you say it should be on every note Jerry played.

I have a great example of Jerry maxing out his clean sound on the 5/31/83 JGB show (maybe this is the sound you are referring to?) but most Dead shows in the same time period (early 80's) are much cleaner. 1982 is particularly clean (unpushed) sounding. 1985 has more "bite" but not quite the same tone as the 83 JGB show. A friend of mine spoke to John Cutler at a JGB show once and John said that he didn't even have Jerry in the PA mix at all because he was too loud already.

Jerry's sound changed slightly from year to year. Sometimes it was smoother and sometimes less. He always had that same MC2300 though.

Jim
User avatar
mijknahs
Senior Member
 
Posts: 1518
Joined: Fri Nov 13, 2009 8:51 pm
Location: Los Angeles, CA

Re: McIntosh Power Guard Peak Limiter

Postby SarnoMusicSolutions » Tue Dec 08, 2009 4:15 pm

I think that we heard Jerry clip his Mac, at least a little, nearly every time he picked a strong note. I think that that's where he found his sound. Jerry's tone was so crisp and bright and full of overtones that most of the time we didn't hear the Mac's distortion artifacts, but instead we just heard the fat presence of the notes he picked or the chords he strummed. If you look at the audio waveform of a picked guitar, you can see that the initial attack creates a visible spike that's many, many times higher in voltage than the sound that follows. For the actual note to be loud and full, that means that the pick transient would have risen far above the power limits of the amplifier. This peak limiting or "leveling" allowed Jerry to make the audible notes very big and clear and full since the spikey transients were shaved off and when they were shaved off, the output transistors created a brief little "squirt" of mild distortion. The VI Limiter (aka Sentry Monitor) naturally activates right where the output transistors are beginning to distort. Also, fast peak limiting in and of itself creates amplitude distortion and likely a bit of harmonic distortion as well. To most ears, this action still sounded like Jerry's "clean" sound. It's not a grunge to speak of, but much more of a dynamic characteristic. Anyone who has played dead clean thru a Mac at power levels well below maximum can hear that it's just not the same as when pushed to the limit. Same goes for a tube amp. Playing clean thru an overpowered tube amp sounds thin and plinky and the pick attacks are spikey. For that reason guitar players will find an amp that they can drive and clip because that's where the smoothing and sustain comes from. Jerry had a round and bubbly "pop" to his notes and strums and the spikey icepick factor simply wasn't there. He used the Mac much like others use a tube amp in that he drove it into that peak/clipping/limiting territory for this smoothing factor, the loud presence, and the ability to dig into a lick and have it sit there on top. Play too cleanly thru a rig and the guitar sounds thin and wimpy. The Mac let Jerry play as if it was a tube amp being pushed, but the Mac-factor made what came out sound far cleaner and more sparkly than a tube amp. A clipped tube amp becomes warm and dark, but Jerry had the clear slice to his sound.

I have a stand-alone Power Guard limiter here, and while it's a very cool limiter, it's very clean and has the rounded sound of a limiter. I'd assume that a Power Guard equipped Mac would have its threshold set so that the Power Guard would activate first. That's kind of why they introduced it. But I agree that the clean-ness of the Power Guard would rob the Mac of that grittier, nastier, more musical Jerry type peak limiting.

While I believe Jerry had the VI Limiter active constantly, that doesn't mean that all of the sound was in the grungy zone. It means that only the peaks of the signal crossed into that range, while most of the audio lived cleanly below it. But it's this shaving (rounding, smoothing) of the peaks that added that bit of grit and mostly enabled the actual notes to sit loudly on top of the music.

There are clearly those more rare moments when Jerry was pushing the Mac so hard that nearly everything sounded grungy, but I'm arguing that the bulk of the time when he was playing what sounded "clean", it really was more complex than that. There was a LOT of activity in that Mac's limiter circuit and a good amount of transistor distortion happening when the guitar signal transients rose above the power threshold. I hear it in the fingerpicked Peggy-O riff, Althea, Scarlet intro chords, Franklins chords, China-Cat intro, Bird Song riff, Sugaree riff, Standin on the Moon chords, ALL clean leads, etc. None of that stuff was actually "clean". It may have sounded clear and defined, but much of that gleaming beauty came from some somewhat gnarly abuse of the Mac and speakers.

Sitting with a guitar at low volume in a mellow setting, it's not hard to get something very closely resembling Jerry's sound, but on a stage with a loud as shit band, cymbals banging, that stuff just doesn't pop thru. It takes some real power and all this limiting stuff we're talking about to make clean electric guitar cut thru the noise and sit on top like it did.



Brad
... and it's just like any other day that's ever been...
User avatar
SarnoMusicSolutions
Senior Member
 
Posts: 1070
Joined: Tue Jan 27, 2009 6:15 pm
Location: St. Louis, MO - USA

Re: McIntosh Power Guard Peak Limiter

Postby waldo041 » Tue Dec 08, 2009 4:33 pm

those sharp peaks are actually peaking already peaked output transistors. it's a situation in the mc2300 that was rectified by mcintosh with the insertion of the "power guard" limiter. all mc's after the mc2300 have both a sentry monitor and power guard. i wonder if it was jerry who prompted mcintosh to insert it.

peace,
waldo
"Tone is in the instruments. Technique in the hands. Do what you will." ~ quote from some guy at the TGP forum
waldo041
Senior Member
 
Posts: 2830
Joined: Thu May 19, 2005 10:58 am
Location: Indiana

Re: McIntosh Power Guard Peak Limiter

Postby mijknahs » Tue Dec 08, 2009 5:16 pm

Brad,

I personally think it's more of the harmonic resonance of his new guitar (Tiger) that introduced that "hair" in the 80's. He was playing the same amp rig in the 70's but his sound really started to "growl" in the early to mid 80's. Rosebud didn't growl the same way Tiger did with it's chambered body.

Jim
User avatar
mijknahs
Senior Member
 
Posts: 1518
Joined: Fri Nov 13, 2009 8:51 pm
Location: Los Angeles, CA

Re: McIntosh Power Guard Peak Limiter

Postby SarnoMusicSolutions » Tue Dec 08, 2009 7:00 pm

I see what you mean about different guitars having different harmonic characteristics, but the issues here have everything to do with dynamic range of audio signal voltage fluctuations and harmonic distortion and especially the dynamic range changes (amplitude distortion) resulting in a leveling and sustaining of the signal at peak loudness. I definitely hear Rosebud doing the same thing to that rig. The changes there may be like the other loudness changes we heard thru the '80s, and I'd guess it had to do with Bob and Phil's stage volume, monitor levels, drug consumption, etc. But this peak limited tone character is something I hear thru the '70s and well into the '90s as long as he was using his Twin/Mac/JBL setup.

A guitar and it's inherent harmonic quality surely takes part in the overall coloration, but I think we're addressing sonic issues here that deal almost entirely with amplification, power dynamics, harmonic distortion, and large amounts of current flowing thru power amps and speakers. Even stuff from '73 with Wolf, its Strat pickups, and the early Mc2300 rig has this same kind of "dirt" and "squirt" going on.

But I agree, Tiger had a certain tone growl that none of his other axes had. I love that axe.

Brad
... and it's just like any other day that's ever been...
User avatar
SarnoMusicSolutions
Senior Member
 
Posts: 1070
Joined: Tue Jan 27, 2009 6:15 pm
Location: St. Louis, MO - USA

Re: McIntosh Power Guard Peak Limiter

Postby playingdead » Tue Dec 08, 2009 7:50 pm

Someone should really get an MC2300 into a studio with some JBLs and record it at different volumes.

Don't discount the pickups, either; the Dual Sounds on the early Tiger were much fatter sounding than the Super IIs, which debuted when that super clean 82 period was.

That's my favorite tone of his, and I did a lot of listening; one thing I walked away with was at that point the Twin's preamp section seemed to be set so it was just short of getting crunchy with the middle pickup on single coil and played hard, and just going to the bridge with both coils dirtied it right up. You can hear that easily by listening to one of those spring 82 soundboards, find one with something like a Tennessee Jed or Peggy-o, which are sparkling clean, and with a Promised Land, and listen to how "hairy" the tone gets when he kicks it to the bridge to play the Chuck Berry riff on the opener. Night and day, like he kicked on a Tube Screamer or something.

Not to get too off-topic here, but since someone raised the difference in tone between Rosebud and Tiger, what effect on tone does a semi-hollow body have, given the same pickups and electronics?
User avatar
playingdead
Senior Member
 
Posts: 1733
Joined: Wed Mar 26, 2008 9:55 am
Location: Boston, MA

Re: McIntosh Power Guard Peak Limiter

Postby mijknahs » Tue Dec 08, 2009 8:45 pm

Hey Brad,

I guess I can't hear it then. To me, '77 sounds so different/cleaner than '85 that it's apples and oranges (but same amps).

Listen to the intro to Loser from 5/8/77:
http://www.archive.org/details/gd1977-0 ... s.266.shnf

I don't hear any "hair" in Jerry's tone. Sounds like a clean strat into a Twin turned up to about 2 or 3 then just amplified cleanly.

Compare with the intro to Loser from 6/24/85:
http://www.archive.org/details/gd85-06- ... sbeok.shnf

This might be the "hair" you're talking about. The gutty, throaty tone of the Tiger. This is the sound I'm interested in. Maybe he is cranking the Mac to overdriven levels. Maybe the Twin is also cranked. I can't prove it. I just know it's different. One thing I know is different is the guitar. Not the amps or speakers.

Jim
User avatar
mijknahs
Senior Member
 
Posts: 1518
Joined: Fri Nov 13, 2009 8:51 pm
Location: Los Angeles, CA

Re: McIntosh Power Guard Peak Limiter

Postby jdsmodulus » Tue Dec 08, 2009 9:09 pm

"Someone should really get an MC2300 into a studio with some JBLs and record it at different volumes."-playingdead wrote.
I for one would volunteer if someone wants to loan me their MC2300 :lol:
jdsmodulus
Senior Member
 
Posts: 1252
Joined: Tue Dec 02, 2008 2:12 pm

Re: McIntosh Power Guard Peak Limiter

Postby SarnoMusicSolutions » Tue Dec 08, 2009 9:19 pm

Jim,

I was just listening to that '77 They Love Each Other. It is a very clean sound, but I most definitely hear what I'm talking about all over that stuff. But in that case, like the boinky riff and stuff during the verses, I hear it mostly clean, but it's the peaks, the pick attacks that you can hear being hard limited or clipped off. That kind of playing into a Twin clean at low volume would have all kinds of spikey pick energy where Jerry's is rounded off leaving a beefy note as the loudest thing. Then in the solo, you can hear the smoothed out sustain and just a bit of sparkle (hair) on top as he hits the more squealy, bendy licks. In a totally clean rig you'd never have that degree of sustain (leveling) on such licks. This is exactly at the very heart of what I think is so freaking cool about Jerry's sound. It "sounds" clean. The fidelity is ridiculous with the cleaned up Fender, the McIntosh and the JBL's, but he uses that setup to get the "dynamics" of a tube amp, that ability to really dig in and play guitar hard and with intensity. But instead of the the amp rig crossing into that darker, thicker tube overdrive sound, he retains all that clarity. I'm arguing that it's the way the McIntosh clamps the peaks that allows this to happen. Jerry really could lay into his rig. I've tried setups using extremely loud power amps that wouldn't offer that "give" and it just has a more sterile, clean-country kind of result. The McIntosh seems to make for a much more exciting and interesting tone at the top, and the dynamic leveling makes it so you can enjoy it and not get jabbed in the ears by an icepick. It's smooth and sustainy and kind of juicy with overtones. It takes limiting/clipping to do that. The illusion is that it's "clean".

Brad
... and it's just like any other day that's ever been...
User avatar
SarnoMusicSolutions
Senior Member
 
Posts: 1070
Joined: Tue Jan 27, 2009 6:15 pm
Location: St. Louis, MO - USA

Re: McIntosh Power Guard Peak Limiter

Postby mijknahs » Tue Dec 08, 2009 9:31 pm

Brad,

Listen to the '85 show I posted and compare it with the '77. The '85 show is not "clean" like the '77.

So, do you have a Mac? Which one?

Jim
User avatar
mijknahs
Senior Member
 
Posts: 1518
Joined: Fri Nov 13, 2009 8:51 pm
Location: Los Angeles, CA

Re: McIntosh Power Guard Peak Limiter

Postby SarnoMusicSolutions » Tue Dec 08, 2009 9:39 pm

I'm currently in the final stages of helping build up a rig for Stu Allen. He's got an SG that I'm about to install the OBEL and Waldo's buffer and all the right electronics. It'll be electronically like a 1980 Tiger with the Dual Sounds and the SDS-1 in the neck. He's got the SMS Classic tube preamp and a Mc250. He's about to grab up a mint Mc2300 as well for larger shoes. He's got 2 K120's in a Soundscaper cab. He just scored a clean Mutron III, and it's one of the best I've heard. MXR+, OD-2, Phase 100, Boss octaver, MXR analog delay, Adamas picks, and I'm not sure what else I'm missing. But it's a pretty complete Jerry rig. At some point I want to do some recordings of the thing, and will definitely set up somewhere where we can put the Mac's thru their paces and really find that limiter action. Hopefully I'll be able to get some sound samples to demonstrate that factor nicely and clearly so we can all talk more about it. If I were a better Jerry picker, I'd do it myself, but I can't quite pick a string the right way to get "that" sound. Stu's real good and knows that stuff, but the JG gear setup is fairly new to him.

Personally, my eardrums haven't had the pleasure of driving a Mc2300 to the limit, yet, but my Mc250 was a nice scaled down version of the same basic process with the same circuit. It wasn't too hard to find that point where the Mac began to smooth out and then become quite dirty. That really convinced me and confirmed a lot of theories. There's a zone in there between totally clean and audibly dirty. It's kind of fat and boinky in the zone and high licks get sustained, but not like a compressor pedal. It's more dynamic feeling, and there's a crystalline sparkle that happens (the "hair"). The Scarlet intro really comes to life there. Working in that zone seems to be where it really happens. Just the tops of notes get evened out a bit. Really laying into the guitar with a squealy lick or hard scrubbing can push it into some audible dirt. So it seems to me that learning to operate in that range would be the trick. At lower volumes, the Mac sounds real nice for a transistor amp, almost tubey but not quite, but not necessarily all that exciting either, and surely not as warm as a real Twin with real power tubes. After all, it is still a transistor amp. Much more fun to hear and play in that peak power zone. Just pick the right Mac for the gig. Not too big or the soundman will never put you in the mix.


Brad
... and it's just like any other day that's ever been...
User avatar
SarnoMusicSolutions
Senior Member
 
Posts: 1070
Joined: Tue Jan 27, 2009 6:15 pm
Location: St. Louis, MO - USA

Re: McIntosh Power Guard Peak Limiter

Postby SarnoMusicSolutions » Tue Dec 08, 2009 10:35 pm

OK,

just listened to the '85 TLEO. Man I love that stuff. I hear a couple things different in the '85 compared to the '77. Mainly the guitar and pickup configuration is very different. I don't recall exactly but wasn't 'the '77 a Bean? And whatever pickups Jerry has on in that '77 tone has always sounded weird to me. The '85 is WAY Super II sounding, ultra clear mid and sweet and slicing high treble. With clipping, whatever frequencies are loudest will dominate in the generation of distortion artifacts or overtones. The '77 has a real phasey midrange and that seems to dominate and the sound of the clipped mac sounds a little mellow, and Jerry isn't getting all that dirty, but he is a little and you can hear it in the solos. That's where I think the actual dirt of "hair" or distortion is most audible. I'm hearing the bulk of all the playing having that real up front, punchy, sound that kind of bounces off the limiter, but just hitting it, rounding things off, but not so hard that it's dirty, but hard enough that it's being leveled off.

The '85 is just way extremely Dimarzio single coil slice. I agree that the '85 also sounds dirtier and more pushed, but I think the main factor is that the guitar/pickup tone itself is setting off a whole higher band of harmonic distortion since it's that high treble of the Dimarzio that dominates. That's the Jerry tone I grew up with.


Brad
... and it's just like any other day that's ever been...
User avatar
SarnoMusicSolutions
Senior Member
 
Posts: 1070
Joined: Tue Jan 27, 2009 6:15 pm
Location: St. Louis, MO - USA

Re: McIntosh Power Guard Peak Limiter

Postby mijknahs » Tue Dec 08, 2009 10:51 pm

The only thing it sounds like Stu is missing is a Cocobolo/Maple guitar.

Jim
User avatar
mijknahs
Senior Member
 
Posts: 1518
Joined: Fri Nov 13, 2009 8:51 pm
Location: Los Angeles, CA

Re: McIntosh Power Guard Peak Limiter

Postby mijknahs » Wed Dec 09, 2009 12:52 am

Brad,

How loud does your MC250 get when using only one side (50W)? Do you think it is as loud as a stock Twin Reverb (using the power tubes) or louder?

Another thing to consider is the slight breakup of the JBL E120s when they get pushed to *their* limit. Jerry was know to blow them more often than most of us ever will (I've never blown one in the 15 years I've been using them). I've seen Parish change a few out. A 50W Mac isn't going to breakup the JBLs like a 300W Mac will. Then there's the volume of the Twin preamp as well. It sounds totally different at 3 or 4 than it does at 7 or 8. (again -gotta check out that JGB 5/31/83 Rhapsody in Red opener. Talk about pushin it!)

Also, I think our definition of "hair" has been somewhat different. I interpreted it to mean a very slight breakup in his clean tone - what I hear in the low A chords of an '85 Deal or something like that. That real gutty tone. But you meant the smoothed out sparkle on the high end while still sounding "clean" (even in ''77).

I'm still not ready to accept the idea that every note he played was in Sentry Monitor mode but I am willing to try a 50W Mac out and see how it sounds.

Jim
User avatar
mijknahs
Senior Member
 
Posts: 1518
Joined: Fri Nov 13, 2009 8:51 pm
Location: Los Angeles, CA

Re: McIntosh Power Guard Peak Limiter

Postby Rusty the Scoob » Wed Dec 09, 2009 5:02 am

Awesome discussion!

Would it be possible to build an outboard limiter that emulates the Macs VI limiter? Seems like you could run something like that between the preamp and any totally clean poweramp (even a high-tech Class D or something) and get the right "hair" at whatever volume you want.
User avatar
Rusty the Scoob
Senior Member
 
Posts: 2315
Joined: Mon Mar 03, 2008 5:28 am
Location: Concord, MA

PreviousNext

Return to Grateful Dead Equipment Discussion

Who is online

Users browsing this forum: No registered users and 1 guest