Jerry's 90's Amp Rig Questions

Jerry's 90's Amp Rig Questions

Postby midnight » Sat Oct 17, 2009 5:18 pm

Hi everyone. Iv been trolling this forum for some time now. I must say this has got to be the best site Iv come across when it come to just about anything related to the GD. So I decided to join. Yay me...lol...

OK, so here are some questions I just can't seem to figure out regarding Jerry's 90's amp rig.

1. In Jerry's 90's rig there is a piece of gear under the foot pedals. It looks like an EQ. What is it?

2. What are all the other rack components the have blank face plates? There are several 2 space and one 1 space units. One of the 2 space units looks like it has 8 IN/OUT led's.

3. If Im correct in assuming that at this point in time Jerry was going straight to the house board, why then is the MC2300 in his rig?

4. In regards to the MC2300 and using 3 JBL E-120's......Im no pro audio whizz, but from what I understand it is better to overpower you speakers then to under power them. Heres what JBL has to say on the subject..."JBL recommends that, in general sound reinforcement situations, you use an amp that delivers equal to or up to double the IEC power rating of the loudspeaker, i.e., a speaker rated at 300 watts capacity needs a 300- to 600-watt amp. Contrary to popular belief, you're more likely to damage your speakers with an underpowered amp than with one that has too much power, so don't scrimp here!" (taken from Sweetwater.com). And also from Sam Mallery (taken from B&H)...A common misconception about speakers and amplifiers is how you can potentially damage the two. People often mistakenly believe that a speaker will be blown if you overpower it--- by plugging the speaker into an amplifier that produces a higher wattage than is that for which the speaker is rated. In actuality, the opposite is true. The danger lies in under-powering a speaker. If you plug a speaker into an amplifier that isn’t powerful enough for the rating of the speaker, you’re a lot more likely to destroy the speaker. This scenario is also bad news for the amplifier. The amplifier will have to work extra hard to keep up with the demands of the speaker with the higher rating. Plugging more speaker into an amplifier than the amplifier can handle shortens the amplifier’s life dramatically. The key is to buy an amplifier that is twice as powerful as the rating of the speaker. For example, if you have a pair of speakers rated at 50 Watts continuous at 8 ohms, you need to buy a two channel amplifier that produces 100 Watts per channel at 8 ohms. It’s also very important not to attach more speakers to the amplifier once the proper balance has been struck. If you have an amplifier that comfortably powers two speakers, and then you add one or two more speakers, the amplifier will be pushed too hard, and soon the speakers and the amplifier will be on their way to the trash.

So, Jerry was using 3 JBL E-120's at 2.6 ohms and a total of 900 watts...right?...But the MC2300 could only pump out 600 watts in bridged mono, and from what Iv been reading on this forum is that he used only one side of the MC2300 in stereo mode. Which would put the MC2300 at 300 watts. So he was pumping 300 watts into a 900 watt cab??? Was he going through a lot of speakers and amps with this setup???
midnight
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Re: Jerry's 90's Amp Rig Questions

Postby SarnoMusicSolutions » Sat Oct 17, 2009 6:06 pm

I think that it's best to understand why JBL would say that about under vs over powering speakers. I think the idea is that if you want to use the full potential of a speaker's power handling, it's better to have an amp that will be running clean and without distortion AT that power rating. An underpowered amp will distort before reaching that full power capacity of the speaker, and will likely send it more damaging square waves and distortion artifacts that actually can hurt the speaker at levels below its rated limits. This is due to the harsh nature of distortion. Speaker ratings are made based on clean signals, sine waves and other test pulses.

Word has it that Jerry, for most of the stretch, used only one half of the Mc2300 which is a 300 watt amp. If he had the 3 jbl's in parallel that would be about a 2.7 ohm load. That slight mismatch on the 2-ohm taps of the Mc2300 would bring the power output at the speaker cab to about 230 watts.

For many years Jerry used the K120 JBL's, those sweet alnicos. That was before he switched to the high power handling E120's that use the ceramic magnet and have a harder, crisper tone. But Jerry beat the crap out of the K120's with that Mac, he'd overdrive the Mac a bit a times, and really pummel the things. He did blow JBL's. The K120's were rated at 100 watts continuous power. So he had 300 watts of speaker and 225 watts driving them, and the amp would clip and, indeed you're right, the speakers blew. But I think it was all worth it to him for the tone that resulted. It's a rock and roll mentality to a large degree. Can you bang on your guitar and make a cool sound? That's generally the rule above all others. Theories and specifications are merely guidelines, but it seems that many cool rigs come from experimentation and the real test of playing on a loud stage. Eventually he did make that E120 switch, and I bet he blew far fewer, but he blew those too. I witnessed it.

And if you saw Jerry's Mc2300 and JBL's on stage, you were hearing the JBL's being mic'd. It wasn't until he removed the Mac and speakers that we were hearing a direct signal from the GT Trio tube preamp, if I'm not mistaken.

It all went downhill for me when the Mc2300 and JBL's left the stage. Never again did we hear the real Jerry tone with the Grateful Dead, IMHO. It was an interesting and sort of acoustic guitar sounding tone, but severely lacked the warmth, body, balls, dirt, grit, and overall juicyness that came with the real rig driving real JBL soundwaves thru the air. It lost it's 3rd dimension.

Brad
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Re: Jerry's 90's Amp Rig Questions

Postby midnight » Sat Oct 17, 2009 6:47 pm

Thanks Brad...So if I understand correctly He was powering a 900 watt cab (3 JBL E-120's) with a 230 watt output from the MC2300 because of the impedance mismatch...correct???

Any info on my other question?
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Re: Jerry's 90's Amp Rig Questions

Postby waldo041 » Sat Oct 17, 2009 8:48 pm

midnight wrote:1. In Jerry's 90's rig there is a piece of gear under the foot pedals. It looks like an EQ. What is it?

In Ear Mixer Dbx 933
Image


midnight wrote:2. What are all the other rack components the have blank face plates? There are several 2 space and one 1 space units. One of the 2 space units looks like it has 8 IN/OUT led's


mostly blank rack space units. the 2 space with the 8 in/outs With LED's is the "90's" Cutler Effects Switcher. the 70's and 80's version didn't have LED's.

midnight wrote:3. If Im correct in assuming that at this point in time Jerry was going straight to the house board, why then is the MC2300 in his rig?


he still was using the JBL's onstage in the JGB, so still used the MC2300 also. HUGE difference in GD tone Vs. JGB tone.


peace,
waldo
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Re: Jerry's 90's Amp Rig Questions

Postby midnight » Sat Oct 17, 2009 9:02 pm

Thanks Waldo, you rock!!!

I still can't believe Jerry was powering such a big cab (900watts) with only 230watts from the MC2300...Some live sound guys I know would be pulling their hair out over that...lol.
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Re: Jerry's 90's Amp Rig Questions

Postby waldo041 » Sat Oct 17, 2009 10:03 pm

midnight wrote:Thanks Waldo, you rock!!!

I still can't believe Jerry was powering such a big cab (900watts) with only 230watts from the MC2300...Some live sound guys I know would be pulling their hair out over that...lol.


the e-120 is 300 watts continuous program and 150 watts continuous sine wave. 150 watts is what it's rated for in this application, so it is in fact a 450 watt cab. the k-120's are 200 watts continuous program and 100 watts continuous sine wave for a 300 watt cab.

Brad, with the autoformer, isn't the mc2300 designed to deliver 300watts at max power into any ohm? and in fact that is a conservative rating as most mc's will perform higher then their rated output?

peace,
waldo
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Re: Jerry's 90's Amp Rig Questions

Postby midnight » Sat Oct 17, 2009 11:08 pm

Ah..ok, I see...Still underpowered, but not nearly as bad as I thought.
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Re: Jerry's 90's Amp Rig Questions

Postby jeffm725 » Sun Oct 18, 2009 6:46 am

OP asked about the MC2300 onstage during the 90's rig and whats the point. That is actually a good and loaded question, because I was cleaning out my basement the other day and came across one of those GD year calendars(2002) with a bunch of shots by Stephen Dorian Miner.There are 2 pics of the in- ear years that have no speakers on stage but a Mac 2300 still sitting at the bottom of the rig. Probably not being used obviously, but there nonetheless for whatever reason.

Couple of other interesting shots from the 90' in regards to Bobbys ever changing tastes.
a 91 show he has a Marshall head onstage (looks like a JCM 800 or 900, I am not a Marshall guy so I am not positive)

Then in a 93 shot The Marshall full head is gone but replaced by a Marshall unit in his rack.

I am going to grab the calendar and get the dates.........hold on :D
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Re: Jerry's 90's Amp Rig Questions

Postby jeffm725 » Sun Oct 18, 2009 6:54 am

OK dates:
9/18/94 Shoreline: Mac2300 on stage bottom of Jerrys rig, no speaker cabs anywhere
also bobby has gold Marshall rack unit in rack

Shoreline 1991: Bob with the Marshall JCM 800 (I think....)

Also Red Rocks 8/2/79 : Jer on Tiger...gotta be one of the earliest Tigers, right? is there a definitive first date for Tiger?
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Re: Jerry's 90's Amp Rig Questions

Postby SarnoMusicSolutions » Sun Oct 18, 2009 5:20 pm

waldo041 wrote:
Brad, with the autoformer, isn't the mc2300 designed to deliver 300watts at max power into any ohm? and in fact that is a conservative rating as most mc's will perform higher then their rated output?

peace,
waldo



No. You still have to match the speaker impedance to the correct output tap on the Mac's autoformer to get rated power. What's different here is that on a normal (non-autoformer) amp you can't get full power at various impedances, only at the lowest impedance allowed. The autoformer lets you use various speaker loads and get full power with any of them, but you still match the load to the correct amp output tap. If you connect an 8 ohm speaker to the 8 ohm taps, full power. If you connect a 2 ohm load to the 2 ohm tap, full power. On a normal amp, the lower the impedance load of the speaker, the more power you can utilize. An 8 ohm cab on a "normal" amp will not take full advantage of its available power if that amp can also drive 4 or 2 ohms.

But this is often confusing with the Mac's. The autoformer does NOT automatically deliver full power to any load. For example, if Jerry's 3-JBL cab was 2.7 ohms and they tied it to the 2 ohm tap on the Mac, then that mismatch, like any impedance mismatch, will reduce the available power to the speaker.

Rumor has it that Jerry actually did have a 4th JBL connected, but it was on its own cord and was on stage behind the drummers. I guess for the crew's enjoyment, or maybe so Parrish could keep a close ear on his rig in case something weird happened during the show. In that case, if there were 4 JBL's on the Mac, it would be the full 300 watts being delivered, but still only about 230 watts being delivered to the 3-JBL cab since a portion of that power was diverted to backstage.

Also, it's true about the power rating. The 2300 is fairly clean (.25% distortion) at 300 watts per channel, but peak power jumps quite a bit higher, maybe by 20% to 30% more for brief surges and transients. Somewhere I have some bench test results from a Mc250 and peak power was quite a bit more than the rated 55 or so. But still continuous power ratings are the better number to go by. Most amps will be able to pulse out brief amounts of power but can't sustain it.

I just looked more closely at the actual power graph of the Mc2300, and really it looks pretty clean at levels over 300 watts, more like 350 or so at the same .25% harmonic distortion thru the audio band. So yeah, these things are very conservatively rated.

This discussion on "underpowering" and how that would have the sound people pulling their hair out, well I wouldn't really go there with it. I think you may be reading too much into the idea of underpowering. If you take that theory even further, then a 1 watt amp driving a 3000 watt speaker cabinet would be frying speakers easily. This just isn't the case. For Jerry with his 230 watts or so into the 3 JBL's (450 continuous and 900 watts peak) isn't necessarily a recipe for disaster. In fact, the whole world of guitar amps is ALL about having an amplifier running out of power and overdriving while the speaker doesn't blow. This is the normal world of guitar tone. Even in Jerry's case, the slightly driven McIntosh is where a lot of tone and musicality happens. Again, the idea that JBL was trying to get across is that for cleanly driving PA speakers, you want plenty of power so that IF you drive the speakers at their full rated power that the amplifier power is clean and not distorted.

Brad
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Re: Jerry's 90's Amp Rig Questions

Postby midnight » Sun Oct 18, 2009 5:34 pm

Thanks Brad, :cool: that clears things up a lot for me.
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Re: Jerry's 90's Amp Rig Questions

Postby tigerstrat » Sun Oct 18, 2009 7:50 pm

jeffm725 wrote:OK dates:
9/18/94 Shoreline: Mac2300 on stage bottom of Jerrys rig, no speaker cabs anywhere
also bobby has gold Marshall rack unit in rack

Shoreline 1991: Bob with the Marshall JCM 800 (I think....)

Also Red Rocks 8/2/79 : Jer on Tiger...gotta be one of the earliest Tigers, right? is there a definitive first date for Tiger?


8/4/79 Oakland is the debut of Tiger. Red Rocks was 8/12-14, the very next shows.
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Re: Jerry's 90's Amp Rig Questions

Postby jeffm725 » Mon Oct 19, 2009 5:15 am

Hmmm So the calendar had red rocks mislabeled as 8/2/79...there are a couple other date mislabels as well. There is a full group shot listed as 12/31/79 that is so wrong for a ton of reasons, Most notably Bobby and Phil are both playing Modulus and they are in their standard 80's- 90's config (L-R) Phil, Bobby, Jerry, Brent. That final stage set happened in 81 IIRC. Does anyone know the first show where they essentially flip flopped Jer and Phil? (1980 still had Jer on the far left and Phil next to Brent)
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Re: Jerry's 90's Amp Rig Questions

Postby playingdead » Mon Oct 19, 2009 6:52 am

I believe they switched sides for the spring 82 tour, Duke was the first time I saw them that way, at any rate.
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Re: Jerry's 90's Amp Rig Questions

Postby astroman99 » Mon Oct 19, 2009 11:55 am

I think the stage swap was hampton, Va-- 1981, I have a tape, where they apologize to the audience, because they had't told the Lighting Director(Candace Brightman?), so the lights were screwy :?
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