jerry amp

Postby tigerstrat » Tue May 23, 2006 2:53 pm

aiko wrote:Jerry, used mesa boogies in the studio only.....everything live began with a twin blackface or silverface,.....and then went through the mac and the rest of the jerryizing machine!


Simply not true. I'll just re-post this info FYI; this is in reference to Jerry's LIVE gear:

"3/23/75(possibly earlier) to 10/3/76: Mark I (or 'Super 60') combo preamp-only out to the usual (by this time) MC2300 power amp(s)> JBL K-120 speakers, usually in several 2x12's. At the July 76 Orpheum run he is actually using an MC3500 tube power amp.

Feb+March 1980(JGB only)
: Mark IIA head, again preamp-only out to an MC2300> 4x12 w/ JBL E-120 speakers"

There's lots of pics around to back me up
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Postby acidrain30005 » Thu Nov 16, 2006 5:24 pm

I read in a guitar magazine that Jerry's favorite amp was a Fender Twin Rverb and that would help you get a good Jerry tone.
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Postby Crazy 9.5 Fingers » Thu Nov 16, 2006 6:03 pm

As a player who has played the Twin and the Boogie, together which sounds quite nice, I can say that the Twin will probably give you a better shot at the classic Jerry sound which in itself is a very large subject. I think a lot of Jerry's tone has more to do with his fingers, the guitars, and their setups. Get a Strat, use 10's, set it up high, and off you go.
There are only two mantras. Yum and yuk. Mine's yum.
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Postby mutant_dan » Fri Nov 17, 2006 7:57 am

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Postby zambiland » Fri Nov 24, 2006 12:21 pm

Jerry did use a Boogie live very briefly in the mid 70s, I saw it a couple of times. I used to have a poster that showed Jerry and Bob both with Boogies.

Check out Blair Jackson's book, Grateful Dead Gear, it will let you know all about things like this!

Edwin
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Postby tigerstrat » Fri Nov 24, 2006 1:02 pm

18 months or more. The earliest photo I've seen w/ it was 3/23/75, but I theorize he could have started using it for many many Legion shows as much as six months earlier. Then on the other end there's a photo of 10/3/76 Cobo Arena that shows Jer & Bob with the matching Boogie stacks which had been seen all year to that point- and the next show is Day On The Green 10/9/76 which can thusly be pinpointed as the first appearance of the dual Twin Reverb chassis housed in one Twin combo cab, his main preamp rig for the next 16 years or so... Except for the legendary Winter '80 JGB tour with the Mark IIA.

Hope my book didnt get sent to the wrong address...

That you, EH?

eeeeee wrote:Jerry did use a Boogie live very briefly in the mid 70s, I saw it a couple of times. I used to have a poster that showed Jerry and Bob both with Boogies.

Check out Blair Jackson's book, Grateful Dead Gear, it will let you know all about things like this!

Edwin
"There, in huge black letters, was 'The Grateful Dead'. It just... cancelled my mind out."-Garcia
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Postby DreamNightWind » Thu Jan 18, 2007 4:12 am

Greetings, I just found this forum today, thanks to a gratefuljams post by tigerstrat.

I'm wondering why Jerry used only the preamp portion of the Twin Reverbs?

I've been running my rig for years using all of the twin (including power tubes), then a custom load box converts the speaker out signal to line level, which I send to a digi fx unit and the stereo out of that goes to a solid state Crest Audio amp. It sounds pretty good but I'm always looking for improvement.

Should I be having my twin reverb modded to use a preamp out? I would think using the power tubes would be a good thing, but obviously Jerry didn't think so. Anyone know why he did this?

Also I want to say that I've been reading a number of posts on here the last couple of hours, and I'm really grateful this place exists.

Later,

Will
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Postby strumminsix » Thu Jan 18, 2007 6:39 am

The reason he only used the preamp as I understand it was to utilize a seperate higher quality (Mac) poweramp and push multiple speakers that the Twin was not able to do cleanly.

Also keep in mind poweramp distortion...
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Postby DreamNightWind » Thu Jan 18, 2007 7:10 am

"The reason he only used the preamp as I understand it was to utilize a seperate higher quality (Mac) poweramp and push multiple speakers that the Twin was not able to do cleanly.

Also keep in mind poweramp distortion..."

True, that was the main reason (clean and loud). But you can do that whether or not you use the twin's poweramp if you take your signal off of the speaker out. You setup your distortion or lack thereof using your guitar level and the twin's volume knob, then adjust the solid state amp for volume so if you want to play clean at high volumes you can, or you can play dirty at low volumes. I'm pretty sure Jerry and his techs knew they could do this if they wanted (then again maybe not, or maybe there's a good reason not to run a rig this way), so I'm thinking there must have been some other reason they only used the twin's preamp section.

On the modded twins, does the preamp out come before or after the reverb? I know this should probably be obvious to me but I don't know much about amps...

Did Jerry think the power tubes were hurting rather than helping his sound?
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Postby strumminsix » Thu Jan 18, 2007 8:12 am

I think you are missing a few concepts from your equation:

- Ohms and the OT --> how low could you run the Twin's ohms without frying the OT? Jerry had a lot of speakers and different configurations and IIRC the OT on the Twin expected 8 ohms.

- Full volume on the guitar sounds great but can add to the equation to overdriving the poweramp. Depending on the setup of the gain stages it is very possible to drive duals into a preamp at full guitar volume and not begin to clip the preamp BUT that high signal level could clip the poweramp.

- Direct boxes that convert a speaker level signal to a line level signal are not horribly reliable from what I hear and I'm not quite certain they were around then.

Overall he travelled with a Black and Silverface taken out of the combo and combined into a box. Seems logical that when upgrading the amp, taking it out of its original enclosure and preparing it for using an external poweramp they'd remove that circuitry. Keep in mind that it would require some sort of "dummy load" to ensure the amp won't fry when not having speakers connected.
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Postby DreamNightWind » Thu Jan 18, 2007 9:28 am

Hey, thanks for wading through this stuff. Some comments:

"- Ohms and the OT --> how low could you run the Twin's ohms without frying the OT? Jerry had a lot of speakers and different configurations and IIRC the OT on the Twin expected 8 ohms."

The Twin expects to run at 4 ohms. With a direct box/power brake kind of thing (mine converts speaker to line level, switchable 4/8 ohms, provides a dummy load to the amp, and has an output level pot) that's the load the Twin sees.

"- Full volume on the guitar sounds great but can add to the equation to overdriving the poweramp. Depending on the setup of the gain stages it is very possible to drive duals into a preamp at full guitar volume and not begin to clip the preamp BUT that high signal level could clip the poweramp."

Yes, I see your point here, if I overdrive the preamp I'm also overdriving the Twin's power amp, with no independent control over to what degree the power amp will clip (I'd have to turn down the preamp input levels to make the Twin's power amp clip less). That's not so bad though, just not perfect.

Did Jerry generally run his Twin preamp clean or did he crank it? Probably it depended on the context, I don't know though, maybe you do. If he wanted to overdrive the preamp for a particular sound that it gave him, he could do so without also adding clipping from the Twin's power amp (since he wasn't using it).

On the other hand, he didn't have any power tubes, and I've always thought of having power tubes as a good thing. That's partly why I opened this issue was to see what people think of that, since it's entirely possible to play loud and clean if the power tubes are used not to drive speakers but to add tone to a signal that eventually goes to a solid state power amp. Is that squishy tube amp feeling because I'm using the power tubes instead of just the preamp?

"- Direct boxes that convert a speaker level signal to a line level signal are not horribly reliable from what I hear and I'm not quite certain they were around then."

This could also be part of it, I don't know. Mine is pretty good, although there is some rare (very rare) thing that happens when I'm playing at high volume where I'll get an odd feedback that I haven't been able to figure out, and it may be related to "the box".

I was just reading the preamp out mod description on Dozin's site. It says you lose the vibrato, what about the reverb? It looks to me like the reverb is still in there, is that true? If so, did Jerry have one of those "dwell" pots so he could crank the preamp without overdriving the reverb? So many questions...
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Postby strumminsix » Thu Jan 18, 2007 9:45 am

RE: Poweramp tubes

This is a classic debate. For my tastes which is mostly clean and only a bit of dirt occasionally the preamp tubes are what adds most to my tone.

However, for more overdriven players they are into poweramp tubes clipping.

Now consider the trifecta of clipping: pre, power and speaker.

Tubes that add rich harmonics and bite are ELs. The 6s really seem to carry more transparent tonal qualities but still have the tube feel.

Let's keep thinking of whys.....
Solid state poweramps are more reliable
Solid state poweramps are less sensitive to temp changes
Solid state poweramps require less maintenance
Solid state poweramps require no tubes
External poweramps can be swapped easily in case of failure


My ultimate guess is that as Jerry wanted different speaker configurations and louder stage sound he took the chasis out and started using a Mac.
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Postby strumminsix » Thu Jan 18, 2007 1:04 pm

Just read on another GD site that somebody believes that using the Mac poweramp allowed more dynamics to signal and tones.

Tubes have a natural compression to them maybe jerry wanted to eliminate that from his rig?
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Postby waldo041 » Thu Jan 18, 2007 1:10 pm

DreamNightWind wrote:I was just reading the preamp out mod description on Dozin's site. It says you lose the vibrato, what about the reverb? It looks to me like the reverb is still in there, is that true? If so, did Jerry have one of those "dwell" pots so he could crank the preamp without overdriving the reverb? So many questions...


NO dwell pot! jerry's stage twins were NOT master volume twin reverbs like the one dozin used for his tutorial. the reverb AND vibrato BOTH are functional with the preamp out mod if done like jerry had it. DOZIN's site Preamp out MOD, is correct for 1 of the 2 preamp taps jerry had. Dozin also used the vibrato jack out the front. disengaging it, that is why he says it is unuseable. THAT IS NOT NEEDED. Jerry's preamp out's were ADDED to the back of the amp. NOT the front as dozin shows. Jerry also Used the Vibrato channel for the input of the preamp.

the mac 2300 was used for it's POWER and DURABILITY and RELIABILITY.

for the most part i believe jerry ran a clean preamp, which when ran thru the mac stayed clean. any overdrive he had came from his effects.

peace,
waldo
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Postby DreamNightWind » Thu Jan 18, 2007 2:15 pm

Interesting. The reverb was functional, but did Jerry use it, or just the rack reverb?

If he ran his preamp at "clean" levels (this sounds right to me, though I don't know), it weakens the argument that says the reason he didn't use power tubes was to be able to drive the preamp hard without introducing serious clipping in the Twin's power amp.

Maybe there was something to the claim strumminsix relayed about not introducing compression from the power tubes so as to preserve dynamics.

I haven't seen or heard the classic debate of just preamp or preamp into power tubes that he mentions, unfortunately. What are the basic pros and cons to the preamp-only approach? Has this been fleshed out on this forum before?

I'm guessing the power tubes might also take away crispness from the attack side of a note? I don't know since I haven't played the preamp-out setup.
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