Groove Tubes Trio preamp

[FEBBDAYBAND]

Brad,

I just skimmed back through all the replies - I can't find the 'first link of Brown Eyed Women'. Do you know who posted it or could you someone point it out? I'm curious to hear whether it's the same sound I was hearing. Thanks.

[playingdead]

Brad,

I just skimmed back through all the replies - I can't find the 'first link of Brown Eyed Women'. Do you know who posted it or could you someone point it out? I'm curious to hear whether it's the same sound I was hearing. Thanks.

http://www.playingdead.net/040494bew.mp3

[FEBBDAYBAND]

Thanks Playingdead... Sorry, I don't know how I missed that - it was sitting right there. I guess I thought he meant something posted much earlier... anyway, I can agree about the sound of those studio recording outtakes. It's pretty weak and lifeless. Though, to me, they were usually pretty lifeless in the studio with the acception of "In The Dark" - it was the curse of the Dead - in house anyway. Most years, I just don't know how he could have 'that' sound in the earphones and think to himself... "yeah, that's a keeper"

Anyway, I spent the day conducting an electronic experiment and listening to as many archive clips (from various '94 shows) as I could find. Fun homework assignment. I did hear a number of tunes that have that strong, distinct (I'll call it "tinkly") acoustic tone. So, I've come to a number of different conclusions about this whole topic:

1) There was definitely some kind of sonic blending and tone shaping happening - either on Jerry's guitar or at his rack or at the board. It's such a dramatic change (concert to concert/song to song). These shows don't all sound the same. Some do, but most don't - some have a strong tinkly acoustic-simulation vibe and others just sound like a thin electric direct sound while some are closer to that old '70's-'80's tone. My best guess at this point is that there was either a splitter in the rack (like the Rane SM 26 or maybe one of those mysterious shiny custom paneled rack units!?!?) which allowed a buffered signal from all/any of his pickups to be independantly processed and/or blended and sent direct to a board. The funny thing is it doesn't sound like any mic preamp or direct box I've ever heard. I took enough college credits to have been a music major - including studio recording/engineering and entertainment law.

I happen to own a GrooveTube 'Brick' (all tube preamp/direct box) that definitely fattens up the tone of any guitar (usually used for bass). It sounds nothing like Garcia's tone. I also have a high quality stereo mic preamp/eq/compressor rack unit that sounds like most of the great studio recording consoles of the 60's and 70's. It's got a different sound entirely. Warm and clean. It's the sound you expect from a vintage board. I've also got a Mackie mixer. Crisp 'straight wire' gain. We all know the sound of this preamp. It's on half the pop/rock recordings of the 80's (mixed on Mackie boards direct to ADAT). That's definitely not it.

2) The tinkly acoustic sound is also definitely not from a direct out of a GT Trio either. I own two of them and I tried them both "direct" to all three preamp types. It sounds nothing like that tone. Each of these Trios is from a different era of manufacturing (at least ten years apart) and while they have subtle differences in tone (sent through an amp), the direct out (from both the "effects send" and the "line out") is strong and clean. If you crank up the gain a bit you get a hot overdriven signal just like you'd expect.

I tested this with a guitar with DiMarzio Super II's. The closest I got to Jerry's sound was using a BOSS GE-7 Eq pedal pumped straight into my acoustic amp (Fender Acoustasonic SFX II). It was like artificially creating a weak timbre though since I had to boost highs and pull out lows and mids on the Eq and mess with the "feedback notch" control on the amp. It was close, but not really the same thing - probably helps to have 10,000 watts of Crest amps breathing through a Meyersound PA.

3) Also, I've noticed that when the band was hot and Jerry was "on" (both vocally and musically) some of these shows sound very different from the nights surrounding them. These hot nights are some of my all time favorite shows and that acoustic sound is definitely part of it. I admit it's partly because it takes me back to being there. I also like the effect it has on the rest of the band - it turned them into a psychadelic jug band with the best PA sound system on the planet (those custom Meyersound drivers)!

It all depended on strong vocals to bring the band alive and Jerry cranking up the volume a little to stand out while hitting all the right notes. The best quality audio example I found last night on archive.org was the soundboard recording from Nassau Coliseum on 3-27-94. It just had that energy and the recording is much better than most. There are quite a few tunes that shine here - mostly from strong vocals and tight guitar lines. However, none of the tunes from my "Spring Break '94" CD are actually from this night.

I did find some of the songs from my CD on archive.org but the recording quality was really poor. My CD was a soundboard/audience mix at the board - it's fantastic - lots of bass with loud, clear vocals. It got me thinking (and reading the comment sections) that this tone sounded a lot better in a soundboard mix than from the audience's perspective. In other words, better on tape than if you were even at the venue! If you listen to some of these clips I can see what you mean that it just seems too thin from the audience. But, on my soundboard/aud mix Jerry's tone was loud clear and warm AND 'tinkly acoustic'.

Here's the dates I found from my CD. Whoever put my CD together had access to the soundboard/audience mix that the FOH engineer was making, in other words, not just a soundboard but a bootlegged mix from the tour:

Mama Tried - Richfield Coliseum OH 3/20/94 (good soundboard on archive.org)
Big River - Richfield Coliseum OH 3/20/94 (good soundboard)
Peggy-O - Richfield Coliseum OH 3/21/94 (great solos -terrible sound)
Me & My Uncle - Nassau Coliseum NY 3/24/94 (great energy -terrible sound)
Maggie's Farm - Nassau Colisum NY 3/24/94 (all time fav fun -terrible sound)
Black Throated Wind - The Omni GA 4/1/94 (good soundboard - nice building solo)

[jdsmodulus]

Very nice sumation of what your expeirment yeilded. I was at those shows and I agree that there is something more at work here then just the rack and guitar. Jerry also had 2 Boss EQs on all the time. His MIDI setup might be a factor, he had it wired seperatly but did use a Rane mixer and he had a HUGE library of sounds, he also used that Digitech Whammy/wah pedal in 94 so maybe its something there. I really am leaning to his MIDI rig, I am not sure but to me it seems he could be running a MIDI Timbre the whole show and then louder at some points than others. I saw alot of shows from "the rail" and during 94 he was constantly changing settings on the fly. Most notable the EB pedals and what seemed to be the MIDI. plus with the talk back mics, they all did kind of a "dance" during the show.

[FEBBDAYBAND]

JDS: I was just thinking about what you said "Jerry also had 2 Boss EQs on all the time"...

While most of his setup was based on loops (so that all his devices weren't strung together creating lots of noise), it's also true that every stage of his signal was kept boosted and buffered as hot as possible - something I don't do. His guitar buffer changes the impedence and boosts that weak guitar signal right up to line level before it ever hits most of is pedals and rack effects. This could mean that the sound of his buffer hitting either those eq pedal loops, the midi stuff or even the GT Trio into the rest of the rack or even the board could sound entirely different than my guitar straight through. I think to find out for sure we'd have to ask someone who owns one of those preamp buffers to try it direct out of any/all of these devices and into a board (or a few different types of boards)!?

[SarnoMusicSolutions]

A couple of clarifications if I may.

The buffer never boosts the guitar signal up to line level. In fact, the reason that it's called a unity gain buffer is that it's unity gain, or in other words NO gain. It keeps the signal voltage level the same, instrument level, NOT boosted up to line level. It's the impedance that is lowered, and that means the signal after the buffer can drive miles of wire and encounter lots of cable capacitance and not even blink (or suffer tone change). Essentially the buffer doesn't change the tone of the pickup, but actually captures it right out of the gate and preserves it the whole way thru. It's when you don't have a buffer that the pickup's tone changes as result from the changing conditions of cables and loads and stuff.

Regarding the two Boss EQ pedals being on all the time, they were actually each paired up with a corresponding overdrive pedal for tone shaping, but they only were part of the signal chain when either overdrive pedal was selected and made active. Otherwise, the pedals, all the pedals, remained completely bypassed and out of the path. And most of the time, Jerry's guitar had the whole loop bypassed, so really it was just the guitar to the preamp and the pedal effects weren't part of the sound at all. Only for certain efx or solos did he kick in the effects pedal loop.


Brad

[FEBBDAYBAND]

Brad: Thanks for the info. I just re-read the description of the Cutler unity-gain buffer on the 'Tiger page'. I had always thought the Cutler buffer had some kind of on-board boost to drive the signal from the guitar. I thought that was the whole point of it. I see now the point was just to keep the impedences low and get full volume to the pedals before the guitar volume knob. Clever idea. I think the word "preamp" printed on that page is what threw me. It's not a preamp - it's just a buffer. Apparently, I've got to stop believing what I read - that's twice so far the printed word has led me astray... first Mike Christian's piezo pickup and now the Cutler buffer.

I actually own a unity gain buffer of another sort - the VHT Valvulator tube buffer/splitter/power supply (more or less the same thing only out-board instead of on-board and with a tube). It lives on my pedalboard as the second device I jack into. I've read reviews from people who love it and some who hate it (as with anything). I've read claims it's an unreliable unit (mine's lasted 15 years so far & not one problem) and claims that it adds too much artificial warmth to the tone. I love both the sound it helps create and the fact that it does just what it says and more. Sometimes I use the split signal to drive a stereo rig or just separate amps in my living room. It has a very, very slight warming effect (maybe 3% - barely perceptible to my ears). I love that too - I play rock and blues so the warming is welcome in my book.

Anyway, back to the tone quandry... I've tried all the connections I can think of and nothing sounds remotely like Jerry's tone. I totally agree that a buffer would only add more clarity and less noise to whatever it was jacked into. I'm out of ideas unless Jerry's Fender Silverface preamp was unique? Does your SMS Classic preamp have a noticeably different sound than my Trios coming from it's direct out? There's just no way a Trio would put out that weak or tinkly sounding a signal. Mine are way, way more balanced - warm and clear on the clean channel - with plenty of tube grit if you crank the gain.

I'm starting to lean toward the thought that the answer's in one of those mysterious blank panels...

[SarnoMusicSolutions]

Well there is some real confusion out there when people refer to the buffers as preamps. In fact, one of CAE's buffers does offer "preamp" gain. And Jerry did have some guitars that were equipped with the "Blaster" which is a booster/preamp and not technically a buffer.

The GT Trio is fairly similar to an original Fender preamp circuit. There are a few things that make the Trio a bit thinner, but not radically different. The SMS Classic is nearly exactly a Twin Reverb circuit, extremely close to what Jerry would have had going with his Twin pre (to the best of our knowledge). I think the thin, splatty sound we hear from some of Jer's Trio shows has everything to do with going direct and not thru a speaker. And I understand that at some point they actually did begin to send the Trio to a speaker off stage. I don't for sure on that at all, but it may explain why some Trio shows sound different than others. And maybe they messed with the tone at the board trying to make sense out of the direct sound.

Brad

[John K]

So I've just finished tweaking my GT Trio... the stock sound lacked low bass & upper mids, still passed signal with all tone knobs at 0, and was too clean... inside most caps were either WIMA plastic rectangles or brown silver micas... here's what I did to get it to "Fender" specs:

change the cathode bias resistor and bypass cap on the first tube stage... old components were classic Marshall values 2.7k & .68uF

move the signal line feeding the tone stack strait to the 1st tube stage plate (there is a coupling cap feeding the "clean" & "mean" channels from the same tube stage... unnecessary, the tone stack doubles as coupling cap, left the feed to the "mean" channel as is)

bypassed a couple of high-pass RC arrays

bypassed an "optional" resistor between the treble pot and gain pot

short 2 lugs of the mid tone control to make it a variable resistor instead of voltage divider

replaced the treble tone pot... was 200k (actually reading 196k after tolerance factored in) with a 250k log pot

changed & upgraded the coupling cap from the 2nd tube stage... was .047 (twin 1st channel standard) and changed to .02 (twin reverb channel standard)... thins the bass back down but after the 1st 2 tube stages...

I had a couple of Tungsram ECC83's lying around, so put those in...

After this, it was still too clean... I could get some growl now by overdriving the "3rd" cathode follower mixer stage, but I wasn't digging that sound, so I put an E-H LPB1 in front of the whole thing and, voila! There was the tone I love. I also tried a BBE Boosta Grande, but that wasn't happening for me. I might try building a booster circuit around a Burr-Brown opamp with an 18v Vcc, but for now, $40 is a nice price for the LPB. Its an ultra-simple 1 transistor circuit... kind of low impedance input, but that doesn't affect my tone with the low-impedance buffered output of most of my guitars. And supposedly it was Jimi Hendrix's standard tool in front of all of his Marshalls (the original version back in the 60s was a little box barely bigger than a 9v battery that had a jack and a plug and would plug into your amp input)... FWIW

Happy circuit bending!
-John

[John K]

Also, in regards to the other discussion on this thread, I'm fairly certain that Jerry was experimenting with a piezo bridge pickup in the 90s... I think it started showing up the same time they changed to in-ear monitors... some photos I thought I saw a fourth cable coming off the guitar, but this could have been accomplished with a stereo output jack, as well, without adding an extra hole. Several companies make these pickups now (RMC, Graphtek, Fishman) but back then I think is was pretty much Christian that made those pickups (Stew-Mac still sells a stereo-switching 1/4" jack that references this brand).

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

[keirweir]

I have the Fishman powerbridge in my strat and it sure sounds a lot like Jer from 93 til the end . I run the piezo (seperate input jack) to the PA or an accoustic amp my buddy lets me borrow. When I run the peizo at say 6-7 and the guitar full on it sure nailes that Bolt tone. I originally had the stero cable coming out of one jack but I felt the guitar lost clarity of tone so I switched it out to an additional jack.

[waldo041]

i have held both rosebud and bolt and NEITHER of them have a piezo pickup in them. that said, there is a piezo wiring schematic labeled "new bolt schem" that shows a bartollini preamp with both magnetic and piezo wiring i have but do not have the permission to post. the schem was drawn by gary brawer and it was recovered at cripes and recovered from the shed after his death. the founder of graphtech DID make jerry a primitive set of piezo saddles, but they were not seen on any of the guitars i have have seen. brawer also stated that he never installed a piezo in any of them, and i have never seen any photo showing anything otherwise. that sound comes from an impedance mismatch from the trio to the board once they went to in-ears. the same timeframe, and guitars sound like vintage jerry in JGB with Budman(jer's mc2300) and JBL's.

peace,
waldo

[tcsned]

lol - maybe Irsay will let you look at Tiger . . . I guess we've covered that ground before

I use one of those graph-tec piezo/synth pickups - the piezo sounds ok - kind of like the crappy old thin body Yamaha acoustic/electric I played some in the 80s but passable if no acoustic is available for a tune or two. Pretty stable as a synth pickup.

[keirweir]

i have held both rosebud and bolt and NEITHER of them have a piezo pickup in them. that said, there is a piezo wiring schematic labeled "new bolt schem" that shows a bartollini preamp with both magnetic and piezo wiring i have but do not have the permission to post. the schem was drawn by gary brawer and it was recovered at cripes and recovered from the shed after his death. the founder of graphtech DID make jerry a primitive set of piezo saddles, but they were not seen on any of the guitars i have have seen. brawer also stated that he never installed a piezo in any of them, and i have never seen any photo showing anything otherwise. that sound comes from an impedance mismatch from the trio to the board once they went to in-ears. the same timeframe, and guitars sound like vintage jerry in JGB with Budman(jer's mc2300) and JBL's.

peace,
waldo

Thats mind blowing to me Waldo. So that Oregon 93 show had no piezo... Wow...

[John K]

i have held both rosebud and bolt and NEITHER of them have a piezo pickup in them. that said, there is a piezo wiring schematic labeled "new bolt schem" that shows a bartollini preamp with both magnetic and piezo wiring i have but do not have the permission to post. the schem was drawn by gary brawer and it was recovered at cripes and recovered from the shed after his death. the founder of graphtech DID make jerry a primitive set of piezo saddles, but they were not seen on any of the guitars i have have seen. brawer also stated that he never installed a piezo in any of them, and i have never seen any photo showing anything otherwise. that sound comes from an impedance mismatch from the trio to the board once they went to in-ears. the same timeframe, and guitars sound like vintage jerry in JGB with Budman(jer's mc2300) and JBL's.

peace,
waldo

When I was seeing Dead shows in the "back in the day," I was already *very* familiar with the piezo pickup sound (and actually the other guitar player in my band at the time had a Christian pup installed on his SG,) and instantly recognized it when Jerry started using it here and there, experimentally, the same way he brought in the synth sounds. With all due respect to your "hands on" experience, I know piezo sound when I hear it, it was *not* impedance mismatch (which, btw, only matters when putting high-z signals into low-z inputs, and usually sounds dull, dark, lacking in high frequencies. The Trio final output stage is a cathode follower: low-z) Phil was also tinkering with piezo bridge pups around that time. I also got to play another Cripe guitar, same design as "Bolt," and it had custom piezo bridge saddles on it. Also, I stopped hearing that sound later on... maybe when Jerry brought back the Twins with an off-stage speaker... and perhaps had the piezo pups removed in favor of standard brass bridge saddles of his old bridge.