Wednesday, 23 April 2014

Jerry Garcia Tiger Preamp

Request. Info about Jerry's original guitar with inbuilt electronics

Tiger was Jerry Garcia's main guitar from 1979 to 1989. It was built by Sonoma County luthier Doug Irwin. The Tiger is named after the tiger inlaid on the preamp cover located on the guitar's top, just behind the tailpiece.

The electronics of Garcia's Irwin guitars are unique, and feature an onboard preamp and effects loop. Much like a Stratocaster, the three pickups are selected with a five-way switch. Signal from the pickups passes through the tone controls, followed by an op-amp based buffer preamp, or Unity Gain Buffer, which is designed to prevent signal loss due to capacitance when long cables are used.




21 comments:

  1. Mark, do you think a TL071 (or maybe even TL051) would work appropriately in this or would it be worth it to chase down some LF356n?

    I checked the data sheets, and I'm comparing stuff between the LF356n and the TL0*1 chips and I'm all nodding my head when it occurred to me that I had no idea what the hell I was looking at.

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  2. To be polite, since I'm asking for help:

    LF356
    1 Number of Channels (#)
    10 Total Supply Voltage (Min) (+5V=5, +/-5V=10)
    36 Total Supply Voltage (Max) (+5V=5, +/-5V=10)
    5 Iq per channel (Max) (mA)
    12 Slew Rate (Typ) (V/us)
    10 Vos (Offset Voltage @ 25C) (Max) (mV)
    5 Offset Drift (Typ) (uV/C)
    80 CMRR (Min) (dB)
    5 GBW (Typ) (MHz)
    8000 IIB (Max) (pA)
    12 Vn at 1kHz (Typ) (nV/rtHz)
    Military Rating
    0 to 70 Operating Temperature Range (C)


    TL071
    1 Number of Channels (#)
    7 Total Supply Voltage (Min) (+5V=5, +/-5V=10)
    36 Total Supply Voltage (Max) (+5V=5, +/-5V=10)
    3 GBW (Typ) (MHz)
    13 Slew Rate (Typ) (V/us)
    70 CMRR (Min) (dB)
    18 Vn at 1kHz (Typ) (nV/rtHz)
    10 Vos (Offset Voltage @ 25C) (Max) (mV)
    200 IIB (Max) (pA)
    2.5 Iq per channel (Max) (mA)
    18 Offset Drift (Typ) (uV/C)
    Military Rating
    -40 to 85 Operating Temperature Range (C)


    TL051
    1 Number of Channels (#)
    10 Total Supply Voltage (Min) (+5V=5, +/-5V=10)
    30 Total Supply Voltage (Max) (+5V=5, +/-5V=10)
    3.1 GBW (Typ) (MHz)
    20 Slew Rate (Typ) (V/us)
    75 CMRR (Min) (dB)
    18 Vn at 1kHz (Typ) (nV/rtHz)
    1.5 Vos (Offset Voltage @ 25C) (Max) (mV)
    200 IIB (Max) (pA)
    3.2 Iq per channel (Max) (mA)
    8 Offset Drift (Typ) (uV/C)
    Catalog Rating
    0 to 70 Operating Temperature Range (C)

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    Replies
    1. Man... that was a lot more nicely formatted before I hit "publish" :/

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    2. Socket and try it out. Since it is basically just a buffer, i don't think you'll hear much of a difference between any single opamps.
      +m

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  3. Oh, I always socket, and I'm definitely going to to give this a try as soon as I have a project guitar nearly completed (got several close). I just wanted to make sure I was "in the ballpark" on what I was going to test it out with. I get confused... an opamp is an opamp, but then there is this extra stuff like BiFET, JFET, Slew Rate, DiFET, Single Supply, Rail to Rail, FuKET, and shit that makes me start second-guessing myself.

    Thanks! :)

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    Replies
    1. I think the TL071 or even the LF741 or whatever will be fine. At unity gain I don't think I could tell the difference between any of them, although I did order some LF356's, just because my OCD kicked in :o) Although the original builder probably only used them because he had a thousand he got cheap on eBay

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    2. I have the same affliction. I have so many transistors and ICs that I will probably never use again because I need them for this or that pedal and I know if I buy just what I need then I'll blow one up or find out one is bad or find out the next 10 pedals I want to build need the same thing, etc. so I end up ordering way more than I need. Gah!

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    3. I know what you mean, the only time I ever order 1 or 2 of something is when they're really expensive like the AD797, everything else I get at least 10. I definitely think I've got more than enough opamps to last me for the rest of my life, and possibly the next few generations of my family :o)

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    4. Ebay didn't exist when Doug Irwin built the Tiger. Back then, the LF356 was considered the new, hip thing.

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  4. Tag it. This one's a pretty decent buffer.

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    Replies
    1. Excellent, thanks for verifying Ross

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  5. I built this and it sounds nice. The original Tiger buffer has oversized Caps. The .022u are 400v and the 2.2u is 250v. Is there a sonic advantage to using the bigger caps? The size disadvantage is obvious, but I wondered if there could be a benefit beyond the Mojo factor.

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    1. I built one with the high voltage caps and one with lower voltage caps. I couldn't hear any difference whatsoever. My chips seem to be a little noisy, though: I got some hiss. I tried them both in my guitar and got a VERY Garcia-like tone, very sparkly. I went back to the AMZ Super Buffer because of the hiss and because it was a little more Garcia than I wanted.

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    2. Hi Jeremy, I too have compared both versions now, and there is not a noticeable difference. I was just reading a thread about "mojo" caps in guitars, and there was some logic in the idea that the larger, high voltage caps may stay true to specs and not drift off value for longer.

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  6. I've heard that, too. That 2µ2 electro will drift eventually, so that's the one to replace with a poly cap. Of course, at that value the poly cap will automatically double the size of the layout. It might be good to consider whether it would be better to replace the electro cap in 25 or so years in order to have a smaller layout.

    I'm sure that's why John Cutler used the poly cap when he built the circuit. When you're dealing with a player who changes his pickups every couple years because he claims to be able to hear the magnets getting weaker, you want to minimize anything drifting out of spec.

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  7. Hi Jeremy, all good points. Most of the guys involved in the GD signal path seemed to have "super sonic" ears! It must have been something in the water-or Kool-aid. Anyway I took another look at the layout here and it looks like you could put the big poly 2.2u along the top row where the positive side of the electrolytic cap is positioned, and just jog the other leg over a row next to the cut to where the negative side connection is. The pitch of the 400v WIMA .022u's should fit where the low voltage poly caps are, just need to bend 1 leg of the input cap under its body for 1 row. When my next parts arrive I'll build it and post again

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  8. I built and installed this circuit in a 1978 Fender Musicmaster guitar. I feeds directly to an onboard effects loop which I also installed. The owner uses 7-9 pedals and it works wonderfully.

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  9. Is this something that is only to put in a guitar?
    Or will it be okay in an enclosure too?

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  10. Thank you!I had thought it would,but figured I'd double check to be sure.Still pretty new to all this.

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  11. Is there a way to turn this into a boosted buffer? Maybe turn one of the grounds into a pot to control the volume? I've been tinkering with it, but haven't come up with a good solution yet... any ideas?

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