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Thread: Anybody have a schematic the JG Tiger Unity Gain Buffer

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    Anybody have a schematic the JG Tiger Unity Gain Buffer

    This device seems to be a giant secret. Can't figure out why.

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    Senior Member HTH's Avatar
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    Quote Originally Posted by bdhact1 View Post
    This device seems to be a giant secret. Can't figure out why.
    what does it use as the buffer? - opamps, BJTs? mosfets?

    I would have a look at Jack Orman's website (AMZ) and read his page on buffers. I'm sure you could build something every bit as good as any commercially available buffer for under $10.00

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    HTH - Heavier Than Hell

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    From what I've seen from pictures, It uses a single opamp, 3 1m resistors, 2 100k resistors, 2 .022 caps, and 1 2.2 cap. How they are all connected together is the great mystery. If I can get a schematic than I would know how they all work as a unit.

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    My guess is this: two of the 1Meg resistors are used to set the gain. The 100k resistors are used to reference the positive input to 1/2 the supply voltage. one of the 22 nf caps is at the input, and the other bypasses the "lower" 100k resistor to ground. The 2.2uf cap is at the output. I'm not sure where the other 1Meg resistor goes, maybe it's in parallel with the load. It's just a guess, but I'm fairly certain that what I described would be a fairly sound design for a unity gain buffer.

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    That arrangement could work well. From the pictures I've seen I have been able to figure out some of the traces. I've attempted breadboard the parts and traces and found a setup that works somewhat:

    With a TL071 opamp The input goes to the non-inverted pin, one of the .022 caps comes off the feed voltage to ground, The other .022 cap filters the input. 2 of the 1M are in series to add up to 2M connected between the supply voltage and the input trace. The final 1M goes from input trace to ground possibly to prevent popping when switched on, one 100k goes in the feedback loop from the output to the Inverted pin, The 2.2 cap filters the output, and the other 100k goes from the output trace to ground after the 2.2 cap. This was functional on a breadboard; But i'd love to see a schematic to check for accuracy.

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    There are a lot of different workable configurations, but I'd say any way you slice it this is a very plain-jane vanilla opamp buffer. Since there is no real filtering happening and the opamp should be operating linearly, the only thing likely to have any effect on tone is the input impedance the circuit presents to the pickups and the op-amp itself.

    Here are some other circuits which are tested and quite good. I especially like the FET preamp. In all cases there will be little effect on the tone except the input impedance presented to the pickups (which you could model at the input with a resistor and a capacitor if you happen to like some loading).


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    Thanks Uvacom. As you said, it just another typical IC buffer. The one in Tiger is just a plain Line Driver with no boost and there a few configurations that will do the job. Thanks for the schematics as well.

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    Question Unity Gain Buffer?

    Is the purpose of this component to eliminate impedence? I'm inclined to build one if that is it's sole purpose and is it worth it. I use alot of analog pedals. I often wish I could have as much depth to my tone as when I plug in direct.

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    As I understand, It converts the pickup's high impedance to low output impedance. It is also used as a line driver for all the true bypass pedals with long cable lengths to prevent high frequency loss. It keeps the true sound of the guitar right to the amp. It's a wide band unity gain buffer. I found picture of all the components and I've been breadboarding them searching for the right sound and I think I've come close.

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    Quote Originally Posted by bdhact1 View Post
    As I understand, It converts the pickup's high impedance to low output impedance. It is also used as a line driver for all the true bypass pedals with long cable lengths to prevent high frequency loss. It keeps the true sound of the guitar right to the amp. It's a wide band unity gain buffer. I found picture of all the components and I've been breadboarding them searching for the right sound and I think I've come close.
    if you figure it out... please please please post a schematic. I know this has a very low part count, but i can't figure it out. I am using a modded EMG pa-2 for unity gain, but it just isn't close enough for me.

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    I will definitely share my findings when I find a good sounding combination.

    all I have to work with are:

    3 1M resistors 1%
    2 100k resistors 1%
    2 .022 capacitors 400V
    1 2.2 capacitor 250V
    1 single channel opamp TL071

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    Talking Yes, Yes I would like to build one, too!

    I would like a simple circuit without bells and whistles, begging your pardon sirs....

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    Ok folks. After hours of trial and error with all the componants this is what i've found comes the closest to the tiger sound, IMO. Combine with .02 ceramic caps in the guitar and it gets somewhat closer to Jerry's sound.

    I hope this helps all the DIYers.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	Buffer Schematic.jpg 
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ID:	9407  

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    Last edited by bdhact1; 05-26-2010 at 07:43 PM.

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    You can also buy the real thing from this guy:

    Wald-Electronics TPC-1

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    Okay, clearer now. Nothing particularly spectacular here.

    1) The TL071, and comparable BiFet op-amps have their best noise performance when the input resistance and feedback resistance are higher rather than lower. This is the inverse of op-amps like the NE5534/5532. You can read more about it here: http://hammer.ampage.org/files/Device1-8.PDF

    2) Metal film resistors can generally provide lower noise figures in certain applications. This is one of them.

    3) The photo clearly indicates use of a non-polarized 2.2uf cap instead of an electrolytic. Does it make an audible difference? Not likely, and especially not when the signal is distorted even a little bit.

    So, in general, this is a BiFet op-amp buffer, optimized to provide lowest noise. In terms of the tonal quality it yields, there is really nothing to separate it from a great many other buffers, including other op-amp, JFET or bipolar-based units. We've had well over 2-3 decades to come up with other buffers, since "Tiger" was built. At this point, there is really nothing special about it.....unless you really like Jerry Garcia.

    I don't think the schematic posted in this thread is accurate. I can't think of any reason why R1 should be connected to the non-inverting input in the manner shown. If it were to go anywhere, it would either be:

    a) going between the input and ground, to avoid popping if the buffer is intended to be switched in/out while plugged in.

    b) tied between the non-inverting input (pin 3) and the junction of R2/R3, as shown here: http://zohars.homelinux.org/tamarchi...es/mxrdist.gif

    One of the .022uf caps seems oddly placed between V+ and ground. Would it provide any noticeable smoothing or decoupling? I doubt it. On the other hand, the other logical location for it, at the junction of R2/R3, as in the linked-to Dist+ schematic, wouldn't provide wads of decoupling of Vref either.

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    Last edited by Mark Hammer; 05-26-2010 at 09:00 PM.

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    The combination of components in the schematic produced the desired sound I was looking for. Some of it may not make sense; But all I had to go by was a picture. I have no way of gauging the accuracy of the circuit except for my own ears. I have attached the picture I used as a reference.
    I definitely love tigers sound.

    BTW, There is no on\off switch so popping isn't a problem. It is always on when the cable is plugged in.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	Tigers_Preamp.JPG 
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ID:	9412  

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    I'm with Mark here, the circuit that you have created may sound right but it really doesn't follow any normal design practices.
    Quote Originally Posted by Mark Hammer View Post
    ...R1 should be connected to the non-inverting input in the manner shown. If it were to go anywhere, it would either be:

    a) going between the input and ground, to avoid popping if the buffer is intended to be switched in/out while plugged in.

    b) tied between the non-inverting input (pin 3) and the junction of R2/R3, as shown here: http://zohars.homelinux.org/tamarchi...es/mxrdist.gif
    Or R1 and C2 could be going to ground from the inverting input.

    Also the green metal film resistor in the original circuit appears to be marked 1000 (either 100 ohms or 1K?) which I think would be the correct value for R5 and not 100K.

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    Quote Originally Posted by 52 Bill View Post
    I'm with Mark here, the circuit that you have created may sound right but it really doesn't follow any normal design practices.

    Or R1 and C2 could be going to ground from the inverting input.

    Also the green metal film resistor in the original circuit appears to be marked 1000 (either 100 ohms or 1K?) which I think would be the correct value for R5 and not 100K.
    I think I tried R1 and C2 to ground and didn't get the right sound. I can't remember. It was a few months ago. I think I tried several layouts of the componants. The schematic I made has worked and sounded the best so far.

    R5, (identical to R4 as far a i can tell) Marked 1000F on a manufacturer data sheet referenced to 100k .

    If anyone wants have a crack at deciphering the the circuit from the picture, I'd love to try other interpretations.

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    If the unit is hardwired to be on all the time (which I assume means once you plug a guitar cable in to turn on the battery), then a terminating resistor on the input, from cap to ground, is not required. So, the likely arrangement then, is that the 3 1M resistors are used in the same fashion as on the Distortion+ to provide a reference/bias voltage from a single-ended 9V power supply.

    Normally, if it was a noninverting unity gain buffer, there would be no feedback resistor, just a wire link between input and inverting pin (6 and 2 on a TL071). I was surprised to learn, however, that BiFet op-amps can actually behave better in some circumstances if a resistance is inserted there. A couple years ago, a fellow in Germany contacted me abuot adapting something I had designed and posted, for use with a 9v, rather than bipolar +/-9v supply. He also added an input buffer stage, using one section of a TL074, and stuck a 510k resistor in the feedback loop, with no additional resistor from the inverting pin to ground. I was baffled at first, but he explained that it resulted in better noise performance. So perhaps that is what the Tiger maker did too.

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    Hmmmm

    I'd really like to wrap my head around this and maybe I'm asking to much or not paying attention enough but I'd really like to build this thing and I'm retarded compared to what you guys know. My 1967 Les Paul Deluxe loses alot of body between output to my amp. I have some materials to build it but just need a simple schematic with the values. I don't want to sound like Jerry I just want to preserve my tone through all my pedals simply and efficiently. infinite input impeadance - zero output impeadance.....nothing else.
    Can you help me?

    Hoony

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    Quote Originally Posted by Mark Hammer View Post
    If the unit is hardwired to be on all the time (which I assume means once you plug a guitar cable in to turn on the battery), then a terminating resistor on the input, from cap to ground, is not required. So, the likely arrangement then, is that the 3 1M resistors are used in the same fashion as on the Distortion+ to provide a reference/bias voltage from a single-ended 9V power supply.

    Normally, if it was a noninverting unity gain buffer, there would be no feedback resistor, just a wire link between input and inverting pin (6 and 2 on a TL071). I was surprised to learn, however, that BiFet op-amps can actually behave better in some circumstances if a resistance is inserted there. A couple years ago, a fellow in Germany contacted me abuot adapting something I had designed and posted, for use with a 9v, rather than bipolar +/-9v supply. He also added an input buffer stage, using one section of a TL074, and stuck a 510k resistor in the feedback loop, with no additional resistor from the inverting pin to ground. I was baffled at first, but he explained that it resulted in better noise performance. So perhaps that is what the Tiger maker did too.

    I did try the distortion + setup and it was a little too bright sounding. I also tried using a straight link between 2 and 6 but there was a huge volume drop. The 1M going to pin3 in combination with the 100k between 2 and 6 makes it just slightly below unity with just a hint of dirt; And is a great line driver.

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    Quote Originally Posted by hoonhout33 View Post
    I'd really like to wrap my head around this and maybe I'm asking to much or not paying attention enough but I'd really like to build this thing and I'm retarded compared to what you guys know. My 1967 Les Paul Deluxe loses alot of body between output to my amp. I have some materials to build it but just need a simple schematic with the values. I don't want to sound like Jerry I just want to preserve my tone through all my pedals simply and efficiently. infinite input impeadance - zero output impeadance.....nothing else.
    Can you help me?

    Hoony
    You can try the schematic I attached. It is a good non boost line driver. There are also a few other schematics that were posted here. General Guitar Gadgets
    web site also has some buffer schematics.

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  23. #23
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    Quote Originally Posted by hoonhout33 View Post
    I'd really like to wrap my head around this and maybe I'm asking to much or not paying attention enough but I'd really like to build this thing and I'm retarded compared to what you guys know. My 1967 Les Paul Deluxe loses alot of body between output to my amp. I have some materials to build it but just need a simple schematic with the values. I don't want to sound like Jerry I just want to preserve my tone through all my pedals simply and efficiently. infinite input impeadance - zero output impeadance.....nothing else.
    Can you help me?

    Hoony
    I would suggest that, if this is not your usual past-time, that you seriously consider NOT building it into the guitar, but rather simply build something like this into a floor box. Unless you know what you are doing, with respect to risk management aspects of wiring and installation, there is just too much to bugger up on a nice axe like that.

    A simple clean boost pedal, like this one - AMZ Mosfet Booster Guitar Effect - will give you all the buffering you could want, plus the option of some extra gain if you ever find the need to push other pedals, or your amp, a little harder.

    The advantage of floorbox over built-in versions is that:

    a) you can disable them with your feet instead of your hands (need those for playing!)

    b) there is no risk to the finish of the guitar itself

    c) space constraints do not oblige you to make any sacrfices with respect to design or features/options

    d) you have a wider choice of powering options, including use of a wallwart or other regulated supply

    e) if you screw it up, you can toss the pedal; hard to do with a guitar

    There is also another approach: not the guitar OR a floorbox. http://www.till.com/articles/PreampCable/

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    Quote Originally Posted by uvacom View Post
    Here are some other circuits which are tested and quite good. I especially like the FET preamp. In all cases there will be little effect on the tone except the input impedance presented to the pickups (which you could model at the input with a resistor and a capacitor if you happen to like some loading).

    Wow. Nothing ever dies on the internet. Those are my drawings from the mid 90s that went into the first schematics repository on the net - Leper's Schematic Archive. Pat Montagar seems to have his own private schematics wayback machine.

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    Update: Please disregard the schematic that I posted earlier.

    After restudying the Tiger buffer photo I realized that I have 2 incorrect resistors. Both 100k resistors actually appear to be 1 100 ohm and 1 10k resistor. After switching them out I am getting a whole different sound from the buffer. The 10k seems to be the pulldown resistor after the 2.2 capacitor; The problem is I'm still not sure if the 100 ohm resistor is part of the feedback loop or is comming off the loop and adding resistance before entering the 2.2 capacitor. Further testing is needed.

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    Old Timer J M Fahey's Avatar
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    A 100 ohm resistor between an op amp output and a long cable capacitance is an old recommended stability add on.

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    So should the 100 ohm resistor should go into the feedback loop ?

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    Old Timer J M Fahey's Avatar
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    No. You build your regular preamp and put those 100 ohms in series with the hot pin of the output jack.

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    Thanks JM! I'm gonna try that on the breadboard tonight.

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    After testing and listening to the results, Here is the next revision. This revised buffer is so close to "The sound". I think I may have a final product.
    Attached Images Attached Images

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    Here is a better picture. this one is .JPG instead of .BMP
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	Dead man's Buffer.jpg 
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    Last edited by bdhact1; 08-15-2010 at 05:56 PM. Reason: Wrong attachment

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    Well, if you like its sound, I have nothing to object.
    Anyway I think I must warn you that that's not a unity gain buffer, but something that introduces a -10dB loss, besides not having the best configuration to avoid hiss.

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    The techs at the RUKIND music forums do mention a slight volume drop, or being slightly less than unity. This condition may be correct for this buffer. I'm still testing it through the effects loop built into the guitar to make sure the volume drop isn't too detrimantal. The hiss isn't as bad with other opamps, but this model opamp is the authentic one.

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    I have yet another configuration of the components that sound more authentic then previous configurations. There are 2 resistors that seems to make no sense in their placement, but the sound is right. somewhat baffling.

    Click image for larger version. 

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    Old Timer J M Fahey's Avatar
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    Hi bdhact.
    Now we are *very* close:
    Everything is the same, with a very slight change :
    1) un-join C1/R1
    2) join right pin of C1 straight to IC pin3
    3) Join left pin of R1 to union of R2/R3
    That configuration works as intended.
    This gives correct bias to IC1, the guitar mics sees an input impedance of over 1M (good !) , the gain is practically 1 and we have the lowest hiss possible.
    Improvements: left pin of C2 goes to union R2/R3, where it is *much* more useful than decoupling +9V.
    As shown it will also work, but what I suggest makes better use of it.
    Congratulations.

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