Anybody have a schematic the JG Tiger Unity Gain Buffer

[bdhact1]

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

[HTH]

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

[bdhact1]

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.

[uvacom]

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.

[bdhact1]

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.

[uvacom]

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).

[bdhact1]

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.

[hoonhout33]

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.

[bdhact1]

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.

[erock]

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.

[bdhact1]

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

[hoonhout33]

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

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

[bdhact1]

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.

[bdhact1]

You can also buy the real thing from this guy:

Wald-Electronics TPC-1

[Mark Hammer]

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.