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Grateful Dead Music Forum

A place to talk about the music of the Grateful Dead 

 #75569  by Jon S.
 Thu Mar 11, 2010 6:19 am
The luthier building my Jerrycaster - it is now in month 26 - is oh so close to finished and I have an appointment for this Sat. to travel to Baltimore to get it. However, it is still being wired up. While he's a sharp and masterfully talented artisan, there's some uncertainty, on my part, on two points. I could use some advice on them here and even, if possible, to discover some way to for us to reach someone knowledgable by cell phone quickly on Sat. if we get stuck on anything and a consultation becomes necessary.

Admittedly, I'm not certain how exactlyTiger was actually wired (though I've seen Waldo's schematic I'm no techie), but here are the outcomes I, personally, would like to achieve with my guitar's wiring.

One, I'd like to preserve the capability to use the guitar with or without engaging the OBEL, i.e., when I want and need to do so, I can simply plug one mono chord into the post-guitar controls jack out to the amp and have a hot signal ready for amplification.

Two, I think (am I wrong?!) I'd like for the UGB to be active in the circuit whether or not the OBEL is engaged.

My followup questions are these.

One, was Tiger actually wired this way and if not, how and why?

Two, we'll be using a CAE UGB. (I know but I bought it a long time ago before I'd even known of this forum or Wald Electronics!) The CAE buffer comes with its own schematic which the luthier has and plans to follow. I'm wondering whether anyone else here who installed one of these previously or is otherwise familiar with it knows if it's designed to work such that when I choose to go with use a single post-controls mono signal/cord out from my guitar there will be both be buffering of the signal *and* a guaranteed signal out from the guitar's output jack to the amp?

Three - related to two - after all of this introductory stuff, what if anything special will my luthier and I need to know/keep in mind when wiring the guitar to ensure positive results?

Thanks very much for whatever advice you can provide. I certainly do hope all goes smoothly on Sat. and I'll be posting pics of the final axe here shortly thereafter. :)
 #75578  by playingdead
 Thu Mar 11, 2010 7:20 am
Just in case anyone ever wonders later ... when it's wired to the usual Garcia specs:

1) The buffer is always active and present in the signal;

2) The guitar works as a normal guitar when there is no cable plugged into the effects loop jack.

However, be aware that because of #1, you must always have a good battery in the guitar, regardless of whether or not you are using the effects loop. If the battery goes dead, buffer goes dead, guitar goes dead. Thus, do not make the rookie error of putting the battery somewhere that you can't get to in a big hurry if you need to, i.e., under a Strat style pickguard. And if you put it under an inlaid plate on the front like Garcia's was, make sure you carry a screwdriver and spare battery.

Also be aware that it's critical to tie the buffer's battery to the main guitar output jack, otherwise you will be constantly draining your battery. That's why a stereo jack is specified for the mono main guitar output, the other side of it controls the battery.
 #75579  by erock
 Thu Mar 11, 2010 7:23 am
I feel the need to answer this just so it's on the site in case someone else is running into the same problems. I know when I was wiring up my WGD i had some of the same concerns.

I have very little background in electronics so i will explain it as I understand it.

if you are using the buffer, it will lower the impedance of your signal, hence the 25k Volume pot. this is a very low value pot. off the top of my head (i am too lazy to google it for sure) I think most volume pots are 500 to 1k in value. so if you wired non-buffered pickups to the 25k volume, the changes in volume would minor and may not even be very effective. So in a nut shell, if you are going to use a 25k pot the signal needs to be buffered when it is going through the effect loop or not.

how you get it to go to the effects loop the third switch in Waldo's schematic. it switches the direction the output from the buffer goes. One way it goes to the effects loop and takes that output then sends it to the volume pot. The other way sends it directly to the volume pot.

If Jerry used a 25k volume pot (I see no reason why he wouldn't) then yes, his guitar would be wired that way.

please let me know if this doesn't make any sense.
 #75580  by jester536
 Thu Mar 11, 2010 7:57 am
I'm cool now. Waldo is assisting me, thank goodness!
Once again...Waldo comes through for one in need...this man has proven himself over and over, to be a valuable resource. We're lucky.
 #75589  by SarnoMusicSolutions
 Thu Mar 11, 2010 9:22 am
erock wrote:so if you wired non-buffered pickups to the 25k volume, the changes in volume would minor and may not even be very effective. So in a nut shell, if you are going to use a 25k pot the signal needs to be buffered when it is going through the effect loop or not.
The central issue with pot values is that the resistance of the pot "loads down" the pickup itself. As you get below 250k in pot value, the pickup's treble response begins to go away. A 25k pot on a pickup will sound VERY dull and dark. But when buffered, the pickup never sees the pot so you can use all kinds of values of pots and it won't matter much. What's interesting is that in reality, you don't really need a low value pot for the OBEL setup. You can actually use a buffer and still use a 250k or 500k pot. It actually works just fine. This has been confirmed by Ron Wickersham at Alembic. I've done it before too. The only benefit by using a 25k or 10k pot after a buffered signal is that the low value insures that at any volume setting, your tone is preserved and immune to cable capacitance. But I've found that even with a 250k pot and decent cable, you still will hear a balanced tone at any volume. It's just not critical to go with the 25k pot. This simplifies things, especially when people are wanting to be able to bypass the buffer and have the "passive" option.

Brad
 #75615  by playingdead
 Thu Mar 11, 2010 1:20 pm
Interesting ... Scott Walker uses a custom audio taper concentric volume pot that has both 500k (passive) and 25k (active) values for his guitars that have the buffer bypassable.
 #75625  by Jon S.
 Thu Mar 11, 2010 2:23 pm
Waldo is even more helpful and interesting live than in our threads - he really is.

Thanks so much for your help, Mike, Phil and I are most grateful.

On my axe, the buffer will be on always so with Waldo's input, we're keeping the tone pot at 500K but the volume pot will be 25K.
 #75631  by waldo041
 Thu Mar 11, 2010 3:26 pm
Jon S. wrote:Waldo is even more helpful and interesting live than in our threads - he really is.

Thanks so much for your help, Mike, Phil and I are most grateful.

On my axe, the buffer will be on always so with Waldo's input, we're keeping the tone pot at 500K but the volume pot will be 25K.

anytime jon!

thanks!

peace,
waldo