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Variac
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Bill
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Joined: 26 May 2004
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Location: Detroit MI

PostPosted: Wed May 26, 2004 12:18 pm    Post subject: Variac Reply with quote

Hi all. New to this. Lots of good info.
I have seen a Variac in some pic's of Robben's equipment. Does anyone know how is it being used?
As to my signature; A long time ago while lusting over some vintage guitar, my bass player (who has been around the block a few times) told me "If it's not coming from your heart, it doesnt matter what guitar your playing. It's just a bunch of wire and wood." I think about that every time I want to buy something new and it's saved me a lot of money.
Bill Cooper
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Buffaloe
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PostPosted: Wed May 26, 2004 3:26 pm    Post subject: Reply with quote

There is an optimum input voltage at which Robben's rig sounds its best. The variac allows for compensation of low or high input voltage so the correct voltage always reaches the amp.
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Daved
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PostPosted: Wed May 26, 2004 3:48 pm    Post subject: Reply with quote

Correct, Toneslasher! I try to keep his rig at 125 volts. After experimentation, I find that less than that and the tone "brown's out" to Robben's ears. More than that really seems to make little difference.
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Aeolian
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PostPosted: Wed May 26, 2004 5:34 pm    Post subject: Reply with quote

Hmm, 125 seems on the high side of nominal. The Dumble schematics I have don't show any regulation so the amp would be sensitive to input voltage. It would seem that this much input voltage would "stiffen up" the amp. A perfectly reasonable thing to do, especially given Robben's incredibly dynamic style. Not sure if the trade off in lowering the current through the output tubes and transformer compensates for the increased plate voltages, but at this level probably no real harm done. I'm sure Dumble would have complained if Robben and Daved were putting the amp at risk. We all know about the Eddie Van Halen stunt of undervoltaging his amps to loosen them up, and the price paid in output transformers for folks who have tried this on their own.
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Bill
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PostPosted: Thu May 27, 2004 3:41 pm    Post subject: Reply with quote

Interesting idea. Is it just for the amp or all effects as well?
Thanks for the reply
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Buffaloe
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PostPosted: Thu May 27, 2004 4:45 pm    Post subject: Reply with quote

My guess is that it's only for the amp. The effects are solid state, and would have regulated power supplies. The amp is designed to operate on a specific voltage, which when everything is tuned just right, has its optimal sound. The most critical operating parameter is the power tube bias voltage, which is downstream of the input voltage. Having been around Robben a couple of times, and hearing him make statements about how he doesn't want the sound to change (one of the reasons he likes the tone and volume controls disconnected on his guitar-so he can't accidentally bump one of them while playing and have everything change) I can see how his very critical ear wants the amp to run at the prescribed voltages all the time. The input voltage, if varied from "perfect", will cause a change in the bias voltage. A colder bias voltage will tend to make an amp sound a little sterile, and a warmer voltage will make it a little "greasy." When you're playing as many different venues as Robben does, you want to start with a known constant of "this is where the amp will sound its best (input voltage), now I adjust the tone stack for the room." By using the variac to assure that the input voltage is always correct, you have one less variable to achieving your sound in ever changing locations.
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nineacres
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PostPosted: Fri May 28, 2004 4:01 am    Post subject: Reply with quote

Tonebutcher wrote:
(one of the reasons he likes the tone and volume controls disconnected on his guitar-so he can't accidentally bump one of them while playing and have everything change)


So, Robben controls all volume and tone settings from the amp?
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Buffaloe
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PostPosted: Fri May 28, 2004 6:27 am    Post subject: Reply with quote

I know he has used a volume pedal in the past. The Les Paul he's currently playing has the tone and volume controls connected as of last Saturday. I don't know that he disconnects them on all of his guitars. Maybe Daved can chime in on this.
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Aeolian
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PostPosted: Fri May 28, 2004 8:20 am    Post subject: Reply with quote

Tonebutcher wrote:
I know he has used a volume pedal in the past. The Les Paul he's currently playing has the tone and volume controls connected as of last Saturday. I don't know that he disconnects them on all of his guitars. Maybe Daved can chime in on this.

At the last clinic, Robben mentioned that he doesn't use the controls on the guitar, preferring to leave everything wide open. This came up as the new Les Paul has a clever push-push pot to activate the coil tap. Push on the knob and it pops up, push again and it stays down. A vast improvement over the ones that you have to grab and pull up. Robben mentioned that on occasion the knob gets turned slighly when he is trying to activate it. This led to the "wide open" discussion. Robben does use a volume pedal put he rarely uses it to turn the guitar down, it mostly gets used for swell effects. If you have been close to Robbens rig at a show, you'll notice that he doesn't turn down. He turns off the boost or lead channel but when comping he just doesn't hit the guitar as hard (usually Wink ), using his touch and the dynamic response of his rig.

Robben mentioned that at one point, he had all the controls bypassed but didn't like the change in sound. This makes sense as even wide open, there is still 250K ohms across the output along with whatever value the tone cap has reduced by 500/250K or whatever. I thought about substituting fixed resistors for the pots but pots have inductance characteristics that a fixed resistor won't exactly mimic. So, I have an idea that I may try on one of my Gibson's. One master volume contol where the neck volumes goes and a pan pot like Garth uses in the bridge volume hole, (maybe Garth can let us know where you get these as regular dual pots won't do this right). One master tone where the neck tone is, and the push-push coil tap in the neck tone slot. You'd have much more versatility but the guitar would look otherwise normal.

So many possibilities... Confused
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Buffaloe
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PostPosted: Fri May 28, 2004 5:12 pm    Post subject: Reply with quote

Aeolian wrote:
Robben mentioned that at one point, he had all the controls bypassed but didn't like the change in sound. This makes sense as even wide open, there is still 250K ohms across the output along with whatever value the tone cap has reduced by 500/250K or whatever.


If you do a true bypass of the tone and volume controls, there is no resistance or capacitance left in the circuit, only the inductive reactance of the pickups themselves. This is much like having the volume and tone controls all set to "10", and the capacitor removed from the circuit. I have done this, and it's essentially the guitar's pickups running wide open without any effect from the pots or caps. Robben mentions that his Fender RF Signature has the controls bypassed on his instructional video tape "Back To The Blues."
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Bill Morgan
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PostPosted: Sat May 29, 2004 3:29 am    Post subject: Reply with quote

Aeolian wrote:
So, I have an idea that I may try on one of my Gibson's. One master volume contol where the neck volumes goes and a pan pot like Garth uses in the bridge volume hole, (maybe Garth can let us know where you get these as regular dual pots won't do this right). One master tone where the neck tone is, and the push-push coil tap in the neck tone slot. You'd have much more versatility but the guitar would look otherwise normal.

So many possibilities... Confused


http://www.stewmac.com/shop/Electronics,_pickups/Components:_Control_pots_and_knobs/4/Control_Pots.html

Bill
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Michael
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PostPosted: Sat May 29, 2004 2:09 pm    Post subject: Reply with quote

Aeolian:

On Garth's recommendation, I had my old ES335 recently done - now I'm able to blend both pick ups - my ears says the results are fantastic - for my money this is far better than always on or always off.

The wiring is a bit tricky. If I'm not mistaken, Garth had someone in the Bay who did the word on his Fender. Mine was done at Hidden Valley Guitars in Scott's Flat just up the hill from Nevada City - by Steve Bagwell. With a phone call, I'm sure he could share with you how it was wired and what parts were used. Steve's a great guy.

The best to you!
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Bill
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PostPosted: Sun May 30, 2004 12:08 pm    Post subject: Variac Reply with quote

I thought of doing the blend thing on my Tele a few years ago, you guys have renewed my interest. Its a 73 with Joe Barden pickups.
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Bluelobster
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PostPosted: Tue Jun 01, 2004 3:02 pm    Post subject: spamming Reply with quote

sorry for spamming, but hey i played qith robben :
deja blues bad juju
http://www.soundclick.com/genres/ChartsNew.cfm?Genre=Blues
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tonemaster2_11
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PostPosted: Tue Jun 08, 2004 3:16 am    Post subject: Reply with quote

Daved- Who was Bing refering to? I love that scene with Sinatra from High Society. Takes me back. Has Robben ever considered putting the band in tuxedoes? :-)
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