ampage Tube Amps / Music Electronics	For current discussions, please visit Music Electronics Forum.

ampage archive

Vintage threads from the first ten years

Re: What is that strat sound?

:

5/2/2003 1:44 AM

Re: What is that strat sound?

Mark:

I was just reading about the Gibson Blueshawk guitars last night, which use the Blues 90 pickups (alnico pole pieces instead of bar magnets). They also use a dummy coil (same coil less the poles) toreduce hum with the bridge and neck positions. The middle position has both of the pickups in series, but with a series RC network to brighten the sound a bit and to make it sound more Fendery. The RC network according to the Gibson schematic is a 68k resistor in parallel with a 0.005uF cap.

http://www.blueshawk.info/intro.htm

BTW the Blueshawk also has a switchable varitone circuit using a 7.2 Henry choke.

--A very interesting guitar!

Steve Ahola

5/2/2003 2:08 PM
Mark Hammer	Here's where the circuit diagram is. http://www.blueshawk.info/images/BH_wiring_update.jpg

5/2/2003 6:22 PM
Steve A.	The guy running the site mentioned that there were some errors in his drawing so he also posted the link to the official one from Gibson: http://www.gibson.com/relations/schematics/diagrams/dsbhwiring.pdf For more fun and games, check out this link: http://www.gibson.com/relations/schematics/diagrams/ --Enjoy! Steve Ahola

5/2/2003 5:41 AM

A cap in series with the pickup winding would give you a -90 degree phase shift. I wonder how much the phase of the string vibration is shifted on the strat between the bridge & middle or neck & middle pickups? In additoin, the cap would only effect the higher frequencies of the signal, which might explain why it sounds like the middle/bridge position and not the middle/neck position.

I need to pick up a cheap Tele or Strat copy and try some of this stuff out!

Chris B

PS. The RC circuit you mentioned in the Blueshawk would really be an LRC circuit, right? The pickup is an inductor too, unless it's viewed as just an AC voltage source, in which case you're absolutely correct.

5/2/2003 11:20 PM

Chris:

The RC circuit you mentioned in the Blueshawk would really be an LRC circuit, right? The pickup is an inductor too...

I was just calling it what Gibson calls it, but you are correct about the pickup being an inductor. You can hear the LCR filter effect especially when you add pickups in series.

I thought I wired up the tone controls on this guitar backwards- when you switch to series mode the sound gets brighter as you turn the tone control down:

http://www.blueguitar.org/new/schem/_gtr/ser_link.gif

Steve Ahola

5/1/2003 4:00 PM
andy fuchs	My summer project this year will be a Warmoth tele hollow body with 3 P-90's (Harmonic Designs likely), and the Guitar-Player super-strat wiring. I'll report when it's done. I'm guessing 3 X-P-90 wired right can do it. It's mechanically out of phase, not electrical on a Strat type axe, combined with scale length...my guess at least.

5/3/2003 6:57 PM

The out-of-phase sound comes from the 'in between' positions, that being positions 2 and 4 of the strat pickup selector switch.

To get true out of phase sound requires that one of the pickups be reverse wound. Usually it is the middle pickup that is reverse wound because this allows both the neck and the bridge pickup to operate out of phase with the middle pickup.

Pickup manufacturers such as Lindy Fralin are well aware of the need for a reverse wound pickup and will automatically supply one when you order a complete 3 pickup set from them. In fact, if you don't want it reverse wound, you need to specify this need since many pickup manufacturers are making reverse wound of the middle pickup the delivered standard. I'm not sure if Fender supplies their guitars reverse wound right off the shelf.

Before I switched to Fralin's I could not get a proper out-of-phase sound from my strat. With the Fralins, because of the reverse wound pickup, the out-of-phase sound is extremely easy to get.

The moral of the story is that only a reverse wound middle pickup will do if you are looking for the best out-of-phase sound. Technically, I believe you can use a normal wound pickup and then reverse the wiring on the middle pickup which will cause it to be out of phase with the other pickups, but this does not sound as good as using a middle pickup that is reverse wound.

LFO

Page 3 of 6