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What the Bleedin’ Treble!

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In part one of this, video I explain what treble bleed is, and how to evaluate and select the right cap.  I demonstrate my G&L ASAT III which has a treble bleed cap on the master volume, and I compare that with my Epiphone Riviera P93 which has no treble bleed caps (yet).

Silver Mica, Ceramic and Orange Drop Capacitors

The caps I tried are (as shown left to right): Silver Mica 100pf, 390pf and 1000pf, a tiny 1000pf ceramic cap, and Sprague Orange Drop (polypropylene) 1000pf, 3300pf, and 6800pf.

The tolerances on the caps are a bit all over the place.  I measured the 1000pf caps on my DMM and all were closer to 1250.  The 100pf silver mica was over 250!  This is assuming I can trust my Mastech DMM.

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Epiphone P-93 Circuit Diagram

Riviera P93 Circuit Wiring

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Epiphone P-93 Circuit Diagram

Here’s the diagram of the electronics in my Epiphone Riviera P93, looking at the circuit from the rear.

It has three volume pots and one master tone pot.  All knobs are 500k audio taper.  Strangely, there appear to be three different brands of pots used in my guitar, Alpha, JS and a 3rd that I can’t identify.

There’s a .022uF capacitor on the tone knob.   No capacitors on the volume pots.

My parts order from Mouser just arrived!  Getting ready for lots of tone tweaking!

Capacitors from Mouser

A new series on guitar electronics

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This is part 1 of a new series on guitar electronics.  In the video, I demonstrate how to get the electronics out of a semi-hollow body guitar, with some useful tips and tricks.

Once the electronics are out of the guitar, it’s relatively easy to try some experiments on the circuit to see how it sounds.    I’m planning a number of upcoming experiments including:

  • Experimenting with replacement pots
  • Adding treble bleed to the volume pots
  • Trying different tone capacitors to see how it changes the sound
  • Replacing the jack with one with a longer bushing Switchcraft jack
  • Replacing the pickups
  • Putting all the electronics back into a semi-hollow body guitar through the f-hole

Every step of the way, I’ll be recording audio examples, how-to videos, and text writeup.

I look forward to hearing any comments or suggestions.  Please let me know your experiences too!

Don’t know jack

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What is up with the jacks on these semi-hollowbody Epiphone guitars.  When I was shopping for guitars in the stores, I often saw Epiphone Dots and Sheratons with the jack missing inside the guitar.   How can that be good for sales?!  And when reading in the Epi forums, I saw folks complaining of this happening to them.  Does this happen on the more expensive Elite Epi’s, or other semi-hollow body guitars?

Update: I added a 1/4″ inner-tooth lock washer between the nut and round washer, and it has stayed tight ever since.

I never thought it would happen to me.  I made a point of periodically hand-tightening the jack when plugging in a cable, just to be sure.

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bumblebees

Pots and caps

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I’bumblebeesm assuming that the tone caps are more critical to the sound than the pots themselves.  Please leave a comment to share your recommendations or experiences.

Here’s some background reading for the upcoming capacitor and potentiometer mods.

Auditioning Tone Capacitors Part 1 (Premier Guitar)
Auditioning Tone Capacitors Part 2 (Premier Guitar)

Article about pots in general, with good charts about tapers

Treble Bleed Mod for Volume Pots

Pot quality CTS versus Gibson

Resistor-Filter Cutoff Calculator

And here’s some shopping resources:

CTS Pots at Guitar Parts Resource

Sprague Drop caps at Guitar Parts Resource

Pickup experiment- bypassing electronics

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Speaking with Pete Biltoft at Vintage Vibe Guitars about possible dog-eared P-90 pickup replacements for the Riviera P93, Pete recommended I first try bypassing the guitar’s electronics to see if they’re sucking the tone away.   This experiment requires disconnecting the pickup wire from the electronics, and routing it directly to the output jack.  The results are interesting.   Read on for pictures, and audio, video before/after.

Open Heart SurgeryIt felt a bit like open heart surgery!  I held the neck volume pot with locking pliers so I could use a soldering iron to remove the red wire from the pot.  Old baby blankets and polish cloths came in handy here to protect the finish:)

Alligator Clipped Jack

 

Rather than fishing out the output jack through the f-hole, I used alligator clips to attach an extra jack hanging off the side of the guitar.  The green alligator connects the jack ground to the pickup ground.  The red alligator connects to the red signal wire of the pickup.   With this setup, I can easily swap the red alligator between the new output jack and right back to the neck volume pot.

P-90 Pickup Exposed Epiphone Riviera Three P-90's Baby Blankets and Clamps

Audio Examples

Through Electronics Bypassing Electronics
Pattern 1 Pattern 1
Pattern 2 Pattern 2
Pattern 3 Pattern 3

 

So, it’s time to find and order some pots and caps!  I’ll do a post on installation, and the followup for sound comparison.