Boss PQ-4 Parametric EQ

[spacecase96]

Boss PQ-4 Parametric EQ

They stopped making this pedal in 1997. I bought one these back in 1994. I have a Randall RG200 G3 and have added this pedal in the effects loop. It's makes this amp sound like hell's fire with the adjustable Mid and High frequency’s on this pedal. It kinds of adds the same feature Dimebag Darrell had on his Randall Warhead amp with the adjustable Mid frequency. Don't want to see this Gem of a pedal to Disappear.

[Alex]

That's double but what would you eliminate to make it true bypass?
I was thinking: Q2, Q7, Q8, R2, R6, R51, R52, C4 and C29.

[nocentelli]

Delete R49 and leave R52?

[Alex]

Just seen R52 is 100K and not 1M!

[Alex]

Another question:
Pres, High, Low and Mid pots are all connected to a 47uF cap going to ground.
From which lug are they connected?
They should be W taper center-tapped pots and I'm not sure how to build (if at all possible) a clone with regular pots.

[spacecase96]

I don't know if this helps. Can you use this schematic to reference how to hook up the lungs.
Furman PQ3

[spacecase96]

Sorry just googled W Center Tapered Pots I now see what you mean now.

[spacecase96]

After reading your replies had to pull this thing apart and get some guts shots.

[spacecase96]

The pdf below shows how the prong s are numbered.
http://www.mouser.com/Search/m_ProductDetail.aspx?R=RK11K114F30C0B104_WITH_CENTER_TAPvirtualkey68800000virtualkey688-RK11K114F30-104

http://www.mouser.com/ds/2/15/RK11K11_VARIETYOTHER-253030.pdf

[Alex]

Only thing those are Linear instead of W Taper.
Don't know if they would sound the same.
Any idea?

[spacecase96]

I did skowered the internet for some a100kw found some from China but don't really trust those they did not look right. I did found some duals on eBay http://www.ebay.com/itm/3-pcs-Alpha-100KA-Dual-Stereo-With-Center-Tap-Potentiometer-Pot-15mm-Volume-/300921422458?hash=item461050827a:g:WiYAAOSwabhUVRi9

I did buy 8 of the b100kw from Mouser I am going to do a test and build that boss pq-4 circuit with a solderless pcb board. See how they sound.

[Alex]

Cool. Let me know how it works.
A layout wouldn't be too complicated.

[spacecase96]

http://www.eleccircuit.com/audio-loudness-control/

I did some home work. That 47uf cap is basically a loudness control. That 47uf cap give the circuit the extra 3db. That's why all the other parametric EQ or Graphic equalizer only do -15 to +15. In the Boss PQ-4 circuit the add the loudness control which is one 47uf cap and center tap potentiometers. A pretty cool and cheap way to get an extra -3 to +3 in stead of being -15 to +15 you get the -18 to +18.

[Sphere80]

Here's a clone pcb/kit with instructions in Polish. Anyone have experience buying from them?

http://www.efekty-diy.pl/pq4.html
https://guitar-electronics.eu/en_US/c/PQ-4/59

How important are the W100K pots? Is it to get better fine tuning at max/min?  I'd just cannibalize one of my DOD pedals.

[enzosorgy]

hello, I would need more detailed photos of the electronic board, the upper side to see all the components well, that from the opposite side where the welded track is visible, there are many values that do not result from the file of the Boss file and the drawing nn reflects in all electronics ... could you photograph it? could you even take pictures of the potentiometer codes? I have to repair my PQ-4, you do me a huge favor, thanks!

[Mulekicker]

I dont know if this ever got finished, but Tayda has 100kW center detent pots for .60 cents each.

[aelling]

Mulekicker wrote

I dont know if this ever got finished, but Tayda has 100kW center detent pots for .60 cents each.

Those aren't dual stereo though.

[Mulekicker]

 I should read more carefully.