Ibanez PD7 Hiss - I think it's solved?
I remember posting on here a few years ago, about how the PD7 is one of my favorite drive pedals, but it has noise and what not.
Well...I finally just pulled the trigger on upgrading/modifying the board. I didn't do anything too outstanding, I mainly changed the cheap film capacitors to Topmay low-voltage replacements. I replaced one film cap with a ceramic, simply because I happened to have it. I also changed the JRC4558 chips with sockets and LM833N's.
These are some pics of the board before:
Most of the hiss it had before, is now gone when the Attack switch is off. Some noise comes in when the switch is on 1 and 2, but it's very tame and manageable. The lows still have some of that mush in the higher gain settings, but part of me wonders if the diodes they use might have something to do with it. It feels like they clip and compress way too much, especially on OD.
Here's the list of components, if you guys want to take a stab. Some aren't factory values, but I tried to get them as close as possible. They didn't seem to have a major impact on the overall sound.
C1 0.1 uF (film)
C9 0.001 uF (film)
C10 0.047 uF (film)
C15 0.033 uF (film)
C21 0.047 uF (film)
C25 0.01 uF (film)
C26 0.01 uF (film)
C27 0.001 uF (film)
C28 0.047 uF (film)
C29 0.0047 uF (film)
C31 0.01 uF (film)
C33 0.022 uF (film)
C52 0.01 uF (film)
C53 0.022 uF (film)
C54 0.00047 uF (Ceramic)
Love the Phat Hed. Good job. Thanks for posting that!
getting rid of the JRC's seem to get rid of some of the harshness of the drive. It felt like it was always up at 8-10. Now, it's like there's no low drive to it at all. Some of that may just be the way the circuit is designed, like I said. I'm not sure what diodes are in it, I've had thoughts of converting it to LED clippers...probably infrared.
Maddening because I love that pedal but it is definitely noisy as all getout. I'd like to fix that also but it takes a more sure hand than mine.
Find the schematic here:
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