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Ibanez PD7 Hiss - I think it's solved?

Discussion in 'Effects [BG]' started by isher1992, Oct 20, 2013.


  1. 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:

    2013-10-06170940_zps1c8987a7.

    2013-10-06154032_zpscb1bec73.

    After:

    2013-10-20173646_zps5b1d0225.

    2013-10-06170940_zps1c8987a7.

    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)
     
    StayLow likes this.
  2. The Mouse

    The Mouse

    Jun 2, 2009
    Ireland
    Love the Phat Hed. Good job. Thanks for posting that!
     
  3. 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.
     
  4. avvie

    avvie

    Oct 12, 2010
    Maui, HI
    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.
     
  5. Thanks. :)
     
  6. Yeah, the PCB on this is very unforgiving. I almost lifted a pad, and half of it came up but luckily I fixed it. I used to have an Ibanez Phaser that didn't have those mylar caps, part of me wonders if they did like Boss and changed their manufacturing location and switched to cheaper components.
     
  7. ex-tension

    ex-tension

    Jun 11, 2009
    You can also 'upgrade' some electrolytics on the audio path (like C3, C43, C44) with polyester ones.
    Find the schematic here:
    http://www.ibanez.com/parts/2004_PARTS/electronics/tonelok/circuit diagram/PD7-01.pdf
     
  8. I hate necro'ing my own thread 3 years later, but I had sold that PD-7 and I'm about to try it again with some clipping circuit modifications.

    I had changed the clipping diodes on that particular model to red LED's, but I think I'm going to do something different this time. Just so I have something to refer back to, these diodes are clippers:

    D1/D2 (pair,1SS133T, believe this pair is on both OD and Dist sides)
    D3/D4 (Pair, 1SS133T, believe this pair is only on Dist)

    The first pair (D1/D2) is in the feedback loop of an op amp...figures it would be set up like a Tubescreamer. I will probably replace these with 1n400x diodes. I did that on a few tube screamer clones (DOD Bass OD comes to mind) and rather liked the sound of that.

    The second pair is on another gain stage that is switched from what I can tell (D3/D4) so it's more than likely just on the distortion side. I'm still on the fence of what I will put in here...I like the idea of another 1n400x pair, but I'm not ruling out the possibility of maybe an LED pair (I like using IR emitters), or an asymmetrical IR/1N400x pair.

    I still love my OKKO Basstard, but this thing just has a unique character to it that even on the Clean channel, it gives a nice bit of grit. I use it into the input of my Basstard to sort of brighten it up.
     
  9. An almost complete list of every capacitor (missing two that are such a small value there's no way to really replace them with film):



    C1 0.022uF FILM

    C3 1uF FILM

    C8 0.0001uF FILM/CERAMIC

    C9 0.0012uF FILM/CERAMIC

    C10 0.047uF FILM

    C13 0.1uF FILM

    C15 0.033uF FILM

    C18 68p CERAMIC

    C21 0.047uF FILM

    C24 68p CERAMIC

    C25 0.015uF FILM

    C26 0.015uF FILM

    C27 0.0015uF FILM/CERAMIC

    C28 0.047uF FILM

    C29 0.0056uF FILM/CERAMIC

    C30 0.0001uF FILM/CERAMIC

    C31 0.015uF FILM

    C33 0.022uF FILM

    C35 1uF FILM

    C40 0.047uF FILM

    C41 0.001uF FILM/CERAMIC

    C42 0.001uF FILM/CERAMIC

    C43 1uF FILM

    C44 1uF FILM

    C47 0.047uF FILM

    C48 0.001uF FILM

    C49 0.001uF FILM

    C50 0.002uF FILM

    C52 0.01uF FILM

    C53 0.027uF FILM

    Will update this list after I go through and see what can be easily replaced.
     
  10. Updated list that gets rid of the tiny value caps that are ceramics:



    C1 0.022uF FILM

    C3 1uF FILM

    C10 0.047uF FILM

    C13 0.1uF FILM

    C15 0.033uF FILM

    C21 0.047uF FILM

    C25 0.015uF FILM

    C26 0.015uF FILM

    C28 0.047uF FILM

    C31 0.015uF FILM

    C33 0.022uF FILM

    C35 1uF FILM

    C40 0.047uF FILM

    C43 1uF FILM

    C44 1uF FILM

    C47 0.047uF FILM

    C48 0.001uF FILM

    C49 0.001uF FILM

    C50 0.002uF FILM

    C52 0.01uF FILM

    C53 0.027uF FILM

    All these caps can be found at Mammoth Electronics in polyester film. This also does away with non-polarized electrolytic caps and changes them to film.
     
  11. Finally got all the parts in today. I'll record some soundbites before and after to see if any improvements can be heard.
     
    theunknowndude likes this.
  12. I loved my pd7 but hated that apart from one setting dialled in everything else was noisy... Got my OFD in its place but still can't recreate the deep bass boom the overdrive gave me...
     
  13. Indeed, I'm hoping this not-so-simple mod will work. Almost all the caps are ceramic or mylar, which I think is where a lot of the noise comes from.
     
  14. Well, that's interesting. I pulled C1 and although the schematic from Ibanez says it should be 0.022uF, to my surprise, I pulled a 0.01uF.

    Hmmm...
     
    theunknowndude likes this.
  15. Granted I know nothing about electronics.. But it looks like quite a convoluted peice of work compared to say a Devi ever peice!
     
  16. Considering the PD7 is a Clean Boost, Overdrive, and Distortion all in one, it does have a pretty large circuit. It's fairly complicated, but luckily, it's pretty easy to follow on a schematic.
     
  17. StayLow

    StayLow

    Mar 14, 2008
    I love this pedal too. Never thought mine was extremely noisy, but less noise would certainly be nice.

    Am interested to hear the forthcoming clips. Thanks.
     
  18. It doesn't get really noisy unless you crank the gain or use the attack switch. Which, I like the attack switch.
     
  19. I usually had attack off in overdrive mode with bass at 2 o'clock, hi at 11, drive and level at noonish... Gave me massive lows without the compression of the distortion setting but yeah any other setting was too much string noise / treble / gainy to be usable with my bass and rig.
     

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