Author Topic: Phase 90s, always noisy using feedback resistors  (Read 1357 times)

marauder

  • Solder Ninja
  • ****
  • Posts: 235
    • View Profile
Phase 90s, always noisy using feedback resistors
« on: January 21, 2016, 11:38:01 AM »
Is this normal?

Every time either me or John build a Phase 90, and put the 22k feedback resistor in, it always noisy and pretty much unusable.  Take it out, so it V1 script spec and its perfect. 

Doesn't matter who's PCB we use the result is the same.

Is this normal, I've never used a real Phase 90.

Govmnt_Lacky

  • Electron Doctor
  • *****
  • Posts: 2221
  • Dinner at Dorsia? No problem...
    • View Profile
Re: Phase 90s, always noisy using feedback resistors
« Reply #1 on: January 21, 2016, 11:48:59 AM »
It has been a long time since I have heard a P90 that I have built (currently in work on one now) however, the last one I built had a script/block switch with a feedback resistor (22K or 24K... cant remember) and I do not remember it being noisy.

I am not sure the exact purpose of the feedback resistor other than I 'believe' I read it was implemented to compensate for 'not so closely matched' FETs in the circuit. I could most certainly be wrong though...

jimilee

  • Global Moderator
  • Electron Doctor
  • *****
  • Posts: 9220
  • Jimi Lee
    • View Profile
Re: Phase 90s, always noisy using feedback resistors
« Reply #2 on: January 21, 2016, 01:10:41 PM »
I experienced it on 2 different phasers.
Pedal building is like the opposite of sex.  All the fun stuff happens before you get in the box.

pickdropper

  • Electron Doctor
  • *****
  • Posts: 6175
    • View Profile
Re: Phase 90s, always noisy using feedback resistors
« Reply #3 on: January 21, 2016, 02:05:12 PM »
The feedback resistor can introduce distortion but can make the phasing more pronounced.

If you play clean, the distortion can be annoying.  If you tend to play it with dirt, it's not as bad.

All in all, I far prefer the script mode (no feedback resistor).  I tend to leave the feedback resistor off these days.
Function f(x)
Follow me on Instagram as pickdropper

jimilee

  • Global Moderator
  • Electron Doctor
  • *****
  • Posts: 9220
  • Jimi Lee
    • View Profile
Re: Phase 90s, always noisy using feedback resistors
« Reply #4 on: January 21, 2016, 03:58:32 PM »
Mine was just noise in one build and radio and noise in the other.
Pedal building is like the opposite of sex.  All the fun stuff happens before you get in the box.

juansolo

  • Electron Doctor
  • *****
  • Posts: 4704
  • John - Wakefield, UK
    • View Profile
    • Juan's Gnomepage
Re: Phase 90s, always noisy using feedback resistors
« Reply #5 on: January 21, 2016, 04:46:27 PM »

Is this normal, I've never used a real Phase 90.

Not actually true. Phil's was a block casing with script internals (no feedback) and sounded like the ones we build without it.
Gnomepage - DIY effects library & stuff in the Stompage bit
“I excite very large doom for days” - playpunk

marauder

  • Solder Ninja
  • ****
  • Posts: 235
    • View Profile
Re: Phase 90s, always noisy using feedback resistors
« Reply #6 on: January 22, 2016, 04:08:16 AM »
Not actually true. Phil's was a block casing with script internals (no feedback) and sounded like the ones we build without it.

Forgot about that one, the trimpot had turned to dust in it.