Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Please login or register.

Login with username, password and session length
Advanced search  


SSGuitar has moved to PHP 7.1, enjoy the speed!

Pages: 1 2 [3]   Go Down

Author Topic: Compressor Mods  (Read 10944 times)


  • SSGuitar Regular
  • ***
  • Chip Points: 1
  • Posts: 24
    • View Profile
Re: Compressor Mods
« Reply #30 on: October 17, 2017, 01:44:49 AM »

Yes standard 5mm Green LED's (wired back to back) hard up against the LDR inserted into a short length of black shrink tube.
[/qu ote]

Hi Phil,

I breadboarded up the oscillator Rod Elliot's IC based tremolo circuit ( which works really well. So as an adjunct to making these LDR/LED units, which LDR did you use? Both Altronics and Jaycar carry the same 2 versions of these CdS cells

One is a ORP-12 equivalent: Dark 10m   to   Light 48k - 140k,

while the other one is: Dark 500k   to   Light 2k8 - 8k4,

I think the ORP-12 was what was used in the old Goldentones and the EA Playmasters 116/117 tremolo circuits




  • Legendary
  • ******
  • Chip Points: 221
  • Posts: 1928
    • View Profile
Re: Compressor Mods
« Reply #31 on: October 17, 2017, 11:56:32 PM »

This is the LDR I have used in 2 builds
As you noted,, Jaycar sells 2 types,, while testing I found the larger unit seemed to work better.
Both types will work and they are not expensive,, I can't recall why I went with the RD3485 but it felt better to my ears.

I tested the circuit with TL072, LM883, LF353 and some 4558 chips that I had in the bitz box. They all seem to work the same with no notable difference.
Green leds have a special quality which is beyond my ability to explain,,, some time back there was a whole posting on the subject of LED colour differences and why some are better than others. Something to do with doping If I recall?


  • SSGuitar Regular
  • ***
  • Chip Points: 1
  • Posts: 24
    • View Profile
Re: Compressor Mods
« Reply #32 on: October 18, 2017, 01:36:27 AM »

The super bright leds will drop the resistance to virtually zero from my tests so far with an old LDR from that original Playmaster 116/7 parts list, but that is probably not really what is required I suspect.

Varying between a few K up to 1/2 meg seems to make more sense too especially with that tremolo circuit where you want to vary the volume level up and down but not turn it completely off. I guess the same goes for that compressor circuit of mictesters that you utilize.

Standard green, yellow, orange and red leds gave varying degrees of resistance with that LDR with red & yellow dropping lower than orange and green. That LDR varies from 10m+ (Dark) down to virtually zero (Light) using a white led.
Pages: 1 2 [3]   Go Up

* User Controls
Welcome, Guest. Please login or register.
Did you miss your activation email?
* Recent Posts
Peavey Filter Caps by phatt
[December 13, 2018, 04:50:35 AM]

HH IC100L schematic anyone? by maxkriz
[December 12, 2018, 05:22:35 AM]

Fried Ampeg SVT-200T by Used.Benz.Parts
[December 07, 2018, 02:57:06 PM]

Simple SS Power Amp Build - +/- 40V Push/Pull by Jazz P Bass
[December 05, 2018, 01:19:15 AM]

British Maine solid state amps by FanofJapan
[December 04, 2018, 03:11:47 PM]

* Sponsors