Delegate (Warden) Upgrades

Would a vactrol work here or do we specifically need a LED/LDR combo? I think I've got a few vactrols from Electronic Goldmine and am wondering if those would work here.
 
Good afternoon everybody. I want to thank D. Bones because I installed the Compressor with his modifications and it sounds wonderful. I finally found "THE" Compressor for my bass.
 
I would like to propose just one modification to the circuit: I connected another white LED in parallel to the LED that drives the photoresistor, a second LED that I mounted on the front panel of the pedal, and which visually gives me an estimate of the amount of compression applied.
 
Another thing I've been working on for a while and I'll share with you: I've developed a Linkwitz-Riley type crossover scheme, 24dB oct with variable cut-off frequency. I tested it with the oscilloscope just today and it works fine. It separates high and low frequencies into two channels, with cuts ranging from 100Hz to 1120Hz (selectable with a 4-position selector). The original diagram comes from magazine number 177 of "Nuova Elettronica", a magazine of electronic kits which unfortunately bankrupt in 2015. I took the diagram, which had a 15+15vdc power supply and I adapted it to work at +18vdc (obtainable with a simple tc1044). This circuit could be the basis for developing a multiband optical compressor, similar to FEA, using two Wardens modified according to D. Bones. I attach the diagram (tested and working).
 

Attachments

  • FIltro 24dB -Linkwitz-Riley_2.jpg
    FIltro 24dB -Linkwitz-Riley_2.jpg
    148.6 KB · Views: 21
The next phase, if someone wants to develop the project, would be to prepare a printed circuit (but I don't know how to do it, when I graduated they were still using acids to etch the tracks, I believe that now there are more efficient and precise techniques). The TC1044 part is missing from the diagram, but it can be easily copied from the Warden diagram.
 
Fab64 said:
I would like to propose just one modification to the circuit: I connected another white LED in parallel to the LED that drives the photoresistor, a second LED that I mounted on the front panel of the pedal, and which visually gives me an estimate of the amount of compression applied.
Click to expand...
Series connection would be better because parallel LEDs won't share current equally. One may hog most of the current.

Fab64 said:
This circuit could be the basis for developing a multiband optical compressor, similar to FEA, using two Wardens modified according to D. Bones. I attach the diagram (tested and working).
Click to expand...
Very clever!

Fab64 said:
...when I graduated they were still using acids to etch the tracks, I believe that now there are more efficient and precise techniques...
Click to expand...
It's still done that way. Commercial PCB fab has become so economical, even in small quantities, that it's hard to justify doing it at home. I've seen PCBs etched using a CNC engraver, but it's slow and expensive.
 
Chuck D. Bones said:
This post describes the mods in the Col. Klink.
The EQD Warden is a good optical compressor. Basic design is mostly sound, with one major defect, one minor defect and a few opportunities for improvement. Parts of this design were lifted from the Ross compressor.
Major Defect
The signal path is routed through Q1, where is gets distorted by the non-linear loading from D2 & Q3. This is easily corrected by disconnecting C14 from Q1-E and connecting it to IC1 pin 1. You can do this on top of the board simply by lifting the + lead of C14 out of the pad and running a jumper to the end of R5 closest to IC1. I did it by cutting and jumpering on the bottom of the board. If you're not experienced in trace cutting, then do the mod on the top of the board.

View attachment 4365

Minor Defect
The bottom end of the TONE control is useless. I don't know about you, but I have no use for a treble cut in a compressor. A little treble boost brings the sparkle back that gets lost in compression. The stock tone control is flat at about 8:00 or 8:30 and below that cut treble. At 7:00 it's a very strong treble cut. Installing a 20K resistor in series with pin 1 of the TONE pot fixes that. Now 7:00 is flat and it's all treble boost above that. You can cut the TONE pot's lead short and install the 20K resistor between pin 1 and the board, or use a solder lug pot like I did.

View attachment 4366

Opportunities for Improvement
1. Q1 biasing. Q1 is biased close to saturation, which reduces its dynamic range. If we correct the major defect above, this mod is less important. However I wanted to maximize the performance of the envelope detector and remove any loading effect from the output of IC1.1. Replace C5 with a 3.3K resistor (stand it up). Replace R6 with a 10K resistor. Do not solder the bottom end (the end furthest from Q1) to the pad, solder it to the next pad over at the end of R7 (also 10K).

View attachment 4367

2. Better component values.
2a. Change R3 to 2.2M, change R1 to 2.2M or larger; I used 4.7M. R3 = 10M makes no sense when R1 = 1M. Change C2 to 100nF, 1uF is at least 10x larger than it needs to be, even with R3 reduced to 2.2M.
2b. Change R4 to 10K for 6dB more sustain.
2c. Change the LEVEL pot from B50K to A50K. Gets unity closer to noon.

Parts Substitutions
This is all very optional. I did it because I had the parts.
Q1-Q3 can be any high-gain NPN transistor. I used 2N5210. They can all be 2N5088, 2N5089, MPSA18, etc. Don't waste your best transistors here.
I used some fast rectifiers for D4 & D5 to improve the charge pump efficiency. 1N5817 is also a good choice.
I used TC7662 for IC2, it is slightly more efficient that the usual suspects.

A note about the LED & LDR.
I used a frosted white LED. It's very bright even at low current. It turned out to be overkill. The LDR I used is in a TO-18 can, obtained from Electronic Goldmine. They were dirt cheap on sale, like 40 cents each. One ot two stinkers in the bunch, but the rest went from under 2K (illuminated) to over 2Meg (dark). Cadmium Sulfide LDRs have a quick response to light, their resistance drops in a few milliseconds. Their response to dark is much slower, over 100ms to get from 2K to 500K. The more light that hit them, the longer it takes for the resistance to go up. That's why a bright LED isn't always a good thing. I find it best to set the ATTACK at 8:00 or 9:00 so the peak LED current is less and the release is quicker.
Click to expand...
I have half a dozen warden pcbs on the way and danng im glad i found this thread. You lost me with the LED's....but thats at the bottom of the mod list so we'll see when i get there. Thanks for the contribution
 
You must log in or register to reply here.
Back
Top