VFE Switching notes

[Aentons]

I found this old interview with some interesting details about the VFE switching system and thought I would share:

http://www.effectsbay.com/2011/02/review-of-the-vfe-pale-horse-dynamic-overdrive/

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– Can you tell me a little more about the switching mechanism? How did you address the 'pop' with true bypass?
As I wrote earlier, that is still something I strive to improve. Right now I use a latching relay switching system designed by Jack Deville electronics. The relay switching opens up some options for players with more sophisticated switching/looper systems, custom multi-effect pedals & even rack-mounted custom builds. The relay switch operates at 5V, which does help to minimize the pop (the magnetic field produced by the inductor is less prone to induce a charge on the switch contacts at lower voltages), so it's a little quieter than the boutique industry-standard mechanical switching. Jack Deville actually makes a great switching system that can be purchased after-market. I decided not to use his system for two primary reasons. First, I would have to use his circuit board design, which won't work with my need to build both flexible & compact pedals. Second, it would have added about $15-20 to the end cost for my customers.

I do have some ideas that I continue to test to see how to make the switching as quiet as possible. I don't want to discuss these yet, as I don't want to build hype over something I haven't yet designed! However, one trick I employ now is to use a low-pass filter + series resistor in front of the LED. This simple circuit both allows the player to tweak the brightness of the LED via an internal trimpot, but it also makes the LED ramp on/off. This quick ramp softens the abrupt current strain on the power supply, and in many cases, helps reduce the amount of pop produced by the circuit.

[cooder]

However, one trick I employ now is to use a low-pass filter + series resistor in front of the LED. This simple circuit both allows the player to tweak the brightness of the LED via an internal trimpot, but it also makes the LED ramp on/off. This quick ramp softens the abrupt current strain on the power supply, and in many cases, helps reduce the amount of pop produced by the circuit.

Now that sounds really interesting... how would this low pass filter be implemented, I can quite see it on the snippet of schematic from MB build doc... would need another cap somewhere wouldn't it?

[Aentons]

It's a guess on my part but I think it's the 100k/ 100n off of pin 7. I think Brian mentions them in the build doc as having a slow discharge.

Also remember this is an old comment so it could have been removed. He used to have a diode in there for P3 power compatibility but removed it at some point

[gordo]

Interesting

[madbean]

My guess is just an larger electrolytic cap in parallel with T1. This should create a slight charge/discharge delay to ramp the LED on and off.

I use a similar idea on the Bypass#3 board although it's executed in a different way. I actually like the LED going on and off more slowly and it probably does help lessen some pop on mechanical/relay switching.

[Aentons]

This pic of this switchboard is from a production Enterprise v2.5 that I have. It has the "Center" knob and the center "PV" on the mode switch, plus you can see it's purple from Oshpark,so prob from sometime just before the name change.

You can see it has some anomalies "? ? ?" in the top left and what I think are maybe some smd pads over in the right. Go figure

[Aentons]

Here is a pic that I sent Peter where he circled the P3 power diode.

Here is the email back and forth I had with him about it:

ME ---------------------------------
Hi, I know you built in support for P3 phantom power for a time but stopped at some point. How can I tell if the pedals I have have P3 built in? I attached a pic of the inside of  3 of the 4 I have. If I buy a used one of your Standard series pedals in the future, what do I look for to be able to tell?

PETER ---------------------------------
There is a single diode that allows for P3 phantom power compatibility. It must be used in a "pass through" only setup, meaning that the 9V power is set to connect the ring of the output to the ring of the input every time.

I put a red oval around the part in question. It is installed in 2 of the 3 pedals in the picture. This part number is 1N5817, and it is a Schotkky diode.

ME ---------------------------------
Great, Thanks for all the info. Can I just solder in the missing diode or is there more to it? Also, Do you happen to know if the Fuchs Plush P3 power station uses "pass through"?

PETER ---------------------------------
All you need to do is solder the 1N5817 in place, in the same orientation as the other pedals.

"Pass Through" just means that the P3 9V power passes from the output ring to the input ring. This has nothing to do with the power supply, but rather the gear surrounding the pedal. If your whole system (including guitar) runs on P3, then you've go nothing to worry about.

It only matters if you plan on using a pedal or guitar that isn't P3 compatible - in this case, you would not be able to connect a VFE Pedal run on P3 power to a pedal or guitar that doesn't run on P3 power. There are workarounds, but unfortunately I don't have the time to write about each potential scenario.


ME ---------------------------------
Thanks, I see... you just mean that there is no switch to keep power from coming out of the pedal. I really appreciate your all your good work.


PETER ---------------------------------
Yes, exactly.