04/03/2015

Analog FET Switch, daughter board for Deep Blue Delay with Tails mod

I'm aware that my Deep Blue Delay with TAILS mod is being used as it is one of the most visited post on this blog, and the DBD is quite popular in the DIY community, but I'm not happy with my mod. After using it I realized that it doesn't always open completly, so the delay line continues engaged. In this post I present what I think it's a better alternative, although I haven't tested it so this is NOT VERIFIED,

I took the mod idea from the Small Time Delay and used the same implementation, but the mod is just an Analog Fet Switch, used in a lot of pedals in the "non true bypass" era. In the next article you can see how it was used by DOD.


It uses a flip flop and two fet switches. You can simulate the switches easily in LTSpice with the next schematic, but we only need one.


You can read more about FET switches at this thread on DIYSB, I have read a lot but I don't feel qualified to try to explain it. I just realized that it should work better with the DRAIN and SOURCE of the FET biased properly rather than relying on the previous and next circuit sections to do it.

I haven't tested it so this is NOT VERIFIED, but this should work better as a daugther board for the DBD Tails mod. The green wire should connect to A in my modified layout, and the blue wire to B. For the indicator LED take the V+ from the control wire.


This is the DBD modified layout (the same I posted on 12/2013)


If anyone try this, let me know to tag it as verified.


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Location: Madrid, Madrid, España

6 comments:

  1. Unknown16/03/2015, 11:16

    This comment has been removed by the author.

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  2. Unknown20/03/2015, 17:07

    Built this today and it works perfectly, thanks for your hard work designing it. I used a 2sk30a, and a 1n914 for the diode.

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  3. Veit30/04/2015, 13:33

    I`d like to give this a try, but i`m wondering about the direction of the diode. Which side (anode or cathode) goes to the fet? Thanks a lot for this.

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    Replies
    1. Unknown24/07/2015, 13:20

      Veit ->anode goes to gate of your fet. Mine works great. Ive used 2sk117 for fet. Thanks for schematic. Verified.

      Delete
  4. Unknown09/05/2016, 15:04

    Hi, If I plug : board in on Input Delay and board out on Output Delay, it does works? My Carl Martin Delay is on a loop of a DIY analog switching system

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  5. François01/04/2020, 23:58

    Hey man. Is it possible to update this post, as well as the original one on the DBD tail mod? Is this verified yet? I know it's been 5 years, but people still want to build DBDs with tail you know. It's great you share but the information is incomplete.

    I just discovered this post while I was doing revision on the layout before soldering. I was about to go with the previous JFET switch circuit. So now, how can I know for sure which is better? I only have the parts for the other JFET switch. Should I wait and build the one above?

    Thanks

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