adding "hold" to Danelectro Delay

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Dimitree
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adding "hold" to Danelectro Delay

Post by Dimitree » Tue Mar 17, 2020 2:03 pm

I've modded my Danelectro PB&J digital delay stompbox, adding a "hold" feature.
I simply used a SPDT switch to connect/disconnect the Write Enable line between the echo chip and the RAM (found this mod online).

schematic

it works, but now I'd like to do some improvements:
instead of using a SPDT, I'd like to use one of the two stomp switches already on the unit. Indeed, one of these is used to alternate between two memory buffer sizes (long/short), and since I don't use this feature, I'd sacrifice this switch (forcing the buffer to "long", already done that).
As an experiment, I used a CD4053 to replace the mechanical SPDT, driven by the flip/flop that handles the switches on the unit. It worked, but with two flaws: at power up, the stompbox is forced to "hold", and since the delay memory is full of garbage, as soon as I power up the pedal I got loud and nasty noise.
Is there a smart way to handle that?
Also, since the "write enable" is a logic signal, I guess, instead of CD4053, I can simply use a logic gate combined with the flip/flop, that would be more elegant

jorg
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Re: adding "hold" to Danelectro Delay

Post by jorg » Tue Mar 17, 2020 4:47 pm

Dimitree wrote:
Tue Mar 17, 2020 2:03 pm
I've modded my Danelectro PB&J digital delay stompbox, adding a "hold" feature....
Is there a smart way to handle that?
Also, since the "write enable" is a logic signal, I guess, instead of CD4053, I can simply use a logic gate combined with the flip/flop, that would be more elegant
Yes, a simple gate would suffice, or you can choose a different output on the CD4053 you have already installed, so you reverse the on/off states (i.e. make it default to normal at power-up).

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Dimitree
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Re: adding "hold" to Danelectro Delay

Post by Dimitree » Tue Mar 17, 2020 6:01 pm

I actually tried to reverse the NO/NC connection on the 4053, but it didn't make any difference..I still get nasty sounds as soon as I power up..
I should try again, probably I made something wrong

jorg
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Re: adding "hold" to Danelectro Delay

Post by jorg » Wed Mar 18, 2020 7:38 am

Dimitree wrote:
Tue Mar 17, 2020 6:01 pm
I actually tried to reverse the NO/NC connection on the 4053, but it didn't make any difference..I still get nasty sounds as soon as I power up..
I should try again, probably I made something wrong
Have you remembered to include a pull-up or pull-down resistor at the write enable pin, so when your CD4053 switch is open, you know what state the enable will go to?

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Dimitree
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Re: adding "hold" to Danelectro Delay

Post by Dimitree » Sat Mar 21, 2020 3:34 pm

so I moved some wires and now it works an intended, at power up Hold is Off

but..

since the stompbox goes Active by default at power up, you can still hear that noise as soon as the pedal is powered, and then it decays (it goes through the feedback path).
So maybe the CD4053 is not fast enough. I used a pullup resistor on the center lug of the switch, and a pulldown resistor on the flipflop driving the switch, but it didn't help.
Is there a way to force the stompbox to Bypass when powered?

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