Deep Blue Delay....

[Snare227]

I'm working on a Deep Blue Delay and I have something I'd like to work out, but I can't find the answer.  

I have built the regular DBD, the modded one with the volume control (4 knob DBD), and a tails version with the volume control (4 knob DBD with tails).  They are all great, but I am wanting to build something similar to the Boost DLA by Tech 21 if possible.  I'd like to have a normal volume going through when the pedal is bypassed and then when I click on the pedal I get a boosted volume along with the delay, and when I click the pedal off the dry signal is back to the original volume and the tails continue to ring out.  Basically a low volume rhythm sound, then a boosted delay with tails, and back to a low volume rhythm sound.

The four knob DBD with tails is close to this, but the volume control changes not only the volume of the wet signal, but also the bypassed volume as well.  Is there a way to make the volume knob only change the wet volume?  Or have two controls one for the bypassed volume, and one for the engaged volume?

[Ubertech_s]

I think the issue is that the tails mod requires you to forego the true bypass

one option is not to do the tails mod and go back to true bypass - this would mean the effect, including the volume, would be bypassed when the effect is off

I suppose if you want to keep tails the answer would be to create a different path for the volume in 'bypass' mode so that it misses out the volume part of the circuit

unfortunately I dont know the answer for option two, but Im sure if its possible some one on here will work it out as it would be very useful to keep the tails

[induction]

The volume of the wet and dry signals are controlled by the resistors in the final summing amplifier. Since the stock bypass scheme only requires two switching poles (one to bypass the wet signal, the other for the led), you could use the 3rd pole of a 3PDT to sub a resistor or pot in the summing amp to alter the dry volume.

Look here for information on summing amplifiers, and compare to the DBD schematic.

Let me know if you need more help.

[Snare227]

Going with what you said I thought about this... using a 4PDT switch and using one pole for the LED, one pole for the effect bypass, and two poles to swap between two different resistances (maybe one as an external pot for the boost volume and maybe an internal trimmer to set the unity gain of the bypass?)  If there is a way to do this with a 3PDT switch that would be better. I may need a little more spelled out for me Induction if you don't mind. Thanks for your help.

[induction]

Snare227 wrote

If there is a way to do this with a 3PDT switch that would be better.

You can do resistor (and capacitor) substitutions with an SPDT like this:


If you want independent control over both volumes, then the third way is best, with variable resistors (trimmers or pots) for both A and B.

[Snare227]

Exactly what I needed.  Thanks Induction!  I did a test run last night with test leads and it worked great.  I'm going to figure out the best value for unity gain on bypass using a pot and replace it with a resistor, then wire an external pot for the boosted volume.  Thanks again man!

PS. Do you have a book or website you keep all this info at?  

[induction]

Glad it worked out for you. I don't have a website or anything. In fact, I don't build very much these days. I'm transitioning careers at the moment, so I have very little free time for my hobbies. I check the forum a few times a day to see if there are any questions or debugs I can help with in a few minutes or less. That's pretty much all I have time for at the moment.

[Snare227]

I'm a daily lurker, and I've picked up a lot from your posts in the past... thank you for your contributions.

[nocentelli]

Snare227 wrote

I'm a daily lurker, and I've picked up a lot from your posts in the past... thank you for your contributions.

+1

[induction]

Aw, shucks.  

Thanks guys, that means a lot.

[motterpaul]

There are a lot of helpful people here, but induction is the best when it comes to knowing his stuff.

Hey - a question on this:



On that last one (switch between A/B) - why don't you need to tap into the middle? If half the switch is off, I don't see how the signal isn't open there. I thought you needed a 2PDT to do A/B switching. What am I missing?

[cylens]

if you number 1 2 3 from top to bottom

when the lever is down, 1 and 2 are connected, hence component B is shorted and component A is "in the circuit"

[motterpaul]

Okay, I see it now. At first it was looking like an open switch to me, but now I see that with the resistors there it is more of a "path of least resistance" scenario. So, if you close the circuit between resistor B it goes directly to A and goes through. Thanks.