Deep Blue Delay Simulation (FV-1)


Well-known member
I finished up a pedal that I’m pretty excited about. It's a FV-1 implementation of the Mad Professor Deep Blue Delay, where the FV-1 handles the delay time and modulation, but the filtering is analog circuitry around the FV-1.

The DBD clone was the first build I attempted, first try (on vero) went in the trash but the second try worked great. At the time, I had read a lot of great things about it and I still do really like the tone of the repeats, which filters both high and low frequencies. It's been my favorite sounding delay circuit, and I'd encourage anyone to build it as is.

A couple things I always thought about it:
-There's a static sound on the repeats, especially at longer delay times. You can swap chips to find the lowest noise, but it's hard to get rid of entirely in my experience. Although it hasn't really stopped me from enjoying the pedal.
-I’d love to have a modulation knob.

If my only goal was modulation, I'd probably build the DBD filters on the magnetron pcb (nothing against the magnetron filters, I haven't tried it). But, I was also interested in experimenting with this hybrid/digital style.

So I made this circuit to use an FV-1 to handle the delays and modulation, but the feedback path and filters are analog circuit built around the Fv-1. The electrosmash article about the PT2399 was really helpful at explaining the PT2399 built-in filters and signal path. Then it was just a matter of splicing that info with the DBD circuit.

I did have some confusion about the modulator and de-modulator Low-Pass Filters. The modulator LPF is not in the signal path, but the de-modulator LPF is, so I kept it. The result was that the repeats were exceptionally dark and loud, indicating that I should not have included this filter. I marked it on the schematic and changed it on my build (1.2k resistor added in parallel with 4k7 to approximate 1k).

I was inspired to try this concept by a couple of threads here, that discussed building analog circuits of analog delays with a digital delay engine. In the Benson, they use the PT2399, but say that the filtering and pre/de-emphasis removes any noticeable noise. Anyway, I think the concept of using FV-1 or another digital chip could be applied to many PT2399 or analog delays. I would be interested to try or see someone else try the DM-2 or Memory Man this way.

The result is as imagined, same tone as the DBD, but with no noise, modulation is great, and the possible delay time is longer. I really like playing through it so far.


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Need two types of imojis for this build.


This is what D I Y is truly about.
Very kind of you to offer up your schematic, a gentleman and a scholar!
This is awesome @phi1
Did you solder the SMD or have have it done for you? I’m sure I wouldn’t be alone in wanting to hear a sound clip of this?
I had the smd soldered by the pcb fabricator (JLC). Mainly, I thought it’d be easier to fit the pcb layout, though I’m guessing through hole could all fit with a well done layout.