Recently I became interested in improving the sound of my DD-20 Giga Delay. To that end I replaced the original cheap/low performance M5218 and NJM2100 op amps with modern low noise/high performance OPA1612 and OPA2365 respectively. Additionally, I added film bypass capacitors across the electrolytics which couple the various analog stages. Bypass capacitors help retain transparency in AC coupled circuits. The end result is that the DD-20 now sounds very close to the unaffected signal (when using a true bypass A/B switch for comparison). Before the mods it seemed to compromise the tone somewhat. It still loses a very slight amount of clarity, but the difference is unlikely to be noticed in a gig situation. I also did some experimentation with placing the DD-20 before the input of my Eden WT-500 and using it in the effects loop. When used before the amp, the DD-20 adds a noticeable amount of background hiss, even in bypass mode. This noise increases as you turn up the effect level. I was hoping to reduce the background noise with the low noise op amps, but I'm not sure how much effect they have had. At some point I would like to compare my modded DD-20 to another stock unit. What I found, however, was that placing the DD-20 in the Eden's effects loop reduced the hiss considerably, such that it is hardly noticeable. Thus, for lowest noise, I would recommend using this particular pedal in an effects loop, if possible. Another finding is that, when used in mono, the DD-20 sounds better using the "B" input and output. My suspicion is that the "A" input gets split and fed into the "B" input when used in mono, and that this reduces the input impedance by half, thus loading down the input and dampening the signal somewhat. For those who are curious, the A/D-D/A converter is an AK4552 (IIRC), which is an AKM 24-bit/96 kHz CODEC with decent, but not stellar, specifications. No idea of the sampling frequencies/bit depth used in this application. My suspicion is that most of the "sound" of this pedal comes from the analog circuitry, not the digital sections.