Well, certainly consult this thread, and see if there is anything I might have missed: Deluxe Memory Man, MN3008 building Actually, reading through it now, it seems the schematic showed what a guy was going to do, not what exists in the 4xMN3005 issue. However, here's another potential source of noise. It is common on delays where there is a single bias trimpot to "decouple" the bias voltage by means of a cap between the wiper of the trimpot, and ground. Think of it like smoothing the power supply, but at a micro/local level. As near as we can tell, EHX skipped out on that part. It likely isn't make or break, but since it is dead easy to experiment in a nondestructive way, try sticking a cap to the relevant solder pads on the solder side of the board for each of those trimpot, and see if it makes any difference. A quick scan through the schematics of a number of well-loved commercial analog delays says that a 1uf electrolytic (+ side going to the trimpot wiper) ought to do it. Finally, part of the objectionableness of the hiss is the way in which it seems almost gated. Here is most of the schematic of the 2xMN3005 reissue: https://img.photobucket.com/albums/v474/mhammer/DMM.png You can see that there is a 1uf capacitor from pins 1 and 16 of the NE570 compander chip. This sets the attack/decay constants of the compressor (pin 1) and expandor (pin 16) halves of the compander circuit. Pin 16, however, has an additional 1.5M resistor in parallel with the cap. This helps to produce a slightly faster decay in the expansion than in the compression (normally, they would be identical). Just for the hell of it, if you have a 1M resistor, and can find the pads where the 1.5M goes, tack on the 1M on the solder side for a moment, and listen to what happens. It might produce a more gated sound, or maybe decay fast enough that you don't notice the hiss as much. Hard to predict. Now, the NE570 is touted as being a bit quieter than the NE571, so there is that to consider, but I've never heard anyone rave about how much quieter anything was, now that they stuck an NE570 in there. So it may not be worth the trouble and cost to source one. In the case of the 4558s, though, an NE5532 or LM833 (both easily and cheaply available) is a quieter pin-for-pin replacement. Conceivably, there is some sort of magic voodoo cap replacement, of the sort that guys like Keeley does, that may be quieter in this context. Unfortunately, I have no words of wisdom to provide here, other than it might be possible.