Hmmmm. The first one of these I built had 1K metal film resistors for I/V and bias. Overall this combination works well but the sound can be a tad thin. I built a second one with Allen Bradley carbon comps using 2.8K for I/V and 1.4K for bias (the stripes say 2.7K and 1.4K, but they measure a bit higher.) The second one sounds fuller, more dynamic, more natural, and overall better, but at high volume there is a lot of high pitched background noise that is not in the other one. There are other difference like different bypass caps and a different voltage regulator, but these are all higher quality, lower noise parts, so it seems unlikely that they are the problem.
So, does anyone have any experience with AB resistors? I've heard they are noisy, but this seems absurd. Or, any other ideas as to where the noise is from? It sounds like grainy static, so don't think anything is oscilating, but what do I know. Oh, also the noise is most pronounced into my Melos which has a higher input imedence than my other amps, so that may be a factor.