> >From Brad:
>
> My own listening tests have been very subjective. I think we'd need
> some "blind" tests to validate the differences I think I hear. The
> poorest of the preamps I tested make the receivers (a Mk V and an
> '817) sound more "mushy" under noisy conditions. (Preamp gain and
> receiver attenuation were adjusted to prevent overloading.) But the
> effect is certainly down at the "Maybe it's there, maybe it's not"
> level. The best of my preamps, an Aiken Industries AMP-1200-9 ($1725
> current, single-unit price), is completely transparent to the ear.
>
Brad,
With the "mushy" preamps, were you using any kind of bandlimiting
filters ahead of them. I am wondering if you have any local BC that
is loading up the preamps. Your rigs would high pass filter it out,
but a cheap preamp with a wide open front-end could start to
overload on strong BC and you might not realize it. The good
preamps with very high IP3s would be transparent even in the
presence of strong BC. I have this kind of problem when I
use my JPS ANC-4 noise cancellor. If there is any strong local
BC present, the ANC-4's internal preamp starts to overload
as it has no bandlimiting filters ahead of it. If I put a high-pass
(BC reject filter) in front of it, it cleans right up.
Just a thought.
Mike, W4EF...................................
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