Paul;
Have you heard, observed or measured the artifacts of this receiver? If not,
you have no clue as to the minuscule magnitude of the issue. Your generalizing
is of little value and grossly misleading.
Yes I agree that every receiver has certain artifacts. Most are related to
cost and space available and resultant trade-offs. No receiver is perfect and
without faults. Any brand, any model, any price. Bar none.
Bob, K4TAX
Sent from my iPhone
On Aug 20, 2018, at 11:41 AM, Paul Christensen <w9ac@arrl.net> wrote:
>> "I must emphasize what Bob says about different headphones."
>
> Unless it masks another problem, then it's a design issue for which I extend
> no forgiveness. There's no excuse for hiss, noise, or high-distortion
> levels in any receiver, especially those designed within the last decade.
> It costs a manufacturer no more to design and include a low-noise,
> low-distortion AF stage. Any compromise is flat-out sloppiness, often
> attributed to . LM-386 class of amplifiers have no place in today's
> receivers.
>
> An extreme example of a "fix" was designed by Yaesu engineers into the
> FT-950. The residual hiss is so high they implemented a relay to cut off Rx
> audio when the AF control is full CCW. The activation of the relay can be
> heard just short of the CCW stop. Yaesu actually made the transceiver more
> costly by utilizing the relay as a crutch. In its place, they could have
> used a low-cost, low-noise op-amp, followed by a complementary-symmetry
> PNP/NPN pair. The op-amp is responsible for low-noise in the high gain
> stage while the NPN/PNP pair allows for zero gain but high AF current to
> drive a speaker and headphone. Doing it right means adding one or two
> 1N914 cross-over distortion-cancellation diodes. The result is no hiss and
> audiophile-grade low distortion with power to drive just about any speaker.
> Such a circuit can be seen on my QRZ.com page.
>
> Dave's suggestion of using an in-line audio attenuator will work with
> residual hiss (i.e., hiss that is independent of the AF control). However,
> as the AF control is advanced in unison with the attenuator, be careful of
> clipping. Most transceiver AF stages do not produce much power before
> clipping occurs.
>
> Paul, W9AC
>
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