EMRFD Message Archive 5098

Message Date From Subject
5098 2010-09-14 03:54:51 Nick How does a DC receiver sound?
for long time now I have been wondering how does a good DC receiver sound in comparison to a good superhet. I know that "good" can be quite subjective, but I am refering to designs like microR1,R2 etc. I had never had the opportunity to hear one, so I was wondering whether there is an audio sample somewhere of such a receiver in order to be able to appreciate it. Does any of the members have any recordings that he can upload? It would also be nice if there was also a sample of a superhet for comparison, not necessarily an A/B comparison but something close..
At the same time I was wondering whether there would be any additional, noticable difference in audio quality if for example a receiver like microR1 was implemented with tubes.Keeping the same architecture and same topology, with only the necessary modifications to accomodate the peculiarities of the tubes, would someone benefit from better audio? (I am not touching the issue of performance, just the audio quality, which may not be 100% independent, but anyway!)

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5099 2010-09-14 06:06:36 Jim Glover Re: How does a DC receiver sound?
5103 2010-09-14 10:07:22 Nick Re: How does a DC receiver sound?
5105 2010-09-14 11:02:40 Tayloe Dan-P26412 Re: How does a DC receiver sound?

This link has two sound files. In each sound file is a clip of a weak
signal as received using a NC2030 and then the same signal received
using a K2. The NC2030 was a high performance single sided phased DC
transceiver that was offered by Norcal back in the 2004 time frame. You
can hear on the second file the someone was adjusting the SCAF filter as
you can hear the width of the audio narrow with widen out again.

Both are high performance receivers. I am not saying that all DC
receivers sound like the NC2030, but people have often commented that
the audio of DC receivers seem "crisper" than most superhets.

- Dan, N7VE


5106 2010-09-14 11:55:29 kb1gmx Re: How does a DC receiver sound?
5115 2010-09-14 19:04:02 Tim Re: How does a DC receiver sound?
Thanks for the sample files Dan, way cool!

With regard to the sample files, I think they illustrate well what a typical superhet sounds like vs what a typical direct conversion receiver sounds like.

That said, the real difference is not superhet vs DC, the real difference is the filtering. Superhets (with few exceptions) have filters optimized for shape factor - meaning nonlinear phase response - which causes the "ringing" on static bursts that you hear in the K2 clips Dan pointed out.

Direct conversion receivers usually have filters designed by real CW afficianados who know that ringing, especially
5118 2010-09-16 01:08:26 Nick Re: How does a DC receiver sound?
5151 2010-09-16 21:14:42 sp2qca Re: How does a DC receiver sound?

here you have R2 samples of how it sounds like:

73! Artur sp2qca