John Curl's Blowtorch preamplifier part III

[hhoyt]

Originally Posted by jan.didden

The audio is cut at 15kHz with a very steep filter (100 dB/oct roll-off and 1000's of degree phase shifts) to avoid interference with the 19kHz pilot.
I once did DB listening tests on such a filter with a few guys; 3 out of 4 could reliably identify whether it was in the chain, and they preferred it with the filter in ...

Jan

The best stereo encoders like the Orban 8500 use a high-order 19 KHz notch coupled with a 20 KHz brickwall anti-aliasing filter, both implemented in the digital domain, not a LP filter. The result is 2 Hz to 15 KHz +/- 0.1 dB encode, 0.01% THD rising to 0.05% at 15 KHz, with 110 dB s/n, with 144 dB of processing dynamic range. There is significant encoding of 15-16 KHz signal. On my Kenwood 600T in full quieting I can measure >80 dB S/N from my station with the board potted down. Of course I hear little above 15 KHz at this point in life....

Either way, I consider the sound quality of WXYC-FM very high fidelity. All bets are off once a station adds HD subcarriers to it's signal which I have steadfastly refused to consider. These noise sidebands often raise the noise floor in many FM tuners, and the sound quality of the HD is often inferior to the main linear FM carrier, having been compressed, phase scrambled for symmetry and in a tragic final attack on quality, psychoacoustically data reduced.

The only reason for HD Radio is to allow station owners to have multiple channels and extract more revenue. Analog FM offers a gradual stereo-to-mono transition in weak signal areas, HD offers a full mute in these situations, so I guess it is quieter!

My $0.02 worth...
Howie

[Joe Rasmussen]

Originally Posted by scott wurcer

That is why IMO folks that are used to casual sighted comparisons have strong reactions to suddenly going "blind".

Hi Scott, I hear you. I have mixed feelings about this and perhaps my unease has led to misconceptions as to where I stand. I also have a similar unease when we have audiophiles who turn into instant reviewers and can make major pronouncements in nanoseconds, that cause me to turn (so as they not see my face) and roll my eyes, where it is clear that often "brand bias" or some elitist name thinking has influenced them. So I see both sides of the coin.

Sometimes I just ignore them, mainly because I think that the 'defective' piece of equipment, where an instant flaw was detected, actually sounded like music to me. So go figure?

BTW, I did coin the "JLTi" acronym that the late Allen Wright also used, it stands for "Just Listen To it. This was definitely a shot at 'branding' mentality.

[gpauk]

Used to be three fourths of FA (old UK slang...) FM signal around here -- but now with DAB, for all it's faults, we have in house signal and on the road coverage all through the mountains here... They co-located a bunch of DAB repeaters with cell sites; which would not have worked with FM. Mostly I listen to Radio 4 - speech - or 6 (digital only anyway) so there's no real loss vs quality FM. Sometimes you win...

[jan.didden]

Originally Posted by hhoyt

The best stereo encoders like the Orban 8500 use a high-order 19 KHz notch coupled with a 20 KHz brickwall anti-aliasing filter, both implemented in the digital domain, not a LP filter. The result is 2 Hz to 15 KHz +/- 0.1 dB encode, 0.01% THD rising to 0.05% at 15 KHz, with 110 dB s/n, with 144 dB of processing dynamic range.

My experience was with traditional analog FM. I realize that more performance can and has been squeezed from the format. Your numbers are very good.

Jan

[morinix]

Originally Posted by TNT

More distortion to the people.

[scott wurcer]

Originally Posted by morinix

TNT didn't say that as far as I can tell but of course "the people" seem to love their distortions how ever they appear.

[morinix]

Originally Posted by scott wurcer

TNT didn't say that as far as I can tell but of course "the people" seem to love their distortions how ever they appear.

It is in his signature so I injected it in the quote field. I just caught me at the right time to hit my funny bone.

[DF96]

Originally Posted by Tournesol

It is nice to get some background music, or in a car stereo, but, in a hifi system ?
Who cares about ceramic caps distortions in a FM tuner ?

There was a time when a decent FM tuner receiving BBC Radio 3 was an essential part of most British hi-fi systems. I cannot comment on Belgian radio, but I would be surprised if there was not an analogous station.

On my system, FM radio is just awful (trebles). While it sound ok in little speakers.

You may have a bad tuner, or a bad antenna (causing multipath reception). Or maybe you just listen to a bad station - there are a lot of them these days.

[scott wurcer]

Originally Posted by morinix

It is in his signature so I injected it in the quote field. I just caught me at the right time to hit my funny bone.

No biggie, it's becoming more and more obvious that the cold analytical hardcore accurate (by conventional standards) electronics are not what folks want, more and more people are admitting to their preferences for a little of this or a little of that.

[scottjoplin]

I think this is the case, identifying what they are could be tricky. I wonder if it's more prevalent now due to the ability to do more speaker and room correction that may also have made the perceived sound too dry, for want of a better word