Monday, March 21, 2011

Let's Party

After 3 weeks of plugging, I finally finished updating Acoustat interface with new 47uF Solen Fast Cap (630V).  With my monthly discussion party coming up next weekend, I decided not to bother starting to modify second interface until after next weekend.

I think I did very nice job with this modification, every detail was carefully thought out, and the soldering was done nicely with Kester eutectic solder and my new digitally controlled soldering iron from Radio Shack (works nicer than my old flaky digital Weller) set to 720 degrees F.  When it appeared an old wire might have come loose and was being held by solder alone, I vacuumed and then resoldered that joint.  There are two new pieces of 18g solid core wire connecting to the capacitor.  The capacitor itself is held in place with tie wraps, with insulation from Belkin 16G speaker wire covering the leads up to the last 1/4 inch on the outside, which is deliberately left bare for attaching additional capacitors or test instruments.  Enough insulator is present that it's impossible to move any farther.  The capacitor rests on a small pad of polypropylene Tyvek tape which has lifetime acrylic adhesive.  Great care was used in removing all debris from drilling and soldering.

The system sounded far better than I had remembered.  The newly modified right speaker seemed to disappear, you couldn't tell where the sound was coming from it was so clean.  There is still noticeable grundge from the other channel; when there was any annoying sound it was from the left.  But as with clearing one half of a dirty window, the overall effect is still much clearer than before.

Hooked up newly acquired Kenwood KT-6040 tuner.  I would say right off I expected a lot from this tuner, but it seems to have delivered even more than I expected.  It is the only non-DSP based tuner I have tested and found to receive KPAC 88.3 without annoying whistles.  (The only other tuner than can do this is Sony XDR-F1HD).  But even compared against the modified XDR tuner (analog modification from RadioXTuners with replacement of output amplifier and correction of frequency response), it can't hold a candle to the pure analog sound (warmth and musicality) of the KT-6040.  The Kenwood simply sounds alive, very much like my old KT-8300, but without the noise that usually plagues analog tuners like that one.  The XDR (from memory) sounds dead and processed by comparison (still one of the best sounds...because of lack of noise and noticeable distortion).  The Kenwood even seemed slightly superior in ability to pick out the very weakest station I can get at 90.5 on main living room antenna (though I did not bother switching back to the Sony for same night comparison).

On weak college radio station KSYM I did turn on the Kenwood's high blend switch to reduce apparent noise, which it did well if not perfectly (still some noise left, IIRC the Sony sounded noise free).  This worked very nicely to reduce noise without making highs sound dull, and even with high blend the Kenwood stereo separation was great.  One can expect that the Sony does stuff like this, adding variable degrees of high blend, so it's only fair to allow use of the Kenwood's manual control.  To be more competitive, the Kenwood could benefit from an adjustable high blend control, with the ability to adjust cutoff frequency and blend depth.  Then it could probably match the noise free sound of the Sony.

The Kenwood may unfairly "benefit from the euphonic effect of having wrong HF de-emphasis.  It is currently set to 50uS de-emphasis, the European standard, whereas US tuners are supposed to have 75uS deemphasis.  The deemphasis error would add a slight boost to frequencies in the range 1kHz to 4kHz or thereabouts.  Thus, the Kenwood will have artificially boosted presence until I fix it.

Even with the slight noise, I was so inspired by the liveness of the sound from college radio station KSYM that I hooked up my Nakamichi RX-505 to make a dance party tape while the sound was really rocking.  I set it up so I could monitor party tape through Sonos throughout house.  When the music cooled down around 3:30, I simply played back the tape I had made.  With bias set approximately correct for TDK SA tape (requires less bias than Maxell UD-XL II, as you can tell tuning bias control by ear for best HF response, bias knob now needs to be set all the way down for the TDK) sound was very close to source, with incredibly nice bass.  Using Dolby C, which perhaps only Nakamichi made work correctly on cassettes (they set a standard which nobody else followed in cassette HF response).  Digital recorders still can't match the covenenience of cassette, which works great for making party tapes from radio.

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