Tuesday, April 17, 2012

Thoughts about Day-Sequerra and other tuners

I sent this email also:

The D-S "FM Reference" isn't any fun, IMO, without the Panalyzer.  Few models had that because it doubled the price.  I'm not sure that one does.  It is said to be a very good performing tuner.  There are so many different sequerra models over the years I'd like to hear some for myself.  The Reference got very good reviews in Stereophile, fwiw, better than what Accuphase had in 1992 they said.  It uses better BB audio chips than japanese tuners (other than recent accuphase) and has balanced output.

Nowadays D-S makes professional broadcast monitors, and their specialty seems to be monitoring HD radio with all possible options.

The original Sequerra Model One only came with the Panalyzer.  There's been one of those listed on eBay for $5000 obo for several weeks now.

It's a steep price to pay for by-many-accounts-lousy tuner with spectrum analyzer.  I got boat anchor HP unit designed for certifying cell phones that has spectrum analyzer that works reasonably well in 100Mhz band, I can get FM spectrum displays that look similar to Sequerra.  That cost me $400, but far too inconvenient to use mostly.  Now I was thinking, if I could have some gizmo that sampled the LO on my Marantz, sent the info to the HP serial port,  HP generates appropriate display, then sends it back out to marantz scope.  Actually, though, the HP has NTSC video output, not X-Y, and the unit has very annoying lag and menued controls.

I think 10B had 4" scope, the 20B has 2" scope, and the 2130 has 3" scope.  The scoped sequerras have have 5" scopes, the nicest of all.

Nice interface.  What they needed was user replaceable module for the actual tuner.

I'm now of the opinion that 10B wasn't Marantz best tuner.  20B and 2130 were.  The 20B especially exemplifies the correct classic design principles: single RF amplifier, extremely wideband IF and detector.  By all accounts, the 10B has relatively narrow "compromise" IF, they bragged about (hypothetical) 150dB selectivity, and dual RF amplifiers that are very sensitive but infamously prone to IM, and quasi-vestigal MPX which throws away half of the stereo infomation.  I think the 2130 tames its two RF stages by virtue of well tuned AGC with dual gate Mosfets.

Dick Sequerra was on to something with the mostly underappreciated 20B.  But the virtue of wide bandedness was lost in the noise of selectivity spec wars of the 1970's.  His second tuner was better than the first.  But reaching for the gold ring, with the Sequerra Model One, he reached prematurely to make a great tuner with varactors, which didn't work.

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