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In Reply to: RE: How low do we have to go??? posted by TomWh on November 19, 2014 at 08:39:35
Wideband preamp into a very good 4th order electronic crossover set at 125hz. Then you can use about any tube amp to drive the high efficiency mid/tweet through a 12db passive. Very low impedance solid state amp driving 125hz and below into moderate efficiency bass cabinets. The tube amps can be really focused on the mid to high frequency voicing. Without the bass pumping through the tube amp, the clarity improves.
While not a purist approach, it does have a ton of flexibility. It can go from ear bleeding chest thumping disco, to the breathy audiophile junk without missing a beat. Designing a tube amp for high frequency is a different animal.
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was just a bit too bizarre for me to glance over. Why on earth would someone want to do this? It is a pure voltage stage.
"Why on earth would someone want to do this?"
For the same reasons you would want to use a plate choke on any other gain stage: to get full gain and low distortion from the tube without the heat and high B+ from resistive loading or possible solid state sound effects from a CCS, and most importantly for the good sound!
I built a plate choke loaded phono stage earlier this year and can say that, in my opinion, it sounds very good. From a measurement perspective with my AP it has a tight RIAA EQ tracking and low distortion.
nt
I would cross over at or below 100Hz and no higher than that. Other than that, 12db passive creates a fairly significant insertion loss and also places several reactive elements in the signal path. So, if anything more than first order crossover is desired, I prefer active vs passive. I agree with the idea in principle, but there is no free lunch.I have two systems. One is based on a Beveridge 2SW, with which I use home-made transmission line woofers, driven by a vintage Threshold solid-state amp, crossed over at 80Hz using a Dahlquist DQLP1 (18db/octave, I think) for the low pass and the internal crossover in the 2SW (slope unknown but steep) for high pass filtering. (The Bev has a built-in direct-drive amplifier.) I am surprised at how much I like this set-up, because I previously had a strong bias against active crossovers. My other system is based on a full-range ESL with no reactive elements in the signal path; I love that too, and it does sound a tad more "coherent" in the region between the low midrange and extreme low bass.
Edits: 11/20/14
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