I highly recommend biamping with Nelson's 6-24 active crossover and powering your Altecs or Faitals with their own dedicated amp.
I have thought about that. I have an SHD studio and I could use that and all I would need is a second DAC. I have had mixed results with analog active xovers in the past and some practicality issue. At the moment, I really like my passive xover. Some exploration is needed.
After scrounging extra parts, I was able to put together the VFET amp this weekend. Thanks to 6L6 for his build guide that made it very easy and quick to assemble. Getting a late start, I was able to take advantage of everyone's experience. It worked immediately. No turn-on/turn-off thumps. No hum or background noises. The sound has lots of musical details. The VFET is now my favorite amp. I set the voltage before connecting a source or speakers. Then ran it for 45 minutes, streaming music, and then made a minor adjustment to the voltage. Thanks to all you have had a part in the design.
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So this is a curiosity. I've measured my P-ch amp temperatures assiduously since I started using it, and I've never seen TO-3 case temps (with an IR gun, through the slots in the top lid) on either device higher than 42C. 39-40C is more typical. And another thing, the fins near the middle of the heat sink consistently read ~2C higher than the TO-3 case tops, which seems like witchcraft.
It's biased at 20V, so it's not running under spec.
It is mine! the amp fits well the mandarins (joke). The driver is a folded PCC88 that is choke loaded - the big trannies, in fact 10K:10k that I wired in series. Great clarity. The driver goes 25Vpp with ease. Without a HV!
The red cables from pre- to main are Isoda cables. [These are wires made up of a selection of many metals to give a harmonical transfer funtion; acqired from advice by J Hiraga.]
There are two plates with the drives and a faux bottom under which I have the power supplies (40V, 12V), filter structures and power buffers.
I have the 1.27 amp idle current and never go beyond the First Watt at home.
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Here some innards of my build. I deviated and designed my own driver with as constraints: 1) Must have Tube. 2) Must run on the Vb of output stage = <40V. 3) Must allow > 8Watt. 4) Must have good bandwidth. I succeeded. Less than 5 Hz to >50 KHz. or so. Yes it is still inverting, but my preamp also inverts.
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