DM me when you're ready to build. We've been printing a few samples of the stands with different fill patterns, and may have some functional extras laying around to share.
Re-biased the amp earlier today
Just spent a couple of hours this evening listening at very modest levels (40 to 50dB SPL) and am very relieved to report that re-biasing completely fixed the lack of imaging precision, and lower/mid-bass vagueness. And it tamed the wild soundstage -- no more getting smacked upside the head by stray bass players out in left field. The soundstage is now comparable to the ACAs, extending back away from the speaker plane, as is the imaging, also excellent. Same sweet mid and upper highs, with no listening fatigue after extended listening. And deeper bass.
This is just a lovely, medium-sized amp! I may try running it at higher bias current just to see, but I suspect the character won't change all that much.
- target 500mV, +/- 5% across R6/R7 for 25-30 watts/channel
- <10mV DC offset at Vout. (The smallest reliable change I could effect with the pots seems to be about 5mV)
Just spent a couple of hours this evening listening at very modest levels (40 to 50dB SPL) and am very relieved to report that re-biasing completely fixed the lack of imaging precision, and lower/mid-bass vagueness. And it tamed the wild soundstage -- no more getting smacked upside the head by stray bass players out in left field. The soundstage is now comparable to the ACAs, extending back away from the speaker plane, as is the imaging, also excellent. Same sweet mid and upper highs, with no listening fatigue after extended listening. And deeper bass.
This is just a lovely, medium-sized amp! I may try running it at higher bias current just to see, but I suspect the character won't change all that much.
Attachments
In general more bias=better performance when you're speaking of almost any of these Class A amplifiers using MOSFET output devices. Attached is a picture from NP's "Leaving Class A" article to demonstrate the point. As expected, you eventually reach diminishing returns, and we are obviously limited by the hardware on how far we can push things. Heatsinks @ a maximum 50 to 55C at thermal equilibrium, under worst case conditions (middle of summer, etc.), is a reasonable target.
