By kind permission from AudioXpress, the ImPasse preamp article is now available. This preamp can also be used as a single-ended very high performance lineamp by grounding the non-inverted output (i.e., the capacitor coming from the plate of the phase splitter). Article here.
I am very grateful to fellow diyaudio.com member Pierre Lavoie for putting me onto
the Impasse preamp, saying that it was designed to drive my First Watt F4 power amp.
I’ve been working with Jim Salk http://salksound.com/ to build Gary Dahl’s speakers.
Gary co-designed them with Lynn Olson. Last month, Gary demoed his system at a Seattle audio club. Though I couldn’t make the trip out there from Long Island, as you can see his audience was quite enthused and pleased with the performance.
Thanks to Gary’s very generous assistance Jim and I should have no trouble cloning
Gary’s Azurahorn 425/Radian 745 Neo Be driver combo, RAAL Lazy ribbon tweeters, sealed GPA Altec 416-8B midwoofers and crossovers. My subs will be Jim’s version
of the Rythmik 12” sealed servo subs
Here’s Gary’s summary of the last of his basic system tweaks, and where he becomes more pleased than he ever thought possible with the sound
However, it turned out that further refinements made to the ribbons’ high pass filter
delivered even better performance.
Gary uses his build of Lynn Olson’s Amity amps to drive his speakers
http://www.nutshellhifi.com/triode1.html . But I will most likely want to use the
Impasse/F4 combo to drive mine.
I do happen to have two F4 amps which I suppose, depending on signal sources, would allow me to drive at least most of the entire system with balanced power. However, aside from losing common mode noise rejection protection and higher output voltage, would I give up significant sound quality if I configured the Impasse
with single-ended inputs and outputs to drive only one F4 amp?
Also, if you happened to have since found any tweaks or upgrades that will
further improved the Impasse’s performance, please refer me to those revised
or supplemental schematics, procedures, parts substitutions, et al. I will be sure
to incorporate them in my (unbalanced ?) version build of it.
Finally, please let me know where I could obtain approved etched pc boards for
the Impasse and for the recommended power supplies.