Having the right speakers is critical, although it's really pretty gutsy. But it sounds its best with pretty efficient speakers. Mine are powering a pair of moderately efficient PSB 800's and sounding good.
I've actually had two of these. The first HF81 I got from my uncle, who bought it factory-wired in 1958-9. When I got it, it hadn't been played in 20 years. It had leaky caps and a loose power supply (bolts needed tightening). I replaced the coupling caps with russion PIO's. The cathode bypass caps on the EL84 output tubes were gone too, replace with Sprague atoms. And the plate resistors had all drifted pretty far off spec, replaced with carbon films. that was all last year. this year I put in new power supply caps, which tightened up the bass considerably.
No, it's not a modern amp (the Manley Stingray is a lot more extended and clean-sounding, for instance), but it's lovely to listen to as a second (bedroom?) system. I've been through a lot of stuff, and this one's a keeper. Yes, the parts are crap. Yes, it looks like shit. It sounds WORSE if you upgrade all the parts (heard one with all audiophile-approved parts--my mostly original one with all the crummy mica caps sounds much better). I guess it was voiced with the components of the day. Yet somehow it all seems to work together.
A lot of them (most?) were kits, many badly assembled, with cold solder joints and mis-wired circuits. You can certainly find really cruddy-sounding ones out there. The last one I got was less than $200, and required less than $150 to replace out-of-spec parts, plus another $150 in tubes. But the result was/is a terrific sounding amp. Go figure. I gave it to my neighbor after she spent a week dog-sitting. She loves it, and I'm pleased every time I go over to visit and hear it.
I wouldn't build my main system around one, but it's certainly more musical than a lot of stuff being sold today as high-end, that deliver detail but lose the magic. Hard to beat the bang for the buck IMHO.
HTH!
