I purchased this HF-81 a few months back on the bay. The seller had done some work on this one, mainly changing the coupling and power supply caps. He also changed a few out of spec resistors, but left most of the ceramic caps as they tested fine? I am a believer in keeping vintage amps as close to stock as possible, circuit/component wise, to retain their original sound and to keep them operating in their original design paramters. I did replace more caps and resistors, and bypassed the funky focus (balance) control which induces gain and actually raises the volume of the channel it's moved to. I also bypassed the function switch which inverts left/right channel, mono selection etc. I did this mainly to get a bit more detail from the preamp stage as it is a bit veiled. Future changes may include changing resistors in the signal path for better quality mainly to help with transparency. Except for the pair of Eico branded Mullard 12au7's, all tubes tested at 100 on my mercury tester.
Cosmetically, I polished and cleared the brass faceplate, repainted the panels argent silver rather than the original military grey, and painted the cage gold to accent the faceplate. I also repainted the brown knobs a satin black.
The great thing is it sounds even better than it looks. It is a very musical and involving piece of equipment. Big toe tapping factors going on here. Nice bass, never boomy, liquid smooth but detailed mids with nice layering and separation, and nice highs. The biggest suprise was the tube phono stage using the mullard 12ax7 tubes. Very nice!!! Great dynamics, detail, and especially vocal timbre is excellent. Attack and decay with drums is very quick fast and punchy as is the timbre of piano and acoustic guitar. For an all in one unit these are a great value in my opinion.
Cosmetically, I polished and cleared the brass faceplate, repainted the panels argent silver rather than the original military grey, and painted the cage gold to accent the faceplate. I also repainted the brown knobs a satin black.
The great thing is it sounds even better than it looks. It is a very musical and involving piece of equipment. Big toe tapping factors going on here. Nice bass, never boomy, liquid smooth but detailed mids with nice layering and separation, and nice highs. The biggest suprise was the tube phono stage using the mullard 12ax7 tubes. Very nice!!! Great dynamics, detail, and especially vocal timbre is excellent. Attack and decay with drums is very quick fast and punchy as is the timbre of piano and acoustic guitar. For an all in one unit these are a great value in my opinion.