Eico HF-81 with Klipschorn

Have you done any tube rolling in your Eico? I put a pair of Mullard rectifiers in mine, and some NOS Amperex Holland EL84's and gained a tremendous dose of palpability compared to the modern production tubes that I had been using.

Nice to hear it will make Klipschorns sing!

Sorry for the shorthand. I rescued my HF-81 from my uncle's attic and needed to do a fair amount of restoration. If you are interested in a lot (too much) of information on Eico's you can check out the Yahoo Groups on Eico. The Eico has a pair of rectifier tubes (which convert AC power to DC) which are marked 6CA4/EZ81 on them. They seem to have a substantial impact on the sound quality. Many people prefer Mullard brand or Amperex brand for these tubes.

There are four identical tubes labeled 6BQ5/EL84 which are the output tubes. They are the final amplification stage tubes and they supply amplified signal to the speakers through the pair of output transformers. Some people like vintage NOS (New Old Stock) tubes in these positions, but I've been fairly happy with modern production JJ tubes or Russian equivalents in these positions. Good thing because the NOS varieties are getting expensive.

The other tubes provide amplification for the phono stage and the line stage. They are marked 12AU7 and 12AX7. The 12AX7 tubes can be replaced with modern "Mullard" label long-plate 12AX7 tubes which sound quite good.

I hope this is a bit clearer and more helpful to you. Again, this should be a nice amplifier for you long term.

Speaking of which... If yours has had nothing done to it, then you should have someone check the health of the electrolytic capacitors in the power supply. Mine were bad, and replacing them (and increasing their values somewhat) contributed a MUCH stronger bass line to my music.

I am surprised somewhat by your findings.

I know the Dynaco sound very well. I still own the Dynaco ST70 I built as a kit in 1968. Mine has been in continuous use up until 2005 when I had to rebuild it due to deteriorating circuit boards and dying electrolytic capacitors. It sounds very pretty, but is not up to the standard of many of today's best amplifiers. On the other hand, the HF-81 can be very competitive if it is working correctly!

When I upgraded the power supply electrolytic capacitors in my Eico HF-81, one of the main improvements was much more powerful bass. I would expect the HF-81 to sound sweeter than the Dynaco pair.

Anyway, I think the warmth you hear may be a combination of weak mid-bass output of the HF-81 due to weak power supply caps and the very round sound that the PAS3 produces. I like the phono section of the PAS3, but it is not really all that good a line section, especially for extended treble or deep bass. On the other hand, the Klipsh speakers may be a perfect match for that combination. You may have discovered something.

Whatever works best for your ears is exactly right! Enjoy the music!