Eico HF-81 question for those that have one and moved on from it or returned

thanks guys for the responses. It has been helpful.

Been a long time since I rebuild it (maybe 2002_2003).

My recollection is I used cardas wire for the signal paths, Sprague 716p to replace the coupling ceramics and Angela oil for the .1 uf caps, Riken carbon resistors in EL84 grid network with new carbon comps for others, replaced the phono section ceramics with upgraded caps and kept the metal film resistors marked West Germany as they were within 1% of value.

Upgraded the negative feedback resistors and caps and el84 bias caps (Blackgate) and resistors (Mills wire).

I found a schematic for the tone control wafers and build new ones with upgraded caps and resistors. Power capacitors were replaced.

Replaced all the rca sockets and upgraded the speaker terminals (8 ohm) to modern banana gold plated types and replaced all the tube sockets.

Oh and replaced the EZ-81 rectifiers with NOS Mullards. Only thing I didn’t touch were the vol, balance, and tone controls.

I’ve got a spare HF-81 and have often thought about using it for a custom unit without all the tape and mic stuff, tone controls, and with a modern input selector and ALPS volume control I have.

Maybe after I retire and am looking for a project. :-)

@atmasphere 

Funny you suggested trying 6SN7 tubes in my amp. I already bought a pair of octal to noval adapters to do just that in the preamp stage. Got a pair of Raytheon 6sn7 gray plates. Was an improvement in soundstage depth, detail, and air but have edgy highs. Bought a pair of what looks to be Sylvania black plates with bottom getter branded Zenith. OMG do they sound fantastic. Big deep soundstage, luscious detailed midrange, vocals to die for, sweet highs, good bass, and well balanced. The NOS 50s Mullard 12au7 are great tubes, but the Zenith branded 6sn7 mop the floor with them.

The HF-81 sounds absolutely superb now. It was excellent before but it’s on another level now.