Tone Control Bypass
Many have wondered how the EICO would sound without the tone control compromise in the circuit. This mod below, outlined by Jean-Francois Lessard, does bypass ONE HALF of the 12AU7 stage but the tone controls are out of circuit.  You need to be the judge whether you think the mod beneficial. It might just sound better, tone circuit left intact. > Tone Control Bypass



Balance Pot Bypass
The Balance, or FOCUS, as it's known on the HF-81, is a pretty mediocre pot and strangely enough, seems to be wired wrong in a few units I've heard.  Bypass the whole affair if you desire - Coming Soon



The Humming Buzzing Power Trans
The Eico HF-81 power transformer has always been a slightly weaker affair.  It seems to be problematic in quite a few of the units with many samples bringing hum and buzz after years.  It gets extremely hot and sometimes the wax has seen better days.  Solution?  Heyboer Transformers makes a great replacement.  It's a recommended mod for any suffering from the EICO PS Trans Blues (or buzz as it were) - coming soon



The Power Switch Failure Solution
Almost every EICO HF-81 I know finally succumbs to the dreaded power switch failure.  It's embedded in the treble control so it's not an easy fix to keep stock.  Many have bastardized their HF-81 with holes for a new unsightly switch.  Here's a neat solution that makes the most sense and is not visible to boot - Coming Soon



Cap and Resistor Choice:
How to keep the HF-81 Magic Intact
Although the Super Eico HF-81 has been the subject of debate, it's becoming somewhat evident that some of the magic and quality of the original HF-81 does not come out in the wash.  It seems the modern HF-81 with trimmed down circuit and hi-po parts might reap some rewards but at a loss of others.  The same can be said for an all-out mod of the original.  Just what is the best selection of parts to avoid changing the entire character of the amp?  - Coming Soon



The EICO HF-81 Phono Stage:
Any Improvements to make this quiet?
While the HF-81 is known for its sonics via the line stage, not much is said about the phono section.  There seems to be a universal problem with some residual hum out of the left channel. Many use an outboard phono stage including myself.  Can the little HF-81 phono be brought to a better light?  > Phono Stage Mods




If you have any questions or comments concerning the EICO-HF-81, please drop me an email:

eico_hf81@earthlink.net