Wiring Tips - Stevens Hints
Before I received a schematic, I actually e-mailed Roger Stevens
with a detailed shot of the HF-81 guts with labels on parts imploring
ole Roger to fork up some advice. This page is a reprint of his
e-mail to me. I added my own perceptions based on what I have come
to find out since then. I think an upgrade to the ELNA Cerafines
in the PS and Hovlands as the coupling caps might be in order. Not
so sure about the bias change either. A very informative page, nonetheless.
I also temporarily posted his entire page of HF-81 comments as well
(with his permission).
Roger Stevens EICO HF- 81 Mods
Roger goes over some mods for the solder slingin' fools; many good
tips here although I am not sure I would use all his steps. Regardless,
the best place on the guts of the HF-81. In addition, Roger is a
super nice guy with an amazing life story as well! This is a must
visit. EDIT 2015:
Sadly his site is gone and I'm not sure he's still around.
Was a great guy and resource
The EICO Unofficial
Home Page (OFFLINE)
The "Fiddler" home page for all things EICO. Good
basic info and specs for all the classic EICO gear with brief descriptions
of the sound if ole Fiddler has heard it. He loves the HF-81.
Review - EICO HF-81
Audio Review.com is a site dedicated as an outlet for consumer reviews
of electronics. There is a rating system of 1-5 stars and results
are instantly tallied. While there are not as many vintage pieces
here, a place is occupied by the HF-81. Currently, there are seven
reviews for an amazing average of 5 stars.
Valves - Tube Amp Repair - Rebuild
Greg will try and work with you to repair, rebuild, or restore your
EICO HF-81, among others. NOS
Valves specializes in keeping the sound of the vintage piece
intact but will customize and add modern caps upon request. NOS
Valves is also a HH Scott specialist as well. Tell them that
Kelly sent you for the HF-81.
This is a custom transformer house that has done replacement iron
for EICOs in the past, including the EICO HF-81. Tom Mobley wrote
me about these guys a while back and I just got around to adding
their link, a link well worth the effort seeing as how the power
transformers can have problems on some EICOs. All of the PS trans
will run hot to the touch, sometimes VERY hot, but if you are getting
excessive buzzing, vibration, and noise, you might need a new power
trans. They can make a replica that is the same size but with specs
to match modern voltages and more current draw. Drop them an email.
They supposedly do the outputs as well but that is part
of what makes the EICO so good.
EICO HFT-90 Mono
All tube Tuner
This is a page I worked up when I thought of selling my little 50s
EICO HFT-90 tube tuner. I'm glad I never sold the little beast as
I really love the sound. It is mono but sounds so warm and natural
on public radio jazz late at night on low compression stations.
Some good shots of the HFT-90 here.
GROUP - Yahoo List - SUBSCRIBE
This is a GREAT source for EICO banter and information although
it is slightly more focused on the EL-34 EICO options such as the
excelletn HF-35, HF-50, and Acrosound output HF-60. But there is
exhange on ALL models of EICO, including the HF-81. If you own an
EICO of any kind, I really recommend joining this list to read and
Fi Primer - JC Morrison
This is literally the online version of JC Morrison's "Fi Primer"
and is well worth a look if you are considering building your own
tube equipent or to just soak in the imformation - Well worth a
perusing despite the annoying popup windows from the free server
Files Online - Tube Amp Hints
This is such a great page and I had forgotten all about it until
receiving a mail from EICO HF-81 owner/mod King Carsten Rauth from
Germany. This page has schematics and contruction tips for many
amps from EICO to Heathkit etc. The EICO HF-86 notes are helpful
with the HF-81 since they have similar circuits. Other points of
interests are the discussion of the various parts such as resistors,
tubes, rectifiers etc.
A neat resource ie
Need the EICO HF-81 Manual?
I also have a complete manual and can be bribed to copy with a small
fee and a six pack of fine ale... or just the small fee.
The Tube Asylum has great discussions on all things tube with
experts and novices alike giving and sharing experience and information.
Ask questions to your hearts content. Be sure to also check out
Asylum for older valve amp info and SET
Asylum. And if into Tube DIY, the Tube
DIY Asylum gets heavy into contruction, focusing
on both SET amps and PP designs.
This is a great place for NOS valves! One of the largest selections
on the Net and at fair but rather high prices. Very honest and a
good product with backup. Much better selection than at Neds. Another
great tube outlet that can be trusted so is worth the extra price
depending on need.
Brent Jessee's selection of NOS and used vintage tubes is a good
source. Although I have not orderred from Brent, I have heard only
good things about him. He has a dedicated page for his 12AX7
selection, as well as a main page with EL-84/6BQ5 offerings. I believe
he even has some EZ-81/6CA4.
at Triode Electronics
Ned has some of the best prices on new and NOS tubes for most amps
as well as the HF-81. See the tube selection at right. While NOS
is the BEST way to go, the price is too much for many to justify.
I believe in both camps; nice to know some new options exist without
breaking the bank.
Great place for parts including caps, resistors, and even some info
to boot. Mouser and Angela always seem to be at the front of the
regulars although Michael Percy is damn good. Ditto for Welborne
Labs for hardwood chassis and parts.
great little "out of own house" deal in Inverness, CA.
Michael is nice and has an excellent free catalog of hi-end parts
for the DIY'er. Not really dedicated to tubes, per say, but a fine
selection of wire, resisters, and caps. Download Michael Percy Parts
Catalog in .pdf form.
Vacuum Tube Valley
Everything under the tube sun here; they even used to have
complete prepackaged EICO HF-81 rebuild kits but have discontinued
at moment. VTV Magazine, books, tubes, parts, kits, wire, transformers,
etc. A lot here but some pricey and best to pick and choose your
options. I don't favor this place as much as I used to since the
prices are rather outlandish.
you have any questions or comments concerning the EICO HF-81,
please drop me an email:
Send to: firstname.lastname@example.org
EICO HF-81 Specifications
@14 watts RMS
twin tube rectifiers
triode wired to output section
and right click;
Click SAVE TARGET AS
Click to see tubes & hookup layout
299B - For Sale
This is an extremely nice,
totally rebuilt, Scott 299B that sounds excellent. It's been
in my home for several months and I have to admit, it's very
good. Both musical and punchy with that tube warmth and harmonic
richness that is right there with the best. The Scott has a
more technicolor type sound and is quite vibrant. Perhaps a
bit brighter than the EICO and while the HF-81 might sound more
natural overall, this Scott 299b really boogies. It has a very
full sound. Owned and Rebuilt by hobbiest Rick Warren using
excellent Russian Oils and new resistors where needed. Full
bias mod controls for each output and Selenium Rectifier replacement.
Excellent output iron and classic Scott aesthetics - See Scott
EICO HF-81 on Adcom 555 Amp Stand
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Eico HF-81 & HFT-90
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lease be sure to click on ALL shots above
for full size, detailed pictures