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


eico_hf81@earthlink.net
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EICO HF-81Click for larger shot EICO hf-81

LINKS


I have amassed some excellent links relating to the EICO HF-81 either directly or indirectly - Take a look... If you have any other links or pages of reference, please drop me an email.

By Kelly Holsten

LINKS OF IMPORTANCE.


EICO HF-81 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,



The EICO Unofficial Home Page
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.



Audio 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.



NOS 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.




Heyboer Transformers
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.




EICO 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 share input.




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 space.




Dusty 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, caps,
power 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. 



Tube Asylum
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 the Vintage 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.



Tube World
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.



audiotubes.com
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 and 12AU7 selection, as well as a main page with EL-84/6BQ5 offerings. I believe he even has some EZ-81/6CA4.



Ned 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.



Angela Instruments
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.



Michael Percy Audio
Download the complete Micheal Percy Parts CatalogA 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.


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

Send to: eico_hf81@earthlink.net




Click for larger image






EICO HF-81 Specifications
    

integrated amp
@14 watts RMS
all tube
twin tube rectifiers
triode wired to output section


tubes
12AX7(4)
12AU7(2)
EL-84(4)
EZ81(2 Rectifier)



Downloadable Schematic

Hover below and right click;
Click SAVE TARGET AS

Right Click and SAVE TARGET to Download 258K Schematic

 


Click to see tubes & hookup layout

 

 

Scott 299B for sale - see site

Scott 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 299B





EICO HF-81 on Adcom 555 Amp Stand
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Eico HF-81 & HFT-90
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See full Size - EICO HF-81 Face Plate
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NOTE: lease be sure to click on ALL shots above
for full size, detailed pictures

 

 

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