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Old 23rd December 2004, 09:13 PM   #1
percy is offline percy  United States
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Default Any comments on Eico HF-14 and HF-85

I have an opportunity to acquire two Eico HF-14 mono amps and also a Eico HF-85 preamp. I believe the HF-14 is a good amp. I dont know about the preamp but I am willing to - in fact I would love to - do mods and upgrads to make a better sounding amp. But I want to find out it there atleast worth getting or not.

http://users.rcn.com/fiddler.interport/HF14.HTM
http://users.rcn.com/fiddler.interport/HF85.HTM

Its a pretty good deal too and I think this could very well be my long awaited entry into vacuum tubes. Has anyone used this amp or pre-amp ? How is it ? Any comments/opinions would be very helpful and appreciated.
Thanks!
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Old 26th December 2004, 12:30 AM   #2
anatech is offline anatech  Canada
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Hi Percy,
I own an HF-85 preamp. It has good sound and my wife likes it as well. It did have high heater hum. I made two circuit changes that improved things.

First, I split the B+ bleeder to give a 30V tap and hung a 10uF cap from there to ground. The heater hum balance control was disconnected and the heater midpoint was connected there. Hum all but gone.

Second, the 10K dropping resistor in the B+ circuit (R54 I think) was removed and a regulator circuit installed. Much quieter now.

These two changes made a very positive difference in the preamp. The caps were already changed before these modifications.

The HF-87a that goes with the preamp is a joy to listen to. It was rebuilt and caps changed. No "magic" parts were used in either unit. I recently (about a year) replaced both sets of tubes with Electroharmonix branded ones. Another positive change.

I own several SS and tube amplifiers & preamps, the Eico's are my favorite tube products so far. Most people who have heard them agree.

-Chris
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Old 11th January 2005, 08:46 PM   #3
percy is offline percy  United States
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Anatech, thanks for your reply.

Well, looks like I have finally made my long awaited entry into the tube audio world! Two HF-14 and one HF-85 are mine now!

I realize there are many mods out there for the HF-85. Right now I am more excited about bringing up (upgrades like caps, resistors for now) the HF-14 first and then go from there. I already have a Dynaco FM-3 tuner.

Also, noticed in the HF-14 schematic that the screens are held at +375V. I havent measured yet what is the actual but isnt this more than the rated max for the EL84 ?
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Old 12th January 2005, 12:09 AM   #4
anatech is offline anatech  Canada
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Hi percy,
Yup, but it depends on the circuit as well. Don't worry. Just don't use junk tubes.
-Chris
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Old 12th January 2005, 10:28 PM   #5
percy is offline percy  United States
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yeah I guess the dissipation must be within limits. Once I power it up (this weekend maybe?) I should get an idea of what bias, class etc is being used. Not much info available for the HF-14 out there.

By the way, any idea if there are any assembly/service manuals available for download ?
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Old 13th January 2005, 12:11 AM   #6
anatech is offline anatech  Canada
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Hi Percy,
I have the schematic only. PM me if you want it. It's too big to attach I think.

-Chris
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