Eico HF 81 or Heathkit UA-1...What's better

sberger

Hard Core Geezer
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So I already own the UA-1 mono blocks, beautifully restored, that I'm using with an updated Dynaco PAS pre. Great sound. But I have an opportunity to buy an HF 81, a legend in some audio circles. As far as I can tell, not a lot of difference between the 2 amps. Or is there? So my brothers and sisters, forgetting about cost for a moment, would it be worth it in terms of improvement to jump on the 81 or stick with what I have?
 
Much of the 81's sound (IMO) is due to the active tone control section that many others did not spend the $ to incorporate. If only for the this reason, the 81 does sound very nice. The PAS has active tone controls as well, but they do not operate as smoothly (electrically that is) as those on the Eico do. The controls on the PAS seem to almost immediately jump to excessive levels of boost or cut. This is not a dirty control or malfunction issue, just the way it is designed. In the PAS, the tone control feedback circuit is around two stages, whereas in the Eico, it is a classic Baxandall design around a single stage.

In the power amplifier section however, the Heath units are (again IMO) the hands down winner. UL operation with OPTs that have virtually twice the iron than the Eico units do. As a result, the Heath units have a much greater power bandwidth, at lower distortion levels than the Eico output section is capable of. Plus, mono block operation over a single power supply for everything in the 81 is a plus too for your existing setup, too. I'm sure it sounds quite nice.

Another factor to consider is that your Heath amplifiers have a much higher damping factor than the Eico has relative to your speakers. The Eico can therefore present itself with a potentially fuller sounding low end -- but it is a misnomer to think that this is better, or more bass. It's simply sloppier control of the speaker, manifesting itself as more bass bloom. The Heath units are capable of full power output right down to 20 Hz, where as the Eico will start struggling below 40 Hz.

Good luck with your decision!

Dave
 
So the 81 is completely restored. All vintage tubes(mostly Mullard's). $1000. Worth it?. A tough decision to be sure. Thanks for the replies.
 
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Cool, is it a stock rebuild, or did the guy do any mods?

Here's the deal:

All new pots, new input selector switch, all new RCA jacks, all new speaker connecting jacks allowing for banana plugs or bare wires or spades
Entirely rebuilt with all electrolytic caps from Sprague Atom, circuits caps a combination paper in oil caps and silver micas, all of identical value as original design
All new resistors (all plate resistors are carbon comps), Dale power resistor
All new pots, including two Alps for volume (250k) and balance aka "focus" (1Meg).
Tone control section entirely rebuilt with polystyrene caps, carbon comp resistors and dual pots
Multi-section power supply cylindrical cap is brand new as well
Every single wire inside is Silver plated/Teflon. NO PVC anywhere...
Power switch (formerly on treble pot has been moved to the rear)
Grounding screw for turntable has been added.
All new stainless steel hardware
All new tube sockets with brand new tube shields for tone control tubes and phono section tubes
New three-prong power cord, therefore amp is now properly grounded. Safety "death cap" also replaced with x/y rated.
Phono section entirely rebuilt as well with RIAA EQ components moved under chassis for noise free operation
Overheating power supply tranny replaced by brand new replacement clone made by original tran's manufacturer for years of buzz/hum free operation (a MUST for all HF81 as that is)
Output transformers original of course and 100% free of noise of buzz of any sort.

Tubes complement is ENTIRELY Mullard/Blackburn plant vintage made in England and was tested with calibrated TV7 tube tester. Quad of Mullard EL84 picked and properly matched in pair by for current draw with digital Maximatcher tester. All tubes are almost all perfect in terms of Mullard ink.
 
Real close to what I did on the last one. Iused a PT by Heyboer that is designed as a hefty replacement. I guess the originals were a little puny. Let us know what you think. I'd say you got a bargain.
 
I bought the damn thing. More thoughts to follow...

Mucho congrats. Please let us know your thoughts with some pics. After reading your rebuild list.... the damn thing is better than new! I once asked the tech I use what he considered to be the sonic holy grail of vintage tube amps. The 81 was it. He`s very good and has seen and heard a ton. It`s been on my list ever since. He`s rebuilding Quad II`s for me at the moment. Anxious to hear more. :smoke:
 
I will. My UA-1's(which DanO55 rebuilt) are sounding so sweet right now I cannot believe I sprung for the Eico. At some point I'm gonna need sell something, but the problem is I love them all. In any case, it will be fun comparing.
 
Hmmm, well, when you get the Eico give it a listen (they're delightful) and compare to your UA-1's. I concur with Dave that it is the pre of the 81 that make it "legend". I own both an Eico HF-81 and a Heathkit AA-151 and the Heathkit has more control and fidelity when it comes to the low end. If you like the Eico, you could sell it, and get an Eico HF-85 pre to drive your Heaths, having your cake and eating it too. Money back too.
 
I have a couple of Heathkit AA-13 mono integrated amps, I bypassed the stock Heathkit preamp section and use the Eico HF-85
preamp to drive the mono amps, it's hard to beat the combination and I prefer it over my Fisher 400 and my Dads Eico HF-81.

I also agree with guitbanger's suggestion and as dave mentioned the Heathkit transformers perform extremely nicely with low
end bass.
 
Hmmm, well, when you get the Eico give it a listen (they're delightful) and compare to your UA-1's. I concur with Dave that it is the pre of the 81 that make it "legend". I own both an Eico HF-81 and a Heathkit AA-151 and the Heathkit has more control and fidelity when it comes to the low end. If you like the Eico, you could sell it, and get an Eico HF-85 pre to drive your Heaths, having your cake and eating it too. Money back too.

Excellent suggestions. I actually was looking for a restored 85 but they are scarce. So I went for the 81 instead. Again, don't need it, but couldn't resist.
 
Well I got it today and I am telling you this is the smoothest and ballsiest amp I have ever owned. Yep, 14 watts or so, but with this restoration, my room, my Cornwalls, that gain knob has plenty of room to go a lot higher if the ladies are not home. But even at low levels, the fullness, the richness of this amp is astounding to me. What has really blown me away is the phono piece. It's outstanding. Perfect synchronicity with My Dual 1219/Shure M91ED w/ Jico SAS stylus. Like they were mated together in a planned marriage from birth.

Anyway, here's some pictures. I'm a pretty happy guy tonight and expect to be listening late into the eve.










 
Yep, those push pull 6BQ5 tube amps are awesome sounding amps for the low amount of watts they put out,
you have a very fine amp there and I see it has had the PEC circuits on the tone controls upgraded to discrete
components and the ALPs volume pot installed too, clean work that was done.

It's a keeper, enjoy...:)
 
The UA-1's are terrific amps, particularly with the restored/modded PAS pre. The 81 beats them however on fullness of sound. Stock maybe not, but obviously the 81 has been restored with a lot of improvements, and with that it is an extremely powerful amp in my system. Not quite the full on thump of say my Fisher 400, but not far from it. I'm extremely impressed.
 
Every time I see a thread about the HF-81 it makes me want to dig out mine and get busy with re-furb. Inertia usually takes over however. Maybe not this time...

I'm curious about the way the input wiring has been done as well as removal of the selector switch (ridiculously complicated IMO) and the discrete replacement of the tone control circuitry. Any more details about how it was done?
 
Every time I see a thread about the HF-81 it makes me want to dig out mine and get busy with re-furb. Inertia usually takes over however. Maybe not this time...

I'm curious about the way the input wiring has been done as well as removal of the selector switch (ridiculously complicated IMO) and the discrete replacement of the tone control circuitry. Any more details about how it was done?

I didn't do the restoration but I'm happy to contact the fellow who did for some details.
 
I almost purchased one of those HF 81's a while back, I didn't really know anything about them, but it looked so small that I thought it might not be worth the few hundred the seller wanted, I am thinking I made a mistake.

By the sounds of it looks like good things come in small packages. The restoration job on your amp looks like it was done very well. Next time one of these comes my way, I will be sure to not pass up on one again.
 
That Eico HF-81 basically has the HF-85 preamp integrated into it, if you took a HF-85 and did a complete rebuild with
the upgraded tone circuit boards and replaced that crappy stock volume pot with a ALPs blue velvet and replaced film
and electrolytic capacitors along with most the resisters with carbon film, upgrade the wiring with shielded wires in
many places and of coarse replace those crappy RCA jacks you would have a fine preamp and when connected to those
Heathkit UA-1 amps it might just tip the scales and come out to be the better performer.
 
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