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

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.

I hope one day to have the opportunity to do just that. As I noted previously, I really wanted a restored 85, but they are far and few between. At least where I look.
 
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.

It is small, but I couldn't believe how heavy it was when I went to lift it. Almost like my Fisher 400 believe it or not.
 
Love this amp! That said, I'm curious if I should consider rolling some different tubes. I know I know "How can you think about taking out any of those Mullards???".... But I'm wondering nonetheless. Thoughts on rolling some 5751's for the 12AX7's in the tone spots? Anybody do this and how was the change, if any? I'm guessing these are probably the only one worth rolling? Thanks.
 
The trick would be to put some UA-1 output transformers into an HF-81. :D

That, with the output circuit optimized for the bigger output transformers, could be simply spectacular.

Might want a heavier power transformer, too, to get max benefit...

Regards,
Gordon.
 
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.

Sell the preamp and upgrade to better preamp.
 
Sell the preamp and upgrade to better preamp.

I assume you're referring to the PAS? It's a pretty good pre, has Curcio mods. Also have a Decware CSP2 that I should try with the UA-1's. No, I think I'm set for pre's for now. Maybe later if given the opportunity I might be inclined to pick up a HF 85. But for now I'm good.
 
Glad to hear you're enjoying the little Eico; not surprising!

I consider myself very fortunate to have been able to purchase a low-mileage HF-81 from a very talented friend several years ago, who built it from a kit in 1960. It is all original except for a few caps and a pair of Sylvania 12Au7s, and I hope to keep it that way in consideration of who built it. It would be great fun to find a second HF-81 someday to rebuild to better than new specs like yours, and to hear the difference.

The Eico has such a seductive midrange that it's easy to overlook any faults, such as, in my case being a bit underpowered for my speakers. But it really draws you into the music and, between the Eico and a modified Dyna SCA-35 with EFB in regular rotation, my PAS and ST-70 have been more or less put out to pasture after 30+ years.

Hope you get many hours of listening enjoyment from your new acquisition :music:

Best regards,
Mike
 
Glad to hear you're enjoying the little Eico; not surprising!

I consider myself very fortunate to have been able to purchase a low-mileage HF-81 from a very talented friend several years ago, who built it from a kit in 1960. It is all original except for a few caps and a pair of Sylvania 12Au7s, and I hope to keep it that way in consideration of who built it. It would be great fun to find a second HF-81 someday to rebuild to better than new specs like yours, and to hear the difference.

The Eico has such a seductive midrange that it's easy to overlook any faults, such as, in my case being a bit underpowered for my speakers. But it really draws you into the music and, between the Eico and a modified Dyna SCA-35 with EFB in regular rotation, my PAS and ST-70 have been more or less put out to pasture after 30+ years.

Hope you get many hours of listening enjoyment from your new acquisition :music:

Best regards,
Mike

Thanks! It's a great amp and I'm having a blast with it. Choice of speakers are obviously a very important consideration and I'm lucky to have my Cornwalls, perfect for just about any amp that I would care to own. Would love to know what you or anyone else might have done regarding rolling tubes, but I'm pretty lucky to have all this great stuff. Tomorrow I'll thrown the UA-1's back in the rig with both the Decware pre and then sans pre with just switch box. I have a hunch they're not going to beat the 81 but we'll see. This one was rebuilt very well.
 
I assume you're referring to the PAS? It's a pretty good pre, has Curcio mods. Also have a Decware CSP2 that I should try with the UA-1's. No, I think I'm set for pre's for now. Maybe later if given the opportunity I might be inclined to pick up a HF 85. But for now I'm good.

I reworked a PAS-3X and it is the first tube gear in 25 years of playing I could not get it to sound worth a damn. I DIY a simple 76 tube preamp and it blew the PAS-3X away.
 
I reworked a PAS-3X and it is the first tube gear in 25 years of playing I could not get it to sound worth a damn. I DIY a simple 76 tube preamp and it blew the PAS-3X away.

I've never done it before but tomorrow I'll going to try the UA-1's without a pre. I'll just use my RCA switch box and go direct. I know the guy who rebuilt them liked them better without a pre so maybe there is magic in them thar hills. We shall see and report back.
 
Well had a bit of extra spare time tonight whilst watching my beloved Bruins take one on the chin so conducted a little experiment with the UA-1's, running them both without a pre, and with the PAS(which I do believe to be a very good version of it) and my Decware CSP2, also a very nice pre. And for me the conclusion is that I dig the Eico more. I simply find a more satisfying listen. It does not sound like a 14 watt amp. No matter how loud I play the Heaths, they just can't provide the same rich, huge tone that the Eico can, which easily does it even at quiet levels. Honestly, if they were both stock it might be a different scenario, but I do think that the Eico's restoration is what's keeping it in front here. That, and perhaps I just like the sound of the Eico more than the Heaths. Personal preference does play a role here as well. And yes, I do admit to being curious what a similar restored Eico HF 85 pre would do teamed up with the Heaths. Additionally, the Eico is simpler, I don't have to play around with different gain settings as I do using the Heaths, with or without a pre. I think the Alps gain control is fantastic. Even at the lowest levels I get great sound, and great balance. So that's it for now. My Fisher X-101C is having some small issues and will be looked at by my tech next week, so we'll see how that fits in to all this craziness then.
 
We all seek to find what is most satisfying personally. I'm glad the Eico is helping to provide that.

Based on you description, there is a strong possibility that what you like about the Eico then is not only the sound of its active tone controls, but also the reduced damping that unit imparts to your speakers, over that which the Heath amplifiers provide. Reduced electrical damping typically manifests itself as enhancing mid and lower bass frequencies, adding a richness like you describe, which many find pleasing -- or, it may be that your speakers simply require less damping for accurate low end response.

It would be interesting to see if you can achieve the same sound qualities with the Heath amplifier set up as produced by the Eico, through careful manipulation of the tone controls in the Heath system. Once set, then it would be interesting to see which set up has more appeal, if any.

I have no preconceived notions with these comments, but simply find interesting what electrical parameters relate to listening preferences.

Good luck with your Eico!

Dave
 
We all seek to find what is most satisfying personally. I'm glad the Eico is helping to provide that.

Based on you description, there is a strong possibility that what you like about the Eico then is not only the sound of its active tone controls, but also the reduced damping that unit imparts to your speakers, over that which the Heath amplifiers provide. Reduced electrical damping typically manifests itself as enhancing mid and lower bass frequencies, adding a richness like you describe, which many find pleasing -- or, it may be that your speakers simply require less damping for accurate low end response.

It would be interesting to see if you can achieve the same sound qualities with the Heath amplifier set up as produced by the Eico, through careful manipulation of the tone controls in the Heath system. Once set, then it would be interesting to see which set up has more appeal, if any.

I have no preconceived notions with these comments, but simply find interesting what electrical parameters relate to listening preferences.

Good luck with your Eico!

Dave
Dave thanks for your comments. I agree it that I would love to see if I could get the Heaths closer but for now I'm just happy to have put the competition to rest.
 
Last one I did got regulated screens and a completely different phono stage, as well as a few circuit tweaks. The guy I did it for liked it pretty good he said.
 
Thanks! It's a great amp and I'm having a blast with it. Choice of speakers are obviously a very important consideration and I'm lucky to have my Cornwalls, perfect for just about any amp that I would care to own. Would love to know what you or anyone else might have done regarding rolling tubes, but I'm pretty lucky to have all this great stuff. Tomorrow I'll thrown the UA-1's back in the rig with both the Decware pre and then sans pre with just switch box. I have a hunch they're not going to beat the 81 but we'll see. This one was rebuilt very well.

I haven't done any tube rolling with the HF-81. The 12AU7s were weak when I got the amp, and I put a pair of Baldwin labeled Sylvania tubes in it with good results. I think the Sylvania's were real sleepers for a long time, but the cat seems to be out of the bag now, at least with the 12AX7s. The rest of the tubes are original Mullards, and I doubt those can be bettered to any great extent. In my SCA-35 however, I have compared the original RCA EL84s with JJ and GE. All are good, but I would put the General Electric tubes first.
 
I haven't done any tube rolling with the HF-81. The 12AU7s were weak when I got the amp, and I put a pair of Baldwin labeled Sylvania tubes in it with good results. I think the Sylvania's were real sleepers for a long time, but the cat seems to be out of the bag now, at least with the 12AX7s. The rest of the tubes are original Mullards, and I doubt those can be bettered to any great extent. In my SCA-35 however, I have compared the original RCA EL84s with JJ and GE. All are good, but I would put the General Electric tubes first.

Thank you!
 
Well, I just restored an EICO HF-12, which is basically one channel of the HF-81. New gold connectors and new coupling caps. It did have the original Mullard el84 tubes. Since I had some Russian 6P14P military spec tubes, which are EL84 equivalents, I gave them a try. Don't get me wrong, with the Mullards the amp sounded great, but with the Russian tubes it blew me away. They are very cheap and there seems to be an ample supply.
 
I am having a hf85 restored at the moment and own Heathkit UA1 restored amps. I will share how they sound when I receive the preamp back. The Heathkit sound great when hooked up to mx110z. I brought them to a friends house hooked up to a Sansui preamp and klipsch chorus speakers. The quicksilver mid monos beat them when turned up really loud since the Heathkit started to clip but the Heathkit to me sounded better at lower to average volumes…it was close.
 
Check your tube number. JJ E80CC does not exist. E80CC was, of course, made by some vintage manufacturers, but “rolling” that in place of a 12AX7 is a crapshoot.
 
It's pin compatible but not an equivalent.
You may or may not like what you hear but it won't operate in its optimal zone and could conceivably damage gear.
It draws twice the filament current also
 
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