Daddy Dee Posted October 8, 2003 Share Posted October 8, 2003 Mobile Homeless made me do it. I got curious enough about the HF-81 and have been looking out for a good deal on Ebay. Craig and I had visited months ago about the Scott 299 vs Eico HF-81 and his preference leans toward the Scott amps. For sure I enjoyed my 299c. He did allow that I would probably prefer the HF-81 sound since it is more like 2A3 sound than the Scott's. (I think that is a fair characterization of what Craig told me, it's what I heard, anyway, even if I missed something in the translation, which is easy for someone who is not only out to lunch... me, that is, but sometimes on another planet) Well, I found one and fired it up today with my Tjoebs and LaScala's. This amp is dirty and definitely will need a rebuild, it has some occasional popping sounds. Other than that, it is quiet and no hum. I was surprised as heck that listening to Stan Getz Finest Hour, I heard some quality and clarity in the guitar material that I don't think I'd heard before on my Scott or the Wright 2A3's. How can this be? What is the deal with this amplifier? Also, what does the "focus" control do? Dee Quote Link to comment Share on other sites More sharing options...
dubai2000 Posted October 8, 2003 Share Posted October 8, 2003 Dee, I cannot answer your question, but after a longish stop at my local tech I got my HF-81 back, powerde it on .......... and it just blew me away again. The tech only resoldered some ground connections and I put back the original Mullard EZ81s (used like all tubes), so no big changes, but the amp is certainly more 'quiet' and with my Heresy I surely have a great sounding combo in my study. So whatever the reason, this amp deserves the praise it has received from Kelly and others. For me it's certainly a keeper . Wolfram Focus = Balance Quote Link to comment Share on other sites More sharing options...
No Disc Posted October 8, 2003 Share Posted October 8, 2003 The williamson circuit, point to point wiring, tube-rectified, great PS iron all contribute to a great sounding amp. Have you tried the Focus? If you didn't notice a difference then yours is broken! Focus = balance Have fun. Tim Quote Link to comment Share on other sites More sharing options...
NOSValves Posted October 8, 2003 Share Posted October 8, 2003 The focus pot should be bypassed is my opinion the thing is a joke to say the least. If yours is like most the volume not only shifts to one side but also raises the actual volume to the side you turn it to. The pot is always limiting the volume when centered. I would hope your not going to compare a 299C 7591 based amp to a EL84 based amp drawing some major opinion of a Scott versus a EICO ! The only fair way to compare is EL84 to EL84 7591 to 7591. I personally think 7591's are slightly vailed sounding on the top end in and of themselves compared to a EL84/7189. But all the same I figured you would love a HF-81 !! Craig Quote Link to comment Share on other sites More sharing options...
mobile homeless Posted October 8, 2003 Share Posted October 8, 2003 Jeff would argue that this amp isnt really a Williamson circuit after all. I tire of championing the EICO since it brings too much debate here. On the other hand, I cant tell you how SOME of these amps (the nut is that ALL dont sound this way) can totally AMAZE. And I mean the word LITERALLY. One thing, is has dual rectifiers and a relatively simple PS filtering that doesnt slow the amp down. I think there is something to this now. But the Dual EZ-81 Mullard rectifiers are a good start. SEcond, and I think really importantly, it has an ALL TRIODE FRONT END. Many of the other integrateds DO not have this all triode front end. Add on top of this, I think it just plain has some EXCELLENT output iron. The thing about the HF-81, is that its magic can be hinden to those quick to turn it up all the way to rock on. It is perhaps a more subtle amp, but an amp that also have AMAZING BASS and top end clarity, even with the most mundane parts! Jeff, who has built many custom PP and SET amps, including those with quite exotic tubes and designs, was blown away by the EICO as well. I had to laugh! He still has his. Some prefer the Scotts. Some love Fisher. I love many tube integrateds and all are good (You have to love that EL-84 tube...my favorite pentode!). But damn if that little EICO HF-81 doesnt sound more open and alive than some heavy hitters, even BETTER than a few. I prefer it to the most tweaked EL-34 amp I have had in my system. I sometimes prefer it to SET when all is said and done. As I told many that have offered, I will NEVER SELL my first EICO. I have a second one that I would...but not my first. kh ps - You cant go wrong with any of these vintage deals for the money. They all have merits. By the way, if you havent seen it, head to the painfully outdated EICO HF-81 site I did too long ago. EICO HF-81 Review - Tweaks - Links Online Quote Link to comment Share on other sites More sharing options...
Painful Reality Posted October 8, 2003 Share Posted October 8, 2003 ---------------- On 10/8/2003 5:02:07 PM mobile homeless wrote: Jeff would argue that this amp isnt really a Williamson circuit after all. I tire of championing the EICO since it brings too much debate here. On the other hand, I cant tell you how SOME of these amps (the nut is that ALL dont sound this way) can totally AMAZE. And I mean the word LITERALLY. One thing, is has dual rectifiers and a relatively simple PS filtering that doesnt slow the amp down. I think there is something to this now. But the Dual EZ-81 Mullard rectifiers are a good start. SEcond, and I think really importantly, it has an ALL TRIODE FRONT END. Many of the other integrateds DO not have this all triode front end. Add on top of this, I think it just plain has some EXCELLENT output iron. The thing about the HF-81, is that its magic can be hinden to those quick to turn it up all the way to rock on. It is perhaps a more subtle amp, but an amp that also have AMAZING BASS and top end clarity, even with the most mundane parts! Jeff, who has built many custom PP and SET amps, including those with quite exotic tubes and designs, was blown away by the EICO as well. I had to laugh! He still has his. Some prefer the Scotts. Some love Fisher. I love many tube integrateds and all are good. But damn if that little EICO HF-81 doesnt sound more open and alive than some heavy hitters, even BETTER than a few. I prefer it to the most tweaked EL-34 amp I have had in my system. I sometimes prefer it to SET when all is said and done. As I told many that have offered, I will NEVER SELL my first EICO. I have a second one that I would...but not my first. kh ps - You cant go wrong with any of these vintage deals for the money. They all have merits. By the way, if you havent seen it, head to the painfully outdated EICO HF-81 site I did too long ago. EICO HF-81 Review - Tweaks - Links Online ---------------- The Eico is not a Williamson circuit, unless all amps with a cathodyne phase splitter qualify to be one. My Eico is actually playing as otherwise I would be ampless. It's such a nice integrated. Joe Roberts could also have said "I never heard a PP EL84 amp I didn't liked". Quote Link to comment Share on other sites More sharing options...
No Disc Posted October 8, 2003 Share Posted October 8, 2003 mea culpa. Would it be correct to say it has a Williamson Output? Or perhaps Williamson type push pull? The Williamson refers to the output amplifier section according to the Eico FAQ pages. Why ampless? Don't you have the Tenor running? When will the 2A3 PP have life? - tb ---------------- On 10/8/2003 5:20:26 PM painful reality wrote: The Eico is not a Williamson circuit, unless all amps with a cathodyne phase splitter qualify to be one. My Eico is actually playing as otherwise I would be ampless. It's such a nice integrated. Joe Roberts could also have said "I never heard a PP EL84 amp I didn't liked". Quote Link to comment Share on other sites More sharing options...
BigBusa Posted October 8, 2003 Share Posted October 8, 2003 I would have to argue that a particular component may sound absolutely fantastic to one person and horrid to the next. While I think it is good to take advice from people on what gear to buy I do not think it's smart to lay out a lot of $ without 1st hearing it for yourself. I've seen MH put down nearly every piece of stereo gear that he does not currently own. Everything is just not "coherent" enough or "lordy" it's too inexpensive to possibly be any good. Do your own thing and you'll find what you're looking for eventually. Plus, Kelly is a girls name. How can anyone take stereo advice from someone with a feminine name? Quote Link to comment Share on other sites More sharing options...
Painful Reality Posted October 8, 2003 Share Posted October 8, 2003 ---------------- On 10/8/2003 6:33:26 PM tbabb wrote: mea culpa. Would it be correct to say it has a Williamson Output? Or perhaps Williamson type push pull? The Williamson refers to the output amplifier section according to the Eico FAQ pages. Why ampless? Don't you have the Tenor running? When will the 2A3 PP have life? - tb ---------------- It doesn't share much with a Williamson. The original Williamson was triode connected. I've seen later Williamson with ultra-linear connected. The Eico HF-81 is pentode connected with a distinct screen supply. The Tenors are in dire need of new tubes. I have the original prototype and it was never retubed since aeons. It doesn't keep it's bias anymore and has a strong DC offset. Something you don't want with an OTL. I don't envision life for the PP2A3 before 2 months or so. Quote Link to comment Share on other sites More sharing options...
leok Posted October 8, 2003 Share Posted October 8, 2003 I believe part of the EL84 amps' magic has to do with scaling. They are 12 or 14 Watt amplifiers. This means the point at which the noise and distortion due to feedback begins to flatten or begin to creep up is down around 0.14 Watt. Plenty of personal rules of thumb there. They are operating in a sweet spot for Klipsch speakers. SS topology doesn't scale well. That's why McIntosh uses transformers in ss designs. Tubes do scale, and a 3 to 20 Watt tube amp is a good bet for a 97 to 104 dB speaker. leok Quote Link to comment Share on other sites More sharing options...
mobile homeless Posted October 8, 2003 Share Posted October 8, 2003 Some interesting ideas concerning the power band. On the other hand, I think DaddyDee might be asking what exactly makes THIS sample of integrated sound so good. It's true, I happen to really love a lot of the EL-84 alternatives; but the EICO still has a special place on its own. Still, the EL-84 is perhaps the most overachiever tube there is. IT comes in one of the smallest packages, yet sounds so damn GREAT. And another interesting point; I love the EICO HF-81 even more on my monitor speakers. kh Quote Link to comment Share on other sites More sharing options...
Randy Bey Posted October 8, 2003 Share Posted October 8, 2003 Someday when I get that big bonus check I've been dreaming of, I'll pick up one of those Eicos and a pair of them damn cement monitors to make a living room system. Yep, I'll be rolling in the money then... Quote Link to comment Share on other sites More sharing options...
Klipschfoot Posted October 8, 2003 Share Posted October 8, 2003 Okay okay. Next we are going to hear that an HF-81 driving a pair of Academys is the ticket to audio bliss. Seriously, it's nice to know that you don't have to shell out $1K+ for museum Macs for good sound. For me, my HF-81 to my Valencias is a hard combo to beat. I just wish I had the room for three setups. Check out this pic I googled up. He must know something about the Valencia'a potential. Quote Link to comment Share on other sites More sharing options...
No Disc Posted October 8, 2003 Share Posted October 8, 2003 Don't mean to go off in a tangent, but that is nice looking stand at the bottom of that link. Anyone know what that is? - tb Quote Link to comment Share on other sites More sharing options...
Klipschfoot Posted October 8, 2003 Share Posted October 8, 2003 Gotta be homebrew - really nice homebrew. It looks like plumbing and planks. And I was gonna just build dollys! There's always someone raising the bar. I just wonder if he ever looks at his significant other like that! Quote Link to comment Share on other sites More sharing options...
3dzapper Posted October 8, 2003 Share Posted October 8, 2003 After I started reading this, I just had to hook the HF-81 I have been working on to the Khorns. It sounds very nice, a little brassy, which I attribute to the new EL34s. When I got it it was a little rough. It looked like Kelly's. All black, but with a very poor paint job. I stripped it down. primed and painted the side panels black with clearcoat. I refinished the front in Yamaha Outboard silver blue clearcoat. I used Brasso on Nev-r-dul pads to polish the front panel and clearcoated it. Internally I resoldered all the connections and cleaned all the connections,wafer switch and tube sockets with Deoxit and Pro gold. Replaced the red caps on the chassis and bypassed the stereo/mono switch as it seemed a constant source of noise. I put in a set of EH El34s in place of the gassy RCAs. Like I say they are a touch bright. I'll try a few others tomorrow. One good thing about all this stuff with amps and speakers, it keeps me out of the bars. And from practicing my archery, mowing the lawn, cleaning the garage or my work room. I think I'm gonna get in trouble with the bride soon. No really she's cool, she's happy to have me around after the scare we had last year. Got the piano man on right now. Amazing! The piano sounds like a piano. Ole BJ is serenading us with "Just The Way You Are". Rick Quote Link to comment Share on other sites More sharing options...
mobile homeless Posted October 9, 2003 Share Posted October 9, 2003 I hope you mean EL-84 and not 34...heh. I have to side with good NOS EL-84 over even the better modern alternatives. I think the sweet spot sonically and $$ wise are the RCA/Syl/GE EL-84. Also, it pays to have some really good 12AU7 in there. I will say that all HF-81 do NOT sound the same. I have two and one is better than the other to me. I have heard five or so 81 and some are preferable to others. Remember, most of these were kit amps, so the build is up to what ale he was drinking at the time. kh Quote Link to comment Share on other sites More sharing options...
3dzapper Posted October 9, 2003 Share Posted October 9, 2003 Yes I meant EL84, sorry. I'm listening now to Niel Diamond. I would liken the difference between the HF-81 and 299c to going to shows at two different clubs. Neither is bad, just different. I have yet to hear a SET amp over 1 watt on my Khorns. I am buying an inexpensive 300b set to play with. I just can't afford to pay big money for a solid gold one right now. I am selling off my excess archery gear and boat stuff on eBay to pay for this new way to go broke. Boat,n,a hole on the water that you pour money into. Bow, n,If you buy one like the guy who beat you, you will shoot better. Audio perfection,av,something you search for dropping money along the way. Gotta go practice slinging arrows. Later. Rick Rick Quote Link to comment Share on other sites More sharing options...
Daddy Dee Posted October 9, 2003 Author Share Posted October 9, 2003 Gentlemen, (and perhaps ladies) Thanks for sharing your take on this amp. There's some interesting material in this thread. Months ago I'd run across Kelly's very nicely done review and narrative on his experience with the HF-81 and hadn't made the connection that this was Mobile Homeless on this forum. There was another review out on the net, that made suggestions about mods, and one mod named after someone.. ie: ________ mod., but I haven't been able to locate it again. At first, I'd associated that with Kelly's review, but after going back to read it, I think it must have been another. I'd sure like to hear some recommendations on particular techniques and mods which could be helpful here. I'm not in a rush to take on the project, and unless I can get my brother-in-law in Indy to help me out, the soldering and such is probably beyond my current skill level. There are a couple of schools of thought here that I've picked up on the forum. One is what I'd refer to as a purist approach, that is to restore the amp to original spec, which has it's own appeal and inherent respect for the amp as it was designed in produced in 1959. Then, on the other hand, there have been advances in capacitors and other components since then, which could serve well to improve upon the design by optimizing and tweaking the signal. This school of thought has it's appeal, also, and while I'm drawn to the vintage, conservator type thought, since I'd also like to use this in my system with the most pleasing sonics possible, I lean toward the second. Have noticed the Vacuum Tube Valley has a "kit" for refurbing HF-81's for about $60, though they give a disclaimer that their documentation is done at the "Pro" level and as a step by step for beginners. Any recommendations as to parts and mods to the amp will be gratefully received. Dee Quote Link to comment Share on other sites More sharing options...
Parrot Posted October 9, 2003 Share Posted October 9, 2003 DaddyDee, My advice is not to do any big mods on the EICO. Have the 4 main coupling caps changed to Auricaps and don't change anything else unless a particular part's value has changed to out of spec. The HF-81 sounds beautiful purely stock, provided it was built properly to begin with and you don't get one with a severely buzzing transformer. Quote Link to comment Share on other sites More sharing options...
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