HF89 Output Transformer clones

[erichayes]

Hi All,

All of the research Bud and I did in 2005 ultimately wound up concentrating on the 100 watt monoblocks . . . unfortunately not before I'd ordered up five pairs of Hf89 clone output transformers.

These are not emulations of the 32034 EICO transformer; we sacrificed a '34 (you have no idea how painful that was) and took 55 pages of comprehensive notes on its construction. They are true clones.

I plan to keep two pairs for further research, but that leaves three pairs without homes. These transformers will (obviously) work well with the Eiclone, and also with the Poseidon project.

I figured it was my moral obligation to the brethren to offer this iron to them before I posted on eBay. Cost is $250 for a pair, plus whatever shipping is involved (these suckers weigh in at 25 lbs a pair) and include semigloss black powdercoated bells and 304 stainless hardware to attach the bells (stainless eliminates hysteresis loops within the laminations). I plan to offer them on eBay at $200 opening bid for the pair, with no BIN, so you guys are in the catbird seat if you want to be.

There's a reason HF89s are selling for ridiculous, obscene prices: they sound reeeaaly good, and that's mainly due to the transformers. You just can't find iron like this anymore.

If you're interested, either reply here or send me a PM.

[WA4SWJ]

Hi Eric,

I may be interested in a pair. Can you tell me the primary impedance and if they are ultra linear, etc. please? I have not looked at the HF-89 schematics. What do you think about driving them with 807's?

Thanks!

Regards,

[erichayes]

Hi All,

Ed, the primary impedance is 4300Ω plate-to-plate with screen taps at the usual 43%. Secondary is 16Ω tapped @ 4 and 8Ω. As I said, they are identical, electrically and physically, to the original HF89 OTs.

I abandoned EL34s in favor of 6550s fairly early on in the development of the amp I'm using these trannies on, and they get warm when subjected to continuous high level pipe organ over a period of an hour or so--and that's with 500 volts on the plates and a quiescent cathode current of 72mA per tube. An 807 is nothing more than a 6L6 that's eaten its Wheaties, so there should be no problem. Can't remember offhand who it was, but one of the brethren built up an Eiclone using 6BG6s, which are essentially 807s with an octal base, and it worked just fine, thank you.

[WA4SWJ]

Eric,

I know it's all subjective, but tell me about how your amp sounds. Give me some of that audiophile talk that I can't seem to have roll off my tongue. Have you done any measurements? I've heard the Eico HF-89 called a "Dynaco Killer" and it likely could kill a lot of other amps too.

I'll let you know either Thursday or Friday of this week for sure, but I am thinking positively about taking a set of your transformers off your hands. I hope that's not too long - only a couple of days.

Also, any pictures?

I have some NOS 807's in military style packaging that have obviously not been used. I think it would be fun to use those to drive some good transformers like the ones you have. Or perhaps some 6146's from my older ham radio stuff. I understand those are pretty linear tubes also. I would likely build them into monoblocks and would have to find a power transformer for each. Maybe a Triode Dynaclone for a Mark III. I have some of those already in my other amps and they work well.

Regards,

[erichayes]

Hi all,

Gee, Ed, since the slogan of my company is "Amplifiers that don't make a sound", an unattainable goal, I should needlessly add, about the best description I can come up with is "neutral". Used in conjunction with a modified Yamaha CD player c. 1990 and a pair of ESS AMT-1 Towers c. 1974 with Seas woofers, a good orchestral recording (my primary benchmark, as there is not much a good engineer can do to screw the sound up) sounds like a good orchestra. The oboes are exactly where they're supposed to be, the 6 foot bass drum somehow manages to make a concrete slab floor shake, and the dynamic range is literally breathtaking.

When we quit tweaking the 50/50 in favor of the 100 wat monoblocks, the numbers stood at: 1W F.R. 10~100,000 cps ±0.2 dB, 50 W F.R. 20~40,000 cps ±1 dB (bandwidth measured due to limitations of the Sound Tech 1510 analyzer), THD @ 1W 0.004%, THD @ 50 W 0.3%, both channels driven, power out at 0.4% THD (my definition of clipping) 62 watts, BCD, hum and noise -120 dB referenced to 1 watt. As we discovered with the 100 watters, those numbers can be improved--and will, once we're through with the big guys.

I'll see what I can do about pictures, but if you've seen an HF-89, that's what they look like--big, black, ugly and heavy.

BTW, Bud says he'd take a pair of 6550s over 6146B/8298s any day. Years ago, he said, he had a linear amp that went from 80 thru 10 and had no plate tuning provision. Used a pair of 6550s. How's THAT for linearity?

[WA4SWJ]

Eric,

I'll take two. Write either a private post or direct via my callsign to the left at hotmail.

Thanks!!!

Ed Long

[WA4SWJ]

Eric,

Sorry - what I mean is one pair - two transformers.

Regards,

[EWBrown]

6146Bs aren't all that UL / SG compatible, the plates can go up to 750VDC or so, but the SGs are limited to 250VDC max. Similar restrictions apply to a lot of the (relatively) newer TV sweep tubes.

http://www.mif.pg.gda.pl/homepages/fran ... /6146B.pdf

/ed B in NH

[WA4SWJ]

I'm gonna stick with 6550's or KT-88's.

Regards,

[EWBrown]

Given my druthers I'd go with KT-88s. THe Electroharmonix ones are very good.

[WA4SWJ]

Ed,

I've got 3 sets of EH 6550's now that I'm putting into the poseidons when Shannon is done with the boards. Thanks for the recommendation. I sure like the way the 6550's look. The KT-88's will probably sound and look just as good. I'm not quite ready to order KT-88's but it won't be long.

Regards,