Eric's Z565 clone - 4 & 8 ohm taps

[Shannon Parks]

Eric Hayes mentioned sending me one of his Z565 clones a while back in these forums, and I got my hands on one a couple weeks ago. Eric refers to his output transformer as an upgraded Z565, and indeed, it is a beefy EL84 tranny.








Some head to head stats with the Z565. Note: This is a different amp than the previous transformer shootout, so this data might seem different. The goal is some relative measurements between a Z565 versus Eric Hayes' '015 transformer. As always, I've received nothing for this comparison test and get no kickbacks. I'm happy selling PCBs and not chunks of iron. :mrgreen:

Z565 at 400mV input
020Hz 5.10V +22.0dB .4820%THD+N 3.226W @ 8ohm
025Hz 5.11V +22.0dB .4070%THD+N 3.264W @ 8ohm
030Hz 5.11V +22.0dB .3670%THD+N 3.264W @ 8ohm
050Hz 5.13V +22.0dB .2443%THD+N 3.290W @ 8ohm
100Hz 5.14V +22.1dB .1733%THD+N 3.290W @ 8ohm
200Hz 5.14V +22.1dB .1469%THD+N 3.315W @ 8ohm
500Hz 5.15V +22.1dB .1326%THD+N 3.302W @ 8ohm
01kHz 5.14V +22.1dB .1317%THD+N 3.302W @ 8ohm
02kHz 5.15V +22.0dB .1415%THD+N 3.315W @ 8ohm
05kHz 5.16V +22.0dB .1995%THD+N 3.328W @ 8ohm
10kHz 5.16V +22.0dB .3650%THD+N 3.328W @ 8ohm
20kHz 5.07V +21.8dB .7150%THD+N 3.200W @ 8ohm
30kHz 4.83V +21.4dB 1.071%THD+N 2.904W @ 8ohm
40kHz 4.19V +20.3dB 1.854%THD+N 2.174W @ 8ohm
50kHz 3.42V +18.6dB 1.421%THD+N 1.454W @ 8ohm
60kHz 2.63V +16.3dB 1.753%THD+N .8666W @ 8ohm
70kHz 1.94V +13.7dB 1.572%THD+N .4714W @ 8ohm
80kHz 1.39V +10.9dB 1.617%THD+N .2412W @ 8ohm
90kHz .952V +7.70dB 1.750%THD+N .1138W @ 8ohm
100kHz .711V +5.10dB 1.336%THD+N .063W @ 8ohm

Eric's at 400mV input
020Hz 5.10V +22.0dB .3560%THD+N 3.213W @ 8ohm
025Hz 5.10V +22.0dB .2984%THD+N 3.239W @ 8ohm
030Hz 5.10V +22.0dB .2741%THD+N 3.239W @ 8ohm
050Hz 5.12V +22.0dB .2036%THD+N 3.277W @ 8ohm
100Hz 5.13V +22.0dB .1804%THD+N 3.277W @ 8ohm
200Hz 5.13V +22.0dB .1588%THD+N 3.277W @ 8ohm
500Hz 5.13V +22.0dB .1542%THD+N 3.277W @ 8ohm
01kHz 5.13V +22.0dB .1552%THD+N 3.277W @ 8ohm
02kHz 5.14V +22.0dB .1722%THD+N 3.290W @ 8ohm
05kHz 5.14V +22.0dB .2588%THD+N 3.302W @ 8ohm
10kHz 5.13V +21.9dB .4520%THD+N 3.277W @ 8ohm
20kHz 5.02V +21.7dB .7300%THD+N 3.138W @ 8ohm
30kHz 4.21V +20.2dB 1.075%THD+N 2.195W @ 8ohm
40kHz 3.89V +19.6dB 1.678%THD+N 1.882W @ 8ohm
50kHz 3.49V +18.7dB 1.543%THD+N 1.514W @ 8ohm
60kHz 3.08V +17.7dB 1.541%THD+N 1.170W @ 8ohm
70kHz 2.66V +16.5dB 1.170%THD+N .8831W @ 8ohm
80kHz 2.26V +15.1dB 1.924%THD+N .6407W @ 8ohm
90kHz 1.55V +11.9dB 2.800%THD+N .3026W @ 8ohm
100kHz .763V +5.7dB 2.343%THD+N .0728W @ 8ohm


Z565 at 850mV input
020Hz 10.13V +21.4dB 3.930%THD+N 12.80W @ 8ohm
025Hz 10.26V +21.5dB 1.622%THD+N 13.21W @ 8ohm
030Hz 10.31V +21.6dB 1.295%THD+N 13.29W @ 8ohm
050Hz 10.35V +21.6dB 1.155%THD+N 13.39W @ 8ohm
100Hz 10.36V +21.6dB 1.093%THD+N 13.44W @ 8ohm
200Hz 10.38V +21.6dB 1.025%THD+N 13.49W @ 8ohm
500Hz 10.37V +21.6dB 1.008%THD+N 13.47W @ 8ohm
01kHz 10.39V +21.6dB 1.036%THD+N 13.49W @ 8ohm
02kHz 10.40V +21.6dB 1.169%THD+N 13.49W @ 8ohm
05kHz 10.42V +21.6dB 1.882%THD+N 13.57W @ 8ohm
10kHz 10.39V +21.4dB 2.829%THD+N 13.47W @ 8ohm
20kHz 10.10V +21.0dB 3.720%THD+N 12.75W @ 8ohm
30kHz 09.41V +20.1dB 3.640%THD+N 11.07W @ 8ohm
40kHz 07.73V +18.0dB 5.510%THD+N 7.450W @ 8ohm
50kHz 05.94V +15.4dB 3.800%THD+N 4.396W @ 8ohm
60kHz 04.51V +12.6dB 4.780%THD+N 2.520W @ 8ohm
70kHz 03.31V +9.60dB 4.140%THD+N 1.361W @ 8ohm
80kHz 2.379V +6.40dB 4.010%THD+N .7075W @ 8ohm
90kHz 1.668V +3.10dB 4.190%THD+N .3499W @ 8ohm
10k0Hz 1.301V +.60dB 3.40%THD+N .2119W @ 8ohm

Eric's at 850mV input
020Hz 10.27V +21.5dB 1.520%THD+N 13.24W @ 8ohm
025Hz 10.30V +21.6dB 1.413%THD+N 13.36W @ 8ohm
030Hz 10.34V +21.6dB 1.341%THD+N 13.34W @ 8ohm
050Hz 10.37V +21.6dB 1.233%THD+N 13.42W @ 8ohm
100Hz 10.37V +21.6dB 1.178%THD+N 13.42W @ 8ohm
200Hz 10.38V +21.6dB 1.158%THD+N 13.42W @ 8ohm
500Hz 10.37V +21.6dB 1.159%THD+N 13.44W @ 8ohm
01kHz 10.38V +21.6dB 1.156%THD+N 13.47W @ 8ohm
02kHz 10.38V +21.6dB 1.311%THD+N 13.47W @ 8ohm
05kHz 10.36V +21.5dB 2.139%THD+N 13.42W @ 8ohm
10kHz 10.30V +21.4dB 3.410%THD+N 13.21W @ 8ohm
20kHz 09.78V +20.7dB 6.690%THD+N 11.91W @ 8ohm
30kHz 08.15V +18.8dB 4.650%THD+N 8.282W @ 8ohm
40kHz 06.96V +17.1dB 2.778%THD+N 6.038W @ 8ohm
50kHz 06.08V +15.6dB 4.400%THD+N 4.590W @ 8ohm
60kHz 05.12V +13.7dB 4.110%THD+N 3.264W @ 8ohm
70kHz 04.29V +11.8dB 2.786%THD+N 2.290W @ 8ohm
80kHz 03.51V +9.80dB 4.020%THD+N 1.531W @ 8ohm
90kHz 2.543V +6.70dB 7.290%THD+N .8090W @ 8ohm
100kHz 1.475V +1.7dB 6.72%THD+N .272W @ 8ohm


Epilogue
What's all this mean? It certainly is a well-made transformer, and it matches very closely to the Z565. The fact that it is a 4 & 8 ohm tapped transformer in itself is enough to garner interest from many out there. Just in case Eric has changed his mind, I won't say what his retail cost is, other than it is under $100 each. Small runs and made in the USA. I'll let him add all the particulars.

I also want to mention that Ned is working on a similar transformer - a 4 & 8 ohm tapped Z565. I've got a chance to test of one of his prototypes and am quite pleased with it as well. We are pretty fortunate to have these options living in the 21st century!

Shannon

[sbelyo]

Nice option..... thanks Eric.

I look foward to seeing more info on how to get a pair. As I haven't purchased my Iron yet, maybe I'll start with those.

Could you contact me?

[erichayes]

Hi All,

Thanks for the review, Shannon. Allow me to flesh some things out.

The photos, for some reason, make the HC-015-OT appear larger than the Z-565 in all dimensions, while, in fact, the height and widths are the same (3"X2.5"). The extra laminations increase the core depth by 9/16", and the weight from 3# to 4#, and the larger bells increase the overall depth to 3.75" (Z-565=3.12").

All flying leads are 18ga silver plated Teflon insulated stranded wire, and vary from around 11" to 13".

In the amplifier it was designed with, the frequency response at 1 watt is 10~40,000 Hz +/- 0.1dB and THD of 0.04% @ 1000Hz. (Spec is 10~20,000+/- 0.2dB and <0.1%). Full power spec is 15/15 watts from 20 to 20,000 Hz @ <0.5% THD, but this, too, is conservative.

Needless to say, this performance has its price: the model 1773 amplifier sells for $1850.00 --roughly eight times what a scratch-built ST-35 clone costs.

I will sell these transformers to forum members for $82.50 each, plus shipping and around $5.00 for packing costs. This price will help chip away at encumberence costs (this was a
very expensive transformer to develop), and give members an opportunity to buy excellent iron the first time around.

If anyone's interested in the power tranny designed for the 1773, which is considerably beefier than the PA-774 (7.2# vs 4#), feel free to email me.

[Uncle Ned]

[quote]I also want to mention that Ned is working on a similar transformer - a 4 & 8 ohm tapped Z565.[/quote]

These are currently in the process of being made and we should have them
about 1st of June, (the folks making them are pretty good about meeting delivery
estimates, so barring any natural disasters, that's when we'll see them)
they'll be $59 each.

[Uncle Ned]

First thing, I want to point out why we are having these new
transformers made:
1.Some folks like the way the Dynaco transformer sounds but
for whatever reason need or want a 4 ohm tap on the output.
2.We want to have something to sell that's a better alternative to the
Hammond units and sell it for about the same price.

We are going to continue to sell your transformers and are happy
to do so, when you start producing the new transformer you propose,
we'll be happy to sell that, to. We're trying to fill a market
hole and compete with the less expensive competition, not
displace your product.

The folks who are making these for us have read about and understand the
applicable theory and winding technique of the Dynaco transformers..
for that matter they were reverse engineering the things back when
you & I were still in grade school.
So, yes, it's wound as a Dynaco transformer and we are not trying to
"improve" anything in the winding arrangement.
The primary is wound the same as the original 565, same number of turns,
sections and wire size. Only the secondaries
have been adjusted to accomodate the different taps.
I do not think we err by calling this a "Z565 with 4 & 8 ohm taps",
as Dyna themselves, for example, made 4 different transformers
with different secondaries on the same 60 watt core (A430, A430-500,
A431, and A431-70), and made the same performance claims for all of
them.
IMHO, what makes a Dynaco transformer a Dynaco is the
winding arrangement, not the specific output impedance taps.

As far as insertion losses are concerned, that has been measured and
the two impedance taps are equal within .05 dB. Actually, the loss
on the 8 ohm tap was slightly less! This is because of the way the
secondary is wound tends to cancel out the effect you mentioned.

Back in the days of yore impregnating with varnish was considered
inferior to wax as the varnishes of those days were only
perhaps half solids, leaving fairly large voids upon drying.
Nowadays resins are used, eliminating the voiding problems.
The resins typically used are pretty similar in dielectric constant to
parrafin wax (DC = 2 to 2.5 depending on grade of wax used).
Because the resin is thermosetting, overheating the transformer
cannot cause the resin to melt & run, thus making for a more
abuse-proof transformer.

Any rate, Mr. Parks has tested yours, ours, and the original
Dyna part, and I believe he agrees that they are all good units.

Lastly, you've got plenty to keep you occupied the way it is, Mike!
When we get around to having center-tapped cobalt core phase splitting
autoformers made (yeah, sure!) then you can get worried... ;-)