diytube.com

Hi Ed,

I think Brian Weston was talking about a leaded and endbell version on his forum?

Cheers!

I haven't been on his forum in a l-o-n-g time..... Been kinda offline most of the past few weeks.

/ed B

Found it! :-)

http://audiotransformers.net/index.php?topic=266

Cheers!

They look kinda like this:



/ed B

Y'know you're a tube geek when the sight of that is considered downright sexy ;-)

Cheers!

Steven (TheGimp) over on diyaudio posted a pic of a nice
amp, with an interesting cover over the open frame Edcors -

http://www.diyaudio.com/forums/attachments/tubes-valves/182635d1280888938-firefly-single-ended-tetrode-two_amp_ii-2.jpg

(You have to be registered to see it)

I just received an Edcor GXSE15-16 -10K (10K primary, 16 ohm secondary), which can also be used as 5K:8, with the added benefit of increased primary inductance (29H) This is the new version, with the blue end bells.



Mounting dimensions are 2.5 inches (6.35cm) wide X 2 inches (5.08 cm). Plus two (3/8 inch dia / 9.5 cm)) holes for the leads. The core dimensions are the same as the original open frame version.

Primary DCR: Red (B+) to Blue (Plate): 301 ohms

UL tap to B+: 133 ohms.

Secondary DCR: 1.1 Ohms

Primary Inductance (measured with HP 4276A) Secondary not loaded.

100Hz = 29H
600Hz = 23.6H
1KHz = 26H

(measurements taken above 2KHz were all over the map)

I don't have an actual primary current rating, but I have used 75 mA, as this was the value given for the older XSE15 OPT primaries, several years ago. These larger trannies may be good for as much as 90 mA.

At this point, I only have one of these, so it will end up in a mono UL-SE design, with either 6BQ5 or 6V6GT, TBD...

With two EL84s in PSE, triode mode this is good for about 4Watts RMS and 2.5% 2HD and 0% 3HD. In UL mode, more power, probably 6 to 7 watts RMS.

/ed B

EWBrown wrote:I just received an Edcor GXSE15-16 -10K (10K primary, 16 ohm secondary), which can also be used as 5K:8, with the added benefit of increased primary inductance (29H).

Sometimes I think that's what I ought to have done when I bought my GXSE15-6-2.5K... should've ordered something like the 16-8K, which has a similar ratio but more turns on the primary.

I wonder what price you pay for playing the ratio game. Certainly more inductance comes from more turns, which requires a longer piece of copper. More copper means greater copper losses, which hurts efficiency. Is it a big enough deal that I would notice?

Does the high frequency extension suffer as a result?

EWBrown wrote:Primary Inductance (measured with HP 4276A) Secondary not loaded.

100Hz = 29H
600Hz = 23.6H
1KHz = 26H

(measurements taken above 2KHz were all over the map)

Fantastic iron quality then... most lams I pull from (junk appliance, like clock radios) power transformers "disappear" from their windings anywhere from 300-600Hz. Even a local transformer manufacturer that uses verrrry $$$ lams has them disappearing above 1K.

Cheers!

I wouldn't use this technique for much beyond a 2:1 ratio so using a 10K:16 is good for a 5K:8 equivalent. Using a 2.5K:4 would also (technically speaking) work, but the LF response would be poor In all cases the impedance ratio is 635:1, and the turns ratio, 25:1. The latter case would be OK for SE guitar amp usage, as the low E string is around 82 Hz, so the LF response limitation is of less relevance.

Similarly, with the 6CW5 / EL86, a good PP OPT primary is 3.3K A-A, so I'd just use the more commonly available 6.6K:16 ohm as a 3.3K:8 ohm replacement. The Hammond 1620 comes to mind here. This trannie has secondary values of 4, 8 and 16 ohms available, and an UL tapped primary.

For non-UL PP applications, the hard to find Sansui 1000 (NOT 1000A) OPTs would also be near perfect, with 3200 ohms A-A and 8, 16, 32 ohm secondary. THese OPTs were likely produced by Tango or Tamura, for Sansui.

I haven't yet run the "10K" tranny in an actual working circuit, that may be a while yet to come... The primary DCR as compared to a GXSE15-8-5K is nearly twice as high, 301 ohms vs 156 ohms. If Edcor uses a fixed number of turns per K of primary inductance, then the "10K" would have 1.4 times the number of turns than the "5K" primary. But as more turns are added, each layer of primary winding has a slightly larger diameter, and this adds up pretty quickly when there ar multiple layers of windings.
(think of a roll of paper towels, or of toilet paper).

So, there would be more "copper" losses, but not unreasonably so, I see several other "5K" SE OPTs with around 300 ohms DCR on the primary, and all are decent to excellent, as well as really cheap ones with under 100 ohms DCR (meaning les turns, significantly less inductance, and a resulting poor LF response) .

But then, the GXSE15-16-10K's primary inductance is also nearly twice as high 29H vs 17H), and that definitely will help the LF response. The DCR is a product of the wire gauge used in the winding, as well as the number of turns. Just think of it as a big wirewound resistor, for DC considerations.

The first time I played the "ratio game" was when I cloned Jef Larson's "Abraxas" 12B4A amp, which uses the small German "EL95" SE OPTs with 11 to 12 K primaries and 4 ohm secondaries, as a 22 to 24K, primary, to 8 ohm secondary. This combo may seem extreme for a 12B4A (with a 1.09 K Rp, but then the sound quality is excellent, and about 900 mW max, so it is a strong contender in the "Darling" sub-watt SE amp class.

FWIW, these trannies are even better with 6S4A. MUCH better in fact, probably one of the sweetest sounding amps I've ever heard, but also in the sub-watt class.



/ed B

You had mentioned surplus military 400 Hz trannies in another topic. I cringe when I think of the quantity of those that I simply tossed in the trash or just gave away, over the years. All appeared to be of the hghest quality, all sealed and potted , and developed for service in US military aircraft (mostly) where the higher frequency was important for having smaller and thusly, lighter power iron in the avionics and radar systems.

With their R- or C- cores, and nickel lams, these may have been excellent for audio transformer purposes, given the proper pri:sec turns ratios.

Probably not true with the three-phase 400Hz trannies, but they would still make good paperweights or doorstops

/ed B

Ty_Bower wrote:

EWBrown wrote:I just received an Edcor GXSE15-16 -10K (10K primary, 16 ohm secondary), which can also be used as 5K:8, with the added benefit of increased primary inductance (29H).

Sometimes I think that's what I ought to have done when I bought my GXSE15-6-2.5K... should've ordered something like the 16-8K, which has a similar ratio but more turns on the primary.

I wonder what price you pay for playing the ratio game. Certainly more inductance comes from more turns, which requires a longer piece of copper. More copper means greater copper losses, which hurts efficiency. Is it a big enough deal that I would notice?

I wonder if there is also another consideration on the current rating to be made. If you slide down the ratio ladder, would you have to also derate the wattage because the current will be twice as high? Will the wire gauge handle the load, especially while in Class A?

One thing I have noticed about Edcor transformers so far when "peeking" at their windings (at lease on the XSE and WSM series), the wire is conservatively rated to say the least.

An example was it took some "arm twisting" to get Brian to admit, "OK, maybe 10mA in a XSM...." (paraphrased), but that I think is far more due to core saturation, as the wire could easily handle 5 times that much, continuous duty, IMO.

Cheers!

FWIW, Edcor has moved their website to a new URL:

http://audiotransformers.net/index.php


I received this e-mail from them last week (just in case everyone herer didn't get it directly from them)

/ed B in NC



EDCOR wishes to announce that their new website and e-store will be online starting November 1st of this year.

The new site is full of addition and changes. You can now place, check the
status of your orders and get shipping quotes for orders you place online.
There is also a blog and newsletter to keep you up-to-date about EDCOR and its products. The technical support forum has changed. It is integrated with the e- store, so you only have to register once. EDCOR will still have its Facebook fan site and will still post Twitters so that has not changed.

The sad thing about all of this is that all of you that are registered on
EDCOR's support forum will have to register for the new forum. Sorry about
that.

Regards,
The EDCOR Technical Support Team.

http://audiotransformers.net/index.php

So when you use this trick , using a 10K:16 as an 5K:8 equivalent, do you hook it up the same way or do anything differently?