EDCOR XSE, GXSE and CXSE basic specs and measurements

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EDCOR XSE, GXSE and CXSE basic specs and measurements

Postby EWBrown » Mon Jun 01, 2009 2:56 pm

I just received my trannies from Edcor.

Two each of XSE15-8-5K, GXSE10-8-5K and GXSE15-8-5K.


The XSE15 and GXSE are the same size, and the GXSE is considerably larger, about the same dimensions as a Hammond 125ESE or MQ RH-60.


In order to be able to plug them into SE CAD, I needed to measure the primary DC resistances, and for now, SWAG the primary inductance.

Note: I have measured some SE OPTs with known inductance values, as a "control", in order to verify that I am getting reasonably accurate measurements

Here's what I got:

XSE15-8-5K: Primary DCR 120 ohms, inductance 12 H, Max I 75 mA DC, 50 mA AC.

GXSE10-8-5K: Primary DCR 244 ohms, inductance 20H, Max I 60 mA DC, 40 mA AC.

GXSE15-8-5K: Primary DCR 156 ohms, inductance 20H, Max I 75 mA DC, 50 mA AC.


Secondary DC resistance is about 0.3 ohms for the 15s, and about 0.5 ohms for the 10.


I SWAG'ed the primary inductance by factoring in the lower freq response (40 or 70 Hz) and applying 5000 ohms to that frequency.

Applying Ohm's Law, L = 5000 / (6.28 X F in Hz). Rounding to the closest interger produces 12H for the XSEs, and 20H for the GXSEs.

I will be able to measure the actual induictance sometime next week when I'm back in NC, and can use my LCR bridge.

The current ratings were taken from old data provided on the earlier incarnation of the Edcor website.

Please feel free to add more "basic specs" for other EDCOR trannies, to this topic.

Update 14-June-2009:

The actual measurements (at 100 Hz) for both of the 5K GXSEs is 17H, and only 7H for the XSE15-8-5K. Looks like the GXSEs are the way to go...


HTH

/ed B
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Postby mesherm » Mon Jun 01, 2009 8:10 pm

I have a set of Edcor GXSE10-8-2.5k OTs here.
Measurements taken with my Tenma 72-8155 LCR meter.
Primary inductance (secondary open) measures 5.74 H.
Primary inductance (10 ohms across secondary) measures 3.87 H.
Primary DC resistance measures 149.0 ohms
Sercondary DC resistance measures 1.1 ohms.
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Postby EWBrown » Tue Jun 02, 2009 12:36 pm

As a comparison, the "standard" Hammond 125ESE, has a primary inductance of 9.58 H, DCR around 100 ohms, Max I of 80 mA. THis is rated 100Hz-15KHz.


/ed B
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Postby TomMcNally » Tue Jun 02, 2009 12:57 pm

Did you measure the frequency response, or are you taking
the manufacturers specs ? There has always been some
question that maybe Hammond under-stated the freq
response on the cheaper line, to move people to the
better ones.

How would response be accurately measured on the bench ?

I would assume the input and output impedances would
have to be properly matched to get accurate readings ?
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Postby EWBrown » Tue Jun 02, 2009 1:28 pm

At this point, I'm just using the manufacturer's stated specs, presuming that they mean the lower and upper frequency -3dB points. which may or not be the actual case :/ .

My intent is more for comparitive purposed (and applying to SE CAD) rather than highly accurate laboratory grade measurements.


For measuring the actual freq response to the -3dB points, I'd load the OPT secondary with an 8 ohm non-inductive resistor, and manually sweep the amp's input with a sine wave, starting at 20 Hz and stopping at 20 KHz (or higher). If an oscilloscope is available, monitor the output signal's quality, look for clipping, ringing, wave shape distortion, etc.

This will demonstrate the trannie's true specs (along with those of the amplifier in which it is employed), with any resonances, instabilities, etc.

The primary inductance will measure differently with the rather light signal applied by the LCR bridge, as compared to carrying the full operating plate current in the winding.

My HP 4276A LCZ bridge does allow selecting the measurement frequency, starting at 100Hz and can apply a modest DC "bias" across the primary / inductor under measurement.


/ed B
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Postby Ty_Bower » Tue Jun 02, 2009 5:22 pm

Here's a question for the peanut gallery: Is there any reason for transformers which have the same secondary-to-primary ratio to be wound any differently? For example, does Edcor use the same winding on a GXSE15-16-10K as they do on the GXSE15-8-5K or the GXSE15-4-2.5K? I've heard talk that some winders imply there are differences, but I've never heard the specific details and I can't imagine what they might be.
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Postby EWBrown » Wed Jun 03, 2009 6:07 am

These transformers (2.5K:4, 5K:8 and 10K:16) would all havwe the same 25:1 turns ratio, and 625:1 impedance ratio. The primary impedance simply reflects the secondary's loading. And loudspeakers are NOT a constant impedance across their frequency range, generally the nominal impedance (4, 8, 16 ohms, etc) is at 400Hz or 1 KHz.

Now, if the trannie manufacturer observes the lower frequency's -3dB point, the 10K OPT's primary would have twice the number of turns, as the 2.5K, and 1.414 times the turns of the 5K units., and the sccondaries would also be wound accordingly, in order to maintain the 25:1 turns ratio.

In some cases, like the Hammond 125ESE, the primary is a "fixed" (9.58H, 100 ohms DCR) winding, and the secondary has taps for 4, 8, 16 and 32 ohms. which can then be applied as a 10K, 5K or 2.5K OPT, by changing the loading of the secondary. As shown here:

Image

Apparently, Edcor uses different primary windings for their various specified impedances:


I have a set of Edcor GXSE10-8-2.5k OTs here.
Measurements taken with my Tenma 72-8155 LCR meter.
Primary inductance (secondary open) measures 5.74 H.
Primary inductance (10 ohms across secondary) measures 3.87 H.
Primary DC resistance measures 149.0 ohms
Sercondary DC resistance measures 1.1 ohms.


From Mesherm's data, it apears that the two variations of the GXSE10 (2.5K and 5K) have different primary windings, as the GXSE10-8-2.5K has a DCR of 149 ohms, and the GXSE10-8-5K has a DCR of 244 ohms.

So that pretty much eliminates the likelihood that they use a "standard" primary winding and adjust the secondary winding to reflect the specified impedance.

/ed B
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Postby Ty_Bower » Wed Jun 03, 2009 5:33 pm

EWBrown wrote:These transformers (2.5K:4, 5K:8 and 10K:16) would all have the same 25:1 turns ratio, and 625:1 impedance ratio. The primary impedance simply reflects the secondary's load.

Now, if the trannie manufacturer observes the lower frequency's -3dB point, the 10K OPT's primary would have twice the number of turns, as the 2.5K, and 1.414 times the turns of the 5K units., and the secondaries would also be wound accordingly, in order to maintain the 25:1 turns ratio.


Thanks for straightening that out for me, Ed. So what they say is that an OPT might "ratio down" just fine, but trying to "ratio up" might hinder the bottom end performance. The 10K:16 has enough inductance to meet specifications for its intended application. If I try to "ratio down" this transformer, and use it as if it were a 5K:8 (with appropriate amp circuit and speakers) I may actually have more inductance than I need to meet the low frequency spec at this load. Could the result be better low frequency performance than I paid for?

Of course, every single transformer for a given wattage of the GXSE lineup has exactly the same price. Copper isn't free. If what you say can be applied to Edcor's winding techniques, I'd expect the GXSE15-16-10K to cost a little more than the GXSE15-4-2.5K. Maybe Edcor is eating the cost of the extra windings? That doesn't seem likely.

Is there any disadvantage to having too much inductance on the primary? I suppose it necessarily requires additional turns, which increases the primary's DC resistance, which results in a little extra dB of insertion loss. Is that a big deal? Should I be ordering 16-10K transformers from them if I need a 4-2.5K, and expect the OPT to reach a little deeper in the bass?
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Postby EWBrown » Thu Jun 04, 2009 1:00 pm

For a 2.5K : 4 OPT, a 5K: 8 might be the best choice, as it still gives the same ratio.

As a side benefit, the 5K:8 is almost "universally usable" as an SE OPT.

The rule of diminishing returns would probably apply to the 10K: 16 OPT, if indeed it is wound with accordingly more turns.

I'd SWAG that the higher Z rater OPTs may use lighter gauge wire because the curent rating would most likely be lower, and one can fit only so much copper wire onto a bobbin , for a given power rating. .

I'll try to measure the primaru inductances when I am in NC next week, and I'll post my findings after I get back

/ed B
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Postby EWBrown » Sun Jun 14, 2009 2:56 pm

I took some actual readings on the Edcors when I was in NC last week.

I used an HP 4276A LCZ meter, it's a bit of a "beast" but I couldn't beat the price (free)...


The inductance readings are somewhat frequency dependent, and I got the "best" indications at 100Hz which is the minumum test frequency.


As I tried stepping therough the spectrum, the inductance readings did vary up and down, so for consistency, I stayed with 100Hz.

The GXSE10-8-5K and GXSE15-8-5K both showed 17H at 100Hz.

The XSE15-8-5K showed only 7H at 100Hz.

Just for a "sanity check" I re-tested my Transcendar TT-10-OTs (3K, 10W, 100 mA, 20H) and they were "dead-nuts" on at 20H. within 0,2H.

I teested some other SE OPTs that I had and will post the values at a later time.

So my SWAG for the GXSEs (20H) wasn';t too terribly far off, 17H vs 20H, but the SWAG fo rthe XSE15 was significantly off, 7H vs 12H,

The next step will be to install the trannies in a working amp and get an actual use comparison.

Stay tuned....



/ed B
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Postby Ty_Bower » Sun Sep 06, 2009 8:44 pm

mesherm wrote:I have a set of Edcor GXSE10-8-2.5k OTs here.
Primary DC resistance measures 149.0 ohms


I stuck the ohmmeter on my GXSE15-6-2.5K. It's about 95 ohms on the primary side, but the reading isn't what I'd call stable. It wanders around +/- 4 ohms. Should I be shorting the secondary while taking measurements?

I don't have a good way to measure inductance, but I'm going to swag the value is "not quite enough". With a set of 8 ohm speakers attached (which is a smidge higher than the 6 ohm expected on the secondary) the bottom end rolls off a little sooner than I think it should. I'll guess it's starting to quit somewhere around G♯ˌ or Aˌ.
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Postby EWBrown » Mon Sep 07, 2009 4:50 pm

If you're using a DVM for the resistance measurement, it will most likely jump around a bit, and in some cases, the reading will show as being "over-range". This is especially true with higher impedance primaries and high-inductance chokes.

This is caused by the DVM, when it is in resistance mode, as it will pulse a low DC voltage across the resistor (or transformer primary) connected to it. The inductance of the primary will create weird "peak" voltages which will mess up the resistance readings.

Shorting the secindary leads, or just connecting a 4 or 8 ohm resistor betwen them, will eliminate the unstable readings.

The trannie's lower freq response will be affected by the plate current through the primary winding , a higher idle current will result in a higher frequency roll-off. So your noted roll-off around G sharp / A seems about right. The easy way around this is to use an OPT with a higher power or primary current rating. Also, check your interstage coupling caps, if they are too low value, this also causes an LF roll-off.

HTH

/ed B
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Decware / Edcor OPTs good for 6CK4s

Postby EWBrown » Mon Sep 14, 2009 3:15 pm

Last year I bought a pair of some small Decware SE OPTs (originally designed for converting a "Zen" SE84C to 16 ohm speakers).

These are very obvoiusly made by Edcor, complete with the usual stickers, and blue bobbin, but with wire leads, in place of the solder terminals. There is no UL tap on the primary, these were intended for "triode mode" EL84s or 6P15P-EVs only.

I ran my usual tests on these, and found the winding ratio to be approximately 23.1:1, for an impedance ratio of approx 530:1. So, with an 8 ohm load, they look like 4240 ohm primaries. 4.2K is close enough...

The prilmary DC resistance is 209 ohms, and I measured the primary inductance at two frequencies, and they both checked out as 24H at 1 KHz, and approx 100H at 100Hz (the lowest operating freq of my LCR meter). One read as 96 H and the other read as 104H at 100Hz.

So they definitely have a much higher inductance than the standard XSE or GXSE OPTs. And this translates to better bass response [:)

This impedance works out just about perfect for a 6CK4 SET, running them at 45 mA and with a 620 ohm cathode resistor, for a 28V bias. B+ approx 325V - I'll have to check my old notes to be sure of all the figures. 6CK4 is a vastly underemployed vertical deflection triode, with 12W plate dissipation. AS far as I know, there are no direct European or Russian substitutes or equivalents. One could probably slightly modify a G*S*G to run with these tubes very nicely.

Some folks say that the 6CK4 "sux" as an audio triode, (not very linear curves) but as Andrew Zimmern says, "don't knock until you've tried it"
Octal relay sockets to the rescue, for a quick no-solder test...

4.2K should also be a decent match for 6EM7s, 13EM7s, 6FD7s, etc.


These are the size of the smaller XSE10 series OPTs, and will fit under a 2 inch deep chassis. Probably get a bit more output power than with 5K primaries.

/ed B
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Postby Ty_Bower » Tue Feb 23, 2010 6:46 pm

I thought a few items in the Edcor news might be worth mentioning here. First, the GX line (GXSE and GXPP) have been updated since the beginning of 2010. They are no longer the open frame style like the XSE. They've got end bells and leadout wires. I think they look pretty attractive, and the new style is definitely better suited for mounting on top of the chassis. The downside is that the new frills come with a price increase of roughly 35% ($6 on the ten watt models, and $10 on the fifteen watt models).

The second item worth mentioning is that Edcor is going to have a "cost of materials" price increase as of March 1, 2010. Get your orders in today before the new prices go into effect!
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Postby EWBrown » Wed Mar 03, 2010 1:59 pm

I haven't checked EDCOR's website in a few months, I didn't expect any significant updates or changes...

Having end bells and wire leads is a definite improvement, and should solve the problem of unwanted AC induced magnetic fields getting into the OPTs, which can cause an "uncurable" 60Hz hummmmm problem..

New and improved, but at a modest cost, but it should be worth the additional cost.

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