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Old 19th March 2015, 07:30 PM   #1
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Default SE output transformer

I know I have read about this being discussed but can't find the exact thread.

Are these two transformers the same?

https://www.edcorusa.com/gxse10-16-5k

https://www.edcorusa.com/gxse10-8-2_5k

If the impedance ratio is just a a squared function of the turns ratio these two transformers are the same. BUT somewhere in my soggy brain there is a voice telling me that if I try and use the gxse10-16-5k with an 8 ohm load giving me a primary impedance of 2.5k the primary inductance will be less then what I expect?

Are these the same transformers with different stickers? Or are they different? The reason I just don't order the gxse10-8-2_5k? Because I can purchase the gxse10-16-5k and have them in a week as appose to two months.


Edit: I plan to use them with some Tubelab SE boards. I see he has on his site that he has tried the xse15-8-5k, the gxse line has better low end performance.

Thanks

-bird

Last edited by famousmockingbird; 19th March 2015 at 09:22 PM.
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Old 19th March 2015, 07:42 PM   #2
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They are slightly different (see max current spec.) Chances are for many applications they can be used interchangeably.
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Old 19th March 2015, 07:53 PM   #3
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Thank you for the quick response.

I see that now, for the gxse-8-2_5k they give the spec of 6H for primary inductance, 149 ohm DCR, and 120mA current for rated performance. The gxse-16-5k they only tell you 80mA for the rated performance. Good catch
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Old 19th March 2015, 08:33 PM   #4
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I forgot to mention I want to use them for the Tubelab SE. Any advice? Has anyone used Edcor for these amps? They will be paired with Klipsch Cornwall's most likely.
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Old 19th March 2015, 10:04 PM   #5
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While the reflected impedance between those two OPT's will be the same, the 5K unit will present a higher inductance on the primary at the low end. Given that the K-33 woofer in the Cornwall is nominally a 4 Ohm driver, the amp will have a very low damping factor even in the context of an SET amp. If I were you, I'd probably be looking at the 15W Edcor units at the 3.5K or even 5K:8 impedance ratios. The slightly lower max power to be had with the higher impedance OPT's will more than be offset by the lower distortion and better damping.

https://www.edcorusa.com/gxse15-8-3_5k

https://www.edcorusa.com/gxse15-8-5k

The additional $20 per pair for these bigger OPT's pales in comparison to the cost of the 300B tubes that you will be buying for this amp. Just MHO.
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Old 20th March 2015, 06:42 PM   #6
316a is offline 316a  England
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Quote:
Originally Posted by famousmockingbird View Post
Thank you for the quick response.

I see that now, for the gxse-8-2_5k they give the spec of 6H for primary inductance, 149 ohm DCR, and 120mA current for rated performance. The gxse-16-5k they only tell you 80mA for the rated performance. Good catch
Is this for a 5k transformer ? If so then there may be very limited output under 100Hz . 149 ohms for such a small transformer indicates not many turns . The rule of thumb I use is 20H per 1K of Ra of the driving valve in triode SE . If you want to use midbass and up , probably fine . Hope this helps

316a
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Old 20th March 2015, 07:33 PM   #7
TheGimp is offline TheGimp  United States
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I used both the GXSE15-8-5K and GXSE15-8-3.5K as output transformers for 6P41S SE amps, and have been quite pleased with both transformers.
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Old 20th March 2015, 11:20 PM   #8
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Unfortunately I did not win the auction. The pair went for $15 more then what they go for brand new.

It's probably for the best, I have been looking at Transcendar, the prices seem more then fair to me and the specs look really good.

What can be expected from a current production 300b in class A2? I have zero experience with DHT.
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Old 20th March 2015, 11:42 PM   #9
evanc is offline evanc  United States
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have you considered electraprint?
Electra-Print.com Audio Transformers
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Old 21st March 2015, 12:24 AM   #10
kevinkr is offline kevinkr  United States
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Electra-print and Lundahl would both be good choices.. I've also had pretty good results from modestly priced Transcendars which seem to offer great value for the performance offered.

Note that the 300B is not really intended for class A2 operation. (I have designed and built a significant number of both PP and SE 300B amps over the years..)

8 - 10Wrms is possible with good tube life.. If you really want to push them and bend the rules by running them into A2 you can get 16W or so out of a single tube.. I've not done this, and I hear tube life is quite short even with genuine WE 300B.. (There was a Japanese 300B SE amp rated at 17W per channel from a single 300B per channel!)
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