Tubelab SimpleSE: Edcor XSE15-8-5K or XSE25-16-7.6K? - diyAudio
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Old 20th January 2009, 09:46 PM   #1
pukka is offline pukka  Spain
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Default Tubelab SimpleSE: Edcor XSE15-8-5K or XSE25-16-7.6K?

Happy New Year!

I assured a friend interested into speaker tube amps that a good performing SE can be built for far less than he has seen on Audio retailers, and sound as good, and proposed the SimpleSE as an example.

To make the story short, we're going to build a pair.

I'm still reading all the info I can find, but have a doubt. We will probably settle on KT88's. I wonder which one of these transformers will sound better with 8 Ohms (>90dB) speakers. I read something but nothing conclusive...

George you have a couple mails, know you're dealing with serious matters, just hope your spam filter didn't ate my email
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Old 21st January 2009, 12:13 AM   #2
chrish is offline chrish  Australia
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I have used the XSE15-8-5K (and now 15-4-5K for my 4 Ohm speakers) and they work well. I have an active crossover, however, that pulls off the sub 80Hz frequencies and sends them to a separate solid state power amp to power a set of stereo woofer units. I have a set of JJ E34Ls in the amp at the moment and prefer these to the JJ KT88s. More detailed mid range. The KT88s are supposed to have better bass performance, at the expense of some mid range clarity.

I would look to the Edcor GXSE series (guitar output transformers). The 15 watt version is essentially a 25 watt XSE. I recall a forum member writing to Edcor and asking them if their guitar output transformers were designed for "guitar distortion". Their reply was (if I remember correctly) that hey are designed for accuracy, but have been designed to go down to 40Hz to allow for low notes on guitar. The GXSE also have a wider range of impedances, so you can get a 5K:8Ohm. I have purchased a set of these, but have yet to try them out on an amp. Some day!

http://www.edcorusa.com/products/tra...se15-8-5k.html
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Old 21st January 2009, 02:07 AM   #3
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Quote:
George you have a couple mails, know you're dealing with serious matters, just hope your spam filter didn't ate my email
I have been home for 2 weeks out of the past 5. Most of that time I have been at work until late (8PM tonight) and answering Tubelab email is expressly forbidden. I have managed a few forum posts after the bosses are gone. I have seen your email, but haven't got to them yet. Maybe tomorrow.

Most users build their Simple SE's with a Hammond or Allied power transformer that delivers 375-0-375 volts or more. This results in a B+ of 440 to 460 volts. This much B+ requires a fairly high load impedance even with a KT88 tube. The XSE25-16-7.6K would reflect a 3.8K ohm load. I have found this to cause an unacceptable level of distortion.

The OPT is the most critical component in any tube amplifier, and one that is not likely to be upgraded later. The ability of an OPT to reproduce low frequencies is directly related to its size. Accurate low frequency reproduction requires more inductance meaning more wire and a larger core, both of which raise the cost.

The XSE15-8-5K is a good transformer for the price. It will not be capable of serious low bass (below 80 Hz) without distortion simply because of its size. It does however work well when an active subwoofer is used to remove the requirement for the tube amplifier to reproduce frequencies below 80 Hz. It also works well when the speaker system is not capable of reproducing these low frequencies.

I have used the XSE15-8-5K in a Simple SE on my studio monitor speakers that have 7 inch woofers. They work quite well on these speakers. The "8 ohm" impedance of these speakers is not constant and rises below 80 Hz removing load below resonance so that the amp does not audibly distort on strong bass. That same amp connected to a speaker system with a 15 inch woofer will audibly distort.

I have not tried any transformers from the XSE 25 series or the GXSE series, since my experimentation budget has decreased. I have used the CXSE25-8-5K, and I can reccomend it if it fits in your budget. Othere have tried the Guitar (GXSE) series and report good results. I would not go below 5K with a 400+ volt B+.

I have a Transcendar 3 K OPT in my "industrial" amp. The amp exhibits noticible bass distortion when the 8 ohm speakers are connected to the 8 ohm taps, but works quite well when they are connected to the 4 ohm tap resulting in a 6K ohm load. Transcendar OPTs are another good low cost choice. They have a 5K SE version available on Ebay.
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Old 21st January 2009, 02:26 AM   #4
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I'm quite certain the Edcor transformers are a good value, but I'd suggest you expand the budget slightly and test your patience. Watch eBay carefully for the Transcendar 5K:8, 10 watt transformers. I used them on my Simple SE and I can't complain about their performance. They will likely cost $122 shipped. The eBay seller's name is ggaet. He does not have any up for sale right now - this is where the patience part comes in.

Edit: Here's a pair that sold a few days ago:
http://cgi.ebay.com/ws/eBayISAPI.dll...m=280302185258
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Old 21st January 2009, 02:59 AM   #5
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Default Totally off thread post

I have the TV on while catching up on email. The sound started beeping which attracted my attention to the "Severe Weather Alert" warning on the screen. The following is quoted from the National Weather Services web site in MIAMI FLORIDA! The caps are theres:

URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE MIAMI FL
124 PM EST TUE JAN 20 2009

THE COLDEST AIRMASS SO FAR THIS WINTER SEASON WILL SPREAD SOUTHWARD ACROSS MAINLAND SOUTH FLORIDA TONIGHT. TEMPERATURES ARE EXPECTED TO FALL INTO THE 30S OVER MUCH OF INTERIOR SOUTH FLORIDA.....WHEN COUPLED WITH NORTHERLY WINDS IN THE 5 TO 10 MPH RANGE...THESE TEMPERATURES WILL RESULT IN WIND CHILL VALUES BETWEEN 25 AND 35 DEGREES FOR SEVERAL CONSECUTIVE HOURS OVER MOST OF MAINLAND SOUTH FLORIDA FROM LATE THIS EVENING UNTIL A FEW HOURS AFTER SUNRISE TOMORROW.

A WIND CHILL ADVISORY MEANS THAT VERY COLD AIR AND STRONG WINDS WILL COMBINE TO GENERATE LOW WIND CHILLS. THIS WILL RESULT IN FROST BITE AND LEAD TO HYPOTHERMIA IF PRECAUTIONS ARE NOT TAKEN. IF YOU MUST VENTURE OUTDOORS...MAKE SURE YOU WEAR A HAT AND GLOVES.

and the latest update:

THE COLDEST AIR TEMPERATURES ARE FORECAST WEDNESDAY NIGHT. WINDS BECOME CALM AS HIGH PRESSURE MOVES OVER THE AREA FROM THE NORTHWEST. THIS SETS THE STAGE FOR A HIGH POSSIBILITY OF FREEZING TEMPERATURES ACROSS A LARGE PORTION OF INTERIOR SOUTH FLORIDA WEDNESDAY NIGHT
INTO EARLY THURSDAY MORNING. LOWS BY EARLY THURSDAY MORNING ARE FORECAST TO FALL INTO THE UPPER 20S

This is not uncommon in most of North America in the winter, but it is totally wierd here, I was in the swimming pool yesterday after mowing my lawn (we have to mow in December). I haven't been home much and my yard was starting to look like one of the local forclosures.
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Old 21st January 2009, 03:16 AM   #6
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Default Re: Totally off thread post

Quote:
Originally posted by tubelab.com
...THESE TEMPERATURES WILL RESULT IN WIND CHILL VALUES BETWEEN 25 AND 35 DEGREES FOR SEVERAL CONSECUTIVE HOURS...
You poor bastard. I feel for you - no, really, I do. So sorry to hear about the few consecutive hours of very nearly cold temperatures. If only you had a pair of these around - http://www.audioresearch.com/ref610T.html - you could use them as space heaters to protect yourself from freezing.

/sarcasm off
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Old 21st January 2009, 04:23 AM   #7
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George, I grew up partially in Orlando. I remember coming home one Christmas in the mid '80s and getting a 19 degree Christmas as a present. We still had well water at that time, and our pump froze. My Dad had to deal with the resulting mess. We also lost a few of the more tender citrus trees (lemon, a couple of our orange trees). When I got back to California, it was 65 degrees. Having said that, I also remember an 85 degree Christmas one time when I came home from college.
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Old 21st January 2009, 04:43 AM   #8
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I would like to put my 2 cents in and recommend the GXSE line. I'm running a pair of the 25 watters in a 3-3.5 watt SET amp and they sound pretty OK. Pushing about 65mA of current at 320V. They're just a bit bulky, at 4" long (including mounting tabs)x2.5" tallx2.25" wide, not counting the quarter inch quick connects. I haven't done any measurements but I imagine they're pretty solid, given what people have been saying about the regular XSE line, which is rated at 70Hz as opposed to 40.
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Old 21st January 2009, 05:59 AM   #9
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When I made my "Shrine" 1625 SE amp, the XSE and CXSE were the only things available from Edcor. I ended up using a pair of the 5k/8 ohm XSE series and they sounded pretty good, though with obvious limitations on the low end. I have since refitted the amp with a pair of the GXSE 15W (hah!) transformers. I haven't done much critical listening with the amp, as it also has an RF oscillation issue, but I'll report back once that is straightened out. I expect more bass, at least. I'm currently running the 1625 outputs at about 60ma, 350V (probably more like 320V or so across the tube when you subtract the cathode bias), in ultralinear mode. I bought 3 pairs of the GXSE, and I''ll be finding homes for the other two pairs when I get a chance. The Edcors are a nice bit of iron for the money, especially since Hammond has really jacked up the prices on their 125 SE series. I paid 35 apiece for a pair of the 125ESEs when I started tooling up for my first tube amp - now they're over 50 dollars apiece. Both Transcendar and Edcor are better value these days - nicer finish, too. The baby Transcendars are a good alternative to the 125ESE at about the same price, the only disadvantage being the single impedance outputs on the Transcendars.
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Old 21st January 2009, 06:01 AM   #10
DimZ is offline DimZ  Greece
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Quote:
Originally posted by Ty_Bower
I'm quite certain the Edcor transformers are a good value, but I'd suggest you expand the budget slightly and test your patience. Watch eBay carefully for the Transcendar 5K:8, 10 watt transformers. I used them on my Simple SE and I can't complain about their performance. They will likely cost $122 shipped. The eBay seller's name is ggaet. He does not have any up for sale right now - this is where the patience part comes in.

I use the Transcendar 5K:8, 15 watt with 40% ultralinear and both 4 & 8ohm, sounds just fine. With my diy fullrange 8ohms(fostex 126E) is pretty much what I was looking for (though a fast system i.e adding a sub might help the lf), with my other set of loudspeakers AUDIO SPECTRUM ARTEMIS (http://www.audiospectrum-hifi.com/english/index.htm) I have an amazing sound but a get some distortion when playing loud (sensitivity 91db / 6ohm), but thats quite normal I guess ...

tubes (JJ EL34, EH 12AT, china GZ34), waiting for a pair of KT88 and a sovtek 5AR4 ...

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