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Edcor OPT in S5 Electronics K-16LS kit?
Edcor OPT in S5 Electronics K-16LS kit?
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Old 2nd December 2013, 07:19 PM   #41
Fishstix is offline Fishstix  United States
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Default Edcor Power Trans

Hey All,
First, thanks for the info on the Edcor OPTs. I am building a setup for a friend and looking forward to tuning it up a bit. I will be swapping them out directly, I won't have time to tune for ultralinear, as much as I would enjoy the learning process.

Similarly, I would like to swap out the Power Trans for an Edcor. I see the specs durkla18 posted, and I wanted to double check with everyone that I am twigging to the correct model.

durkla18's PT
Dual 120 Primary
Sec red= 180 V, 0.2 A
Sec yellow=12.6 V 4A White/yellow CT

Which looks much like this puppy... EDCOR - XPWR058

XPWR058 Specs
Power transformer for a 120V or 240V, 50/60Hz. line to 180V at 200mA and 12.6V (6.3-0-6.3) at 4A center tapped.

16-LS Schematic is here... http://diyaudioprojects.com/Forum/do...1453&mode=view

Does this scan? I think I am on the right track but I'll wait to hear from you guys before I pull the trigger.

I always feel my novice coming out with these questions, but I am pretty good at swallowing my pride these days. As always, thanks for the help, guys; you make this hobby so much more fun.

-Fishstix
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Old 4th February 2014, 07:01 AM   #42
Fishstix is offline Fishstix  United States
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Default My Foul Up

Old thread, hopefully this is useful to someone...

In hopes that nobody else makes my mistake, I lay my errors out for all to see. I am most of the way through building a K16LS, and have swapped out all three transformers for Edcors. The CXPP25-8-5K Output transformers work great, improved the sound quality greatly.

But I messed up on the Power transformer. I bought the XPWR058, which has a 12.6v (6.3-0-6.3) center tap. There was a loud hum and the tubes looked *hot.* Swapping out for the stock transformer removed all hum and the tubes look normal again (the same as my previous build.) The voltage from each heater leg to ground (with the stock transformer) was around 3 volts, which is how I found my mistake.

The schematic that comes with doesn't refer to each leg as 6.3v, it is saying the whole center tap runs at 6.3v. So this expensive and long awaited transformer runs twice as hot as I need.

My mistake, I can't point fingers. But fair warning. If you are planning on swapping out the PT, the XPWR227 that runs at the correct heater voltage, but the secondaries run at 300mA; I don't know if that is in spec.

When the stock transformer is installed, the whole thing really sounds great. No hum at any volume, no feedback or oscillation. When music isn't playing I can't tell it is on, even with my ears to the drivers. The Edcor OT's are a nice improvement from the tinny little things that come stock. I know there has been some criticism of this amp, and for the cost of upgrades maybe it isn't a fantastic deal, but it's been a great learning project for me, and I've built an amp that sounds wonderful to my ears. I would recommend it with certain caveats.

Here shortly I am going to try and make the XPWR058 work through judicious use of resistors on the heater legs. I am still hoping to use this PT for a little more power on the very bottom end, where this kit is a bit weak. (For me.) Wish me luck! And if anyone has any advice for me I am all ears. Where is the smiley that is a pair of ears?

I'll try and post a photo when I finish the build.

Thanks All!
-Aaron
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Old 4th February 2014, 12:46 PM   #43
Tom Bavis is offline Tom Bavis
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Since it's a printed circuit board, this may not be practical, but you could wire the 6.3V heaters in series pairs for 12.6V.
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Old 4th February 2014, 07:58 PM   #44
Fishstix is offline Fishstix  United States
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Hey Tom,
I was rolling that around in my head last night, but looking at the PCB this morning, I think it would be a nightmare to divvy it all up evenly. Doable, but with lots and lots of stray wires. I think almost every socket would need it's own set, and lots of the copper traces would have to get Dremeled. I like the layout of the PCB; it's great for learning, and very clean. But not alot of room for changes like this. I think this will be the last PCB build for me; I am chomping at the bit to do point to point anyways.

Again, my fault. I'll play with some resistors and see if I can get close enough to make me happy. Otherwise I need to decide whether or not to wait for another Edcor or just use the stock one. Dilemma. But a good learning experience!

Thanks for the response, Tom, especially on an old thread like this. It's much appreciated.

All the Best,
-Aaron
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Old 4th February 2014, 08:12 PM   #45
Fishstix is offline Fishstix  United States
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Oh, and correct me if I am wrong, but I need to have two equal resistors on the two heater legs, right? The total impedance between the two bringing the voltage down to the correct level. If I were to use one resistor on one leg, the transformer would 'see' two different voltages and... bad things? For similar reasons I wouldn't be able to use diodes for the drop, as the rectification would stress the transformer's attempt to output an AC signal, even if it would dampen induced AC signal at the tubes.

Cheers,
Aaron
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Old 4th February 2014, 09:08 PM   #46
Tom Bavis is offline Tom Bavis
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Is the 12.6V winding center-tapped? If so, then you have 6.3V available. If you use dropping resistors to drop 6.3V at 4.2 A, there's 25W of heat to get rid of...

You could get a pile of 12AQ5s and only have to add resistors for the driver tubes...

And it seems to me if you can find the right spot on the circuit board, one cut will separate the filament network in half, so you connect 12.6 V to the two sides of the cut. Just don't run it with any tubes pulled...
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Old 14th February 2014, 04:48 PM   #47
Fishstix is offline Fishstix  United States
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Hey Tom,

I played with some spare resistors for awhile (got close) and spent some time looking at the heater net for solutions. I think it might have worked but seeing as this is a gift I didn't want to tear up the board too badly. I still have my own K16ls on the shelf (in a terrible chassis) so I might go back and use the now spare PT on that. I want to pick up new OT and try the ultralinear mode, so I'll have the dremel at the board anyways.

I went ahead and ordered the proper PT for the gift amp so I don't have to cringe when she opens it up. Another six weeks and a bit o cash, but the peace of mind is worth it.

It's been a good learning experience; I got alot out of this one, so I am nowhere near bitter. Thanks for bouncing some ideas back and forth with me, Tom. It got my mind thinking in new ways and made me sit down and learn a bunch about heater circuits which will help future builds.

Cheers!
-Aaron
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Old 7th April 2014, 06:18 PM   #48
Fishstix is offline Fishstix  United States
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Hey All,

The XPWR227 works like a charm. Notably more power in the low end, much more than I expected. With the O'scope on the output, I manually fiddled with the location of the PT, and wasn't able to create much noise difference even if I shoved the PT right up next to the tubes. Chalk it up to the end bells? Maybe the valves working in push-pull are less susceptible to gauss fields than a single bulb in SET taking all the gauss field? I don't know, and I don't have a similar SET on the shelf to compare it against. After the fact it seems that transformer location just wasn't as important on this kit than I expected. In the end I just shoved the PT against the left side with room to work, and on the centerline between the two OTs. So it looks good. When my own camera is not on the fritz I'll try and get a good pic of the wiring.

I used screw-down jumpers at the transformer junctions so I could swap things around during the build, and if I ever have to replace anything. That worked out like a *charm.* Super easy and quick to pop things in and out. The Pot is a mil-spec one I found with huge lugs that were easy to solder and a nicer feel than any I've encountered so far. An IEC filter input so the rig would have a ground and some noise dampening; it does a remarkable job quieting noise on dirty metropolis AC. The noise level in the city was just the same as the noise I get at my house, (which is off grid, battery bank, finely stepped inverter, VERY clean AC.) So that will be integral to every build I ever do *ever* again. Interestingly, the left channel has almost exactly twice the noise as the right channel in *both* builds (my personal one having a much different chassis layout and stock transformers) so maybe it's induction on the PCB? It's not terrible; with the volume Pot pegged and no input signal I have to strain to hear some hum in the left channel, and there is none in the right.

I didn't wire the output transformers for ultralinear, nor did I swap out audio caps. But I may go back and do that on my personal rig this winter.

What else.... Amphenol RCA jacks, pretty cheap for the quality, easy to solder up, and built to take a nuclear blast. I think I used Dayton banana jacks, also pretty cheap and nice to both install and solder. I could have used low-profile ones with the chassis space I had, and in retrospect I would have preferred something that didn't stick out as far. (3/4"? Not really bad.) The plastic bushings to keep the signal away from the chassis are sturdy enough that they won't deform or break, but they require a very close drill bit size. Jumped the fuse on the board, and wired a panel fuse directly off the IEC before the switch. The chassis is Stainless scrap from around the yard, I had the box fabbed at a local place and did all the drill work myself, then polished it to a high shine, but kept the deep dings and scratches to give it some class.

This is my second build with the S-5 L16s, and I am pretty impressed with them, though I expect I'll be doing point-to-point from here on out. Again, this was a gift for a lady, and she is pretty happy with it. Paired with a set of KLF 20's, there is certainly more volume than she will ever use, short of DJ'ing a block party. Probably more speaker than amplifier, but maybe someday I can go back and swap it out with a pair of 300b SET monoblocks.....

Thought you all would enjoy the photos; they are my meager thanks for your help and contributing to the thread, I learn so much here, and it keeps me excited for the next project. And the next one. (And the next one.) Love this place!

Cheers!
-Aaron

Tube Amp 6.jpg

Tube Amp 8.jpg

Tube Amp 3.jpg
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Old 30th October 2015, 09:21 AM   #49
emretelci is offline emretelci
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Hey there,

I am also upgrading my S5 16LS kit's transformers with Edcors but have seen that it is very expensive (shipping) if you live in europe. Instead, I have decided to make the transformers here. There are good places where they make toroidal transformers also...

I want to ask the guys to build the replica of Edcor, but I don't know which information I should give them. Here are the two transformers that would be ideal for the upgrade...

for the output:
https://www.edcorusa.com/cxpp25-8-5k

for the power:
https://edcorusa.com/xpwr227

I'll be glad if someone tell me what information to pass the transformer maker guys here. Thanks...
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Old 15th July 2018, 12:53 PM   #50
jhedlind22 is offline jhedlind22
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I just read this whole thread. I've built a few of these amps. I was wondering about the following things.

I see a lot of mention of using power transformers of the 180v variety. The first one I built I used an Edcor XPWR 050 transformer with 250v secondary. The amp worked just fine. The 6005 has a design center of 250 volts so why would you choose to run such a low voltage?

I have another one of these amplifiers I built with the Edcor XPWR 021 transformer. This has a 290 volt secondary. I'll admit with this one it was built in a location where the AC input commonly ran between 105-109 volts. At that location the amplifier ran around 275 volts. This amplifier also operated fine. I've been tinkering with this one here in Korea (where there is no real earth ground) and it runs at 330 volts. The plate to cathode voltage is 353. This is too high because the plates are at 80% dissipation now, but it's hard to work with U.S power devices when you are on 220/60hz in Korea on a step-down transformer.

Another difference I've noticed is that when I've replaced the output trans formers it has always been with the Edcor 10K output transformers. The first one mentioned above has:

GXPP15-10K with 8 ohm secondary windings.

The second one, the monster voltage one has
CXPP30-10K with 4,8,16 ohm secondary windings.

I'll admit, I've always had them hooked up to speakers that were dubiously rated at 8ohms, but never anything as low as 4ohms.

My questions are:

What is the effect of the higher impedance transformers on the output of these amplifiers?

I've seen that in a lot of kit designs where the voltage is abnormally low. I'm looking at a SET amp right now that has a 6550 running at 290v. Why is everyone choosing to run such a low voltage through these tubes?
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