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Old 1st October 2009, 04:26 PM   #31
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A few comments about tranformers: I have a One electron BFT-1B and it certainly is a BFT, it's huge.....and not too sexy either, with it's copper electrostatic shield exposed, complete with varnish drips. Mine is actually an ebay special that has slightly skewed laminations, like it got dropped on a corner at the factory before the varnish dried. It looks like it was built that way. Works fine, looks rough.

I have a pair of Trancendar 5K's with UL taps slated for my Simple SE build and a pair of James 6123s slated for my tubelab SE build. When I ordered the boards from George, I decided that I would build the SSE as a middle-of-the-road build that would be fun to tube roll and experiment with and go a little pricier on the TSE build, hence the transformer choices above. The James output transformers are very nice looking and have a good reputation, they are also available in champagne or black finish. The Trancendars also have a good reputation but look fairly conventional. Both of these transformers are available on ebay for reasonable $$.

Trancendar Gery on ebay has recently offered the 5K SE transformers with UL taps for $5 more than the ones without; this allows UL operation in the SSE.

Like JPeitzman, I am also working to complete Poinz' EL34 music machine so my Tubelab stuff remains half finished.

Last edited by boywonder; 1st October 2009 at 04:28 PM.
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Old 1st October 2009, 04:46 PM   #32
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I am also working to complete Poinz' EL34 music machine
I am doing the 6V6 machine, but maybe one day an EL34 too...same animal, different outputs. I am assuming 6GK5's in front?
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Old 1st October 2009, 07:59 PM   #33
djn04 is offline djn04  United States
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Ok. So I think I'm going with all James transformers at this point.

They've got a 360V-280V-0-70V-280V-360V 0.3A Power Trans, 90mA 2.5/3.5/5k 20W 20Hz~60KHz-2dB OPT's, and a 20 H 150mA 143Ω choke.

Is 143Ω ok? I think George calls for 150 in the choke.

This seems like a good middle point as far as price performance. It's higher than Hammond/Edcor but much less than Tamura/Hashimoto and a good bit cheaper than Electra-Print.

Now onto resistors, caps, tubes . . . ?
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Old 1st October 2009, 08:17 PM   #34
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Quote:
Originally Posted by djn04 View Post
Is 143Ω ok? I think George calls for 150 in the choke.
I used a Hammond P-T159Q choke for my Simple SE. It's rated 7H, 150 mA, 100 ohms. I never had any problems with it - it just works. In my opinion, I'd rather have less DC resistance in my choke rather than more. If you're going to be concerned about anything, think about the total current consumption. Each KT88 is going to eat about 75 mA, and each half of the 12AT7 will take another 8 mA or so. That puts your total over the rated current for your choke, but I'm guessing it'll probably be OK.
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Old 1st October 2009, 08:28 PM   #35
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I was just going to say something too about the current rating. It may be OK, but like I said earlier, if it where me I wouldn't push it. I would look to something like their 10H @ 250mA choke, gives you tons of head room. Best, it will run hot; worst it will vibrate, run really really hot, and eventually maybe fail. I wouldn't worry to much about sizing that choke just right so that you hit about the DCR of what George is using. In the end it shouldn't make a big difference one way or the other if it isn't a DCR of 150R.

Cheers
James
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Old 1st October 2009, 08:40 PM   #36
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I thought about the current rating on my Hammond choke. They didn't describe the 150mA rating as "maximum current" or anything like that. I believe the number is simply where the choke will deliver its specified inductance. From their web page, they state "Units will exhibit less inductance at slightly higher currents or more at lower currents."

I don't know what constitutes "slightly" higher currents. I know the Triad C-14X choke has the same weight, physical dimensions, and nearly identical DCR as compared to the Hammond 159P. The C-14X is rated 6H @ 200 mA. The 159P is rated 10H @ 125 mA. Does this mean anything? Probably not, but deep down inside I'd like to believe the C-14X and the 159P are actually the same unit, just rated under different conditions. That suggests to me that a choke rated for a particular current draw can be operated at a slightly higher load, but you won't get as much inductance. That's pretty much what Hammond said.

Contact the manufacturer, and ask them. Or just buy a choke rated for 200 mA or more and don't worry about it.

If it's worth anything, I have run KT88 in my Simple SE. I've heard absolutely no buzzing from my 159Q choke.

Last edited by Ty_Bower; 1st October 2009 at 08:46 PM.
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Old 1st October 2009, 08:48 PM   #37
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Default Potted transfromers from Eltra Print

In post 30 Tubelab stated that Jack at Electra Print doesn't do potted transformers. Jack will do potted transformers but you have to ask. Off course the cost will be a bit higher.
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Old 1st October 2009, 08:52 PM   #38
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I wouldn't worry to much about sizing that choke just right so that you hit about the DCR of what George is using.
George is using whatever he finds in the junkbox. My industrial amp uses a Triad C-24X because it is small and I wanted to hide its ugliness under the deck it is 50 ohms DCR. I have used surplus chokes from 70 to 200 ohms. I would use just about any choke from 50 to 200 ohms, 1 to 10 (or more but I haven't tried it) Henries, at a minimum of 150 mA. I would give up a little inductance for a higher current rating, but for a reason not previously stated. Since DC flows through the choke, it can saturate if operated near the spec limit, and when it does its inductance drops to near zero. The inductance does vary with applied current, and drops as the current increases.
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Old 1st October 2009, 09:25 PM   #39
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Quote:
Originally Posted by JPeitzman View Post
I am doing the 6V6 machine, but maybe one day an EL34 too...same animal, different outputs. I am assuming 6GK5's in front?
Yup. I have breadborded it with hashimoto HW-60-5's and it sounded very nice except for a hummmm problem, which I attribute to the breadboard (I hope). I also have a pr of the budget 8K PP hashimotos to hopefully use in the 6V6 machine when I find some time. Both pairs of hashimoto's were purchased used from another member here (thanks jazzbo!)


djn04: Additional resistance in the choke will tend to lower your final B+ voltage, which may or may not be a bad thing. Download and model the simple SE PS with PSUDII (power supply designer II) from www.duncanamps.com if you haven't done so already. It's free, easy to use, and lots of folks here will answer questions. You will see quickly how your PS transformer, choke and caps will perform.

Edit: Here is the link right to the PSUDII download page: http://www.duncanamps.com/psud2/index.html

Since you will have a CLC PS design, you can vary the value of the first cap (within a range) to dial in your B+ voltage, so if the choke R is high, you may be able to compensate by adjusting the first cap. Also, your B+ voltage needs can vary somewhat depending on what output tubes you want to run and at what current.

Look at the computer sims on the bottom of this page from Tubelab:

http://www.tubelab.com/AssemblyManua...ormers_SSE.htm

The tables have B+ voltage, OT load, cathode R, etc and the corresponding power out and distortion.

One question: What is the sensitivity of your Zaph Audio ZRTs?

Last edited by boywonder; 1st October 2009 at 09:31 PM.
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Old 1st October 2009, 10:01 PM   #40
djn04 is offline djn04  United States
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Originally Posted by boywonder View Post

One question: What is the sensitivity of your Zaph Audio ZRTs?
Somewhere around 86-87. Also impedance stays above 6.5 ohms, averages 8 ohms through most of it's range and does not exceed 14 ohms above the bass tuning peaks.
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