Electra Print OPT selection for TSE 45?
I've settled on Electra Prints for a new TSE build that I only intend to use 45's in. The question is regarding the OPT max power level, which I haven't found good answers for (or questions asked) here. Is there any compelling reason to order anything larger than a 3 watt max power rating for my application? Here's what I intend to order, but before laying out the cash, I would appreciate any guidance (or confirmation):
5K, 50ma., 3w, 8 ohms, C for 45 tube
Since this will be a 45 only build, is a 40ma actually a better choice? Example:
5K, 40ma., 3w, 8 ohms, C for 45 tube (a bit cheaper too)
Electra Print site for reference: Electra-Print.com Single-Ended Output Transformers
Any guidance appreciated!
I've settled on Electra Prints for a new TSE build that I only intend to use 45's in. The question is regarding the OPT max power level, which I haven't found good answers for (or questions asked) here. Is there any compelling reason to order anything larger than a 3 watt max power rating for my application? Here's what I intend to order, but before laying out the cash, I would appreciate any guidance (or confirmation):
5K, 50ma., 3w, 8 ohms, C for 45 tube
Since this will be a 45 only build, is a 40ma actually a better choice? Example:
5K, 40ma., 3w, 8 ohms, C for 45 tube (a bit cheaper too)
Electra Print site for reference: Electra-Print.com Single-Ended Output Transformers
Any guidance appreciated!
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FWIW, I am planning to finally complete my TSE, and decided to go with 45's and most likely Electra print output iron and had the same question.
My application is headphones though, so I likely need less power.
I noticed on the electra print examples
5K, 50ma., 3w, 16 ohms, C for 45 tube $120.00 each
Don't think I need 50ma, 3w, but its not much more the 40ma, so maybe the safer route?
My application is headphones though, so I likely need less power.
I noticed on the electra print examples
5K, 50ma., 3w, 16 ohms, C for 45 tube $120.00 each
Don't think I need 50ma, 3w, but its not much more the 40ma, so maybe the safer route?
I send a question through the website, and Jack responded within 30 mins.
Have a couple follow up questions, but it looks good so far.
Hope I'm not hijacking this thread.
Randy
I traded emails with Jack over the last couple of days.
He said a 40ma tx would work if I was only biasing to 25-30 ma
But he also recommended biasing higher, if I had a "good" 45.
I ended up ordering a 50ma tx, to give me a little more flexibility down the road.
I figure I'll be using this iron for many years, even if I decide to change tubes or even build a different amp.
Randy
He said a 40ma tx would work if I was only biasing to 25-30 ma
But he also recommended biasing higher, if I had a "good" 45.
I ended up ordering a 50ma tx, to give me a little more flexibility down the road.
I figure I'll be using this iron for many years, even if I decide to change tubes or even build a different amp.
Randy
After some back and fourth with Jack, and explaining the application, I ended up with his standard $120 5K/50ma/8ohm OTs. No idea what the wattage rating is, which is still a point of confusion on my part.
Regardless, my TSE is now assembled and tonight was "checkout night". I'm pleased to report no issues after running it for an hour or so continuously after tweaking the pots and monitoring the voltages.
Running the Edcor XPWR131 with a 5U4 and I'm seeing 292v B+ and my 45's are biased at 28ma. This amp sounds amazing with zero hum, even with the rat's nest of open-air temporary wiring. Thanks to George for his excellent detailed step-by-step instructions and the wealth of knowledge given on this forum.
I can't wait to get it buttoned up and finished now!
Regardless, my TSE is now assembled and tonight was "checkout night". I'm pleased to report no issues after running it for an hour or so continuously after tweaking the pots and monitoring the voltages.
Running the Edcor XPWR131 with a 5U4 and I'm seeing 292v B+ and my 45's are biased at 28ma. This amp sounds amazing with zero hum, even with the rat's nest of open-air temporary wiring. Thanks to George for his excellent detailed step-by-step instructions and the wealth of knowledge given on this forum.
I can't wait to get it buttoned up and finished now!
kilokat,
FWIW, at some point, Jack told me
As for using a 40ma or 50ma trans for 25-30ma is perfectly fine for the transformer but you will have a higher distortion from the 45 tubes, and being not fully dissipated, only about 1 watt to use!!?
Run the 45 at 40ma, if it’s a good one it will give you near 2 watts or so.
Good 45’s are rare!!!
So I guess you could run a higher bias, depends on if you want to take a chance or not. I don't need the power so I'll likely stay under 30ma.
I ordered a low imd version, with secondaries for headphone impedances.
He said it would be good for around 2-3 watts, so I'd imagine yours is similar.
Waiting for mine, just ordered it last week.
Randy
FWIW, at some point, Jack told me
As for using a 40ma or 50ma trans for 25-30ma is perfectly fine for the transformer but you will have a higher distortion from the 45 tubes, and being not fully dissipated, only about 1 watt to use!!?
Run the 45 at 40ma, if it’s a good one it will give you near 2 watts or so.
Good 45’s are rare!!!
So I guess you could run a higher bias, depends on if you want to take a chance or not. I don't need the power so I'll likely stay under 30ma.
I ordered a low imd version, with secondaries for headphone impedances.
He said it would be good for around 2-3 watts, so I'd imagine yours is similar.
Waiting for mine, just ordered it last week.
Randy
My Lexan TSE uses Electra-Print OPT's that were specifically ordered for 45's over 12 years ago. He called them "10 Watt" transformers and they cost $100 each in 2007. I have stuffed 300B's into my amp and they will indeed pass at least 7 watts down to 30 Hz or so. 7 watts is all I get with 300B's on a 320 volt supply with a 5K OPT.
I run my 45's at around 27 to 30 mA, but they see an over spec 325 volts. They don't make any more power if I crank up the current, but the damping factor goes up a bit.
After accidentally blowing up a pair of 45's by leaving the filament jumpers set on 5 volts after playing with 300B's, I settled on a pair of NX483 tubes plucked from a discarded Sparton radio. The tubes had stickers from 1929 on them, making them now 90 years old. They are still going strong.
An NX483 is similar to a 45, but with a 5 volt filament. That way I can stick 300B's in the amp without worry. I have never seen another NX483, nor has most anyone else.
I run my 45's at around 27 to 30 mA, but they see an over spec 325 volts. They don't make any more power if I crank up the current, but the damping factor goes up a bit.
After accidentally blowing up a pair of 45's by leaving the filament jumpers set on 5 volts after playing with 300B's, I settled on a pair of NX483 tubes plucked from a discarded Sparton radio. The tubes had stickers from 1929 on them, making them now 90 years old. They are still going strong.
An NX483 is similar to a 45, but with a 5 volt filament. That way I can stick 300B's in the amp without worry. I have never seen another NX483, nor has most anyone else.
I am also looking into a headphone build for TSE 45.
Which transformer did you end up ordering and which headphones will be used with the amp? Thanks
I found the answer to this in the build thread, 46 and 300?
What were the considerations to choose those values?
I have low impedance cans (HE-500 and alpha dogs) and high impedance (hd800), so decided it would be nice to have a tranny with taps for either.
48 was about the middle of the he500 and alphas from what I remember.
In an email, Jack said this:
We checked out files on SE HP output designs. The one you describe is do-able within this reasonable spread of low to high output impedance, 40 to 300 ohms. The most efficient and widest BW, HP output, is a single output Z. this will work better as 50-300 ohms, if you chose. Provided your HP's have the correctly stated impedances.
Randy
Thanks. And did you end up putting any load or series resistors on the output? Or are the HP's connected directly to the secondary?
No load resistors, HPs directly on the secondary.
If you want to use a speaker output tx with a 4 or 8 ohm output, then you need resistors, I don't know of a reason to use resistors for my case.
Randy
I'm still very happy with my electraprints.
But if I was over there, I'd try contacting Lundahl to see what they have with a 5k primary. I'm pretty sure they have something, seems like their output trannies have lots of configuration options to support different tubes with same tranny, and they make a few different ones.
Someone smarter than me would have to answer your 6k questions.
But if I was over there, I'd try contacting Lundahl to see what they have with a 5k primary. I'm pretty sure they have something, seems like their output trannies have lots of configuration options to support different tubes with same tranny, and they make a few different ones.
Someone smarter than me would have to answer your 6k questions.
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