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What tubes is this Electraprint? SE OPT designed for?

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Posted on October 15, 2014 at 21:50:23

DAK
Audiophile

Posts: 2712
Location: PACIFIC
Joined: August 8, 2010

I have this pair of supposed Electraprint Single Ended OPT. The primary I just tested to come up with about 1.2K impedance, red and black wires. and there are 3 wires, green purple blue in the secondary which measure, green to blue .7 ohms, and green to purple .8 ohm. If I use purple as ground I measure green at .4 ohms, and blue at .7 ohms. I measured the inductance on the primary at 5 Henries. The dimensions are sizable at lxwxh being 3 3/4" x 4 3/4" x 4 1/2".
If anyone knows what tubes they were designed for I would be very pleased to know. TIA, Dak

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Just email and ask Electroprint...

ABliss

07:05:57 10/16/14

RE: What tubes is this Electraprint? SE OPT designed for?

Chip647

05:11:19 10/16/14

RE: What tubes is this Electraprint? SE OPT designed for?

DAK

09:09:46 10/16/14

...

Show full thread outline!

Just email and ask Electroprint...

ABliss

07:05:57 10/16/14

RE: What tubes is this Electraprint? SE OPT designed for?

Chip647

05:11:19 10/16/14

RE: What tubes is this Electraprint? SE OPT designed for?

DAK

09:09:46 10/16/14

What if they're 8 and 16 ohms?

Tre'

10:42:01 10/16/14

DAK

11:02:52 10/16/14

Tre'

07:52:46 10/17/14

chrismercurio

22:50:04 10/16/14

RE: What tubes is this Electraprint? SE OPT designed for?, posted on October 16, 2014 at 05:11:19

Chip647
Audiophile

Posts: 2649
Location: The South
Joined: December 24, 2012

You need to calculate the impedance ratio. I would expect it to be 2500 ohms to 3000 ohms. In the old days he used to wind primarily the multi-tap outputs. These are probably more recent transformers.

Since he does not usually put any markings what-so-ever on the transformer, to know for sure you will have to calculate the ratio of input to output.

Determining Output Transformer Impedance

Just email and ask Electroprint..., posted on October 16, 2014 at 07:05:57
ABliss Audiophile Posts: 1482 Joined: March 16, 2001 Contributor Since: August 3, 2002	they are very helpful.

RE: What tubes is this Electraprint? SE OPT designed for?, posted on October 16, 2014 at 09:09:46
DAK Audiophile Posts: 2712 Location: PACIFIC Joined: August 8, 2010	Hi Chip, I used that method and measured about 12vac to 1v on the secondaries. Squaring that gives 144 x 8ohm is 1.2k reflected impedance. I am assuming that the taps are 4 and 8 ohm in the secondary. regards, Dak

What if they're 8 and 16 ohms? , posted on October 16, 2014 at 10:42:01

Tre'
Industry Professional

Posts: 17297
Location: So. Cal.
Joined: February 9, 2002

So now you have 2400 ohms (2500 ohms, close enough).

This would be what I would assume although the 5Hy is confusing. Should be more.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

?, posted on October 16, 2014 at 11:02:52
DAK Audiophile Posts: 2712 Location: PACIFIC Joined: August 8, 2010	Yeah, it could be 8 and 16. Is the actual DCR any indication? I wrote electra print and am expecting a response soon. Anyway, if the secondaries are 4 and 8 ohms what tubes would be suitable for a 1.2k impedance?

RE: ?, posted on October 16, 2014 at 22:50:04
chrismercurio Audiophile Posts: 155 Joined: August 4, 2008	Jack will know. In the meantime, I'd take a look at this: http://www.one-electron.com/Trans/UBT1_20.pdf That is a 1600 ohm output transformer and the data sheet gives you all kinds of tubes you can parallel to be in the ballpark. Single ended parallel.

RE: ?, posted on October 17, 2014 at 07:52:46
Tre' Industry Professional Posts: 17297 Location: So. Cal. Joined: February 9, 2002	parallel 2a3's would be happy with a 1.2k ohm load. Tre' Have Fun and Enjoy the Music "Still Working the Problem"

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