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 Post subject: Replacement Audio Output Transformers
PostPosted: Jun Tue 21, 2016 9:30 pm 
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Joined: Nov Wed 12, 2014 9:35 pm
Posts: 1046
Location: Ann Arbor, Michigan 48108
I needed an audio output transformer for a 30s radio I am working on so I took my last donor out of my parts crib. I hate to have none on hand, so I ordered three of these. Just came today. They are really nice! And less than $4 a piece!

http://www.parts-express.com/70v-10w-sp ... r--300-040

Where have they been hiding all my life?

Mark K8KZ


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 Post subject: Re: Replacement Audio Output Transformers
PostPosted: Jun Tue 21, 2016 9:41 pm 
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Location: Maryland 20709, USA
Hi ark,

Those are line-to-voice coil transformers designed for use on a 70-volt (or 25-volt) distribution line.

They're not meant to connect directly in a tube plate circuit.
The insulation on the primary might not even be suitable for the expected plate voltage.

- Leigh

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 Post subject: Re: Replacement Audio Output Transformers
PostPosted: Jun Wed 22, 2016 12:18 am 
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Location: Ann Arbor, Michigan 48108
You don't say?

As Rozqnna Rozannadana would say....never mind. :lol:

Mark K8KZ


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 Post subject: Re: Replacement Audio Output Transformers
PostPosted: Jun Wed 22, 2016 12:25 am 
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Joined: Nov Wed 12, 2014 9:35 pm
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Location: Ann Arbor, Michigan 48108
Who carries those universal audio output transformers any more? You know something 20 bucks or less. I wanted to order a couple to keep on hand.

I thought AES had them, but I can't seem to bring them up.

Thanks,

Mark K8KZ


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 Post subject: Re: Replacement Audio Output Transformers
PostPosted: Jun Wed 22, 2016 12:29 am 
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Location: Ann Arbor, Michigan 48108
I think this is what I want.

https://www.tubesandmore.com/products/P-T291

Do you ever feel like you're talking to yourself? :lol:

Thanks for the advice Leigh.

Mark K8KZ

EDIT: Oh man, just realized that's a push pull transformer. Not what I want. I'll keep looking.


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 Post subject: Re: Replacement Audio Output Transformers
PostPosted: Jun Wed 22, 2016 2:02 am 
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The best source of modern transformers for tube work that I know of is Hammond Manufacturing in Canada.
http://www.hammondmfg.com

Their products are carried by all major US distributors.

- Leigh

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Click "Grebe Stuff" for Synchrophase info


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 Post subject: Re: Replacement Audio Output Transformers
PostPosted: Jun Wed 22, 2016 4:25 am 
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Location: Phoenix, AZ
This site makes excellent transformers http://www.edcorusa.com/class-x

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 Post subject: Re: Replacement Audio Output Transformers
PostPosted: Jun Thu 23, 2016 7:43 pm 
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Joined: Jun Mon 15, 2015 9:05 pm
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Location: Kalispell, Montana
+1 Leigh

I was going to suggest Hammond myself, but you got there first.

Mark, those transformers you got...not a good idea to use them for the reasons Leigh pointed out. AES does have audio output transformers for tube equipment, but I generally go to Mouser as they carry a larger variety of Hammond products and generally their prices are a little better than AES.

Good luck with your project

Tony
KC7ZWH


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 Post subject: Re: Replacement Audio Output Transformers
PostPosted: Jun Fri 24, 2016 1:08 am 
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Location: Ann Arbor, Michigan 48108
No I get it Tony. I'm not going to use them as audio output transformers.

I paid less than 4 bucks a piece, and it would probably cost me 10 bucks to return them. I'll hang onto them or toss them. Not sure.

Thanks!

Mark K8KZ


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 Post subject: Re: Replacement Audio Output Transformers
PostPosted: Jun Fri 24, 2016 5:41 am 
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Joined: Nov Sat 26, 2011 4:09 am
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Location: Texas. USA
Technically 'line transformers' aren't gapped and so should be unsuitable for single ended operation but there are reports of them being used successfully, or should I say 'acceptable enough', as an AA5 OPT. Some folks say they can be used if you're 'in a pinch'.

Since you have them anyway you might as well tack one in and see how they do, or don't do.


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