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Old 6th April 2012, 11:10 PM   #1
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Default Transformer info needed

Hi all, I wasn't sure if this post should be in the Parts forum but, since it is related to one used in Fender amps, I thought it could be more relevant here.
I am seeking data on the Fender NSC041318T output transformer.
I know it is a 6.6K to 8 Ohm capable of 25 Watts but lack connection information, frequency range and type of tubes suitable for use with it.

I just need to know if it's what I can use before outlaying money for it.
Even if someone can post a schematic of an amp that uses it, I could possibly glean what I need from that.

Thanks
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Old 6th April 2012, 11:55 PM   #2
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Looks like it crosses to Hammond 1750H. This is the pdf: http://www.hammondmfg.com/pdf/EDB1750H.pdf
See if the wires correspond.
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Old 7th April 2012, 12:10 AM   #3
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Thanks Loudthud
I can't access that document from here ATM for some unknown reason.
I will keep trying though.
Perhaps some more information might help.
I want to build a modest powered PP amp for domestic music listening.
I would like to use 6L6s and I can get the Tx at a good price.
From the research I have done, these transformers were used in the Fender Deluxe series amps which used 6V6s but looking at the characteristics of both tubes, the 6L6 would appear to be a better match for load resistance.
I have been out of the tube scene for quite a few years now but want to get my feet wet again.
Cheers

Last edited by Bibliophile; 7th April 2012 at 12:37 AM. Reason: additional information
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Old 7th April 2012, 09:39 AM   #4
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Hi Bibliophile (good avatar, btw ;-)),

just keep in mind that output transformers, as used in guitar amplifiers, generally do not suit well for music reproduction - unless we consider a Partridge transformer form an old HIWATT. A Hammond transformer, e.g., might be a better choice for you.

Best regards!
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Old 7th April 2012, 10:49 PM   #5
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Thanks Kay Pirinha
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I appreciate that results would not be ideal but wondered just how bad they might be. I am trying to do this on a tight budget. I have seen elsewhere that 70/100 Volt line matching transformers could be used for OT in some applications.
Their specs look reasonably good but finding the right ratio could be difficult. Do you have any thoughts on that?
Thanks
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Old 8th April 2012, 12:03 AM   #6
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Quote:
Originally Posted by Bibliophile View Post
Thanks Kay Pirinha
(Avatar?)
I appreciate that results would not be ideal but wondered just how bad they might be. I am trying to do this on a tight budget. I have seen elsewhere that 70/100 Volt line matching transformers could be used for OT in some applications.
Their specs look reasonably good but finding the right ratio could be difficult. Do you have any thoughts on that?
Thanks
Thought I wrote it down but I guess I did not. I used a 70V transformer on a small guitar amp I built, it had respectable low end and I think the high went to 15kHz with NFB and a bit less without. This was at 5W for a 10W transformer.

I picked up the Hammond 1750H for use on a 20W 6V6 amp but would have preferred an 8k primary if I could get it. Not sure if being on a tight budget and 6L6's should go in the same sentence, the amount you would save on the difference between 6L6's and 6V6's would pay for the difference in the transformer costs.
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Old 8th April 2012, 12:18 AM   #7
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Thanks Printer2
The tube price difference is not that great if I go for non-matched pairs.
It's only $3 each from my chosen vendor. Both are Electro-Harmonix brand.
I would use variable bias for each tube to try and get them close.
I don't expect "great" but "good" would be nice.

Last edited by Bibliophile; 8th April 2012 at 12:24 AM. Reason: Additional information
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Old 8th April 2012, 01:12 AM   #8
Simon B is offline Simon B  United Kingdom
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Quote:
Originally Posted by Bibliophile View Post
Thanks Printer2
The tube price difference is not that great if I go for non-matched pairs.
It's only $3 each from my chosen vendor. Both are Electro-Harmonix brand.
I would use variable bias for each tube to try and get them close.
I don't expect "great" but "good" would be nice.

Matching isn't just about the bias point, it's also about gain. If you want to be able to use unmatched pairs, you need to be able to adjust the relative strengths of the signals coming off the two halves of your phase splitter.

Otherwise you end up with much even harmonic distortion, and net dc current flow in the output transformer primary, not a good thing.
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Old 8th April 2012, 01:41 AM   #9
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Thanks Simon B
Your point about the different gains is well taken.
Adjusting the drive votage to each tube is doable.
Can you see any other major drawbacks in the idea.
I'm trying to get as many pros and cons as I can to way up if this project is worth persuing.
Cheers
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Old 8th April 2012, 08:09 AM   #10
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Hi Bibliophile,

please have a look on here. This guy describes a push-pull amplifier, running 6GM5's in ultra-linear mode at line matching transformers which are available in your country from stock and for little money. If shipping fees from Australia weren't that high, especially for rather heavy goods, such as transformers, I'd have given them a try yet.

Ok, the UL tappings he uses are not really symmetric with respect to the center tapping, but if we do the math, we discover surprisingly low differences. And: 6CM5's, which still are cheap, do feel much more comfortable when running in pentode mode at a screen voltage of 150 volts only.

Best regards!
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