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Output transformer for 845, GM70, 813 and FU-13 - cheap and good

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Here a my tests result with a 845 Valve Art at only 900V 90mA on 8ohm
 

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45

Member
2008-12-18 2:29 am
UK
It looks good at medium-low frequencies, although there is no info about distorstion at low frequency, for example. From the measurements and the other specs it appears to have significantly higher losses in treble region.
The great difference in primary and secondary DC resistances (the secondary resistance translated to the primary is about 325 ohms) makes me think that most of the useful winding space has been used to minimize the primary DC resistance.
As a starting point for me, the configuation for overall minimal losses is half space for the primary and half for the secondary because there is the possibilty to minimize the forgotten AC resistance of the windings which adds up to the DCR.
Basically here the high end response has been traded-off for more bass performance. It's a necessary compromise in affordable high power SE amps however this not necessarily is a bad thing for the final sonic performance.

45
 
Yes, with the 900V and 90mA at 11.4Vrms we are near to the limit of the output characteristics of 845, near to A2 class operation with higher distortion level.

In the future I will make other test at 1100V and 70mA
 

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I would like to promote this article and get feedback about it.

This transformer have an insteresting price and it sound like more expensive products.

Like for all my projects I don't get money for this promotion.

I receive only materials to test and review with a good price reduction.
 
After about one month from my payment I have received a pair of SE transformers for my GM-70 tube amplifier.

Double C core, 0.1mm laminated. I saw pictures from AudioDesign (0.35mm laminated), but my transformers are not 'bare'. I did not ask for special aesthetics, but they really surprised me. I do recommend Fiat SRL to everyone.

Just for the record, I do not have any type of benefit for recommending this company. Just another happy customer.

P.S. I think that picture can't describe how big and heavy they are :D

Greetings
 

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