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In Reply to: RE: Losses in Output Transformers posted by Triode_Kingdom on September 15, 2021 at 17:01:27
Vintage or new production tubes?
Tre'
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The EL34 amp made enough power to meet my requirements, so I didn't go to much trouble regarding troubleshooting. The output tubes were new EH.
The 6L6 amp is on the bench now. I brought it up with brand new 6P3S-Es in both channels, later subbed one channel with a NOS pair of Sylvania 5881. The 5881 performed slightly better, maybe squeaked out two more watts or so. Plate and screen voltages were measured at full output, just below clipping, and they're close to the chart. I also subbed screen voltage from 300V to 400V with a regulated bench supply. No improvement. I don't know the DCR of the anode windings, but the drop at idle isn't large, I think it was about 5 volts. And just to cover all the bases, the driver has much more gain and swing than is needed to drive the 6L6s to full output.
Again, I really think there's a significant loss in the OPTs, and I came to the same conclusion regarding the EL34 amp. Do either of you know how companies like RCA arrive at those output numbers? Did they actually build an amplifier with output transformers? Or did they load the plates in a different way and make voltage/current measurements?
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Buy Chinese. Bury freedom.
On loss in output transformers. Let's take a look at Monolith MagneticsThe S9 (Rp=3300 Ohm) has 0.27dB loss and thus an efficiency of 94% (good)
The S11 (rp=5000 Ohms) has 0.50dB loss and an efficiency of 89% (not special)
That is copper loss. The core also has losses and that depends on signal level, frequency, core quality and even winding technique.
Those losses can be measured but are almost never published.The S11 has in my opinion-if we are looking for a high quality audio transformer-a bit high copper losses. Both transformers suffer from low inductance. This is good for lower copper losses, but less good for low frequency distortion.
I have noticed that MM's datasheet is not very good, in my opinion they are not quite right. I infer this from the specified inductance and the low frequency response they specify. Something is not right there. There are definitely errors in there. (small)
Doesn't take away from the fact that they make the effort to publish data and while I think Tango is lord and master for audio transformers and datasheets they do a pretty good job. Lundahl doesn't do a good job and a well-known foodoo brand like Tribute is just bad.
Edits: 09/16/21 09/16/21
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