A few years ago, I have proposed a high-current, ultra-low dropout regulator for a member (I adapted one of my earlier designs for him), and he was very satisfied. I don't remember the voltage, but it was in the region of 6V, and it was in the "Tubes" section, IIRC.
I was not the thread starter, which will make it difficult to find, due to the new search function of this forum, but with enough patience, it should be possible.
Note that even an ultra-low dropout reg combined with this synchronous rectifier will not manage a steady 6.5V: you can see on the sim that the waveform sometimes goes below 6V. It depends on the actual value of your AC input
I was not the thread starter, which will make it difficult to find, due to the new search function of this forum, but with enough patience, it should be possible.
Note that even an ultra-low dropout reg combined with this synchronous rectifier will not manage a steady 6.5V: you can see on the sim that the waveform sometimes goes below 6V. It depends on the actual value of your AC input
Using Google, I managed to retrieve the regulator in question:
https://www.diyaudio.com/community/...for-high-current-consumer.329949/post-5603233
And here, it has been put to test:
https://www.diyaudio.com/community/...l-single-ended-amplifiers.315889/post-5619209
Adapting the voltage would be extremely simple, and the good properties would be retained
https://www.diyaudio.com/community/...for-high-current-consumer.329949/post-5603233
And here, it has been put to test:
https://www.diyaudio.com/community/...l-single-ended-amplifiers.315889/post-5619209
Adapting the voltage would be extremely simple, and the good properties would be retained
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I used a 5Vac supply to heat a tube. It turned out that I was not fully loading the winding and Hammond primaries are not always calculated on the actual wall socket voltage so I had enough to light the tube just using AC with no worries about rectifiers and noisy pulses.
If I remember correctly, it’s all in here: https://www.diyaudio.com/community/threads/yukon-gold-a-spud-amp.280167/
If I remember correctly, it’s all in here: https://www.diyaudio.com/community/threads/yukon-gold-a-spud-amp.280167/
Certainly a lot can depend on the transformer, and on the local mains (both the rms voltage and 'flat-top' distortion). With a full bridge of 1N5819, I powered a single 6.3V 300mA heater at 6.2Vdc with 0.46Vpp ripple using 4,700uF filter from a 5V 3A rated secondary. That increased to 6.3Vdc with 0.22Vpp ripple using 2x 4,700uF filtering.
Note that the dc voltage doesn't have to get to 6.3V, as even -5% at 6.0V would be well within tolerance. Also, the benefit to hum is still substantial even with the example 0.46Vpp ripple, as that is circa 0.2Vrms (or -30dB) compared to 6.3Vrms from normal ac heater powering, so quite a reduction in the source of any hum. There comes a level where reducing 6.3Vrms will suppress any hum transfer into the audio signal to below the noise floor.
Note that the dc voltage doesn't have to get to 6.3V, as even -5% at 6.0V would be well within tolerance. Also, the benefit to hum is still substantial even with the example 0.46Vpp ripple, as that is circa 0.2Vrms (or -30dB) compared to 6.3Vrms from normal ac heater powering, so quite a reduction in the source of any hum. There comes a level where reducing 6.3Vrms will suppress any hum transfer into the audio signal to below the noise floor.
