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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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In Reply to: RE: UTC output transformers LS-63 posted by mqracing on April 16, 2015 at 14:49:08:
I think you missed VS's point.He was running 31.25Hz and 3125Hz at the same time and then filtering out the 31.25Hz at the output to show the IMD at 3125Hz.
If you filter out the 31.25Hz before the OPT then the IMD never happens.
"How does the low frequency load line affect the high frequencies?
As the load line varies, the tube characteristics (gain) will vary. This variation causes intermodulation distortion (IMD). To keep this example reasonable, the grid drive was set to be +/ - 25V at 31.25 Hz and +/ - 25 V at 3125 Hz. This results in a +/ - 50 V waveform at the grid of the 2A3 which is the same as what we had at just 31.25 Hz.
To see the effects of the variation in tube gain I put a buffered filter on the load to strip out the 31.25 Hz.
With 27 H, the 3125 Hz waveform is modulated by the 31.25 Hz signal. The 3125 Hz signal varies from 246.6 V peak to 225.9 V peak or 20.7 V peak to peak modulation"
BTW I use a simple 6db per octave high pass filter at 130Hz at the input of my SET amps. The idea is to keep the tube from ever traversing the nasty LF load line.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 04/16/15
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Follow Ups
- RE: UTC output transformers LS-63 - Tre' 15:49:29 04/16/15 (1)
- RE: UTC output transformers LS-63 - hennfarm 13:20:07 04/17/15 (0)
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