Hi Sumotan,
Single transformer:
1) Avoid capacitance coupling between main coil for PA and 9V coil for drivers to reduce undesired feedback.
Mr K minimised it by narrowing the 9V coil footprint to 5mm width. This is the reason why he emphasised on wire diameter by choosing the gauge 0.3mm just barely enough for 200mA (your thin wire)
2) Avoid magnetic flux crosstalk between main coil and 9V coil for same reason as above, by shielding the 9V coil.
3) Equalise the shield terminals (the entire shield as 1 turn coil) to ground with dual 10R resistor , fixed 33pF and variable 10pF for balancing the 50Hz residual.
Dual transformer:
Less stringent then, due to power supply isolation between PA and drivers.
Still needs shielding to avoid crosstalk between channels.
Drawback for dual transformer is the turn/volt ratio is higher for low VA transformer, mine does need 150 turns to provide 15Vac.
AC ripple is a concern for the Bi-Circleton as all floating power supply does need a different filtering technique, not a common RC or LC approach.
Mr K in his last version, used An 7809 regulator. The original version that I duplicated had -60dB ac residual.
SMPS is fine but can not provide an instantaneous energy for high dynamic music.
The Bi-Circleton’s PS has a dual coils reversal choke, this arrangement neutralises magnetic filed of DC current flows in opposite direction, a gapped core is unnecessary.
Hope my (self taught electronics + newbie in audio) interpretation will satisfy your question, no guarantee for any correctness.
Cheers
Final
Nearly two months since I started the rat nest.
At my final stage the Bi-Circleton has low noise floor, -85dB at 50Hz! A great achievement, I think.
The unknown reason of 20dB floor noise risen had been found, the SD116 with low Beta was unable to fathom the bottom of my soundcard noise floor.
Thought about using high hfe transistors, fortunately found 4 matched mosfets in the junk box.
The mosfet cap multiplier is doing well indeed, given a -120dB floor, unthinkable when I started this project by using batteries to avoid the floating PS noise.
Pity that I don’t own any hollow state amp for a fair comparison, then will start a new project with real triodes as first wheel driver and SITs as PA second wheel.
Stay tuned and my gratitude to Mr K And Sumotan (the only companion in this thread)
Cheers
Nearly two months since I started the rat nest.
At my final stage the Bi-Circleton has low noise floor, -85dB at 50Hz! A great achievement, I think.
The unknown reason of 20dB floor noise risen had been found, the SD116 with low Beta was unable to fathom the bottom of my soundcard noise floor.
Thought about using high hfe transistors, fortunately found 4 matched mosfets in the junk box.
The mosfet cap multiplier is doing well indeed, given a -120dB floor, unthinkable when I started this project by using batteries to avoid the floating PS noise.
Pity that I don’t own any hollow state amp for a fair comparison, then will start a new project with real triodes as first wheel driver and SITs as PA second wheel.
Stay tuned and my gratitude to Mr K And Sumotan (the only companion in this thread)
Cheers
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