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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: Eli, if your integrated uses... posted by gkargreen on December 12, 2014 at 10:34:10:
Sorry, I missed this post until now.
IMO, 2 obvious defects of "Cheap Charlie" DC heaters are the possible modulation of phono stage heater current by the power O/P signal and the use of a single bias network for all 4 O/P tubes.
The solution to the problems is a separate, true, RC bias network in each channel's O/P stage and a regulated 12 VDC phono section heater supply.
A good 12 VDC heater supply for 2X 12AX7s can be made from an AnTek AN-0112 toroidal transformer, a MBR20100CT common cathode twin Schottky diode, a large valued 25 WVDC 'lytic, and a 7812 3 terminal regulator IC. Wire the trafo's secondaries in series, FWCT rectify, and cap. filter. Refinements include a 1 muF. Panasonic ECQ-V cap. physically adjacent to/electrically across the regulator IC I/P and a 15 muF. 'lytic physically adjacent to/electrically across the regulator IC O/P. Don't forget a clip on heatsink for the regulator IC. OTOH, the (sic) 10 A. diodes in a MBR20100CT will be loafing.
Eli D.
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- RE: Eli, if your integrated uses... - Eli Duttman 13:56:04 12/12/14 (0)
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