Timeline for Regulated multi-voltage PSU given a center-tapped transformer and a single regulator/zener
Current License: CC BY-SA 4.0
15 events
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| Oct 25, 2020 at 14:12 | comment | added | Nikolai Kim | All tubes, except one triode are AC heated. The first preamp stage is DC. This is/was an industrial design, and i guess the paradigm is solid. As for MCU, there is no need for a middle ground, MCU+peripherals can reference +/- just fine. It was only for the mentioned tube-heating symmetry reasons. Given that, i am just going to stick to the schematic updated above | |
| Oct 25, 2020 at 14:08 | comment | added | Nikolai Kim | Thank you mate, appreciate your effort. The thing is, pro-musicians/technicians are extremely picky about their equipment. It's like telling Michelangelo to change the brush. A single tiny extra switch in a vintage piece may (might) cause a war :-). | |
| Oct 25, 2020 at 11:37 | history | edited | fraxinus | CC BY-SA 4.0 |
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| Oct 25, 2020 at 11:31 | history | edited | fraxinus | CC BY-SA 4.0 |
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| Oct 25, 2020 at 11:28 | comment | added | fraxinus | added some more | |
| Oct 25, 2020 at 10:40 | comment | added | Nikolai Kim | @fraxinus Indirect cathode heating 12AX7, the mains does vary considerably, but yes, you are right, there is in fact no serious need for a regulation. Going to stick to a simple scheme. | |
| Oct 25, 2020 at 6:56 | comment | added | fraxinus | What kind of triode is it? Direct heating? Or your mains voltage varies more than 10% and you want the heating stable? | |
| Oct 25, 2020 at 0:40 | comment | added | Nikolai Kim | @fraxinus So, essentially DC heating for 1 triode (whether regulated or not) is a MUST. The center tap of the transformer secondary is preferably preserved (if twisted wires are patented, i wonder if this is patented too :-) ). | |
| Oct 25, 2020 at 0:33 | comment | added | Nikolai Kim | @fraxinus Thank you again for the detailed explanation, very helpful indeed and much appreciated. I think i am going to stick to a simple solution very similar to yours. Drop the regulator, remove the "virtual ground" by replacing the series of the filter caps by 1 and use 1 additional forward diode for an additional voltage drop. Just one question though. If i wanted to preserve the transformers center tap being GND, can i put the BDF rail on GND as well (assuming the cap connection is NOT grounded) ? I know i can leave this circuitry without GND, but that again doesnt appear very neat to me. | |
| Oct 24, 2020 at 22:20 | history | edited | fraxinus | CC BY-SA 4.0 |
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| Oct 24, 2020 at 22:14 | comment | added | fraxinus | @NikolaiKim don't worry. You can power the lamps from the transformer directly and use 7805 to get 5V. Almost here. I'll add some to the answer. | |
| Oct 24, 2020 at 20:30 | comment | added | Nikolai Kim | Yes, all true, didnt account for the voltage drop of the diode bridge either. Amateur :-( | |
| Oct 24, 2020 at 20:23 | comment | added | Marcus Müller | The thesis here is that this transformer is meant to directly drive your filament, no diodes required. | |
| Oct 24, 2020 at 20:20 | comment | added | Nikolai Kim | Ok, thank you for your insight. My understanding was that having ca. 8V between A and B (6.3 * 1.3 = 8, representing a "loaded" case) is plenty for 7806 to stabilize properly. Adding a 1N5817 schottky would give a "close enough" voltage of ca. 6.3-6.5V :-( | |
| Oct 24, 2020 at 20:12 | history | answered | fraxinus | CC BY-SA 4.0 |