Hi!
I would like to build an amp of my own (SE stereo), but I have some questions... Let say that I have 12sn7gt, 6l6, a power trans 110V/12V only and a output trans 2k5/8ohms. Don't want to know if it will be crap or something like this, but I only want some explanations...
1- Can I connect 2x 6L6 in series (because I have a 12V source for heater)?
2- Can I build a voltage doubler (with caps and diodes) with the power source 110V to make the high voltage?
3- How can I determine the Load Resistance of the output tube in a schematic (or if I create a circuit), to choose the right output trans (here in SE, I think my output trans will be OK)? Because with the same tube, the load is never the same If I refer to my Tube Manual...
Thank you!
Jean-Francois🙂
I would like to build an amp of my own (SE stereo), but I have some questions... Let say that I have 12sn7gt, 6l6, a power trans 110V/12V only and a output trans 2k5/8ohms. Don't want to know if it will be crap or something like this, but I only want some explanations...
1- Can I connect 2x 6L6 in series (because I have a 12V source for heater)?
2- Can I build a voltage doubler (with caps and diodes) with the power source 110V to make the high voltage?
3- How can I determine the Load Resistance of the output tube in a schematic (or if I create a circuit), to choose the right output trans (here in SE, I think my output trans will be OK)? Because with the same tube, the load is never the same If I refer to my Tube Manual...
Thank you!
Jean-Francois🙂
1. Yes
2. Yes but it is incredibly unsafe, in fact your lines (input and output) will be floating around -160VDC with several tens of amperes behind it. You need a power transformer, and a 272BX (from Hammond) will supply ample power for stereo 6L6 SE. Brownie points to the student who figures out how to wire the 12V heaters on this transformer! 😀
3. 6L6 is typically 2.5 to 5k. I have such an SE amp which makes a good 5W at 5k.
Tim
2. Yes but it is incredibly unsafe, in fact your lines (input and output) will be floating around -160VDC with several tens of amperes behind it. You need a power transformer, and a 272BX (from Hammond) will supply ample power for stereo 6L6 SE. Brownie points to the student who figures out how to wire the 12V heaters on this transformer! 😀
3. 6L6 is typically 2.5 to 5k. I have such an SE amp which makes a good 5W at 5k.
Tim
Cheap Plate voltage transformer
Here is a low cost plate voltage transformer for DIY projects, $20:
http://www.meci.com/
(click on transformers, then click on "standard")
Its (usually) the first one that comes up, P/N 600-0427 made by Hammond.
Actually is a 300 Watt unit for normal temperature rise (the 500 W rating is for smoking hot temp. rise), weighs 10 Lbs, 120V to dual 240V windings. No electrostatic shield, so use a line filter with it. The fuse holder on top is removable. Make sure to enclose it in the chassis or a box, for safety, since it has exposed terminals.
Here is a low cost plate voltage transformer for DIY projects, $20:
http://www.meci.com/
(click on transformers, then click on "standard")
Its (usually) the first one that comes up, P/N 600-0427 made by Hammond.
Actually is a 300 Watt unit for normal temperature rise (the 500 W rating is for smoking hot temp. rise), weighs 10 Lbs, 120V to dual 240V windings. No electrostatic shield, so use a line filter with it. The fuse holder on top is removable. Make sure to enclose it in the chassis or a box, for safety, since it has exposed terminals.
>>Brownie points to the student who figures out how to wire the 12V heaters on this transformer!<<
Connect the 2 6L6 heaters in series; their current draw is 0.9 A. at "12" V. The draw of the 12SN7 is 0.3 A. at "12" V. Total draw for the 3 tubes is 1.2 A. at "12" V. SS rectify the B+. Connect the 5 V. and 6.3 V. filament windings in the voltage enhancing series arrangement. Considering that the current draw is less than the filament windings are rated for, the actual working voltage should come out within the 12.6 VAC +/- 10% spec.
The same sort of "trickery" is involved when the 6.3 VAC heater of a 7Y4 rectifier is connected to the multi-Ampere 5 V. filament winding of a power trafo.
Connect the 2 6L6 heaters in series; their current draw is 0.9 A. at "12" V. The draw of the 12SN7 is 0.3 A. at "12" V. Total draw for the 3 tubes is 1.2 A. at "12" V. SS rectify the B+. Connect the 5 V. and 6.3 V. filament windings in the voltage enhancing series arrangement. Considering that the current draw is less than the filament windings are rated for, the actual working voltage should come out within the 12.6 VAC +/- 10% spec.
The same sort of "trickery" is involved when the 6.3 VAC heater of a 7Y4 rectifier is connected to the multi-Ampere 5 V. filament winding of a power trafo.
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