L-Adapter - Page 2

Salas · 15th April 2019, 03:38 PM

Quote:

Originally Posted by jackinnj

In a similar vein, you can bias a pair of MOSFETs the Blue LED will get Q2 into its linear region -- this is an adaptation of "Art of Electronics", Volume 3. Figure 9.110. You could use a resistor to bias the LED at the expense of PSRR. If the resistor values are successively doubled, you can get 8-bit resolution.

Good for HV

PKI · 15th April 2019, 05:04 PM

Can this be used if someone wants a regulated tube heater PSU?

Salas · 15th April 2019, 05:16 PM

Yes, tube heaters PSU is one of the uses I wanted to mention and I forgot.

carlthess40 · 15th April 2019, 05:42 PM

Could this be made to run a baby Huey EL84
Tube amp pcb ? It has 1 pre tube and 2 power tubes for one channel

Salas · 15th April 2019, 05:51 PM

It can run anything between 1.5V and 20V for enough Amps of current. Because heaters will be a constant load you can predict your trafo, your ripple loss, and your sinking scheme pretty accurately. 3A at 6.3V is four EL84s plus a couple of drivers is surely doable. Say 8W dissipation for 2.5V across Q4.

You see those side notches. They are to help you mount the diodes and the big transistor on a back surface also. In other words on a potent external sink if needed. Like a solid state amp against a flat sink with its big semis mounted under the PCB edges. He he, now a PSU with a notch and a status bar. Trendy.

derekr · 16th April 2019, 12:06 AM

Now that’s quick work, sir! Thanks, appreciate the effort. Will it be sold complete with parts - or a mini kit? Any idea of pricing?

Salas · 16th April 2019, 12:25 AM

That's Tea's area of expertise. Ask him later on. Me I will just send him a finalized PCB design with typical BOM to include in his next GB the soonest I feel I haven't missed the odd mechanical detail to include. Meanwhile I will continue with tests and beta tests acquiring various apps experience and third party feedback from local DIY friends that I will hand most of my few proto green PCBs to. So we can build a better knowledge base on what is best to use it for and what's enough trafo/bridge diodes/reservoir caps/sinks to configure in each case. Because the range of gear it can probably serve instead of their own fixed voltage SMPS bricks seems very wide.

jameshillj · 16th April 2019, 01:29 AM

Could this be extended up to 24V dc and about 3A for the various First Watt amps?

Salas · 16th April 2019, 01:51 AM

If you will use a higher value VR1 trimmer or a Zener in its place (cathode towards the LEDs), yes. When you don't jumper any side pins all LEDs are full on and the 500R trimmer offers 2.5V extra trim range. Whole Vref is fed with 5mA constant current. Maxing out at 20V output as it is after one Vbe is deducted via an output transistor.

jameshillj · 16th April 2019, 02:02 AM

Thanks for that - so simple.

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15th April 2019, 05:04 PM	#12
PKI diyAudio Member Join Date: Aug 2011	Can this be used if someone wants a regulated tube heater PSU?

15th April 2019, 05:16 PM	#13
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	Yes, tube heaters PSU is one of the uses I wanted to mention and I forgot.

15th April 2019, 05:42 PM	#14
carlthess40 diyAudio Member Join Date: Oct 2017 Location: Lake Mary Florida	Could this be made to run a baby Huey EL84 Tube amp pcb ? It has 1 pre tube and 2 power tubes for one channel

15th April 2019, 05:51 PM	#15
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	It can run anything between 1.5V and 20V for enough Amps of current. Because heaters will be a constant load you can predict your trafo, your ripple loss, and your sinking scheme pretty accurately. 3A at 6.3V is four EL84s plus a couple of drivers is surely doable. Say 8W dissipation for 2.5V across Q4. You see those side notches. They are to help you mount the diodes and the big transistor on a back surface also. In other words on a potent external sink if needed. Like a solid state amp against a flat sink with its big semis mounted under the PCB edges. He he, now a PSU with a notch and a status bar. Trendy.

16th April 2019, 12:06 AM	#16
derekr diyAudio Member Join Date: Mar 2009	Now that’s quick work, sir! Thanks, appreciate the effort. Will it be sold complete with parts - or a mini kit? Any idea of pricing?

16th April 2019, 12:25 AM	#17
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	That's Tea's area of expertise. Ask him later on. Me I will just send him a finalized PCB design with typical BOM to include in his next GB the soonest I feel I haven't missed the odd mechanical detail to include. Meanwhile I will continue with tests and beta tests acquiring various apps experience and third party feedback from local DIY friends that I will hand most of my few proto green PCBs to. So we can build a better knowledge base on what is best to use it for and what's enough trafo/bridge diodes/reservoir caps/sinks to configure in each case. Because the range of gear it can probably serve instead of their own fixed voltage SMPS bricks seems very wide.

16th April 2019, 01:29 AM	#18
jameshillj diyAudio Member Join Date: Feb 2005 Location: Melbourne	Could this be extended up to 24V dc and about 3A for the various First Watt amps?

16th April 2019, 01:51 AM	#19
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	If you will use a higher value VR1 trimmer or a Zener in its place (cathode towards the LEDs), yes. When you don't jumper any side pins all LEDs are full on and the 500R trimmer offers 2.5V extra trim range. Whole Vref is fed with 5mA constant current. Maxing out at 20V output as it is after one Vbe is deducted via an output transistor.

16th April 2019, 02:02 AM	#20
jameshillj diyAudio Member Join Date: Feb 2005 Location: Melbourne	Thanks for that - so simple.