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mini superreg for phono
mini superreg for phono
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Old 7th March 2019, 07:29 AM   #1
tubesaurus is offline tubesaurus  Germany
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Default mini superreg for phono

hello,
because I build a shunt regulator for high voltage from the Allen Wright preamp cookbook many years ago , which still works very well, I thought to build a mini superreg using the TL431 applications, with a regulated current source and a shunt regulator.
It can be adjusted from +/- 10-35V and mayebe 50mA, depending on heatsinks. Without a heatsink, it can be used for about 25mA.
The components are very common and cheap. I made also a layout for a printed circuit board, to use it with transistor or OP phono riaa preamps.
The values for the resistors X1,X2, Y1,Y2 set the current and the voltage, and can be caculated, the reference voltage for the TL431 is 2.5V.
The BC337 I replaced later by a BD139, I have also a version with a dual supply for a 2 OP phono preamp.
I used this power supply for meanwhile 5 different phono stages, and set them up individual after measuring the current drawn by the phono circuit, I add min 10mA more to be delivered by the current source. The shunt regulator itselfy needs about 3mA for working. This power supply is short circuit safe.
Due to that phono stages do usually need very little current, the dissipation loss is also little. Mayebe 1-2 watts overall.



Armin
Attached Images
File Type: jpg TL431.regler.jpg (107.7 KB, 570 views)
File Type: jpg MD_phono_TL431.regler.JPG (180.6 KB, 579 views)

Last edited by tubesaurus; 11th March 2019 at 07:25 AM.
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Old 7th March 2019, 08:41 AM   #2
tubesaurus is offline tubesaurus  Germany
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the picture shows the symmetrical board set up to use with a phono riaa preamp. The transformer will be located outside.
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File Type: jpg this is it.jpg (325.9 KB, 518 views)
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Old 8th March 2019, 01:03 PM   #3
tubesaurus is offline tubesaurus  Germany
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by the way, I can supply the files for the board, if there is any interest.
This power supply is good for phono, because it has a very great hum rejection due to the current sources. I use a "wall wart" housing for the transformer, it can be a 2W type, this is in most cases sufficient for a phono stage. It must have 2 secondary windings, of course.
And it is easy to set up, for example, you need 25mA, than you choose for Y a 120 ohm resistor, and for 15V you can take for X1 = 10K and for X2=1K.
I prefer this fixed resistors about trimmers, its cheaper and more reliable.
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File Type: jpg Superreg_Bestueckung.jpg (120.6 KB, 425 views)

Last edited by tubesaurus; 8th March 2019 at 01:08 PM.
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Old 21st August 2019, 08:49 AM   #4
mllum is offline mllum  Malaysia
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Quote:
Originally Posted by tubesaurus View Post
by the way, I can supply the files for the board, if there is any interest.
Hi, Would appreciate your files for the pcb so as to generate gerbers for fabrication to try out the shunt regulated power supply.
Perhaps you could post it here or send it to my email at jdgoonting2@gmail.com
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Old 16th September 2019, 03:10 AM   #5
ticknpop is offline ticknpop  Canada
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mini superreg for phono
The 431 is a noisy reference, LEDs are less thermally stable ( put them in silicon), but 3 or 4 times less noise
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Old 19th September 2019, 02:31 PM   #6
jackinnj is offline jackinnj  United States
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mini superreg for phono
Quote:
Originally Posted by ticknpop View Post
The 431 is a noisy reference, LEDs are less thermally stable ( put them in silicon), but 3 or 4 times less noise
Two "cathode to cathode" zeners are thermally stable.

Let's play around in LTSpice and see how it figures out.
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Old 19th September 2019, 04:25 PM   #7
jackinnj is offline jackinnj  United States
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mini superreg for phono
Just some graphs, noise, PSRR and output impedance:
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File Type: png tubesaurus_noise_no_cap.png (17.0 KB, 145 views)
File Type: png tubesaurus_psrr.png (22.3 KB, 58 views)
File Type: png tubesaurus_Impedance.png (25.8 KB, 52 views)
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Old 3rd October 2019, 10:40 AM   #8
ticknpop is offline ticknpop  Canada
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mini superreg for phono
Jack,

What are the graphs of?
Back to back zener?
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