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Are you really fine with IC voltage regulators ?
Are you really fine with IC voltage regulators ?
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Old 4th September 2020, 07:49 PM   #71
Mark Johnson is offline Mark Johnson  United States
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Are you really fine with IC voltage regulators ?
VRDN can be configured as two half-wave rectifiers, one for positive output and another for negative output; this allows the use of an AC wall wart with a single secondary. It also requires two opposite-polarity regulators (an LM317 and an LM337) since the common ground connection is foreordained and unchangeable. There's only one secondary.

On the other hand, when you abandon the feature to operate from a wall wart transformer with a single secondary, and instead require a within-chassis transformer having two independent secondaries, then you obtain the freedom to use two identical regulators, one for positive and the other for negative.

Personally, I'm fond of the idea of an AC wall wart. It keeps the AC mains out of the DIY chassis, which improves safety and reduces DIY chassis size (volume). The barrel jack connector cutout on the rear panel is smaller and far easier to drill, than a rectangular IEC mains inlet. Not surprisingly, both of the DIY headphone amps I exhibited & demonstrated at the 2019 Burning Amp Festival, used AC wall warts plus dual half-wave rectifiers. Attendees who listened to those HPAs ("Azul" and "Rojo"), liked what they heard.
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Old 4th September 2020, 11:43 PM   #72
MarcelvdG is offline MarcelvdG  Netherlands
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By the way, this is a relatively low-noise bandgap circuit that can be made of discrete dual transistors. It is similar to something that was published in the 1960's, but is almost never used. As drawn here it is relatively sensitive to variations in the input current; the transresistance from input current to output voltage is almost 286 ohm, so a 10 % variation of the input current changes the output voltage by about 31 mV or 2.5 %. A refinement could be to derive the 1.1 mA input current from the 1.23 V output voltage while ensuring the circuit doesn't get stuck at zero current and voltage.
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Old 5th September 2020, 02:18 AM   #73
wiseoldtech is offline wiseoldtech  United States
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Every PS I've make uses THIS to enhance and quiet down any residual noise.
Dead silent.
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Old 5th September 2020, 08:31 AM   #74
gerhard is offline gerhard  Germany
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Unluckily, the 78xx may add more noise than the Vbe multiplier
has removed.

The measurements in #60 have been made with 10*NMH batteries
as the input voltage. These add no visible noise at all. All you see
comes from the regulator.

Those here are measurements of LEDs abused as voltage references.
The LEDs are fed from 14V through a 1 or 2 K wire resistor.
One trace has the diode replaced by 47 Ohms. All you see is the
thermal noise of the 47R, slightly below 0 dB = 1nV/rtHz which
would be the thermal noise of abt. 60 Ohm. Nothing from batteries.

Note the outstanding performance of the HLMP6000. I got that
from someone here, forgot who. I owe him a beer or two :-)
Optically the HLMP6000 is quite a dim bulb.
My belly feeling is: the brighter a LED is, the more noise it does make.
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Last edited by gerhard; 5th September 2020 at 08:49 AM.
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Old 5th September 2020, 09:28 AM   #75
bimo is offline bimo  Indonesia
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Quote:
Originally Posted by ginetto61 View Post
Hi thanks for the very kind and valuable reply ... i have to answer without reporting your words as per instructions ...
I am sure you are right. But then i read of some listening tests that push the idea that regulators made out discretes are better received.
Let me elaborate a little my reasoning.
Cheap IC regulator usually have good PSRR at low frequency. But we need good PSRR at high frequency because many audio circuit do not have good PSRR at high frequency.

In my country, it is difficult to get good IC regulator. So I design it. I modify Poogee regulator and Super regulator from Walt Jung with discrete op-amp. It is series and shunt regulator. Using zener or LED as voltage reference the result is better than cheap IC regulator in listening test. But I use shunt voltage reference from Walt Jung, also.

It is fun, the most important things
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Last edited by bimo; 5th September 2020 at 09:33 AM.
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Old 5th September 2020, 09:48 AM   #76
dreamth is offline dreamth  Romania
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"But we need good PSRR at high frequency because many audio circuit do not have good PSRR at high frequency."


Do we? Doesn't it depend on the circuit function they supply?
There are countless recording soundcards that are using analogue circuits with very poor psrr at high frequency supplied by switching supplies alone, lower noise ones, still smps...They have around 80...90 db PSRR at 1khz and much poorer at 10 khz,let alone the 100khz that we'll never hear, yet they are doing what they are supposed to do while artists and sound mastering engineers can't complain about weird noises or artifacts because they can't hear them at all...I have one of these and it sold amazingly well in the last 3 years being appreciated all over the world.Actually it was so well received that its price got higher than it was 3 years ago . Aren't we simply making artificially this problem to look bigger than it really is?

If a circuit supplied by a linear series regulator have poor psrr at 10khz and inaudible at 1khz...that's actually good enough because the mains harmonics around 10 khz are so weak that they can be filtered by a simple rc filter and most audio applications will have decoupling networks after the regulator..

Last edited by dreamth; 5th September 2020 at 10:02 AM.
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Old 5th September 2020, 09:58 AM   #77
gerhard is offline gerhard  Germany
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Exactly. We need the good PSSR at low frequencies.
At high frequencies it is easy and cheap to filter.
At 1 MHz, 100n is a real short.

And circuits that require extra high PSSR are typical for
golden ear stuff. They usually have other problems, too.
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Old 5th September 2020, 10:10 AM   #78
dreamth is offline dreamth  Romania
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"And circuits that require extra high PSSR are typical for
golden ear stuff. They usually have other problems, too."


Or maybe we should read the datasheet of circuits like lt3042 exactly how they were written.
I can understand that they can be used for audio too, but....no mention of professional audio in the datasheet in the first place.LT3042 was simply ment for higher purpose ...
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Old 5th September 2020, 04:19 PM   #79
kasey197 is offline kasey197
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Are you really fine with IC voltage regulators ?
With the additional transistor we can increase the current handling well, but voltage is limited to 20V ish.

Is there anything that does high voltages (30-40v) that comes close to LT 3042?
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Old 5th September 2020, 05:22 PM   #80
wiseoldtech is offline wiseoldtech  United States
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For those wanting a good bipolar 15V supply, this is what I use...
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