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ultra low noise regulators
ultra low noise regulators
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Old 27th April 2019, 12:52 AM   #1
wtnsmk is offline wtnsmk  United Kingdom
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Default ultra low noise regulators

I'm looking for a low noise 18V and -18V linear voltage regulator.

I found these:

MC7918 -> 110μV
MC7818 -> 10μV

LT3015 -> 60μV
LT1969A -> 40μV

Also found the TPS series and there are couple of "three legs" prebuilt version from them.

You guys know any better? Or is it doesn't matter at all in an amplifier PSU?
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Old 27th April 2019, 01:15 AM   #2
Dave Zan is offline Dave Zan  Australia
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Quote:
Originally Posted by wtnsmk View Post
... know any better?...
LT3042 <1 uV (!)

Whether it matters depends on your application.

Best wishes
David
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Old 27th April 2019, 01:22 AM   #3
trobbins is offline trobbins  Australia
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Do you have an amplifier with some noticeable 'noise'?

Have you seen quality amplifiers with standard linear voltage regulators?

My concern is that you may be needlessly enquiring about an aspect of amplifier design that has no relation to amplifier performance. It is also worthwhile using descriptions such as 'ultra' with care, as they likely mean something very different to just a common lower noise variant of a popular linear regulator.
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Old 27th April 2019, 07:40 AM   #4
FauxFrench is offline FauxFrench  France
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You do not write if it is for a power amplifier or a pre-amplifier.

Ultra low noise is important for certain measuring circuits. Depending on your DAC construction it is to play safe.

Low noise (standard) regulators I use for pre-amplifiers. The OP-AMPS I use normally handle noise problems with their PSRR.

For power amplifiers you will hardly notice the difference. And be aware, the very impressive noise data for certain regulators is with a noiseless input voltage and a static load. With an unregulated input voltage and in particular a rapidly varying dynamic load (power amplifier) the noise figures are severely deteriorated in practice.
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Old 27th April 2019, 12:15 PM   #5
wtnsmk is offline wtnsmk  United Kingdom
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Sorry I wasn't clear at all.

I'm building a linear power supply with multiple outputs to feed my phono, dac and turntable etc... For sure for turntable almost doesn't matter.

I'm already feeding my phono as it needs AC power, the converter and the regulator is inside the phono.

I was trying to design the regulator part, but couldn't find any TO220 type low noise regulator.

Currently my phono has the KA7918 and the L7818CV, but I'm sure I can do it better. All the parts caps/opamps etc was the cheapest ones in the phono, so I think maybe worth to upgrade this as well.
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Old 27th April 2019, 01:10 PM   #6
canvas is offline canvas  Taiwan
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MC7818 -> 10μV ? It sounds too good to be true. May I ask where you read the spec?
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Old 27th April 2019, 01:21 PM   #7
wtnsmk is offline wtnsmk  United Kingdom
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Quote:
Originally Posted by canvas View Post
MC7818 -> 10μV ? It sounds too good to be true. May I ask where you read the spec?
Sorry it is not true. I'm not sure where is that information coming from, but double checked it and seem 110ÁV/Vo
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Old 27th April 2019, 01:28 PM   #8
dreamth is offline dreamth  Romania
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Quote:
Originally Posted by wtnsmk View Post
Sorry I wasn't clear at all.

I'm building a linear power supply with multiple outputs to feed my phono, dac and turntable etc... For sure for turntable almost doesn't matter.

I'm already feeding my phono as it needs AC power, the converter and the regulator is inside the phono.

I was trying to design the regulator part, but couldn't find any TO220 type low noise regulator.

Currently my phono has the KA7918 and the L7818CV, but I'm sure I can do it better. All the parts caps/opamps etc was the cheapest ones in the phono, so I think maybe worth to upgrade this as well.
Yes. 78L18 and 79L18 is better .
There's a simple technique used to make lower noise regulators with these parts.First you load it externally with a resistor that equals at least the minimum current for which you have the best results in the datasheet.Depending on the current you need you can increase that load up to the same value of the current taken by the circuit or at least half of it or the idle current through the electronic load you need to supply.You need to make some loading adjustments due to the thermal regime so nothing is very clear about that.

This technique is also used in some interesting capacitance multipliers like the one present in Audio note dac 4.
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Old 27th April 2019, 01:37 PM   #9
wtnsmk is offline wtnsmk  United Kingdom
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Originally Posted by dreamth View Post
Yes. 78L18 and 79L18 is better .
There's a simple technique used to make lower noise regulators with these parts.First you load it externally with a resistor that equals at least the minimum current for which you have the best results in the datasheet.Depending on the current you need you can increase that load up to the same value of the current taken by the circuit or at least half of it or the idle current through the electronic load you need to supply.You need to make some loading adjustments due to the thermal regime so nothing is very clear about that.

This technique is also used in some interesting capacitance multipliers like the one present in Audio note dac 4.
This is very useful thanks!

But I don't understand why 78L18 and 79L18 better than LT1963 and LT3015?
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Old 27th April 2019, 01:55 PM   #10
dreamth is offline dreamth  Romania
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I only quoted your last post...but they might be cheaper than the LT parts and still good enough for the job.What's your phono preamp schematic?
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