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Can amplifier speed and resolution be measured?

stereo coffee

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Why then are you so keen for your product to be measured ?
... a very good question.

1) It will be interesting to see if I have more work to do, and at the same time if measurements agree with what I consider is excellent audio reproduction and what subjective assessments ( as much as they are disliked at ASR ) also agree with.

2) No audio product is distortion-less, and I think awaiting confirmation, that distortion is for the most part negligible

3) That there are indeed differences shown with the measurements proposed with how the led in a LDR is powered,indicating
that there is far more to DC circuitry powering a audio coupling encapsulated LDR, than first thought, that
directly benefits audio reproduction.

4) That attenuation deserves just as much attention, as does amplification in audio discussion.
 

solderdude

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1) It will be interesting to see if I have more work to do, and at the same time if measurements agree with what I consider is excellent audio reproduction and what subjective assessments ( as much as they are disliked at ASR ) also agree with.
That begs the following question. What level and type of distortion do you feel is audible (below that level could be considered excellent audio reproduction)

2) No audio product is distortion-less, and I think awaiting confirmation, that distortion is for the most part negligible
A normal (decent) potmeter is distortion less or at least lower than that measurement equipment can repeatably measure.
Why add components that by physical nature (CdSe) do add distortion ?
Again, here, at what levels and harmonic spectrum would you consider distortion 'for the most part negligible'.
You must have a standard set for yourself somehow.

I do agree that distortions below certain levels and with a certain spectrum can be considered inaudible.

3) That there are indeed differences shown with the measurements proposed with how the led in a LDR is powered,indicating that there is far more to DC circuitry powering a audio coupling encapsulated LDR, than first thought, that directly benefits audio reproduction.
To test for this I propose to ship along an identical LDR board but with the LEDs' driven by a very basic, and acc. to you inferior, design.
Testing your device alone won't show differences in driving LEDs.
Tom has measured a similar divice (when it comes to the used LDRs in any case) BUT the tests and test equipment are not the same.
These measurements thus can not be compared directly to draw the conclusion you expect you could be able to draw.
So it would appear to me that 3) can't be conclusive.

4) That attenuation deserves just as much attention, as does amplification in audio discussion.
It does, that's why a stepped attenuator, normal potmeter or higher quality 'digital' potmeter are exceeding the performance (my estimation based on experience and await to be proven wrong) of the LDR, by definition, alone and seems to be more than enough attention.
 

sergeauckland

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Is the LDR based on cadmium, either CdS or CDSe? I ask as these I understand to be illegal in Europe under RoHS regulations. If not containing Cd, what is their makeup?

S
 
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The fact is, we do not listen to music in the same way as scientific apparatus measures sound waves.
Why is that statement even relevant? Do we agree that sound is just waves in a gas, liquid or solid and nothing more? If the wave that hits your eardrums is sufficiently identical to what has been recorded, then what has the part between your eardrums and your neurons to do with anything? You can't seriously claim that singing or playing an instrument transmits some sort of "magic" through the air that banging a piece of metal with a hammer doesn't? :)

That being said, I genuinely look forward to seeing how your optocoupler based attenuator measures compared to something like the Schiit Sys.

EDIT: Removed some late night unfounded ramblings...
 
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solderdude

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Is the LDR based on cadmium, either CdS or CDSe? I ask as these I understand to be illegal in Europe under RoHS regulations. If not containing Cd, what is their makeup?

S
Well, the datasheet is not specific (maybe for that reason) but clues can be found in the forward voltage of the used LED.
The datasheet states 2.5V at 20mA which rules out IR LED's so most likely the fotosensitive part is thus not Pb based as that requires IR LEDs.
The 2.5V/20mA is more inline with blue LEDs which puts it in the visible range.
The CdS (and CdSe) are both most sensitive in the blue and green part of the spectrum.
So it seems these LDRs must be Cd based, which indeed is not RoHS.
Still.. at most electronic component websites I can still buy many non-RoHS components and solder.
 
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stereo coffee

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Well, the datasheet is not specific (maybe for that reason) but clues can be found in the forward voltage of the used LED.
The datasheet states 2.5V at 20mA which rules out IR LED's so most likely the fotosensitive part is thus not Pb based as that requires IR LEDs.
The 2.5V/20mA is more inline with blue LEDs which puts it in the visible range.
The CdS (and CdSe) are both most sensitive in the blue and green part of the spectrum.
So it seems these LDRs must be Cd based, which indeed is banned in certain (EU) countries.
It will take me a few days to answer the replies thus far,so I will tackle this one first.
The circuit is an attenuator using in a L pad using 4x NSL32SR3 http://lunainc.com/wp-content/uploads/2016/06/NSL-32SR3.pdf
a pair are the shunt for Left and Right , and a pair are for series Left and Right. Another pair of series are activated for the second input
and a third pair of series, are activated for the third input.

A natural asset of the NSL32SR3 is to exhibit extremely high resistance when in its off state - so forms a contact- less switch.
The stated figure of 20ma in my circuit is never used ( and has never been used ). Total current draw volume full off is 2.78ma
and 4.76ma full on of the LDr circuit measured wiper of the cathode arranged potentiometer to the main board. As the volume is increased
current lessens to a minimum of 0.26ma at mid volume. A discovery of a auto circuit found 2 years ago, begins removing voltage from the
series pairs to give silence at zero volume - a problem that has beset LDR designs from their inception.

The internal led has forward voltage in every circuit I have used them in between 1.3v and 1.8v - making them red or pink

The EU provided me a letter in June of 2014 as follows:

"
Thank you for your message.

The Commission Directive 2012/51/EU has enabled the use of cadmium in photoresistors for analogue optocouplers as an exemption from the ROHS directive. Therefore, indeed, the use of cadmium in photoresistors for analogue optocouplers is currently allowed as there are no other substitutes. We draw your attention in this context to the recitals of the Directive:
http://eur-lex.europa.eu/legal-conte...LEX:32012L0051

This new delegated Directive is based on the Recast of the RoHS Directive which entered into force in January 2013. The information relating to the recast of this Directive with the comments submitted during the public consultation is available on the following website of the Directorate-General for the Environment:
http://ec.europa.eu/environment/wast...e/index_en.htm

If you wish to voice your opinion on waste management issues and changes to the EU legislation, we invite you to consult the public consultations webpage on DG Environment:
http://ec.europa.eu/environment/consultations_en.htm

We hope you find this information useful. Please contact us again if you have other questions.

With kind regards,
EUROPE DIRECT Contact Centre
http://europa.eu - your shortcut to the EU!
 

sergeauckland

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It will take me a few days to answer the replies thus far,so I will tackle this one first.
The circuit is an attenuator using in a L pad using 4x NSL32SR3 http://lunainc.com/wp-content/uploads/2016/06/NSL-32SR3.pdf
a pair are the shunt for Left and Right , and a pair are for series Left and Right. Another pair of series are activated for the second input
and a third pair of series, are activated for the third input.

A natural asset of the NSL32SR3 is to exhibit extremely high resistance when in its off state - so forms a contact- less switch.
The stated figure of 20ma in my circuit is never used ( and has never been used ). Total current draw volume full off is 2.78ma
and 4.76ma full on of the LDr circuit measured wiper of the cathode arranged potentiometer to the main board. As the volume is increased
current lessens to a minimum of 0.26ma at mid volume. A discovery of a auto circuit found 2 years ago, begins removing voltage from the
series pairs to give silence at zero volume - a problem that has beset LDR designs from their inception.

The internal led has forward voltage in every circuit I have used them in between 1.3v and 1.8v - making them red or pink

The EU provided me a letter in June of 2014 as follows:

"
Thank you for your message.

The Commission Directive 2012/51/EU has enabled the use of cadmium in photoresistors for analogue optocouplers as an exemption from the ROHS directive. Therefore, indeed, the use of cadmium in photoresistors for analogue optocouplers is currently allowed as there are no other substitutes. We draw your attention in this context to the recitals of the Directive:
http://eur-lex.europa.eu/legal-conte...LEX:32012L0051


This new delegated Directive is based on the Recast of the RoHS Directive which entered into force in January 2013. The information relating to the recast of this Directive with the comments submitted during the public consultation is available on the following website of the Directorate-General for the Environment:
http://ec.europa.eu/environment/wast...e/index_en.htm


If you wish to voice your opinion on waste management issues and changes to the EU legislation, we invite you to consult the public consultations webpage on DG Environment:
http://ec.europa.eu/environment/consultations_en.htm


We hope you find this information useful. Please contact us again if you have other questions.

With kind regards,
EUROPE DIRECT Contact Centre
http://europa.eu - your shortcut to the EU!
Thank you.

S
 

stereo coffee

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That begs the following question. What level and type of distortion do you feel is audible (below that level could be considered excellent audio reproduction)
I use a pair of Quad 306 power amps for my listening which have sine wave figure between 0.01 and 0.03% Dtot
( I presume this means Distortion total ) , so below that figure would indeed be excellent.

A normal (decent) potmeter is distortion less or at least lower than that measurement equipment can repeatably measure.
The history of pots, patented by Mary Hallock Greenewalt this year- 100 years ago, shows they were never intended as invented to pass audio signals, rather they were intended for her musical visual musical instrument called the Nourathar https://en.wikipedia.org/wiki/Mary_Hallock-Greenewalt

I recall spending days and days trying to find professionally measured distortion of pots on the internet, to no avail, however found this https://pinkfishmedia.net/forum/threads/alps-potentiometers-gain-and-distortion.68076/

Why add components that by physical nature (CdSe) do add distortion ?
In 1993 I was using a stepped attenuator a Audio Synthesis PAS02 - I too thought it was quite good. I began research into LDR's in 2008 finding straight away their audio vs a stepped attenuator, was to me quite a bit better. I built up my first circuit using a LM317 as a current regulator and a single gang pot due to a mix up with a order with Radio Spares. I invited a friend to also hear this difference, so began a search for improving further still LDR circuits - as it was apparent even back then, that changes to the way the led anode and cathode were powered caused audio to either get better or worse as the case may be. I concentrated on what was making them better.

So I disagree with you that they add distortion when the anode and cathode are properly catered for. If the anode and cathode are driven by simple circuits having parallel capacitance and resistance forming a R/C and complicated by component internal paths the LDR will still function but will not provide what it is actually capable of. Rather it holds back by limiting the available audio sound stage ( meaning width height depth )and politely is telling me it can get a lot better. Using limiting circuitry -what ever distortions occur, are like walls and barriers to what is possible.



Again, here, at what levels and harmonic spectrum would you consider distortion 'for the most part negligible'.You must have a standard set for yourself somehow.
Let's see how it measures. I listen to a lot of music, particularly piano which is a difficult instrument for audio systems to reproduce properly

To test for this I propose to ship along an identical LDR board but with the LEDs' driven by a very basic, and acc. to you inferior, design.
Testing your device alone won't show differences in driving LEDs.
Tom has measured a similar divice (when it comes to the used LDRs in any case) BUT the tests and test equipment are not the same.
These measurements thus can not be compared directly to draw the conclusion you expect you could be able to draw.
So it would appear to me that 3) can't be conclusive.
Are you sending a Amir a simple circuit or am I ?

It does, that's why a stepped attenuator, normal potmeter or higher quality 'digital' potmeter are exceeding the performance (my estimation based on experience and await to be proven wrong) of the LDR, by definition, alone and seems to be more than enough attention.
Suggest you try the NSL32SR3 as it is in my experience the best type of LDR for music. If you get time try improving the way the led is driven
you should find the device begins responding to those changes - like I did 11 years ago.
 

SIY

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I recall spending days and days trying to find professionally measured distortion of pots on the internet, to no avail, however
There's one posted in this very thread. Cheap ALPS. Distortion is below the AP's residual. This is a complete non-problem.

If the anode and cathode are driven by simple circuits having parallel capacitance and resistance forming a R/C and complicated by component internal paths the LDR will still function but will not provide what it is actually capable of. Rather it holds back by limiting the available audio sound stage ( meaning width height depth )and politely is telling me it can get a lot better. Using limiting circuitry -what ever distortions occur, are like walls and barriers to what is possible.
More claims without any evidence, but bonus points for the added gibberish.
 

DonH56

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Quite the diversion... LDR attenuators offer some advantages over regular potentiometers, generally less so over stepped attenuators, but LDRs don't have slides or switches to go bad. I used them a looong time ago but ran into some issues with their stability over temperature and of course the illumination source can modulate the signal if it is not super-clean/quiet/stable/etc.

I was curious to see how "resolution" was defined in the context of amplifiers but apparently this is not the right thread...
 
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solderdude

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A natural asset of the NSL32SR3 is to exhibit extremely high resistance when in its off state - so forms a contact- less switch.
This is no different from any other LDR.

The stated figure of 20ma in my circuit is never used ( and has never been used ). Total current draw volume full off is 2.78ma
and 4.76ma full on of the LDr circuit measured wiper of the cathode arranged potentiometer to the main board. As the volume is increased
current lessens to a minimum of 0.26ma at mid volume. A discovery of a auto circuit found 2 years ago, begins removing voltage from the
series pairs to give silence at zero volume - a problem that has beset LDR designs from their inception.

The internal led has forward voltage in every circuit I have used them in between 1.3v and 1.8v - making them red or pink
Because you use lower currents (which is a good thing as the R load at -6dB will be higher than a few hundred Ohm) you measure a lower voltage. As mentioned the LED voltage says something about the colour at a specified current. Making the LED blue.
 

solderdude

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I use a pair of Quad 306 power amps for my listening which have sine wave figure between 0.01 and 0.03% Dtot ( I presume this means Distortion total ) , so below that figure would indeed be excellent.
This number says very little to nothing. It's about the spectrum, output power at which is measured and freq. range.
I agree with the 0.01% number as being an upper limit for electronic equipment. Very easy to reach. Especially when using 'normal' potmeters.

The history of pots, patented by Mary Hallock Greenewalt this year- 100 years ago, shows they were never intended as invented to pass audio signals, rather they were intended for her musical visual musical instrument called the Nourathar https://en.wikipedia.org/wiki/Mary_Hallock-Greenewalt

I recall spending days and days trying to find professionally measured distortion of pots on the internet, to no avail, however found this https://pinkfishmedia.net/forum/threads/alps-potentiometers-gain-and-distortion.68076/

100 years ago .. and the application back then was not for audio ? Really that's what you base it on ?
And LDR's were .. ?
The guy at pinkfish measured incorrectly or should I say drew the wrong conclusion.
That's where you base your theory on ?
mechanical contacts are detrimental ?

Have you seen the plot made a few pages back ?
0.5% ?

have you reviewed Tom's article ?
Did it mention distortion is below 0.01% ?
Will a different LED driver lower the measured distortion ?
Is that based on listening tests only ?

So I disagree with you that they add distortion when the anode and cathode are properly catered for.
You can disagree all day long because your ears tell you so. Doesn't make the distortion less. And it has nothing to do with driving the LEDs as they remain in a steady state when listening. It only makes a difference when setting it to another level.
There just has to be as little noise as possible as the LDR/LED is basically an AM modulator.

Are you sending a Amir a simple circuit or am I ?
It's you who wants to know what the circuit improves over another LED driver with the same LDR's and partly seems to be the reason why you sent it in.
Why should I send one to answer your question when you have the exact same LDR's and can whip up a very simple control.

Suggest you try the NSL32SR3 as it is in my experience the best type of LDR for music. If you get time try improving the way the led is driven
you should find the device begins responding to those changes - like I did 11 years ago.
The Tortuga has the same optocouplers. These are already measured and found guilty of poorer performance than pots.
The LED drive is not going to change this, despite you believing such. It's the LDR that is the problem.
A different LED drive might result in less noise and different levels of attenuation or range.

The latter could make it easier to define/have a more 'natural' volpot position versus attenuation.
I am totally happy with the behaviour of a normal RK27 pot though.
 
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solderdude

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It may be wise to split this thread once Thomas is back in his moderator seat.
The whole LDR discussion has nothing to do with 'amplifier speed'.
 
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