I have always assumed that the LED's flicker without a very stable power supply. The ldr's must react very quickly to changes in LED intensity otherwise they wouldn't work in this application. So assuming that is so then it is probable that minute variations in supply will cause minute variations in ldr value and thus smear the resulting signal output.
Tony, don't be such a tease...What pre and post caps values did you settle on for the 7805 regulator?
Well I wasn't teasing I think that all setups may vary a little depending on components. But I ended up with 2200uf x 2 plus 1000uf x 1 plus 100nf x 1 on input side, and 47uf plus 100nf on output side. But as I said it really is tuneable for YOUR system. But I assumed that a salas reg would or should be in a different league. But George has huge experience here and he cites 7805 as more than adequate.Good enough for me unless or until proven wrong.
I use 220uf> 7805 470uf> .1uf MKT.
As for led flicker it's that fast (if there is any), the ldr in no way can respond to it. as they cannot react that fast to that sort of fast change, they are that slow to respond.
Just change the volume knob with a 1khz signal up and down and watch on an oscilloscope how long they take to react to the change in level.
No way can led flicker if any have an effect. They are self damping to this.
Reaction Specs
TR Rise Time 5 msec Time to 63% of final conductance @ IF = 20mA
TF Decay Time 80 msec Time to 100KW after removal of IF = 20mA
Cheers George
As for led flicker it's that fast (if there is any), the ldr in no way can respond to it. as they cannot react that fast to that sort of fast change, they are that slow to respond.
Just change the volume knob with a 1khz signal up and down and watch on an oscilloscope how long they take to react to the change in level.
No way can led flicker if any have an effect. They are self damping to this.
Reaction Specs
TR Rise Time 5 msec Time to 63% of final conductance @ IF = 20mA
TF Decay Time 80 msec Time to 100KW after removal of IF = 20mA
Cheers George
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Wow didn't see that coming Alex, give us more in layman's terms to what's going on with this "Magnetic Field" hopefully with links.
Cheers George
Hi georgehifi, I just doped on top of our discussion table assumption based on theory. I personally don't experience with any type of distortions, thin sound or incorrect audio-spectrum presentation. Maybe my ears are not that sensitive then some other guys have. I use generic rectifier bridge with T317. CRC made with Panasonic FC- 1000uF>51R>1000uF. 100Uf on output. 0.1 MKP Wima on T317 input and output leg. No any issue.... Very nice sound.
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i know the ldr response is very slow and so light flicker is not the reason why it has poor PSRR, so I assumed it is electromagnetc (capacitive or inductive) coupling. Hence my suggestion to separate the LED from the LDR with greater physical distance than the all in one packaged version. Electromagnetic coupling will be far less with larger physical separation. With this approach I thought you may have better PSRR ?
Of course, always make sure the issue isn't contamination of the 'ground'.
Of course, always make sure the issue isn't contamination of the 'ground'.
Did someone tried to use K-Multiplier after V-regulator here? It might help to reduce additional 66dB from incoming ripple.
The K Multiplier
I got an exceptional results of using it in my Salas Phono and J-Mo Mk II headphone amplifier PSUs.
The K Multiplier
I got an exceptional results of using it in my Salas Phono and J-Mo Mk II headphone amplifier PSUs.
This is exactly what I use in my build with T317 regulator and have did not hear any issue with the sound. It is nice and crystal-clear. I meant, for some guys who hear something that I do not, it might related to some small V-ripple and to remove it efficiently, K-Multy is one of the way to do it .
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I think its capacitive coupling. I cant prove it.
The sound does get better with local decoupling and it also gets better when supplying the LDRs from a current source.
The whole magnetic theory with TE and TM could be a possibility but as to the rest of the assumption that varying resistance would be audible as a smear, that doesnt make sense to me. If the music comes through 1k or 100k would be a change in Johnson noise and would cause impedance problems but it would not smear the music. So if its coming through, lets say 5k and a flicker generates a 4k9 value followed an instant later by 5k again there wont be a smearing of music. In fact how would we smear something anyway? That would be a difficult task that a resistor is not up to. Lets remember that what we are playing with here is a variable resistor, not anything active.
The sound does get better with local decoupling and it also gets better when supplying the LDRs from a current source.
The whole magnetic theory with TE and TM could be a possibility but as to the rest of the assumption that varying resistance would be audible as a smear, that doesnt make sense to me. If the music comes through 1k or 100k would be a change in Johnson noise and would cause impedance problems but it would not smear the music. So if its coming through, lets say 5k and a flicker generates a 4k9 value followed an instant later by 5k again there wont be a smearing of music. In fact how would we smear something anyway? That would be a difficult task that a resistor is not up to. Lets remember that what we are playing with here is a variable resistor, not anything active.
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If it's capacitive coupling then there maybe some simple tests that could be performed that might help support or debunk this idea. Injecting a signal into the power supply for the LED and seeing if a listener can tell when the signal is present / not present ?
If capacitive, the coupling would be frequency dependent - higher frequencies would couple more effectively.
As I suggested earlier, separating the LED from the LDR would automatically reduce capacitive coupling - although it may be that this would be more trouble than cleaning up the LED power supply. But understanding the source of the effect would allow each person to design based on their own choice of tradeoffs.
p.s. I realize I'm being a back seat driver here - I don't have any LDRs to play with yet
If capacitive, the coupling would be frequency dependent - higher frequencies would couple more effectively.
As I suggested earlier, separating the LED from the LDR would automatically reduce capacitive coupling - although it may be that this would be more trouble than cleaning up the LED power supply. But understanding the source of the effect would allow each person to design based on their own choice of tradeoffs.
p.s. I realize I'm being a back seat driver here - I don't have any LDRs to play with yet
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If you look back through the thread you'll see we did extensive listening tests, between the standard 7805 based regulators well implemented using a linear wall wart, and pure battery power.
And no one felt confident they could pick the difference in a blind A/B, they thought they preferred the battery but weren't sure.
As the ldr part or the NSL is so slow to react to voltage variations, it is self buffering/regulating, and is probably immune to these sorts of conditions.
Then we substituted the linear wall wart for an smp type, and nearly all thought it sounded brighter, than battery or linear wall wart. But this is due to very H/F injected noise from the SMP wall wart.
Saying all this a lot of my customers have purchased this very nice power supply, some swear by it and some say there's no difference to my supplied wall wart, GO FIGURE!!!
http://www.ab-system.hk/index.php?route=product/product&product_id=64
Cheers George
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Pot.
This threat is very long. I can not to read/understand it complete - I am not perfect in English.
So please could You answer me? I want replace my pot in Millet Max hybrid headphone Amp. Now is there 50k log pot.
I am thinking about LDR att MK II (series+shunt).
A) what pot to use for control LDR att? Linear or Logaritmical ?
I want have logaritmical reaction as it is at old pot.
B) use 2x100k tandem pot or just single 100k pot?
C) will help add rezistor 1k (2k) at input in series to silent at "zero volume"?
D) will help to match series to shunt adding one more trimmer to shunt LDR too?
Thank You very much.
This threat is very long. I can not to read/understand it complete - I am not perfect in English.
So please could You answer me? I want replace my pot in Millet Max hybrid headphone Amp. Now is there 50k log pot.
I am thinking about LDR att MK II (series+shunt).
A) what pot to use for control LDR att? Linear or Logaritmical ?
I want have logaritmical reaction as it is at old pot.
B) use 2x100k tandem pot or just single 100k pot?
C) will help add rezistor 1k (2k) at input in series to silent at "zero volume"?
D) will help to match series to shunt adding one more trimmer to shunt LDR too?
Thank You very much.
Hi Andrew, not sure what you've done, I looked at post 1 and it seems the same??
Cheers George