As the circuit is that I posted with the input shorted I measured the output down to the limit of my Tek scope which ended up being 10uV (that's microvolts not millivolts) of noise!!! (and I think that was the scopes lead noise at that) if you can hear that I'll bite my rear end, and as far as the detail goes that's out in fairy land.
Were only lighting up the led's be it ccs or regulated voltage driven, it's not rocket science, so long as it's stable that's all that matters in this circuit.
Cheers George
Were only lighting up the led's be it ccs or regulated voltage driven, it's not rocket science, so long as it's stable that's all that matters in this circuit.
Cheers George
Are you talking about the the 5V supply being a CCS? If so, is this a CCS followed by shunt regulator set to 5V?
The ldr part of the NSL32SR2S can have a certain very small amount of noise being chemicaly resistive, this is still a constant no matter what you do with the led section if it is stable.
As well the ldr changes it resistance as a chemical change this is not instantaneous but takes half a second or so to change, if there are any noises being induced by the led fluctuating because of a bad unstable power supply, this could only give a noise change on the ldr part in the very low frequency like a hertz or 2.
Cheers George
Hi George, have you listened to the various supplies with the LDR's?
I appreciate a theoretical perspective, but the emipirical data is clear - a quieter PS and a CCS definitely improve the perceived sound of the pre.
Perhaps a few members can try PS variations and post results here? And if you're lucky enough to own measuring equipment with sufficient resolution, a few charts would help to?
I appreciate a theoretical perspective, but the emipirical data is clear - a quieter PS and a CCS definitely improve the perceived sound of the pre.
Perhaps a few members can try PS variations and post results here? And if you're lucky enough to own measuring equipment with sufficient resolution, a few charts would help to?
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Different power supply designs and idle current will effect how current flows through the ground, and thus effecting the perceived sound. Generally, if you have more idle current running, the ground currents are less effected. Thus the sound will be cleaner.
Since the first Lightspeed I developed back in 1972 I have tried numerous mains supplies including batteries,rechargeable, lithium,dry cell and gel cell. there is not much in any of them especially when a blind A/B is performed. The only time is when a switch mode wall wart was used it was detected and measured worse because of the radiated switching noise, infiltrated into the ground plane and chassis earth.
BTW the Lightspeed circuit as I have laid out is a free floating supply to the led's and not referenced to ground in any way.
Cheers George
BTW the Lightspeed circuit as I have laid out is a free floating supply to the led's and not referenced to ground in any way.
Cheers George
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I have always said to intergrate it into amps whether tube or solid state they are asking for trouble due to the wildly varying temperature within the amps power or intergrated, this can cause channel imbalances through temperature instability.
And yes floating supply as I've outlined completely isolates any part of the led's and their supplies from the signal path through the ldr's
Cheers George
And yes floating supply as I've outlined completely isolates any part of the led's and their supplies from the signal path through the ldr's
Cheers George
Hi George, have you tried the CCS posted around post 1000?
http://www.diyaudio.com/forums/anal...uator-new-passive-preamp-100.html#post1390908
http://www.diyaudio.com/forums/anal...uator-new-passive-preamp-100.html#post1390908
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Guys, I have recently tried to calibrate the LSA using a scope. What struck me is the following:
- I managed to calibrate the levels at a certain volume (say 1/4 of my pot). Very nice.
- If I then open the pot further, the matched levels across the channel seems to disappear. In other words, one channel is more attenuated than the other.
I am using a Alps Blue Velvet pot...
What's happening, and how can I counter this?
- I managed to calibrate the levels at a certain volume (say 1/4 of my pot). Very nice.
- If I then open the pot further, the matched levels across the channel seems to disappear. In other words, one channel is more attenuated than the other.
I am using a Alps Blue Velvet pot...
What's happening, and how can I counter this?
Is this the "CCS" you refer to in your posts? This is the design you built and like best?
Sounds like your LDRs are not well matched. Put the volume where you normally listen, and match there using the adjustment pot. Or do better matching on the LDRs.
Your LDR's are not well matched, get yourself one of these and use your DMM with it to match up the resistances from 1-20 mA
And yes Dr H I have tried just about every way of powering the led's short of rubbing two sticks together.
Cheers George
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