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Best volume control
Best volume control
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Old 18th October 2019, 05:06 PM   #31
Chris Daly is offline Chris Daly  Australia
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The thread is titled "The best Volume Control" My point being, the 7805 is totally the wrong part to use with LDR's if we wish to discover what LDR's are truly capable of. Related to the thread, by LDR's being a unique way of controlling volume without contacts.
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Old 18th October 2019, 05:12 PM   #32
scottjoplin is offline scottjoplin  Wales
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Quite a bit of distortion though.
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Old 18th October 2019, 05:34 PM   #33
Chris Daly is offline Chris Daly  Australia
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Quote:
Originally Posted by scottjoplin View Post
Quite a bit of distortion though.
Caused by ? ,,, now we are over the 7805 hurdle, My understanding it IS because of such poor ways of powering, that has contributed to distortion arising.

LDR's are NOT entirely blameless... nothing is , but are not assisted by using voltage regulators where current regulators are the far better choice, along with the suggestions I raised in the post #21 of NOT using parallel resistance or capacitance across the anode and cathode and using high impedance. all of these ideas contribute to a far better listening experience.
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Old 21st October 2019, 03:15 PM   #34
DF96 is offline DF96  England
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The only possible difference between current and voltage drive for the LED illuminating an LDR in a volume control is a tiny improvement in intermodulation caused by noise in the light source. It will make no difference to the much larger distortion and intermodulation caused by LDR nonlinearity. Hence Chris is deploying the usual FUD of the audio salesman: highlight a tiny tiny issue and ignore a bigger issue, and hope that your potential customers don't notice. However, I will give Chris the benefit of the doubt and assume that he is not doing this through duplicity but merely lack of understanding.

As far as I can recall, Chris has presented no evidence to support his view. No measurements of intermodulation, showing an improvement when he swaps from voltage to current drive. Just false assertions of how circuits work, and praise from happy customers who have no idea anout electronics at all.
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Old 21st October 2019, 05:44 PM   #35
analog_sa is offline analog_sa  Europe
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Best volume control
Quote:
Originally Posted by Chris Daly View Post
My understanding it IS because of such poor ways of powering, that has contributed to distortion arising.
This claim is exceedingly easy to prove wrong, as distortion is trivially easy to measure. It is perhaps better to say it sounds better this way, which it probably does.

My understanding is the only way to keep distortion low is by keeping the signal level across the LDR as low as possible. Perhaps even sacrificing a few db of S/N with a passive divider is worthwhile. Or using the LDR in a more creative fashion, per example in an active VC.
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Old 21st October 2019, 06:54 PM   #36
mbrennwa is offline mbrennwa  Switzerland
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Best volume control
Oh, oh... someone pushed the big red LDR button again. Is this going to be another of these silly LDR threads?

Let's just say that there are different opinions about LDRs as volume controls. Then get on with OP question... PLEASE!
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Old 21st October 2019, 07:01 PM   #37
scottjoplin is offline scottjoplin  Wales
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Yes, it was Chris. I like the idea of an LDR active VC, he should pursue that........
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Old 21st October 2019, 09:17 PM   #38
DF96 is offline DF96  England
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A thread with the current title unfortunately will attract all sorts of opinions about all sorts of volume controls. This may or may not be what the OP intended. If he simply wanted a definitive answer which we all agree on then he will be disappointed.
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Old 21st October 2019, 10:28 PM   #39
AudioLapDance is offline AudioLapDance  Canada
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Quote:
Originally Posted by scottjoplin View Post
Quite a bit of distortion though.
Tom tested the Tortuga Audio LDR3 and it does have high distortion.

Review: Tortuga Audio LDR3 - LDR "passive preamp" – Neurochrome

"However, as soon as the volume control is turned down from its maximum setting, the distortion starts to skyrocket with distortion figures reaching 10 %. Granted, this is with 10 V RMS applied to the input of the volume control, but even at the common 2.0 V RMS line level, the distortion is still within 0.1 % to 1.0 % at all the tested gain settings except max. volume. This would barely pass the 1960ies era DIN 45500 HiFi standard."

Cheers,
Jeff

PS Look into ladder stepped attenuators (not series stepped atten.), then there's only 2 resistors in the circuit (rather than the dozens with series stepped atten.)

Last edited by AudioLapDance; 21st October 2019 at 10:35 PM.
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Old 21st October 2019, 10:58 PM   #40
HeyBill is offline HeyBill  United States
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I've built two passive volume controls (PVA) using transformers from Electra-Print and Dual 10K DACT attenuator. The impedence is said to stay fairly constant as the volume is changed. Works very well for me. Regards, Bill
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