Nice resistor, but I do not think that the resistor is in the signal path so it is probably a waste. But I do understand the feelgood factor.
this is my first post. I've 'only' read through the first 200 pages of this thread so forgive my impatience I'm tossing up whether to swap my SAC TVC passive for a Lightspeed passive. the Lightspeed sounds like it's an audible improvement and I was attracted to it's simplicity, but then when I was going to have to add an input selector switch box (turntable, DAC and tuner) and also a buffer between the Lightspeed and my active ADAM speakers (10k ohms impedance), suddenly it becomes a 3 box solution and also much more expensive. I don't have the DIY skills of you guys, in fact I have the DIY skills of a brick so I can't realistically build my own one box solution - I admire you guys who can. Has anyone had experience with the addition of a buffer or source selector switches who is able to comment on the sound quality changes from more boxes and more cables and connections?
Now this is a question that comes from total electrical ignorance, but why can't you change the resistance value of the attenuator to suit the impedance upstream or downstream?
I'm tossing up whether to swap my SAC TVC passive for a Lightspeed passive. the Lightspeed sounds like it's an audible improvement and I was attracted to it's simplicity, but then when I was going to have to add an input selector switch box (turntable, DAC and tuner) and also a buffer between the Lightspeed and my active ADAM speakers (10k ohms impedance), suddenly it becomes a 3 box solution and also much more expensive. I don't have the DIY skills of you guys, in fact I have the DIY skills of a brick so I can't realistically build my own one box solution - I admire you guys who can. Has anyone had experience with the addition of a buffer or source selector switches who is able to comment on the sound quality changes from more boxes and more cables and connections?Now this is a question that comes from total electrical ignorance, but why can't you change the resistance value of the attenuator to suit the impedance upstream or downstream?
Nice resistor, but I do not think that the resistor is in the signal path so it is probably a waste. But I do understand the feelgood factor.
Hi,
bequerel: I was thinking of using the best possible components for both audio path and power supply. I was attracted by the tolerance level of those resistors. I think, the better the power supply, the better will be the performance. Please tell me if I am wrong.
George: What is the required current rating required for the MK II version of Light Speed Attenuator ? (Is it around 100mA or do we need to go for a much higher value ).
Best regards,
Bins.
I think you are wrong.
The LEDs need a quite supply that holds voltage well.
It does not need low output impedance it does not need to react fast to changes.
The fastest change it will ever have to cope with is turning the volume up or down quickly.
The audio side uses the LDRs and is not affected by the PSU driving the LEDs, except for noise leaking through from LED to LDR.
I wondered how long it would take before I was asked this question "3 years".
The production Lightspeed Attenuator that I sell to my customers, is also battery operation friendly. Note this also includes the loses from the internal 5vdc reg supply
@ minimum volume approx 50mA
@ mid volume 5mA
@ max volume approx 50mA
These figures may change with you guys changing things like the power supply, NSL32SR2S for the SR3 and the value of the dual log pot and such.
Cheers George
I wondered how long it would take before I was asked this question "3 years".
The production Lightspeed Attenuator MkII that I sell to my customers, is also battery operation friendly. Note this also includes the loses from the internal 5vdc reg supply
@ minimum volume approx 55mA
@ mid volume 5mA
@ max volume approx 45mA
These figures may change with you guys changing things like the power supply, NSL32SR2S for the SR3 and the value of the dual log pot and such.
Cheers George
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Agreed - and that's why, in principle, I'm using a spare super-reg I had.
Overkill, I know, but as low noise though the LEDs as possible (I hope!).
Cheers
Jon
This then calculates for those who power (watts) is more understandable to.
Using a 12vdc source as I do before the internal 5vdc regulated supply
@ min level .66 of a watt
@ mid level .06 of a watt
@ max level .45 of a watt
Cheers George
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the secondary rating of your 24Vac 1.5VA transformer is 63mAac.
If you use it to feed a capacitor input filter the rating becomes approximately 32mAdc continuous.
If you intend using continuous DC currents then usually it is advisable to run the transformer @ <=50% of it's DC rating, i.e. <=16mA continuous.
If you use it to feed a capacitor input filter the rating becomes approximately 32mAdc continuous.
If you intend using continuous DC currents then usually it is advisable to run the transformer @ <=50% of it's DC rating, i.e. <=16mA continuous.
Hello,
I think the transformer that I am having right now is not suitable for the purpose as it is not a center tapped one. I was planning to design a supply similar to the one used on the bugle phono preamp. It has an output of 15 V DC output @ 100mA. Then use the TI chip to get it regulated to a perfect 5V DC supply for the light speed.
@ George, what is the power supply that you use ? Is that some thing with 5V DC @ 100mA output ? Or is that an over kill ? Do you have any schematic for the power supply ?
Best regards,
Bins.
I think the transformer that I am having right now is not suitable for the purpose as it is not a center tapped one. I was planning to design a supply similar to the one used on the bugle phono preamp. It has an output of 15 V DC output @ 100mA. Then use the TI chip to get it regulated to a perfect 5V DC supply for the light speed.
@ George, what is the power supply that you use ? Is that some thing with 5V DC @ 100mA output ? Or is that an over kill ? Do you have any schematic for the power supply ?
Best regards,
Bins.
it might be better to use two stage regulation.
15Vdc down to 10Vdc then down to 5Vdc.
Go to the link in George' signature. He uses a wallwart, but its a linear one. Linear supplies are often preferred for how quiet you can get them. For instance, I can hear the LED on the LDR whine if I put my ear near it. It is fed from a PWM and I think that thing operates at 5khz which SHOULD make noise. Maybe the LED would whine anyway, but others have complained that PWM is not the best solution. I can hear the whine on my speaker and this has traveled from amp to amp so its for sure the Lightspeed. It doesnt bother me but if I were to do it over again I would go to a small toroid. Use something with at least 200mA. As George just said you are looking at a max of around 60mA and possibly up to about 80mA so, then, as Andrew said you might be using a few caps in your supply so double it up to 160mA and then just double that anyway so that the transformer is not pushed to its limits. So 320mA or thereabouts. At 5V out that would be a 1.6VA transformer.
Uriah
Uriah
On a version I tried recently I used two LM317's. The TO-92 types. There was an improvement in sound. I dont know if it was the fact that the power supply was different or that I put the LDRs right on the input RCAs of the amp, but it sounded better than my original try. Also I used a 9V battery.
Uriah
Uriah
The wall wart is Linear 12vdc @ 300mA then feeds a 5vdc regulated supply.
I have also used a 1800mAh rechargable Lithium-Ion battery instead of the wall wart, and not one of the so called golden ears over here including me, can detect which is which in a blind a/b test, but all say there is a difference but what? they can't say!
Cheers George