Afaik, all volume controls, Alps, Noble, TVC etc have mechanical wipers, switches and mechanical contacts that the signal has to pass through. These things cause distortion and noise. Enter the LDR or Light Dependent Resistor. It's a variable resistor that changes in value according to the light shining on it. So, in a voltage divider volume control arrangement, by changing the power to the light, we change the resistance of the series and shunt and hence we change the volume. All the signal sees is one soldered resistor in its path! So how does it sound? Is this the ultimate volume control that at least one manufacturer used in some usd20k hi-end preamp?

To find out I built one.
The Lighter Note is more sophisticated than the better-known Lightspeed. It refines on that design.


The diy kit - all that to replace 1 pot, crazy?!!



Assembled and being calibrated. Yes it needs extensive tuning to select impedance, max and min resistance and even profile! Just the ticket for perfectly matching impedance between source and amp!
I use two boards for the LDRs instead of one so I have option to mount the LDR board into each one of my monoblocks. Torroid is mounted in external box that now also powers the B1 buffer.



In other thread I built the Pass B1 buffer. The Lighter Note was originally meant to replace its muddling early 20th Century pot. This is how they would look together - their red 'undies' totally match even to their thickness!



But no! the LN is really too good to be stuck with the B1 and deserves its own box
See those black blobs marked SR2 near the RCAs? That'll be the Silonex LDRs.
A little more complicated than the B1 preamp to build!



Still in the mood for sexy see-throughs, here's the LN with its own acrylic box
The B1 hasn't been forgotten, this box is designed for stacking with it, with matched footprints.



What's with that offbeat blue knob? It's the balance control, and happens to be the only knob I had on hand lah. Will look for something matching later.

So does it work? Yes. All those parts - two pots, 8 trimmers, 6 ICs, two power supplies, etc to replace just one pot, it better!

But how does it sound? Let me just say I'm still picking my jaw from the floor Seriously. But I'm going to listen over the next few days before trying to describe the sound for which I was not prepared. This way I'll avoid initial over-enthusiasm and report more objectively. It will be used as passive preamp and compared against the B1 and Yaqin CD3 buffer preamps.

This post has been edited by Bernie7: Oct 4 2010, 11:13 AM

omg..
very nice piece of work u got there,
from the pcb to the casing..
im envious.
simply stunning.

I should add that the Lighter Note (LN) is connected between my DEQ2496 and monoblock power amps (UcD400HG HxR). Speakers are Swan F2.2.

The DEQ2496 has been modded so that its DAC chip plays directly to the output through banks of 0.47uF Dayton caps, bypassing all the stock opamps. The DAC chip has also been changed from AK4393 to the miracle dac AK4396

great works, thanks for sharing.

another item in my wish list.

well apart from my comments above.. these are ancient greeks to me..
still kagum neways..

Wwoew. Very advanced. Looks more ANALOG: )

Btw, I am also contact less volume control, yup digital volume control on my pmp and digital ht avr



Anyway your light volume control is very interesting, and wish can audition it in future.

This post has been edited by bahathir: May 4 2010, 10:16 AM

what it basically means is the rest of the gear should be good enough to assess the LN

cheers!

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Added on May 4, 2010, 10:21 amIt is 100% analog. And makes my whole setup sound more like it too

I have been using 24bit digital volume using the DEQ2496 gain control, and careful not to exceed my quota of digital attenuation. But this LDR thingee is at another level or three higher. Makes me wonder why.... how can a resistor sound so good???!!!

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Added on May 4, 2010, 10:22 amThanks bro.

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Added on May 4, 2010, 10:25 amWelcome to come hear next time you're in S'pore

Help me to confirm what my ears hear


This post has been edited by Bernie7: May 4 2010, 10:25 AM

Great work, great post, envy your knowledge and DIY skill. Very neat and clean. Waiting for your review on the sound.

Unlike a certain fool who might electrocute himself with his own equipment.

In electronics, LCR plays very important role in signal handling. So, in this case, the R or Impedance do make lots of differences. Also, the components quality also effects the SQ too, no doubt about it.. That's why sometime we must use the correct impedance value to get more accurate signal. Impedance mismatch can make thing worse or data errors in digital signal transfer.

Yes, I can imagine how Analog your LN sound like , based on your jaw dropping experiences. It must be, very very very smooooth volume control with very little noise.


TQ. and congratulation with your new 'toy',' errr gear ...Right now, I only can stick and enjoy to my contactless digital volume control right now. ..., jealous nya , but at least it has same 'contactlessness' here he hhe he

BTW... what is the resistance range of your LN ?

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Added on May 4, 2010, 10:56 amNo doubt, Mr. bernie7 is very knowledgeable in this field. I wish I also have that huge amount amount of knowledge and $$$ too,


This post has been edited by bahathir: May 4 2010, 10:56 AM

this i had to laugh

anyways, ya.. bernie7 shown impressive work there.. wish i'd have half that skills..

Yeah LCR and impedance matching, but I suspect the sound of this thing is more than just that. It's just quite stunning! We know that resistors can sound different, so maybe this optico-type resistor has special audio qualities.

Impedance of the LN has been dialed in to 10k. The source O/P impedance is 1R (!!!) and the amps are 100K so all is cool.

But the LDRs are not very linear, so the impedance falls to 4.5K then rises back to 10K as vol goes up. Still cool as the lower Z is better for my power amps. It falls in my listening range.

Huge knowledge, nah, still trying and learning, and the LN kit is not exp lah

Excellent work there!
I did tried this but based as per diyparadise's circuit.

This is the best yet as far as passive attenuators are concerned.
Some people like the sound, some people don't.
I personally like active attenuators..

Keep us posted with a full review ya!

GREAT MASTERPIECE...

Thanks for compliments bros, but it really isn't that hard to diy this with the kit.
Gotta be v careful when soldering and tuning the LDRs though as they are delicate things that damage with too much heat or voltage.

jazzy939, the diyparadise project uses a different LDR part and it's nowhere near this design in maturity. I read it has problems with stability and channel balance which is obvious from the simple circuit. My LN has a measured balance variation of +-0.6% throughout the whole operating range! Noble pots go up to 10% imbalance, so a friend who measured them told me.

What's the link to the diyparadise active volume circuit?

This post has been edited by Bernie7: May 5 2010, 08:23 AM

Bernie7,
Yes, I am aware of the limitations that was based on a simple LDR circuit but that was not my issue. It's just that I simply don't like (the sound of) passive attenuators.

I wonder how's the Lighter note perform compares to the original LSA ? About finishing my LST+DCB1. A shout out should be interesting......

LSA = LST = Lightspeed? One person who has both says the LN is clearly better SQ wise on account of its better psu implementation which includes both voltage and current regulation.

I'd be interested to see how the Lightspeed + DCB1 fare against the LN alone. It already beats the B1 handily.

ultimately it's based on one's taste and perception...it's very subjective when come to this part...

Yes agree absolutely especially when it comes to 'flavour' type of differences

To me and a few others who have heard so far, the LN is clearly better than the B1, but then your DCB1 should be better than the B1 without caps in the signal path.