Lighter Note LDR attenuator

[HighFidelityGuy]

After first finding out about LDR (light dependant resistor) based attenuators a year or so ago I decided I simply must give one a try. After doing some research I stumbled across the Lighter Note (http://www.buildanamp.com/Full-KIT_c5.htm) which is an evolution of the Lightspeed Attenuator (http://diyaudioprojects.com/Solid/DIY-Lightspeed-Passive-Attenuator/) and addresses all of the weak points of the original's design. I should point out at this point that the Lighter Note was designed by and is sold by Uriah Dailey and the Lightspeed Attenuator was designed by George Stantscheff. In theory the Lighter Note is the ultimate passive attenuator as it only has a single component in the signal patch (one LDR per channel, it has adjustable impedance, adjustable volume range, adjustable channel balance, and a low noise power supply that incorporates a current source for the LDR's. It also incorporates a novel solution for preventing high frequency roll-off caused by the capacitance of input signal cables. All of this should mean that the Lighter Note has the minimum possible negative effect on the audio signal while allowing a great deal of flexibility in the way the circuit can be tuned to allow it to be used with a much wider range of sources and amplifiers than the standard Lightspeed Attenuator.

The standard Lightspeed attenuator requires sources with low outout impedance and amps with high input impedance. If your equipment falls outside of the recommended range then buffer stages are often required to solve impedance mismatch issues. This adds extra resistors, capacitors and transistors/valves into the signal patch which all slightly degrade the sound. The Lighter Note can be tuned to remove/reduce these impedance issues and therefore a buffer is often not required. A source with a low output impedance is still recommended though.

If you're not familiar with the Lightspeed Attenuator or the use of LDR's for volume control then I suggest you check the link above as that explains how the Lightspeed works.

So that's the theory, now for the practice...

I ordered the full Lighter Note kit from Uriah in November and it arrived shortly after. The kit includes everything you need to build a Lighter Note with the exception of a case, audio connectors, power connector and fusing and hook-up wiring. All the components, PCB and transformer are included.

I was hoping to start building the kit before Christmas but that didn't happen, so it ended up being my holiday project. The build was really quite straight forward and the PDF guide that Uriah sent me was quite detailed. The only problem I had was that in a moment of stupidity I installed the two power LED's the wrong way round. A pair of new ones from Maplin soon fixed this. :doh:

Once the build is complete there is a simple but extremely important set of tuning steps that must be completed to ensure that the delicate LDR's are protected from being run outside of their resistance range and the impedances and volume range are setup correctly. The supplied guide explains this process very well and I had no trouble in choosing my initial impedance setup.

My existing passive attenuator is based around a 10K Alps Blue Velvet potentiometer, so I set my Lighter Note to 10K to try and keep the impedance characteristics of my system the same to start with. I'll then try experimenting with other settings later. Uriah recommends trying to get the Lighter Note's impedance as low as possible as the lower it is the more detail is let through as less resistance is in the signal path.

As cases and RCA sockets etc can be quite expensive and I wanted to use good quality ones, I decided to only order these once I had a working circuit. So I'm currently waiting for these to arrive. That means I've not yet heard my Lighter Note in my system, so I can't comment on the sound but I'll be sure to provide a comparison between my two attenuators ASAP.

I'll be using the HiFi2000 Galaxy GX283 case and WBT NextGen 0210CU-ms RCA connectors:

http://www.audiophonics.fr/images/Vista_frontale_galaxy.jpg

http://www.tm3connections.com/productimages/display/SS-image-2011-01-03-4d21b88c65a87.jpg

Initially I'm just going to mount the PCB and transformer in the bottom of the case and not attached the RCA sockets etc to the fascias. This is because Uriah is working on a new remote volume control add-on (that I want to incorporate) and I'm not sure if that will need extra or fewer holes and I don't want to drill more holes than I need and ruin the case.

Once I get home I'll take some photos of the project in its current state. I'm afraid they won't be great though as my camera is rather old. :cool:

[HighFidelityGuy]

I'm afraid I don't have much of an update on this yet. I decided to buy a new camera to take the photo's but since placing the order they've run out of stock. :rolleyes: On top of that both the RCA sockets and case I ordered are also out of stock despite them being in stock when I placed the order. :rolleyes: So the project is on hold while I wait for those parts to arrive. I'm really annoyed as I was really looking forward to getting this working but I guess that's the way it goes. :(

[Reid Malenfant]

This looks interesting, consider me along for the ride :)

Pity it isn't balanced with XLR connectors :eyebrows:

[HighFidelityGuy]

Welcome aboard. :)

My sources and amps are all single ended, so no need for balanced attenuation for me at the moment. I think it should be possible to make a balanced version using two Lighter Note kits but Uriah would be the best person to ask.

It looks like I could be waiting 2 weeks or more for all the bits to arrive so I guess I'll have to find something else to do until then. :(

[Techno Commander]

Interesting looking project.

[24bit]

...waiting for an update...
very interesting indeed

[HighFidelityGuy]

I'm affraid I'm still waiting for parts. :(
I now have two pairs of Nextgen sockets with another pair to follow shortly. I've checked with the case supplier and some items on my order have come back into stock but others are still on back order. So things are going in the right direction, just veeerrrrryyyy slowly. :(

EDIT: I've still not been sent my sodding camera either. :rolleyes:

Incompetent retailers with crappy stock level systems are the bane of my existance. :steam:

[HighFidelityGuy]

Good news! The case and related hardware I ordered have finally been shipped and I should have the third pair of Nextgen sockets next week. :)

[HighFidelityGuy]

I finally have all the main hardware I need for putting the PCB in it's case and I've started work on building it all up. I'll hopefully upload some photo's tomorrow evening. :cool:

[HighFidelityGuy]

As promised I finally have some photos:

http://i2.photobucket.com/albums/y48/DTM2000/Hi-Fi/Lighter%20Note/Basic_Layout.jpg

This shows the basic layout on the bottom of the case. I so far just have the transformer bolted down. This has been mounted in it's own little metal case in an attempt to provide extra shielding. I'll put the lid on the small case later. You can also see the thick panel deadening material that I've used. This was applied with a heat gun and a small seam roller. I'll be using this on all of the panels I can to add extra mass and make the case more acoustically dead.

Here's a close up of the LDR's:

http://i2.photobucket.com/albums/y48/DTM2000/Hi-Fi/Lighter%20Note/LDRs.jpg

And here's a close up of one of the Nextgen connectors:

http://i2.photobucket.com/albums/y48/DTM2000/Hi-Fi/Lighter%20Note/Nextgen.jpg

That's it for now. My next job is to mount all the connectors on the back panel. I'll hopefully get that done later in the week. :)

[HighFidelityGuy]

Just a mini update:

I've finished enclosing the torroid in it's own little case and bolted down the main PCB:

http://i2.photobucket.com/albums/y48/DTM2000/Hi-Fi/Lighter%20Note/Basic_Layout02.jpg

The dual gang potentiometer on the left is for the volume control. As with the standard Lightspeed attenuator the quality of this pot doesn't really matter much as the audio signal doesn't pass through it, instead it controls the voltage of the LDR's. The pot on the right is to allow fine tuning of the channel balance. Again, no audio passes through this so the quality doesn't matter much.

I've drilled lots of holes in the back panel. Most of them are just pilot holes which will need widening, or in the case of the IEC socket cut out I'll join the holes together with my Dremel's cutting disc.

http://i2.photobucket.com/albums/y48/DTM2000/Hi-Fi/Lighter%20Note/Back01.jpg

I've also built up the rest of the case to help me measure things out make sure it all fits together.

http://i2.photobucket.com/albums/y48/DTM2000/Hi-Fi/Lighter%20Note/Case01.jpg (http://s2.photobucket.com/albums/y48/DTM2000/Hi-Fi/Lighter%20Note/?action=view&current=Case01.jpg)

That's about all I can do for now until I can get my drill stand and Dremel set up but I don't think I'll have time to sort that out until Wed or Thu....

[24bit]

nice!

[HighFidelityGuy]

Thanks. :)
I'm hoping to get some more work done on this tonight or tomorrow so I should have another update soon.

[Reid Malenfant]

Interesting looking critter that ;)

Did you get the thing built like that or was it a kit? Did you get supplied with a circuit diagram for diagnostic purposes if something isn't right more importantly :scratch:

Looking good so far :)

[HighFidelityGuy]

Hi Mark. It came as a kit and I had an enjoyable afternoon building it up. That's my favourite bit of the process. I don't mind making up cases but its a bit messy and time consuming.

I can't wait to get it all connected up and working. I've got a bit of a dilemma though as the designer is working on a remote volume control and input switching add-on that I want to include but I have no idea what that will involve as it's still in production. So I'm just hoping I've still got room to fit it all in. :eek:

With any luck the add-ons will get released around the same time as I've finished all the main bits. I'm sure it will all work out. :)

EDIT: I didn't get a schematic I'm afraid. I'm guessing the designer is keeping that to him self for now. To be honest the manual is so comprehensive that you're unlikely to run in to serious issues.

[john blackburn]

Hi Dave.

Is the polarity on your ldrs right? Just looking at the batch numbers stamped into them, one is 180 degrees out to the others.

If the dots are right it must be how they are, it just troubled me.

I have a lightspeed clone here, I think you will enjoy this when it is done.

John

[Reid Malenfant]

Is the polarity on your ldrs right? Just looking at the batch numbers stamped into them, one is 180 degrees out to the others.
Hi John, like standard resistors LDRs have no polarity, or at least none that i have ever heard of. The LEDs feeding them light certainly do though :eyebrows:

Besides which they are carrying & attenuating an AC signal so i think that kind of covers it :)

[HighFidelityGuy]

Hi Dave.

Is the polarity on your ldrs right? Just looking at the batch numbers stamped into them, one is 180 degrees out to the others.

If the dots are right it must be how they are, it just troubled me.

I have a lightspeed clone here, I think you will enjoy this when it is done.

John

Hi John,

I've double checked and the LDR's are definitely installed with the correct polarity. I've run the circuit and it works properly, so everything is ok so far. I appreciate your concern though. :cool:

[HighFidelityGuy]

Just a quick update....

I made a temporary front panel out of wood as I don't know how many holes I'll need to drill in the front yet, so I thought this would give me some extra flexibility without any risk:

http://i2.photobucket.com/albums/y48/DTM2000/Hi-Fi/Lighter%20Note/Temp_front.jpg

I've also finished drilling and cutting all the holes on the back panel and mounted the connectors I've currently got. I'll order some more RCA sockets soon. I couldn't afford a full set all at once as they're rather pricey:

http://i2.photobucket.com/albums/y48/DTM2000/Hi-Fi/Lighter%20Note/Back02.jpg

This photo shows the output socket layout with my planed wiring layout indicated by the white lines. I've tried to get the shortest signal path possible. As you can see I've included two pairs of outputs to allow for bi-amping:

http://i2.photobucket.com/albums/y48/DTM2000/Hi-Fi/Lighter%20Note/outputs01.jpg

This photo just shows the overall layout as it currently is. I've left one of the side panels off to give me better access for soldering the RCA connectors:

http://i2.photobucket.com/albums/y48/DTM2000/Hi-Fi/Lighter%20Note/Basic_Layout03.jpg

I will temporarily wire one of the inputs directly into the board for now and then re-wire this once I've got the new input switching add-on.

That's it for now. :cool:

[HighFidelityGuy]

I forgot to mention; the volume knob in the photo's is just temporary. As I don't know how the new remote volume add-on will work I decided not get any knobs yet.

I'll hopefully finish off the soldering tomorrow and start doing some testing of the unit in my system. :)

[HighFidelityGuy]

Another quick update....

I managed to get the inputs and outputs soldered this morning:

http://i2.photobucket.com/albums/y48/DTM2000/Hi-Fi/Lighter%20Note/outputs02.jpg

I've used solid core 5N pure silver wire which I've sheathed in Teflon tube. The input wires are much longer than they need to be at the moment. I've done that to try and prevent me from having to solder new lengths to the PCB once I get the input switching add-on installed. I'd rather re-solder the RCA connector ends if necessary as they will be more robust than PCB pads.

Here's a wider angle:

http://i2.photobucket.com/albums/y48/DTM2000/Hi-Fi/Lighter%20Note/Basic_Layout04.jpg

And here's the wee chap in his new home:

http://i2.photobucket.com/albums/y48/DTM2000/Hi-Fi/Lighter%20Note/Testing01.jpg

I've only listened to it for a few minutes but I can already hear some improvements in subtle detail, especially in the mid-range. The silver wire will take ages to burn in, so I'm expecting the sound to change over the next few weeks.

There is a slight problem though. Currently with the volume control set at the bottom I'm still getting quite a lot of signal coming through. So I need to do some tweaking of the trim pots on the board to see if I can improve that. Luckily the design includes lots of scope for tweaking.

I'll probably do that in a day or two as I want to do a bit more listening for now.

If you're wondering what all the mess sticking out of the top of my Caiman is, that's my version of the passive output mod featuring Italian poly caps and Russian Teflon film caps. It looks messy but sounds good. I've still got my Gator board to install. That's a job for another day. :cool:

[HighFidelityGuy]

Now that I've lived with the Lighter Note for a couple of days I can definitely say that I'm getting a better sound from my system than I was before. The most noticeable area of improvement is the midrange. This is more detailed and sweater sounding which has improved vocals quite a bit. I'm hearing more detail in the higher frequencies and I also seem to have a bit more bass punch and weight. The improvements in detail must be due to the fact I now only have a single resistor between my source and power amps. I think the improvements in the bass department are probably due to the better impedance matching I should now be getting.

There is a slight graininess on some tracks but I'm just putting that down the fact that more burning in is required. I'll see how that progresses.

I still need to do some tweaking to optimise the volume range but I've decided to leave that until I've installed my Gator board in my Caiman as that will move the goal posts again. I'm also going to re-case my Caiman in the same type of case as I used for my Lighter Note, so the two will match. Hopefully by the time I've got my Caiman Gatorised and re-cased, the remote volume control and LDR input switching add-on for the Lighter Note will have been released. Fingers crossed. :eyebrows:

[Reid Malenfant]

Is this thing passive Dave? It certainly looks that way judging by the input & output connections being in close proximity :scratch:

[HighFidelityGuy]

Yep, the input goes straight into a set of LDR's and then straight back out again. All the other components relate to the current source power supply and LDR control circuitry.

I put a link to the designers website in my first post. That should explain things better than I can. It's a very clever design that allows lots of tweaking of various parameters that affect the input and output impedance and volume range etc. This is where it differs from other passive attenuators and because of this it doesn't suffer from impedance mis-match issues as much. It certainly seems to work well. :)

[HighFidelityGuy]

I had a helpful email from Uriah Dailey, the Lighter Note's designer the other day. He suggested that I try connecting signal ground to chassis ground as that may smoothen the sound slightly. He also suggested removing the 250k resistors near the input/output pads at the rear of the board. Apparently he found that these can cause some issues at higher volumes. So I'm going to remove the resistors and implement a simple ground lift switch that will allow me to quickly switch between both grounding methods for evaluation.

Uriah also mentioned that the input switching and remote volume control add-on's are well under way. It sounds like the input switcher is almost ready but the remote volume needs some more work. So it's good to know these are getting closer to being released. :)

[HighFidelityGuy]

I feel I should point out that I made a mistake in my last post. Signal ground shouldn't be connected to chassis ground. Uriah suggested connecting the 0V centre tap from the transformer to chassis ground, I just misread his email.

I'm in the process of doing this and the 250K resistor removal.

[Zuk]

any more news on your progress with this?

Cheers

Simon

[MartinT]

If you're wondering what all the mess sticking out of the top of my Caiman is, that's my version of the passive output mod featuring Italian poly caps and Russian Teflon film caps. It looks messy but sounds good. I've still got my Gator board to install. That's a job for another day. :cool:

Dave - do I read correctly that you're replacing your passive coupling with the active Gator board? I'd be very interested in this as I'm using passive coupling with Auricaps but I also have a Gator board which I've not yet implemented. What do you hear?

[HighFidelityGuy]

Hi Simon. I built the input selector add-on a couple of months ago but I've not had chance to try and fit it in the case yet. It's somewhat bigger than I was expecting. I also need to find a way of modifying one of the inputs so that it bypasses the volume control for my home theatre bypass. I need to get back in touch with the designer about that. I'll hopefully make some progress with this soon.

[HighFidelityGuy]

Dave - do I read correctly that you're replacing your passive coupling with the active Gator board? I'd be very interested in this as I'm using passive coupling with Auricaps but I also have a Gator board which I've not yet implemented. What do you hear?

Hi Martin, that's correct. I fitted the Gator a while ago. It's a bit tricky trying to remember the exact differences I heard but I wrote something about it at the time, so hopefully a quick search should turn up my post. I think I found that the level of detail was pretty much the same between the two methods but the Gator had more oomph. The only problem I had was that I later noticed the whistling noise that several people with Murata regs encountered. I fixed that with Dexa regs. I believe you have Paul Hynes regs now, so you should be fine. I think it's worth trying a Gator. :)

[MartinT]

Thanks, Dave. I found your post and will be putting the Gator in tomorrow for a trial.

http://theartofsound.net/forum/showpost.php?p=238044&postcount=161

[MartinT]

Gator in and it's doing a good job. Sounds fine to me, not too much gain and a bit more welly in the deep bass. It's nice to have the headphone functionality back, too.