Infra Red Remote Control LDR Volume Control.

Paul Hynes · « **on:** 14 Nov 2010, 01:02 pm »

Infra Red Remote Control LDR Volume Control.

I have been using LDR volume control for many years in the form of an L-pad with a series resistor and a shunt LDR without knowing anything of George Stantscheff’s Lightspeed volume control. This was the same configuration George used in his early products. George had a further idea of making the series element of the L-pad an LDR too and this improved the performance even further. A couple of years ago I came across a thread on DIY Audio that was devoted to George’s Lightspeed design and decided to try his latest configuration in my system. It was an immediate upgrade on the previous series resistor/shunt LDR design. As far as I am concerned it is without doubt the best method of volume control I have ever used with respect to sound quality.

Please note that Lightspeed is the name George has been using for his production volume controls and this should not be used for any of the LDR volume control clones that are now available. For those interested in George’s product he can be contacted at georgehifi@optusnet.com.au

The Lightspeed volume control uses a standard dual potentiometer to adjust the current in the LDR LEDs thus varying the signal attenuation by controlling the LDR resistance. There is no remote control option on the Lightspeed. I am used to the convenience of remote control so decided to design one for myself using voltage controlled current sources interfaced with infra-red control modules. I mentioned this on Georges Lightspeed thread on DIY Audio and a lot of interest was shown. I decided that it would be a good DIY project to add to the thread and with George’s blessing offered a group buy to those who had shown interest. The circuit was published around a year and a half ago and a printed circuit board run was commissioned. I offered a set of boards for those with suitable DIY skills and also built and tested modules for those with less experience with a soldering iron. The boards and modules were priced to cover the provision costs with no additional business profit added.

The VCCS LDR current source drivers can be configured for single ended or balanced signal processing and provide Volume up/down and Channel Balance left/right. The VCCS can be controlled with four momentary switches fitted to your preamp front panel and/or used with the Infra Red Transmitter and Receiver modules to give the remote control function. The LDRs are not provided with the module. They should be purchased in matched sets from Uriah Daily at http://www.buildanamp.com/

Some technical information and photos :-

VCCS circuit
http://i700.photobucket.com/albums/ww7/paulhynes/VCCS1C.jpg
IRT circuit
http://i700.photobucket.com/albums/ww7/paulhynes/IRT1A.jpg
IRR circuit
http://i700.photobucket.com/albums/ww7/paulhynes/IRR1A.jpg
VCCS photo
http://i700.photobucket.com/albums/ww7/paulhynes/VCCS1A1.jpg
All modules photo
http://i700.photobucket.com/albums/ww7/paulhynes/LightspeedRemoteControl.jpg
VCCS with ultra low noise regulators
http://i700.photobucket.com/albums/ww7/paulhynes/Picture2019.jpg
LDR remote control review
http://www.tnt-audio.com/accessories/ph_ldr_volume_control_e.html

There is still plenty of interest for the VCCS control system and because of this the boards and modules are still available for anyone wanting to set up a DIY infra-red remote controlled LDR volume control.

The prices are still the same as when they were introduced and are :-

VCCS (voltage controlled current source LED control)
PCB £12
Built module £60
IRT (transmitter module) and IRR (receiver module) sold as a matching pair
PCB £13.77
Built modules £49.60
Low noise regulators for the VCCS (2 x shunt and 1 series)
Built and tested modules only - £96 for the three.

Insured air carriage and packing will be charged at cost and is subject to destination. This can be quoted at the time of enquiry.

If you have any questions about application of the modules post them on this thread for discussion and this will also act as a knowledge source for others considering LDR volume control.

Regards
Paul

TomS · « **Reply #1 on:** 14 Nov 2010, 02:58 pm »

Paul,

Can you please explain how this setup would be configured for a balanced option?

Thanks!

Tom

poseidonsvoice · « **Reply #2 on:** 14 Nov 2010, 03:29 pm »

Quote from: TomS on 14 Nov 2010, 02:58 pm

Paul,

Can you please explain how this setup would be configured for a balanced option?

Thanks!

Tom

+1

And, could you please give us a price for a fully tested, fully built modules for balanced purposes including remote? Please also include the price for the ultra-low noise regulators a well.

And any specifications to ensure compatibility?

Thanks!

Anand.

Paul Hynes · « **Reply #3 on:** 14 Nov 2010, 06:28 pm »

Hello Tom,

I will try to find some time over the next few days to draw the configuration for series balanced operation and for shunt balanced operation. I will post as soon as it is done.

Hello Anand,

I have added the cost of the low noise regulators to the first post. The VCCS set up for balanced operation costs the same as the single ended version.

The number of LDRs and the way they are wired dictates how they operate. This will be clear once I post the drawings for balanced operation. The 12 volt series regulator on the VCCS board is changed for an 18 volt regulator and the shunt regulator at the bottom of the reference chain is set up to operate at a higher voltage level to allow series connection of LDR LEDs.

The overall impedance of the volume control depends on the current source range setting resistor values. These resistor values can be changed to suit your system requirements.

Regards
Paul

catastrofe · « **Reply #4 on:** 4 Dec 2010, 01:39 pm »

I'm using George's LSA now and I love it. However, I have balanced outs on my DAC (PS Audio Perfectwave) and balanced ins on my monoblocks (NAT Audio Generators). I'd be very interested in a fully built/tested balanced LDR with remote.

Paul Hynes · « **Reply #5 on:** 4 Dec 2010, 07:30 pm »

Sorry about the delay Tom, here is a re-draw of the circuitry to allow balanced operation :-

http://i700.photobucket.com/albums/ww7/paulhynes/VCCS4.jpg

Catastrofe, are you looking for built and tested modules so you can finish the build yourself?

Regards
Paul

TomS · « **Reply #6 on:** 6 Dec 2010, 09:03 pm »

Quote from: Paul Hynes on 4 Dec 2010, 07:30 pm

Sorry about the delay Tom, here is a re-draw of the circuitry to allow balanced operation :-

http://i700.photobucket.com/albums/ww7/paulhynes/VCCS4.jpg

Catastrofe, are you looking for built and tested modules so you can finish the build yourself?

Regards
Paul

Paul,

Thank you. It is very clear now. Since you now have 2 LDR's in series, which devices need to be matched for balanced configuration? I just want to make sure that it is achievable given Uriah's matching method, lot sizes, etc. I could probably send a note direct to him if you'd prefer.

Tom

Paul Hynes · « **Reply #7 on:** 7 Dec 2010, 12:52 pm »

Hi Tom,

Ideally all the series LDRs should be matched together and all the shunts matched together. However, Uriah has found it hard to get four LDRs matched so if you get matched pairs you can use a matched pair for phase and anti-phase signals in each of the left and right channels series LDRs and the same with the shunt LDRs. In other words a matched pair for the two LDR LEDs in each op-amp control loop.

Any channel imbalance can be adjusted with the balance control on the VCCS module.

Regards
Paul

TomS · « **Reply #8 on:** 7 Dec 2010, 01:16 pm »

Quote from: Paul Hynes on 7 Dec 2010, 12:52 pm

Hi Tom,

Ideally all the series LDRs should be matched together and all the shunts matched together. However, Uriah has found it hard to get four LDRs matched so if you get matched pairs
you can use a matched pair for phase and anti-phase signals in each of the left and right channels series LDRs and the same with the shunt LDRs. In other words a matched pair for the two LDR LEDs in each op-amp control loop.

Any channel imbalance can be adjusted with the balance control on the VCCS module.

Regards
Paul

Thanks Paul! I've been chatting with Uriah and he indicated that while you could TRY it, he only guarantees matching at 4 points in the LDR's, which isn't enough for balanced use. Based on that he doesn't recommend the balanced option for now but I may still try the single ended just to get a feel for it.

Tom

Paul Hynes · « **Reply #9 on:** 8 Dec 2010, 10:55 am »

Hi Tom,

I can see what Uriah is saying. Because of the limited matching points there may be errors in phase balance at certain settings. I do not see this as a major issue as the effects will be relatively benign sonically in a domestic system. The benefits of using LDRs as the volume control element should far outweigh the lack of absolute phase balance. Absolute phase balance through the audio band and at all operating levels is rare in balanced equipment. This does not stop people using balanced equipment. Channel balance can be adjusted via the balance control if you build a VCCS module modified for balanced LED control.

I’m sure a couple of guys have set up balanced LDRs successfully. Try asking on the Lightspeed thread on DIY Audio. If they have had problems with set up I’m sure they will be willing to share their experience.

Does anyone on this forum who has set up a balanced LDR volume control care to share their experience?

Regards
Paul

NicMac · « **Reply #10 on:** 22 Dec 2010, 02:55 pm »

Quote from: Paul Hynes on 8 Dec 2010, 10:55 am

Does anyone on this forum who has set up a balanced LDR volume control care to share their experience?

Hi everybody,
I have assembled a balanced LDR volume control using series connected LDR's and Paul's VCCS modules set up specifically for this purpose and with upgraded power supplies. I have tested the volume control with LDR's paired by myself and it sounds perfectly great. I would not know how phase unbalance sounds but if this is what I'm hearing then it is truly a very pleasant sound!
I have not boxed the project up yet as I'm not satisfied with the "bird-nest" of LDRs that I created for testing. There is not room for the LDRs on the VCCS module so I would like to place them neatly on a pair of small PCBs (one per channel) together with the XLR connectors. I have no experience in PCB layout so I'm still hoping somebody could help me on this embarrassing and trivial problem.
Cheers,
Nic

ua100k · « **Reply #11 on:** 15 Jan 2011, 07:14 pm »

Quote

There is not room for the LDRs on the VCCS module so I would like to place them neatly on a pair of small PCBs (one per channel) together with the XLR connector

Why don't you put the LDR;s directly on the input and output connectors. You would have to place the connectors strategically close. This would reduce introduced wire length and other noise.

serengetiplains · « **Reply #12 on:** 20 May 2011, 01:33 am »

I just now read this thread and want to pipe in with my experience with LDR volume controls. I have owned several types of volume controls---Placette volume control (Vishay resistors + contacts), various transformer volume controls (including Serge Schmidlin's Silver Rock), etc. None of these came even close to George's Lightspeed. Direct comparisons, for instance, with a Placette and the Silver Rock---no slouches in passive pre's---were obvious: the Lightspeed trumped. And by a wide margin. It took me the whole of probably 30 seconds to judge the Lightspeed's superiority in these comparison.

One issue I piped in on in the DIY Lightspeed thread was the stability of the voltage supply feeding the Lightspeed. A varying voltage across the powered component of the LDR theoretically should modulate, though with the LDR's characteristic response-delay, the music signal passing through the resistive component. I experimented with this and found, to my observation, that a rock-solid supply indeed made a small sonic difference. I was then unaware of Paul's excellent supplies and used an Audiocom Invisus regulator to feed the LDR unit. I would think a Lightspeed modified with a Hynes series reg would be ideal. My 2¢.

richidoo · « **Reply #13 on:** 20 May 2011, 03:44 am »

Are the remote control PCBs still available, Paul? Thanks.
Rich

Paul Hynes · « **Reply #14 on:** 20 May 2011, 09:52 am »

Hi Rich,

I have 60 sets of remote control boards left. Prices are still the same but shipping cost may be slightly different from the original list. If you let me know what you want I can work out the shipping cost for you.

Regards
Paul

uglymusic · « **Reply #15 on:** 10 Jun 2011, 08:18 pm »

Hi Paul

A bit of a simple question, really.

Aside from your boards and the LDRs, I understand I'll need a PSU. What would I actually need to buy? Do you offer a finished PSU that I could purchase?

TIA

Dave

ebag4 · « **Reply #16 on:** 2 Aug 2011, 01:07 pm »

Are these the same remote controls Uriah sells with his Lighter Note volume control?

Best,
Ed

Paul Hynes · « **Reply #17 on:** 2 Aug 2011, 03:25 pm »

As far as I am aware they are not the same as I have no agreement in place with Uriah.

Regards
Paul

pardales · « **Reply #18 on:** 2 Aug 2011, 05:12 pm »

Any word on a fully assembled, finished product, cost, pics, or will this only be DIY?

Paul Hynes · « **Reply #19 on:** 2 Aug 2011, 05:49 pm »

I have an agreement with George Stantscheff not to sell finished products that have a volume control using his Lightspeed configuration. George was happy to allow the use of the remote control modules for DIY projects or the PCBs for total self build.

Regards
Paul