LDR BASED VOLUME CONTROL
I used to build an LDR based volume control with all premium parts including a dual spit chassis and on board power supply. I didn't manufacture the LDR printed circuit board but rather purchased it as an OEM/DIY part from Tortuga Audio. Over time, Tortuga changed this board several times and also has changed the display (7 segment to OLED type) and made other changes. Rather than try to keep up with their changes, I've decided to only build a volume control to accompany my own triode tube buffer/harmonizer if a customer would like one. I'm not going to build, inventory, and sell these units on their own but rather on a customer request only.
After much experimenting, I found that by using a low cost chassis sold by Goldpoint I could reduce the cost of using a substantial aluminum chassis while not affecting sound quality AT ALL. I used to build these using the ultimate vibration chassis control and circuit design methods I've found worked well for other electronic components. However, it didn't seem to matter if I placed the LDR printed circuit board in the best isolated and heavy chassis or one that was "adequate". There really wasn't a sound quality improvement between the two so I've moved on and now use the low cost Goldpoint chassis that I purchase directly from them online.
The Goldpoint chassis is tiny (6" x 6" x 2") and satisfies my need to attenuate the buffer/harmonizer signal. The Apple Remote that I use to control this volume control and the microprocessor features make it one of the highest quality volume controls available for my use and is the reason why I recommend it for my customers and why I still use this LDR solution instead of another. Only an auto former or transformer based unit would be better but at a much higher cost and without the usability features that make this LDR unit really nice to use. The extra cost and lack of usable features (remote control, impedance modification, etc) doesn't justify moving to an auto former or transformer solution - at least, not for me.
I'm willing to build one of these LDR volume control units only if you purchase my buffer/harmonizer and need one to accompany it. You can purchase your own Tortuga passive preamp directly from them or build your own unit if that is all that you desire. However, I can assure you that the sound quality of the unit I build will be the best since I've gained first hand knowledge and hands on experience regarding what works and what doesn't. The Furutech FP901(R) rhodium chassis jacks and the solid silver hookup wire make a huge difference and I would not build this unit without those two items included. They do make a big and positive sonic difference as I've learned by building these units at the highest possible level (and of course with the accompanying expense) and many times.
Because the Goldpoint chassis is very small, I typically build it with two pair of RCA chassis jacks, one pair for input and one pair for output. This would allow for connecting a DAC (for example) to your audio system. If you also have a turntable that you would like to use, I can fit in three pair of RCA chassis jacks to provide for two single-ended input pairs and one output pair. The Tortuga pcb allows for up to 3 switchable inputs so no problem adding a 2nd. This of course will increase the cost of wire and one more pair of FP901(R) chassis jacks. Also, I won't build a balanced volume control unit for the main reason that I won't build a balanced triode buffer/harmonizer unit. It just doesn't make economic sense and is a waste of valuable money by having to use twice the number of the same parts and not improve audio quality. Save your money and invest it in other more productive ways.
You can power this LDR volume control using an inexpensive iFi 12V power supply and that would be my first low cost power supply recommendation. However, that solution won't provide the ultimate sound quality. Instead, I use personally use a Kecees dual power supply and the 12V cable from one of the two voltage adjustable outputs. The Kecees dual supply isn't that expensive and can also be used to power a 2nd digital component such as a USB to AES converter. I use mine to power a 9V Matrix USB/AES converter. The Kecees makes a really nice improvement over the iFi supply sound quality and won't be an excessive expense. Rather, it's my best recommended solution and as far as anyone needs to go to produce the highest level of sound quality without spending precious funds. If you're interested in one of these LDR Volume Control units AND ONLY IF you also are purchasing an Aum Acoustics Triode Buffer/Harmonizer, let me know and we can discuss putting one of these really nice units together for your use. This is what I use in my own system and I wouldn't use anything else.
Here are some photos of this unit as I typically build it: