Or you can do volume, input selection, Mute and Infrared remote control, 8 bits, 256 steps.
Preamp Control - Volume, input, mute, remote
Preamp Control - Volume, input, mute, remote
Ive built a balanced version of this, and using (dual) Pass Labs B1 Buffers it sounds superb.
You have an elegant design which is made practical by the falling price of high end mini relays and precision parts, and a huge advance in sound quality over the old ALPS potentiometer. I was introduced to this concept just a few weeks ago and love it.
I do not have access to a machine shop to make the customized front panel and find ordering small quality parts a little intimidating. (Used to do that when I built from scratch in the 70's) The bay offer is an easy way out and offers opportunity for experimenting.
I found a package on ebay at a reasonable price. The 63 dB volume attenuation should be adequate for most preamp application.
HIFI Remote volume Controller peramp pre-amplifier audio 128 steps /4 way input | eBay
I like the 308mm enclosure depth which would allow easy addition of buffer card or upgrade of transformer. Any first hand experience of this stepped relay ladder volume unit?
I ordered this passive preamplifier after Christmas and received it 11 days into 2019. It came with no instruction. Once you figured out the remote battery type and how to install it, you are in business.
I like the 308 mm deep enclosure which has lots of room for expansion. Most of all, it has not sound of its own as it should be in passive preamp. The remote works surprisingly well and much more responsive than the Apple remote. The 0.5 dB volume control is ideal. After listening to it for 5 weeks and confirm everything is stable, I proceeded to add an output buffer.
I ordered this JC-2 line amplifier board from the same seller.
It is a simple JFET input, symmetry topology circuit. It is not the ultimate line amplifier, but lots of performance for my purpose. The seller has explicit instruction for trimming, which is rare on the bay. The toroidal is from Antek with 2x18V output.
The process is not difficult, just need a lot of careful work. The connections on the preamp are all hard soldered and covered with hot glue. Good for durability, but more work for the DIYer. I ended up destroying the small on-off switch at the back and just threw it away.
I finished the preamp update earlier today. The sound is very neutral as I expect. For just over $200 in outlay, I am very happy with the result.
There's always Rod Elliott's approach; good to integrate into an existing system:
Infrared Remote Control for Audio
Infrared Remote Control for Audio
How does an IR remote control directly related to a stepped relay ladder volume control?
The main subject is the input selection and volume control. The remote is a nice bonus.
Another lesson learned
My lesson may be obvious to many of you.
When I added the JC-2 output buffer board, I have to do some drilling to install the board and its transformer. I also had to relocated the existing transformer. All were just 12 small round holes for the standoff or mounting screw.
I used a powerful shop vacuum to clean after each drill. Same procedure that I did on 2 DAC box and a crossover. The preamp sound very good the first 2 hours after I finished. But the next day, I heard some popcorn noises occasionally as if there were some arcing. It did not get any worse.
I opened the enclosure and looked closely. Then I saw some small debris at one box corner and many fine metal dust on the box floor. I took the enclosure apart and wiped it with fresh paper tower. Put it back together. Now the preamp is quiet again.
My lesson may be obvious to many of you.
When I added the JC-2 output buffer board, I have to do some drilling to install the board and its transformer. I also had to relocated the existing transformer. All were just 12 small round holes for the standoff or mounting screw.
I used a powerful shop vacuum to clean after each drill. Same procedure that I did on 2 DAC box and a crossover. The preamp sound very good the first 2 hours after I finished. But the next day, I heard some popcorn noises occasionally as if there were some arcing. It did not get any worse.
I opened the enclosure and looked closely. Then I saw some small debris at one box corner and many fine metal dust on the box floor. I took the enclosure apart and wiped it with fresh paper tower. Put it back together. Now the preamp is quiet again.
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