47 Labs 0247 vs. RJM Audio Sapphire

I wasn't even aware that the folks at 47 Labs were developing a headphone amplifier until after the Sapphire was finished, and I'm sure they didn't know what I was working on, so it's all the more remarkable just how similar the two designs are. Two separate answers from two separate people sharing the same general design philosophy.

Similarities:

- Solid state op amp voltage stage front end and solid state push-pull buffer running open loop for the output stage.
- Gain of 5-6x (14-16 dB)
- 20-30 mA bias current in the output stage.
- All BJT circuit** (see footnote)
- Use of "diamond buffer" circuit element. (Albeit in very different ways)
- 10 V voltage rails, split supply.

Differences:

- My voltage stage is an OPA134, or any 8 pin DIP op amp IC. 47 Labs voltage stage is a fully discrete current feedback op amp with a diamond buffer...

Back by popular demand, I have decided to go ahead and prepare full kit version of the VSPS300, Phonoclone 3, and Sapphire projects.

10 kits of each project will be available - contact me to reserve.

Phonoclone Kit : $125 (10 availble) Set of two boards and components to populate.
VSPS 300 Kit : $117 (10 available) Set of two boards and components to populate.
Sapphire Kit : $113 (10 available) Set of two boards and components to populate.

Kits will be shipping shortly after the New Year.

Current status: necessary parts shipped from Mouser, should be able to assemble kits this weekend. Also have to prepare the documentation.

RJM Audio Kits

Update: kits were sold, but another run of boards is going ahead!

There will be 10 kits available, at a cost of $100 each. The boards (rev. 14a1) and all parts for the boards will be included. Shipping is included.

Info here and here.