Skip to main content

Posts

Showing posts from August, 2017

Octal EAR 834P phono preamp

During my visit to NYC earlier this summer, my buddy Ding loaned me his home-brewed octal version of the EAR 834P phono preamp using 3 x 6SL7 octal tubes. Powering the preamp is a General Radio 1201-B tube regulated power supply.

Ding is not into boutique parts. Instead, he used carbon film resistors, mylar coupling capacitors and electrolytic caps gathered from Hamfests and surplus stores. Proper grounding and parts placement ensured a very quiet phono stage.

Traditional tube phono stages like the classic Dyna PAS 3 and Marantz 7 employed active RIAA EQ networks inserted in the negative feedback loop from the final stage to the input stage. In the 834P, Tim de Paravicini used active RIAA EQ with a clever twist - theEQ network is fed from the cathode follower output back to the second stage only. IMO, the benefits of this topology are: a 1st stage unimpeded by negative feedback, low noise and low output impedance.

I've been enjoying this phono stage so much that I'm inspired …

Lens Filter Ring Vise

I recently fixed two lenses from my collection which had dented filter rings using this $36 tool from Micro-Tools.

The tool didn't come with instructions but using it is pretty straightforward. As a precaution, I covered the front element with cardboard. First, I positioned the moving jaw of the tool on the dent and aligned the threads from the jaws of the tool to mate with the threads of the filter ring. Then I gently spread out the jaws of the tool to press out the dent. I cannot over emphasize going slowly but surely!




The tool has paid for itself ;)