I “retailed” my Bryston 2B LB PRO

I love the Bryston 2B, its powerful and smooth and is only one rack unit tall. I have a pro model that I got, presumably after it was scrapped by the Canadian Broadcasting System. Its got some wear on the outside, but the electronics are in pristin condition. I replaced the electrolytic caps a couple of years ago, and when I recently re-capped a retail model 2B that I got on ebay, I replaced the stock 4700 uf power supply caps with 6800 uf ones, which due to newer technology is the same size as the original 4700 uf caps were.

The pro model is designed for use in a professional facility and does not have an on/off switch. It also comes with balanced XLR jacks in the back which are standard in the industry. Well, its kind of a hassle to hook these up to my un-balanced home stereo stuff–I was using a high fidelity balanced to unbalanced transformer.

When reading an ad for a 2B on ebay, the seller noted that he had replaced the balanced inputs on a pro with the consumer standard RCA jack. He noted that the input to the amp proper is single ended, not balanced, and the interface to the XLR jack is done with a small adapter circuit that contains an op amp, and horror of horrors to an audiophile, passes the signal through an electrolytic capacitor on its way to the amp. I studied the circuit diagrams of the pro and retail models and saw that the retail simply took the input from the RCA jack and fed it straight to the input pin on the amp module circuit board. I resolved to implement it that way.

To physically mount the RCA jack onto the XLR hole in the chassis, I found an adapter for that very purpose on ebay. They were expensive to my thinking, about $20 each, but when I received them I noted they were made from aluminum and were mechanically and electrically very sound, so to speak…

Working with the tiny shielded cable was tedious but I was able to create good solder connectios on the jacks. Below are some after pictures. The amp works great with the RCA jacks and this is a welcome development for me. Once I was done the top went back on and it was placed back into service.