I've been meaning to post a final follow up to my transformer research and kept forgetting, I blame a distinct lack of sleep!Anyway, as previously mentioned the first shielded transformer that I purchased from SUMR was not sufficient to completely quell the buzzing that I was hearing when using IEMs with the beta22 that I'd built. Therefore I asked Richard what it would cost to get a fully shielded and potted transformer from him, below is his response.
[Quoting SumR]The toroid encapsulated and shielded in the can would costs;
Toroid US $ 50.00 RC0080 044 1
Encapsulated US $ 20.00 Black with centre bolt hole.
Postage US $ 20.00 Canada Post
Total: US $ 90.00 .
He also noted that the final size of the trafo would be approximately 4-1/8" in diameter and 2-1/16" high. The transformer leads can be made to exit either on the bottom or the side of the enclosure, at the buyer's option. And the part number listed above for the transformer is for a 120V primary, dual 30V secondary, 80VA transformer. Here's a picture of what the finished product looks like:
Given that the standard Avel trafo will run around $40 (shipped) and has been known to cause hum issues I would seriously consider using one of these fully shielded units since it would mean that single box, closely packed layouts could be used. That would save the hassle of a separate PS enclosure and the resultant umbilical cord and connectors. I may in fact try this on my next beta build. 
I hope that this information is help to other builders.
View Post: DIY Workshop » β22: A discrete, cascoded, fully complementary, pure class A amplifier (part 3)
posted 08-08-2008 11:39 AM CST (US) 
