[Beefy]

Quote:

Originally Posted by amb /img/forum/go_quote.gif It's hard to shield a transformer well, after the fact. n_maher did that on his first β22 build, and it wasn't trivial (involving a totally enclosed box, lined with special material from EMF Safety Superstore- "Electromagnetic Field Detection & Protection". ). It would have been much better to use a toroid that was manufactured twith built-in shielding. But that shouldn't be an issue for you since you're using separate enclosures for the amp and PSU. Just keep them some distance apart.

For what its worth, I bought a shielded and encapsulated transformer from SumR for my MMM. The amp now has less background hum with the shielded transformer sitting directly on top of the amp box than it did with the old unshielded transformer some distance away from the amp.

 

[TwinFinnley]

Quote:

Originally Posted by amb /img/forum/go_quote.gif It's hard to shield a transformer well, after the fact. n_maher did that on his first β22 build, and it wasn't trivial (involving a totally enclosed box, lined with special material from EMF Safety Superstore- "Electromagnetic Field Detection & Protection". ). It would have been much better to use a toroid that was manufactured twith built-in shielding. But that shouldn't be an issue for you since you're using separate enclosures for the amp and PSU. Just keep them some distance apart.

The toroid I bought was the Avel Lindberg Y236355 (25+25V @ 80VA). I have no idea if it has "built-in" shielding, but I'm guessing that it doesn't - it looks pretty bare-bones.

So Mu-Metal is the best way to go or the stuff that n_maher used?

 

[TwinFinnley]

Quote:

Originally Posted by Beefy /img/forum/go_quote.gif For what its worth, I bought a shielded and encapsulated transformer from SumR for my MMM. The amp now has less background hum with the shielded transformer sitting directly on top of the amp box than it did with the old unshielded transformer some distance away from the amp.

Thanks Beefy, looking them up right now.

EDIT: I'm looking at some material that I might use to line a box dedicated to the transformer, would this work?

 

[Beefy]

I'll save you the trouble: SumR - Richard Sumner Technology

For my custom transformers, I just sent Richard an email. I asked for fully shielded and encapsulated, in the ratings, primary and secondary config I needed...... he quoted, I paid, I received transformers.

Easy as pie. Even easier if you can just ask him to shield and encapsulate one of his off-the-shelf models. You would probably want the RC0080 924 2 as listed here: SumR - Richard Sumner Technology:: Power Dual

 

[Dougie085]

Mu-metal has been said to have the best shielding properties. There was a place over seas that sold sheets of it. Not really sure about state side, maybe someone on ebay has some? I'm not sure about what n_maher used. I've just been told several times that Mu-Metal is the best to use? There is some test data out there if you look.

 

[Dougie085]

Quote:

Originally Posted by Beefy /img/forum/go_quote.gif I'll save you the trouble: SumR - Richard Sumner Technology For my custom transformers, I just sent Richard an email. I asked for fully shielded and encapsulated, in the ratings, primary and secondary config I needed...... he quoted, I paid, I received transformers. Easy as pie. Even easier if you can just ask him to shield and encapsulate one of his off-the-shelf models. You would probably want the RC0080 924 2 as listed here: SumR - Richard Sumner Technology:: Power Dual

How much are his shielded units? I imagine its a good bit more then the standard ones.

 

[TwinFinnley]

Quote:

Originally Posted by Dougie085 /img/forum/go_quote.gif How much are his shielded units? I imagine its a good bit more then the standard ones.

They are around $80 +/- for 80VA with shielding.

 

[Dougie085]

Ah that's not to bad then. 80VA might not work for a power amp of course

 

[Beefy]

Quote:

Originally Posted by Dougie085 /img/forum/go_quote.gif How much are his shielded units? I imagine its a good bit more then the standard ones.

Quote:

Originally Posted by TwinFinnley /img/forum/go_quote.gif They are around $80 +/- for 80VA with shielding.

Sounds about right. I paid just over CA$60 each for 30VA units.

 

[linuxworks]

anyone buy a 24v trafo for an *m3*, while we're on the subject?

I'm thinking that the lowest they offer on the standard page (20va) is going to be enough; for the m3 that won't be (ever) driving spkrs, just phones.

I have not bought a SUMR yet but I might try a shielded one for the m3, first.

any recs for which one to get?

 

[Beefy]

Quote:

Originally Posted by linuxworks /img/forum/go_quote.gif anyone buy a 24v trafo for an *m3*, while we're on the subject?

Yes, I bought one for mine as stated above...... 30VA, 115+115 primary, 12+12 secondary.

I bought the 30VA because the encapsulation was the same physical size for both ratings and moar is betterer.

I think that the RC0030 912 2 is what I got, plus fully shielded and encapsulated, for just over CA$60.

 

[linuxworks]

and let me put a plug in for a VERY remote install; putting JUST the trafo in a box and throwing that on the floor way far away from the main amp:

and then the s22 goes in the same case as the amp boards.

no hum at all

 

[linuxworks]

Quote:

Originally Posted by Beefy /img/forum/go_quote.gif Yes, I bought one for mine as stated above...... 30VA, 115+115 primary, 12+12 secondary. I bought the 30VA because the encapsulation was the same physical size for both ratings and moar is betterer.

good point. thanks! I may just order this

 

[TwinFinnley]

I was just looking at some of Thrice's Rockhopper b22 builds and got to wondering about what ever happened to him? Anyone know? Seemed like he made some really solid amps.

 

[DoYouRight]

dunno he did make a kickin 6 board b22. He is awol though.