[f] AMB on Facebook

Transformer covers

beta24

Transformer covers

Postby trampo » February 2nd, 2020, 1:41 pm

I have just finished my B24 build and am getting some buzzing on the output, which goes away if I mount the transformers outside of the case. This brings me to the conclusion that the transformers need some sort of isolation or need to be changed. But before I spend money on new transformers does anybody have experience with the steel covers that can be purchased from ebay. These would be my first choice as they are a lot cheaper than new transformers but I can't find any useful information on them. Any advice would be appreciated.
trampo
 
Posts: 23
Likes: 1 post
Liked in: 0 post
Joined: November 22nd, 2015, 3:51 pm
Location: Manchester
Country: United Kingdom (uk)

Re: Transformer covers

Postby amb » February 2nd, 2020, 1:57 pm

What kind of transformer do you have? I specifically recommend toroidal transformers with built-in shielding construction. You can try a steel can over an unshielded transformer, but it won’t be the same.
User avatar
amb
Site Admin
 
Posts: 10556
Likes: 191 posts
Liked in: 506 posts
Joined: March 29th, 2010, 9:49 pm
Location: Sunnyvale, CA
Country: United States (us)

Re: Transformer covers

Postby trampo » February 2nd, 2020, 2:13 pm

Here's the link to it https://uk.rs-online.com/web/p/toroidal ... s/1234032/ I thought it was isolated but it doesn't mention it in the specs.
trampo
 
Posts: 23
Likes: 1 post
Liked in: 0 post
Joined: November 22nd, 2015, 3:51 pm
Location: Manchester
Country: United Kingdom (uk)

Transformer covers

Postby amb » February 2nd, 2020, 2:29 pm

It’s encapsulated, which is nice, but there is indeed no mention of any magnetic shielding.

Other than the Plitron transformer I used for the reference build, several other people in these forums used Toroidy transformers from Poland with success.
User avatar
amb
Site Admin
 
Posts: 10556
Likes: 191 posts
Liked in: 506 posts
Joined: March 29th, 2010, 9:49 pm
Location: Sunnyvale, CA
Country: United States (us)

Re: Transformer covers

Postby trampo » February 2nd, 2020, 3:55 pm

Would there be any downside to using them in a separate box?

If so would I mount the rectifiers and caps with the transformers or in the amp casing?
trampo
 
Posts: 23
Likes: 1 post
Liked in: 0 post
Joined: November 22nd, 2015, 3:51 pm
Location: Manchester
Country: United Kingdom (uk)

Re: Transformer covers

Postby amb » February 2nd, 2020, 3:59 pm

The downside is the secondary wire lengths will be much greater which adds impedance, and will cause the voltage (as seen by the load) to fluctuate as the current demand changes. This is normally not a big issue with devices that draw a small amount of current or use regulated power supplies, but for the β24 output stage neither of these is true.
User avatar
amb
Site Admin
 
Posts: 10556
Likes: 191 posts
Liked in: 506 posts
Joined: March 29th, 2010, 9:49 pm
Location: Sunnyvale, CA
Country: United States (us)

Re: Transformer covers

Postby trampo » February 2nd, 2020, 4:07 pm

Many thanks for the replies, looks like a new transformer it is then!
Even though there is a small amount of buzz, I have to say this is a really good sounding amp and a great project with all the help needed in the forum. Thanks for making this available.
trampo
 
Posts: 23
Likes: 1 post
Liked in: 0 post
Joined: November 22nd, 2015, 3:51 pm
Location: Manchester
Country: United Kingdom (uk)

Re: Transformer covers

Postby amb » February 2nd, 2020, 5:09 pm

Welcome to the β24 club!
User avatar
amb
Site Admin
 
Posts: 10556
Likes: 191 posts
Liked in: 506 posts
Joined: March 29th, 2010, 9:49 pm
Location: Sunnyvale, CA
Country: United States (us)

Re: Transformer covers

Postby Hasren » February 3rd, 2020, 12:25 am

trampo wrote:Many thanks for the replies, looks like a new transformer it is then!
Even though there is a small amount of buzz, I have to say this is a really good sounding amp and a great project with all the help needed in the forum. Thanks for making this available.


You can try Block RKD 500/2x30 from RS. It is a very good transformer from Germany, although not encapsulated it is very quiet. Here in South Africa, it is almost the same pricing as the RS you've got but it is relatively expensive if you consider that it is not encapsulated. I had tried the Novutem Telema and it had some buzz to it, then the buzz went away once I changed to the RKD.
Hasren
 
Posts: 14
Likes: 4 posts
Liked in: 6 posts
Joined: February 12th, 2019, 11:49 pm
Location: Pretoria
Country: South Africa (za)

Re: Transformer covers

Postby Pieterh » February 3rd, 2020, 5:24 am

I have a polish toroidy 530VA transformer in my b24. It also hums a bit. I am still wondering whether dc offset on the 230V mains could explain some of that humming. There are threads about that on e.g. diyaudio: https://www.diyaudio.com/forums/solid-s ... ments.html

do you have experience with DC filters on the mains Ti?
Pieterh
 
Posts: 150
Likes: 101 posts
Liked in: 65 posts
Joined: December 29th, 2015, 12:50 am
Location: Netherlands
Country: Netherlands (nl)

Next

Return to β24 fully-differential power amplifier

Who is online

Users browsing this forum: No registered users and 0 guests

Quick Links

AMB audio DIY resources
AMB audio shop