Class D Audio SDS-254

[senmurv76]

@wgscott: The horizontal ellipse is a bracket that I made to hold the gain pots :-). The vertical ellipse is my mains power socket/switch/fuse; an all-in-one unit. The protrusion on the back side is the AC line filter built into the switch. I can hear the hiss when I hold my ear a feet away from the tweeter. I don't have the 60Hz hum which I have read elsewhere people were complaining about (actually it would be 50Hz for me).

 

@firedog: I don't have the bridge mode engaged. I see that the wires connected to the speaker binding posts are soldered. Mine have ring terminals crimped to the wires then fastened to the binding posts with nuts. So maybe when I get a chance I will redo the wiring from the binding posts to the amp out terminals.

 

If I over look the hiss the amp sounds very smooth :-)

 

Just enjoying the album "It takes a Thief" by Thievery Corporation.

 

[wgscott]

"actually it would be 50Hz for me"

 

I thought of that after I posted and was driving the kids into town for school. Sorry. I lived in the UK for 3.5 years. I should know better.

 

If you stick to Radiohead, you can just pretend it is a sound effect.

 

Seriously, though, you shouldn't have a hiss. How loud is it? I am assuming you can hear it from your listening position, or you wouldn't be that worried.

 

All I can suggest is that you disconnect stuff and see if anything makes a difference.

 

Does it come out both speakers? If so, that indicates something upstream of the amp board.

 

If you are still stuck, post to the Audiocircle ClassDAudio thread. I got a tremendous amount of help there.

 

[senmurv76]

I don't hear the hiss from my listening position so it doesn't bother me too much. I only noticed it when I went up close to the speakers the other day. I does come out of both speakers.

 

Actually, I live a good 5500km away from the UK. Although, thanks to the British presence in the region, the country ended up using their ugly looking 3-pin plugs and 50Hz mains frequency. I'm off to enjoy a nice steak and some vino with my wife.

 

[wgscott]

I have to get real close to the speakers to hear it, but I get a little bit of a hiss from one of the amp boards, but not the other. I figure at some point I will pull the whole thing apart and re-assemble it properly. I bought a box in which to put the transformer, and some power-on plugs and sockets to make a connection, so maybe separating the transformer from the power supply might help. I don't know if that will help. I haven't felt any sense of urgency.

 

 

 

[senmurv76]

Actually Tom's initial suggestion was that the transformer may be too close to the amp board. It's true that my enclosure is rather tight, however, I have seen may who have used similar-sized enclosures but I have not come across anyone complaining about their speakers hissing. Whats interesting is that the hiss is coming from the tweeters only. Even with only the amp ON (all other components OFF) the tweeters hiss. I will get myself to post on audiocircle.

 

[4est]

I hate to say this, but a hiss indicates to me that you may have a defective board. Transformers et all most likely (I say it like that because I do not full understand digital amp technology.) will not create a hiss, but a hum. In looking at your project, it seems pretty clean. The red input wires at the top right might ought to be trimmed or the board rotated as the output filters are right next to the transformer, but still that seems a low probability.

 

Does it hiss with the signal inputs disconnected and shorted at the board, not the connectors?