Behringer HA4700 Headphone Amp Schematic

Does anyone have a schematic for this thing? Behringer won't give them out, and I can't find any on the web.

I'm getting a nasty 60 cycle hum that needs to go away. It's only a year old, and the hum has gotten progressively worse. Caps, transformer, other thoughts?

Yeah, I know it's a POS, but it does work fine when there is no hum (of course). Any help would be appreciated.

Steve

probably would save time and money just to buy a new one...

I am also tempted to say 'throw it away and buy another' - but NOT a Bearstrangler of course - don't support a Company that won't support its own products with schematics and information.....

The power supply of most of their products is usually similar - with a mains transformer feeding full wave rectifiers and then 7815 and 7915 voltage regulators.

Check DC voltages on the output of the regulators - then on the input side, across the big smoothing capacitors. Are the voltages equal across the caps? If not - there could be a capacitor failure - with a huge increase in ripple.

If it's only a year old, it may be covered under warranty. If it is, you will be able to exchange it for a new unit. Check their website.

Well, it's too late for the return. I took it apart and removed the caps (the cheapest caps imaginable. Wow! What a surprise!). New caps should be here shortly. I'll let you know how I make out.

Thanks for the replies.

Regards,

Steve

Well, I recapped this thing and all is well. Actually sounds better and quiter than it ever did. But, oh man, what a PITA to take apart, desolder and resolder.

But, hey, for about $15 worth of caps (I recapped the whole thing), it was worth the effort. It now appears to be a decent (hopefully reliable) headphone amp for under a $125 total. We'll see. Hey, it actually has Alps pots! I wish I could say the caps were decent. Go figure????

The 4700 was out of the old good times, a reseller (friend) told me.


tw. do you have crosstalk between the channels (main in / aux)? This is the only thing i dont like on this amp (for that price)