Hi Roclite ,
This is regarding about my previous question about the relay on this board, I forgot that the original version of this does not have relay.
My version of this amp have 2 relays connected in parallel and when I power up the amp , there is about 5 second delay until the replay is engaged .
I think my version of this amp have built in DC speaker protection too. But I can't confirm it. ANd I ODn't wanna test it , It is running fine right now , Except that I have to replace the 2 separate cheap small EI transformer that I added for the protection circuit with a small toroidal transformer , Because they are making mechanical noise . This is DIY audio life
Thanks
This is regarding about my previous question about the relay on this board, I forgot that the original version of this does not have relay.
My version of this amp have 2 relays connected in parallel and when I power up the amp , there is about 5 second delay until the replay is engaged .
I think my version of this amp have built in DC speaker protection too. But I can't confirm it. ANd I ODn't wanna test it , It is running fine right now , Except that I have to replace the 2 separate cheap small EI transformer that I added for the protection circuit with a small toroidal transformer , Because they are making mechanical noise . This is DIY audio life
Thanks
HI roclite ,
Thank you for your reply , But I'm still not sure whether this amp have a short circuit protection , Meaning if I accidentally shorted the output wires , The Amp won't burn , That's what I wanted to know without learning the hard way
BTW , This is my amplifier , It is an updated version with 2 x 10,000uf elna caps. instead of the 4 caps in the original version of the pr-800 board, I use my old Onkyo M504 chassis and transformers , I just finished it and playing some tunes in my test music system as of this writing.
Pr-800 bias settings help
I don't know why I built this amplifier. Have many much better more exspensive. I am a bit afraid of using it. There is no bias at all. Can anybody tell me if I should turn potentiometer clockwise or anticlockwise to raise bias? Thought this could be used as subwoofer amplifier. Should I add series capacitors at output? In that case how many uf and volt?
I built a pair of monoblocks with these and they're great. I didn't use an output cap but i did use a speaker protection board ust to be sure. I biassed mine by using a multimeter on the +ve rail, trimming the pot untiul it drew 36ma with no input and speakers disconnected. Be careful with the input, mine went straight to a transistor base and needed a tantalum capacitor on the input.
What do you mean by 'no bias'?
I used + / - 55v with mine with no trouble. You need to add a 2nd supply for the bias / protection circuit. it's +12v off the negative supply which can be a problem when you also need +12v off the 0v rail too for your speaker protection board. So my power supply gave -55v, -43v, 0v, +12v, +55v. The -43v went to the bias / protection rail (+12v from the -ve supply).
Cheapest option for me was to buy 2 x the chaepest 12v switch mode ($5) psu and use them to power the bias rail (ov tied to -ve rail of main psu) and the speaker protection board (0V tied to main PSU rail).
If you avoid earth loops it sounds sweet.
I used + / - 55v with mine with no trouble. You need to add a 2nd supply for the bias / protection circuit. it's +12v off the negative supply which can be a problem when you also need +12v off the 0v rail too for your speaker protection board. So my power supply gave -55v, -43v, 0v, +12v, +55v. The -43v went to the bias / protection rail (+12v from the -ve supply).
Cheapest option for me was to buy 2 x the chaepest 12v switch mode ($5) psu and use them to power the bias rail (ov tied to -ve rail of main psu) and the speaker protection board (0V tied to main PSU rail).
If you avoid earth loops it sounds sweet.
I'm really interested in your reply, i have maybe been running mine 'cold' all along. They're a great amp but they didn't sound as loud as they should have. I didn't have an issue with common ground as i built mine as monoblocks. How did you measure the bias or did you do it by ear / temperature?