knabsol said:I´m sorry if I´ve stepped on someones toe with starting this thread. My intentions were never to make any GB of it.
My only goal with this is to add a little knowledge and understaning in audio electronics. I followed Carlos circuit because it was an not too complicated one and a good start for me since I had most of the components.
I hope noone´s having an angry eye on me now. Anyway, the pcb is currently etching in the garage...I better go have a look at it!
Thanks for all your help so far, especially to carlos for making this public on this forum.
I´ll be back from the garage...
Not to worry Knabsol, I'm sure no one here is offended! There just a bit of bad history associated with this circut on this forum. If I have offended anyone I appologize too.
Let us know how the project turns out, be sure to post some pics for us to see. I'm particularly interested in what kind of DC offset you see.
Best of luck!
G.
Hi Gcollier and everyone else!
As I´m a better electronics guy than a politician I go back to the practical things here
I etched and built the circuit but there´s something wrong and I cannot understand what It could be. I get a horrible noise when I turn it on and have a low volume, from 1/4 to zero. When I turn it over about 1/4 of the volume it´s ok again. It looks like it´s oscillating or something, there´s this bad noise and it draws alot of current. The weird thing is that it´s only on one channel.
I saw a thing I´ve missed in the circuit, and thats the 33ohm resistor on the output. But it shouldnt have anything to do with how it´s acting now. It´s the same thing even if I havent connected anything to the outputs. For volume control I use an alps blue velvet 20k. Any tips? Should I try and replace the chip?
Another question that maybe is related:
Shouldnt it have an input filter? The ad815 has a large bandwidth where alot of cr** can sneak in
Enjoy the sun!
/Christopher
As I´m a better electronics guy than a politician I go back to the practical things here
I etched and built the circuit but there´s something wrong and I cannot understand what It could be. I get a horrible noise when I turn it on and have a low volume, from 1/4 to zero. When I turn it over about 1/4 of the volume it´s ok again. It looks like it´s oscillating or something, there´s this bad noise and it draws alot of current. The weird thing is that it´s only on one channel.
I saw a thing I´ve missed in the circuit, and thats the 33ohm resistor on the output. But it shouldnt have anything to do with how it´s acting now. It´s the same thing even if I havent connected anything to the outputs. For volume control I use an alps blue velvet 20k. Any tips? Should I try and replace the chip?
Another question that maybe is related:
Shouldnt it have an input filter? The ad815 has a large bandwidth where alot of cr** can sneak in
Enjoy the sun!
/Christopher
Check your connections
It may be a bad connection in the nulling circuit. Losing that voltage could create some noise. That would expalin only seeing it on one channel. And explain why it is pot position related. Check your input and output offset voltages as the pot is opened.
Using those 33 ohm or so resistors is important too. I have used 20 ohm to 80 and all seemed to work fine. But they are needed to decouple the ouput of the chip from any reactance downstream. This may be causing the circuit to ring.
Look at your decoupling also. The high speed devices need some stablization. This might be your heating. Short leads here.
The low impedances seen in this circuit help keep the nasties out. The path from the non-inverting input down through the inverting creates a low resistance path to ground. I have seen this refered to as a virtual ground. I do not believe that applies at radio frequencies though.
George
It may be a bad connection in the nulling circuit. Losing that voltage could create some noise. That would expalin only seeing it on one channel. And explain why it is pot position related. Check your input and output offset voltages as the pot is opened.
Using those 33 ohm or so resistors is important too. I have used 20 ohm to 80 and all seemed to work fine. But they are needed to decouple the ouput of the chip from any reactance downstream. This may be causing the circuit to ring.
Look at your decoupling also. The high speed devices need some stablization. This might be your heating. Short leads here.
The low impedances seen in this circuit help keep the nasties out. The path from the non-inverting input down through the inverting creates a low resistance path to ground. I have seen this refered to as a virtual ground. I do not believe that applies at radio frequencies though.
George
Re: WM8816
I contacted Wolfson directly about this and somone from their office in SanDiego got in touch with me about a Canadian supplier. They were also kind enough to send me 5 samples. Truly great service! Try firing off an email to them and give some project details. I specifically told them it was for a DIY project and they were still willing to help. If you are interested in using this chip with the AD815, remember that it is configured fo inverting gain. You will also not have the "magic" values that Carlos established. I have actually moved on from this chip and am working with the TPA1620 from BB...every bit as good
adwsail said:
I contacted Wolfson directly about this and somone from their office in SanDiego got in touch with me about a Canadian supplier. They were also kind enough to send me 5 samples. Truly great service! Try firing off an email to them and give some project details. I specifically told them it was for a DIY project and they were still willing to help. If you are interested in using this chip with the AD815, remember that it is configured fo inverting gain. You will also not have the "magic" values that Carlos established. I have actually moved on from this chip and am working with the TPA1620 from BB...every bit as good
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