I have been building a little pre-amp from an eBay pcb which is based on a 3850 circuit been going well and have fitted it into an old NAD chassis and using f the NAD volume pot. Which turned out to be way too low at 20kohm. I tried replacing the 5532 with a 4562NA however this oscillated producing a ticking noise. the 5532 was tick free. I added 47k in front of the pot to give it some actual volume adjust ment but I may need to change it for a new one. At the moment I have a 50hz hum issue to deal with once the volume heads towards 1/3rd I am wondering if this is the filtered iec I let at the moment. But hum aside it does sound very good way better than my old cyrus
Attachments
Hi,
you can have a look here https://www.diyaudio.com/community/threads/clon-c-3850.416050/
I have a little hiss with this pre, but no hum. At first you can reduce the gain. How, you can read in the other thread. But LM4562 is not problematic for this board.
If i look to your picture, i think you have a groundloop. You can try to let one shielding at RCA open and bridge the shielding from one RCA connector to the other. Then you will have only one Signalground to the output. Do the same with the input...only one ground/shielding. Use the same, using right input, choose the right output to leave the shielding open. The shielding only on one side soldered, Board or RCA. The input selector needs only one shielding too. I think you have to many ground connections.
Greets
Peter
you can have a look here https://www.diyaudio.com/community/threads/clon-c-3850.416050/
I have a little hiss with this pre, but no hum. At first you can reduce the gain. How, you can read in the other thread. But LM4562 is not problematic for this board.
If i look to your picture, i think you have a groundloop. You can try to let one shielding at RCA open and bridge the shielding from one RCA connector to the other. Then you will have only one Signalground to the output. Do the same with the input...only one ground/shielding. Use the same, using right input, choose the right output to leave the shielding open. The shielding only on one side soldered, Board or RCA. The input selector needs only one shielding too. I think you have to many ground connections.
Greets
Peter
Last edited:
There is still a little above 50% of pot travel but you would never turn the gain that high anyway
Ok...seems to be the right way...
I have marked the open shieldings in my Apex P30ZF. You can see the open connections. But there is no input selector, not nessecary in my case, so I made no starpoint for this little pre.
You can test a connetion from PE to the ground/0 Volt output of your transformer. I can't see the power connection to your input collector. on the pictures.
Make the RCA cable from the C3850 to the output a little bit shorter. No reason for such a longer connection.
AC output i always drill. If possible, i drill everything...DC too
Use good rca cables...
Greets
Peter
I have marked the open shieldings in my Apex P30ZF. You can see the open connections. But there is no input selector, not nessecary in my case, so I made no starpoint for this little pre.
You can test a connetion from PE to the ground/0 Volt output of your transformer. I can't see the power connection to your input collector. on the pictures.
Make the RCA cable from the C3850 to the output a little bit shorter. No reason for such a longer connection.
AC output i always drill. If possible, i drill everything...DC too
Use good rca cables...
Greets
Peter
Attachments
Last edited:
Thanks for the picture going to re-wire when the new phono sockets arrive. I use a silver core cable that is used for accelerometers it is excellent audio cable. Well send pic when update is done.