I am getting some distortion from my AKSA Lender preamp. It is not all the time and seems to come through the left channel mostly. I have not been able to pin point anything that specifically causes the distortion to happen, it just seems to occur randomly. Sometimes I can listen all day and not hear it, sometimes it happens every few seconds. I do know that the preamp seems to be the source. I can unplug my phono pre and dac and still get distortion. If I unplug the pre from the amp it stops. My complete setup is a Schiit audio phono pre and DAC to the Lender preamp to an ACA and subwoofer. The Lender pre is also configured as a headphone amp. Attached is a recording of the distortion. Any tips on how I go about troubleshooting this would be much appreciated.
Just to be sure we know what we talk about to help diagnosis: you wouldn't call this distortion. Distortion is, well, a signal that sounds distorted.
In your case, there is a scratching sound that is not related to the signal, even present without signal. That is important.
There can be several causes, one that occurs often is a volume control going bad. Try to turn it fast fully CW and CCW a dozen times to 'clean' the internal track, or better yet, inject a contact spray on it if you have that. See if that makes a difference. Same with a source selector if present, just switch it rapidly through the settings a dozen times.
This was the low-hanging fruit ;-)
You say it is only one channel. If you swap the input cables to the power amp, does the noise go to the other channel or does it stay in the same channel?
Jan
In your case, there is a scratching sound that is not related to the signal, even present without signal. That is important.
There can be several causes, one that occurs often is a volume control going bad. Try to turn it fast fully CW and CCW a dozen times to 'clean' the internal track, or better yet, inject a contact spray on it if you have that. See if that makes a difference. Same with a source selector if present, just switch it rapidly through the settings a dozen times.
This was the low-hanging fruit ;-)
You say it is only one channel. If you swap the input cables to the power amp, does the noise go to the other channel or does it stay in the same channel?
Jan
Thanks for the clarification. Yes a scratching sound that is unrelated to the music, happens regardless if there is a signal or not. I do have a source selector switch along with the volume control. I'll give both a workout and see if that helps. The volume control is an Alps RK27 and the selector an Elma 01-1264. I have tried switching the inputs to the power amp before and believe that the scratching sound also switched but I will re-verify.
Verified that scratching sound does switch with the inputs. Cycling the volume pot and selector did not help. Sound is also independent of volume pot meaning I can turn it up or down and it is unchanged. Is this type of noise typically related to a bad connection?
Could be but if it is not a switch or pot it may be a cap that leaks intermittently. You said it only happens once in a while, how often, how long at a time?
Could also be a semiconductor (diode, transistor, FET) leaking intermittently.
One way to isolate the problem is to open the box and blow hot air at a small region. If the issue is there it will come on more often/longer/harsher, if not move to another region.
These are hard problems; not to fix, but to find ...
Edit: a long shot, does it change if you connect the source to another preamp input?
Jan
Could also be a semiconductor (diode, transistor, FET) leaking intermittently.
One way to isolate the problem is to open the box and blow hot air at a small region. If the issue is there it will come on more often/longer/harsher, if not move to another region.
These are hard problems; not to fix, but to find ...
Edit: a long shot, does it change if you connect the source to another preamp input?
Jan
Unfortunately changing sources does not make a difference. Generally I notice the noise after about an hour of playing music. The sound clip is a typical pattern. This pattern will repeat every few seconds for maybe a minute then go away for a bit. Sometimes coming back and sometimes not but I think it is getting worse. It's quite so if I have the volume up I am sure I don't notice it most of the time. Really it's the quite evening sessions where it is most annoying.
The preamp has daughter cards so I could try to switch those between channels to see if the noise follows. It will take a bit of work though since the cards are not symmetrical so will require some bending of leads to make it work. At least that may narrow it down some?
The preamp has daughter cards so I could try to switch those between channels to see if the noise follows. It will take a bit of work though since the cards are not symmetrical so will require some bending of leads to make it work. At least that may narrow it down some?
Those daughter cards run hot and depending on how well ventilated your case is, you may be getting overheating on your components? Swapping cards is a good idea. Also get running with cover removed to see if it helps. If that helps, you may need to add ventilations lots.
I have a number of large ventilation holes on top of the case and the bottom is open as well. Never feels really hot. I just opened up the case and pulled the daughter cards, this was after about 2 hours of playing and I would not consider them really hot either. I could touch the little heat sinks and not burn myself.
Ended up I could not swap the cards though. Remembered I had to mount the connector on the base of the board on different sides to get each to clear with the HPA setup and all the caps mounted on the top of the main board. However it was good I took them out. As embarrassing as it is to say I found some metal FOD in rather sensitive places around the legs of the transistors. I could certainly see it causing issues and am glad it never really did anything in. Cleaned everything again, hopefully that was it. I will listen and see.
Ended up I could not swap the cards though. Remembered I had to mount the connector on the base of the board on different sides to get each to clear with the HPA setup and all the caps mounted on the top of the main board. However it was good I took them out. As embarrassing as it is to say I found some metal FOD in rather sensitive places around the legs of the transistors. I could certainly see it causing issues and am glad it never really did anything in. Cleaned everything again, hopefully that was it. I will listen and see.
Oh well. Still have the noise and it seems worse. Odd thing is it is now coming from the right channel. I am sure I did not swap the daughter cards so it must be something else. Can only suspect I moved something in the process of pulling the cards that is the source.
I was also concerned with some loose RCA connectors and posted another thread in parts.
https://www.diyaudio.com/forums/parts/340756-loose-rca-jacks.html#post5867397
Last comment about another user's issues with eBay RCA jacks made me think. Could my noise issue be poor quality connections with the RCA jacks?
https://www.diyaudio.com/forums/parts/340756-loose-rca-jacks.html#post5867397
Last comment about another user's issues with eBay RCA jacks made me think. Could my noise issue be poor quality connections with the RCA jacks?
It does happen once in a blue moon, but unplugging the cable and re-seating it normally fixed it as that acts to wipe the surface.
Jan
Jan
Yes using the connectors and flat cable. X, is there any chance of purchasing just the input PCB board from the AKSA Lender preamp set if I want to redo the input board with better RCA jacks?
Ok now I am even more confused. I pulled the Lender pre amp out and replaced it with a Schiit Vali while I replace the RCA jacks. To my surprise the noise still happens on the right channel. Before when I disconnected the pre it would stop so I thought it was the source of the noise. Now the only things that I have not changed out are the amp, the speakers, and the sub. Does this make any sense?
Sounds like you have a bad RCA jack or a bad solder joint somewhere. Look for cold solder joint or frayed wire. Sometimes pathological instances like this are bad wires. One time I spent a week chasing down bad signals just to find out that a piece of straight wire was bad! How can a plain piece of wire be bad? But it happens - check each piece of the signal chain individually until you eliminate the culprit. Bad connectors on a wire are another source (bad BNC, RCA, JST etc).
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