As title, I get what can only be described as minor low level, doesn't change with volume random crackling in rh ch only. I've tried changing valves around etc, removing the expensive power lead for cheap one actually reduced it slightly.
It's a static sound, with tiny pops, and sometimes goes away. When you turn amp on, usual minor buzzing goes away, but from rh ch speaker a hiss, that then goes away to be replaced with this on off crackle. It's very quiet, but if simple I will fix.
Can't be mains interference surely, if only one ch. If I put amp in ultralinear mode, it's not there.
It's a static sound, with tiny pops, and sometimes goes away. When you turn amp on, usual minor buzzing goes away, but from rh ch speaker a hiss, that then goes away to be replaced with this on off crackle. It's very quiet, but if simple I will fix.
Can't be mains interference surely, if only one ch. If I put amp in ultralinear mode, it's not there.
Could be a bad resistor, if so a freeze spray may be necessary to find it. What's the brand/model?
What is the non-Ultra Linear mode? Pentode? Triode Wired?
If you have Pentode mode, and negative feedback, perhaps the amp with the speaker load you have is on the verge of oscillation (noise during warm-up, and later a crackle). I hope there is not a high frequency oscillation that is heating the tweeter voice coil and that now it is intermittently shorting to the magnet structure.
How about an overstressed electrolytic cap, or an overstressed coupling cap, or too high of a control grid resistance to ground? Can you post a schematic, and with voltages, etc.? Can you swap the tubes from left and right channels?
If you have Pentode mode, and negative feedback, perhaps the amp with the speaker load you have is on the verge of oscillation (noise during warm-up, and later a crackle). I hope there is not a high frequency oscillation that is heating the tweeter voice coil and that now it is intermittently shorting to the magnet structure.
How about an overstressed electrolytic cap, or an overstressed coupling cap, or too high of a control grid resistance to ground? Can you post a schematic, and with voltages, etc.? Can you swap the tubes from left and right channels?
Last edited:
things possible in order :
- grid stopper (s)
- faulty switch
- faulty tubes
Suggestion for fix , zero cost :
leave in ultralinear.
- grid stopper (s)
- faulty switch
- faulty tubes
Suggestion for fix , zero cost :
leave in ultralinear.
Yaqin mc100b
Swapped valves, no change, even changed completely. Its triode, and yaqin mc100b make and model
me too 😉
I posted the schema but I did not control the indicated values so only use the schema to find you
I posted the schema but I did not control the indicated values so only use the schema to find you
Could be early signs of a resistor failing. I had random crackles and it turned out to be an anode resistor which was inadequately specified for voltage rating.
Other likely cause is parasitic oscillation in the output stage. The fact that you hear a hiss at first, and that UL stops it, is evidence in this direction. However, another possibility is parasitic oscillation in the cathode follower driving the output stage. If so, cathode stoppers may help.
Other likely cause is parasitic oscillation in the output stage. The fact that you hear a hiss at first, and that UL stops it, is evidence in this direction. However, another possibility is parasitic oscillation in the cathode follower driving the output stage. If so, cathode stoppers may help.
R6 and R7. Monitor the anode voltages, but be aware that random voltage changes can come from mains variations so compare the two channels.
The 6.3 volts heater supply is referenced to gnd, while the the cathode voltages are quite high on the 12ax7 an 6sn7.
Heater to cathode voltage outside of specifications.
I believe this could also cause similar issues.
Heater to cathode voltage outside of specifications.
I believe this could also cause similar issues.
First isolate which channel it is.
Second, switch one tube at a time from a channel if the amp allows it.
It could be a leaky cap but my experience is that this is a tube which has a defect or going out of specks for some reason, age, leakage, isolation, gassy, anything really.
Second, switch one tube at a time from a channel if the amp allows it.
It could be a leaky cap but my experience is that this is a tube which has a defect or going out of specks for some reason, age, leakage, isolation, gassy, anything really.
In post 1 the OP told us that he has already tried swapping valves between channels. He also knows which channel it is.
Indeed. I opened and tested the r6 and r7, all okay. Its so intermittent, and of course nothing happened after that, so will have to see if it appears again.
Oxide on the valve socket where the tube pins are inserted? As Pcan says- tap the tube with a wooden chopstick or pot tweaker (plastic screwdriver used for adjusting pots).
I had the same thing happen... random crackles, pops, clicks. Was going to replace the tube. Cleaned the pins on the tube and both sockets. Problem solved.
A lot less expensive than a new tube or socket replacement.
I had the same thing happen... random crackles, pops, clicks. Was going to replace the tube. Cleaned the pins on the tube and both sockets. Problem solved.
A lot less expensive than a new tube or socket replacement.
Re solder all rh ch point on pcb board after swap the tubes if problem still there.
Removed ac power wifi internet network if any closed to the amp. It was cost problem for me before. i use ml-1100 universal power filter conditioner block socket and it is help me get out the buzzing away but it is not cheap parts.
Removed ac power wifi internet network if any closed to the amp. It was cost problem for me before. i use ml-1100 universal power filter conditioner block socket and it is help me get out the buzzing away but it is not cheap parts.
- Status
- Not open for further replies.