Greetings to all!
I have a Denon integrated and I noticed on idle or full steam one of the power amplifier heatsinks is noticeably warmer than the other. So I begin by disconnecting all of the wires from the amp, volume to 0, cd as an input and tone defeat ON. Let it cool down for 4h and check the idle current after 10min mark at ON(the amplifier has only this adjustment pot). Left one was a little lower (11mV) but the right one was a little higher (13.5mV). It was very hard to adjust the left one. It drifts too quickly and it's not so stable. So I've only tinkered with that side for now and managed to set it up to 12mV. So I've decided to leave the right one untouched. That way after 60min on time it balanced out to stable L-11.6mV/R-11.5mV. The thing is that now after some testing the right heatsink still heats up more.
So I have a couple of questions on the subject which I'm not sure I understand correctly:
1. Is it normal for the idle current to drift a little constantly (+/-0.1)?
2. The manual states " setup after 2min ON time to 12mV, and after 10min to 12mV ''. So I don't have to bother afterwards if it fluctuates outside 12mV? Or I have to measure again after lets say 60 min ON time? I came to notice that the current stabilizes after about 45min+......
3. Do I have to set up the L and R side to be at 12mV on the 10 min mark or after 60min?
4. The tolerance for setting up is 0.5mV. If I get it set up to L - 11.5mV and R - 12.5mV is that good?
Any advice will be appreciated!
I have a Denon integrated and I noticed on idle or full steam one of the power amplifier heatsinks is noticeably warmer than the other. So I begin by disconnecting all of the wires from the amp, volume to 0, cd as an input and tone defeat ON. Let it cool down for 4h and check the idle current after 10min mark at ON(the amplifier has only this adjustment pot). Left one was a little lower (11mV) but the right one was a little higher (13.5mV). It was very hard to adjust the left one. It drifts too quickly and it's not so stable. So I've only tinkered with that side for now and managed to set it up to 12mV. So I've decided to leave the right one untouched. That way after 60min on time it balanced out to stable L-11.6mV/R-11.5mV. The thing is that now after some testing the right heatsink still heats up more.
So I have a couple of questions on the subject which I'm not sure I understand correctly:
1. Is it normal for the idle current to drift a little constantly (+/-0.1)?
2. The manual states " setup after 2min ON time to 12mV, and after 10min to 12mV ''. So I don't have to bother afterwards if it fluctuates outside 12mV? Or I have to measure again after lets say 60 min ON time? I came to notice that the current stabilizes after about 45min+......
3. Do I have to set up the L and R side to be at 12mV on the 10 min mark or after 60min?
4. The tolerance for setting up is 0.5mV. If I get it set up to L - 11.5mV and R - 12.5mV is that good?
Any advice will be appreciated!
I guess the attachment didn't work.
Here is a link to the schematic:
https://drive.google.com/file/d/1-0J2Rh93DEeL0_rDvPAcQ3nZr5xtXXUo/view?usp=drivesdk
Here is a link to the schematic:
https://drive.google.com/file/d/1-0J2Rh93DEeL0_rDvPAcQ3nZr5xtXXUo/view?usp=drivesdk
From my experience you'll always get a tiny bit of drift between amps.
I'd say your absolutely fine with between 11 and 13mv, and there won't be any audible difference between channels.
These days I check after 10 mins but base the final setting after 45 to 60 mins - do this in a room that has roughly same ambient temp as your listening space.
And measure with the lid on at least partially to recreate normal conditions.
If your left channel is very difficult to adjust, or drifts after a few days/weeks, the trimmer potentiometer should be replaced.
I've worked on PA amps that died because the trim pots were faulty.
And on many vintage UK amps the thermal regulation was terrible so any drift from a dirty trim pot caused issues (Audiolab, Arcam, I'm looking at you guys! ).
However if you got it set correctly and it doesn't change much after using a few times, it's fine.
Last point: Right amp module is beside an inner partition whereas left side isn't, this might account for a bit more heat ending up on right side heatsink. Unless it's very hot I wouldn't worry.
I'd say your absolutely fine with between 11 and 13mv, and there won't be any audible difference between channels.
These days I check after 10 mins but base the final setting after 45 to 60 mins - do this in a room that has roughly same ambient temp as your listening space.
And measure with the lid on at least partially to recreate normal conditions.
If your left channel is very difficult to adjust, or drifts after a few days/weeks, the trimmer potentiometer should be replaced.
I've worked on PA amps that died because the trim pots were faulty.
And on many vintage UK amps the thermal regulation was terrible so any drift from a dirty trim pot caused issues (Audiolab, Arcam, I'm looking at you guys! ).
However if you got it set correctly and it doesn't change much after using a few times, it's fine.
Last point: Right amp module is beside an inner partition whereas left side isn't, this might account for a bit more heat ending up on right side heatsink. Unless it's very hot I wouldn't worry.
Hi Pockobg,
You are fine. I was authorized warranty service for Denon.
Bias is set with inputs shorted (short the selected input), volume minimum and no load connected. Measure DC offset voltages as well in this condition. Sometimes volume controls can be noisy, that's why we short that input.
Bias will vary with time, temperature and line voltage. How much depends on the design and physical layout. As for the trimmer control, a bad one will normally be difficult to adjust and remain stable at the time. I do not recommend you replace anything without a good reason. Do not replace single turn controls with multi-turn - should the recommendation for that come up.
As Kaibosher said, you can't expect each heat sink to be at the same temperature. Air flow and other components dissipating heat can make one heat sink warmer, but not too much. Use a thermometer, not your hand.
You are fine. I was authorized warranty service for Denon.
Bias is set with inputs shorted (short the selected input), volume minimum and no load connected. Measure DC offset voltages as well in this condition. Sometimes volume controls can be noisy, that's why we short that input.
Bias will vary with time, temperature and line voltage. How much depends on the design and physical layout. As for the trimmer control, a bad one will normally be difficult to adjust and remain stable at the time. I do not recommend you replace anything without a good reason. Do not replace single turn controls with multi-turn - should the recommendation for that come up.
As Kaibosher said, you can't expect each heat sink to be at the same temperature. Air flow and other components dissipating heat can make one heat sink warmer, but not too much. Use a thermometer, not your hand.
Oh 100% don't start replacing things without probable cause. A bad trim pot will have variable resistance during heat cycles and any slight movement (Power off, measure resistance on potentiometer and try change the temperature). A good trimmer pot should remain within the correct spec under different conditions.
" Do not replace single turn controls with multi-turn - should the recommendation for that come up "
I have a Leak 2200 here and one trimmer pot is drifting - gets so low that crossover distortion kicks in sometimes. Was hunting for replacements, thanks for that advice... it's only 220ohm so I thought a multi-turn would be more accurate. Will get a single turn now 🙂
" Do not replace single turn controls with multi-turn - should the recommendation for that come up "
I have a Leak 2200 here and one trimmer pot is drifting - gets so low that crossover distortion kicks in sometimes. Was hunting for replacements, thanks for that advice... it's only 220ohm so I thought a multi-turn would be more accurate. Will get a single turn now 🙂
Another thing is that you don't know where the wiper is on a multi-turn control, you do on a single.
Bias is an approximate setting. It will vary all on it's own within a range. Some amps are worse than others in that respect. Extreme precision is not required,. The contacts are also smaller on a multi-turn control and they are not designed to pass current.
If a single turn control is too sensitive, it probably means too much range is designed in. That is a failure in design, you can restrict it's range with resistors in series or parallel depending on the circuit.
Bias is an approximate setting. It will vary all on it's own within a range. Some amps are worse than others in that respect. Extreme precision is not required,. The contacts are also smaller on a multi-turn control and they are not designed to pass current.
If a single turn control is too sensitive, it probably means too much range is designed in. That is a failure in design, you can restrict it's range with resistors in series or parallel depending on the circuit.