Just got a Denon DCD-2700, the right channel is noticeably louder than the left.
Attached is part of the schematics that shows the PS and the stage of from dacs (PCM1702) to the RCA. I already removed the headphone board connection to reduce the possibility of one source of leaking output. I hope some one can suggest some trouble shooting strategy. FWIW, I don't have a o-scope ....
Thanks!!
PS, this is a 220V version, and I am using a step up transformer for it, but I don't think it matters.
Attached is part of the schematics that shows the PS and the stage of from dacs (PCM1702) to the RCA. I already removed the headphone board connection to reduce the possibility of one source of leaking output. I hope some one can suggest some trouble shooting strategy. FWIW, I don't have a o-scope ....
Thanks!!
PS, this is a 220V version, and I am using a step up transformer for it, but I don't think it matters.
Attachments
Is there any distortion on the weaker channel? I would suggest that you play a constant sine wave signal thru the unit and start tracing the signal path from the rca jack back toward the dac until you find where the amplitude(on you dvm) is the same on both channels. Then you just found the weak spot. I don't think it would be a power supply issue as the channels share them.
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I'd look in the output stage and measure crucial resistors from the PCM's to any opamp's before output. Could be a gain problem.
If the volume is gradually degrading compared to the stronger channel as you use the player then I don't know.
If the volume is gradually degrading compared to the stronger channel as you use the player then I don't know.
Thanks for the suggestion, will find some sine wave (1K hz?) to download and burn a CD. I did try a preamp with balance control. Once I adjusted the balance control, the left and the right both sounded right (didn't hear any noticeable distortion).
Just curious, do I understand right or what, it uses half of each NEC uP4570's in the output, I wonder what is benefit of doing so ...
Just curious, do I understand right or what, it uses half of each NEC uP4570's in the output, I wonder what is benefit of doing so ...
Since it uses two 1702 dacs per channel in pushpull, it could be that one channel is not getting the signal from one of it's dacs, either due to a (very rare) bad 1702 chip, or a bad i/v opamp or fault in that path.
It was very common for Denon to use dual opamps as singles. In this case, it's because NEC did not make a single version of the 4570(not a great sounding chip anyway), but in other models there was no such definite reason for it. Maybe just surplus inventory of duals. God knows.
I would recommend that you remove the M5218 chips, and not replace them. This will disable the godawful GIC lowpass filter and make the unit sound instantly better.
It was very common for Denon to use dual opamps as singles. In this case, it's because NEC did not make a single version of the 4570(not a great sounding chip anyway), but in other models there was no such definite reason for it. Maybe just surplus inventory of duals. God knows.
I would recommend that you remove the M5218 chips, and not replace them. This will disable the godawful GIC lowpass filter and make the unit sound instantly better.
I had a similar problem on my project on the Dannon 2900
If the problem is one of the channels is mid frequencies
Check the filter capacitors
on the dac
the Frequency filtering op amp capacitor .
this the op amp Before the buffer op amp
When one of the capacitors have a disconnect or is burnt it creates a hole in the frequency range.
I do not know if similar dac With your model
In Danon 2900
Each channel have 3 dual op amp
good luck
If the problem is one of the channels is mid frequencies
Check the filter capacitors
on the dac
the Frequency filtering op amp capacitor .
this the op amp Before the buffer op amp
When one of the capacitors have a disconnect or is burnt it creates a hole in the frequency range.
I do not know if similar dac With your model
In Danon 2900
Each channel have 3 dual op amp
good luck
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