DC Offset in Oppo DV-981HD

sonidos · 23rd September 2010, 01:19 AM

I've been toying around with an op-amp based head amp that I've put together and hooked it up to my Oppo player. I measured 16 mV DC offset at full volume from the analog audio outputs...yow...and followed it upstream to the Oppo player. On one channel I have 12.5 mV DC and on the other, 12.8 mV DC. Doesn't this seem awfully high for a modern disc player???

Anyone else with an Oppo have the same amount of offset?

sandyK · 23rd September 2010, 02:07 AM

Quote:

Originally Posted by sonidos

I've been toying around with an op-amp based head amp that I've put together and hooked it up to my Oppo player. I measured 16 mV DC offset at full volume from the analog audio outputs...yow...and followed it upstream to the Oppo player. On one channel I have 12.5 mV DC and on the other, 12.8 mV DC. Doesn't this seem awfully high for a modern disc player???

Anyone else with an Oppo have the same amount of offset?

Sonidos
Are you using "Mixed L and R" ?

I normally don't use Analogue Out from mine, as after sound deadening material combined with replacement of the SMPS bridge rectifier diodes with BYV26C, and a 100nF 630V across the main electro , it sounds noticeably better via SPDIF. In fact, even Video via HDMI to a friend's 1280 projector was then also markedly improved. (glossier looking picture)
My friend then did the same with his 981HD.
I just tried mine, and although it started off at several mV, it dropped to
0mV after several seconds, indicating that it is via electrolytic capacitors.
SandyK

sonidos · 23rd September 2010, 02:45 AM

SandyK,

I'll have to check my settings with regards to Mixed L & R, but the offset is constant...it doesn't go to 0.

Thanks for the tips on the mods and checking your Oppo. I don't normally use the Oppo in the way that I mentioned but I was surprised to see that much offset on both outputs, so something is not right.

sandyK · 03:20 AM

Sonidos
Did you realise that you have digital volume control via SPDIF if HDMI is not enabled?
SandyK

P.S.
A quick look seems to suggest that there are 3 dual I.C.s followed by 6 x 47uF16V electros, then a muting transistor for each output.

sonidos · 23rd September 2010, 04:27 AM

sandyK,

No, but I do now! I don't have a DAC and it is used primarily via HDMI to my flat screen. I don't use it for audio purposes, but I've heard it is great if you have a DAC...so definitely on my list to build one.

sandyK · 23rd September 2010, 04:34 AM

Sonidos
It is best not to use much more than 10dB of digital attenuation for best results with 16 bit files.
SandyK.

Mooly · 23rd September 2010, 07:08 AM

There may be HF hash causing an incorrect DVM reading... if using a DVM rather than 'scope then try an RC filter network on the audio output (say 47k and 0.1uf) and remeasure voltage across the cap only.

sonidos · 23rd September 2010, 01:27 PM

Good stuff, guys! Mooly, I'll give that a try and see if that is indeed HF hash.

23rd September 2010, 01:19 AM	#1
sonidos diyAudio Member Join Date: Jul 2007 Location: Round Rock, TX	DC Offset in Oppo DV-981HD I've been toying around with an op-amp based head amp that I've put together and hooked it up to my Oppo player. I measured 16 mV DC offset at full volume from the analog audio outputs...yow...and followed it upstream to the Oppo player. On one channel I have 12.5 mV DC and on the other, 12.8 mV DC. Doesn't this seem awfully high for a modern disc player??? Anyone else with an Oppo have the same amount of offset?

23rd September 2010, 02:56 AM	#4
sandyK diyAudio Member Join Date: Apr 2007 Location: Sydney	Sonidos Did you realise that you have digital volume control via SPDIF if HDMI is not enabled? SandyK P.S. A quick look seems to suggest that there are 3 dual I.C.s followed by 6 x 47uF16V electros, then a muting transistor for each output. Last edited by sandyK; 23rd September 2010 at 03:20 AM.

23rd September 2010, 07:08 AM	#7
Mooly diyAudio Member Join Date: Sep 2007	There may be HF hash causing an incorrect DVM reading... if using a DVM rather than 'scope then try an RC filter network on the audio output (say 47k and 0.1uf) and remeasure voltage across the cap only. __________________ ------------------------------------------------------- *A simulation free zone.* *Design it, build it, test it.*

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23rd September 2010, 02:45 AM	#3
sonidos diyAudio Member Join Date: Jul 2007 Location: Round Rock, TX	SandyK, I'll have to check my settings with regards to Mixed L & R, but the offset is constant...it doesn't go to 0. Thanks for the tips on the mods and checking your Oppo. I don't normally use the Oppo in the way that I mentioned but I was surprised to see that much offset on both outputs, so something is not right.

23rd September 2010, 04:27 AM	#5
sonidos diyAudio Member Join Date: Jul 2007 Location: Round Rock, TX	sandyK, No, but I do now! I don't have a DAC and it is used primarily via HDMI to my flat screen. I don't use it for audio purposes, but I've heard it is great if you have a DAC...so definitely on my list to build one.

23rd September 2010, 04:34 AM	#6
sandyK diyAudio Member Join Date: Apr 2007 Location: Sydney	Sonidos It is best not to use much more than 10dB of digital attenuation for best results with 16 bit files. SandyK.

23rd September 2010, 01:27 PM	#8
sonidos diyAudio Member Join Date: Jul 2007 Location: Round Rock, TX	Good stuff, guys! Mooly, I'll give that a try and see if that is indeed HF hash.

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