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"I had a demo of the Oppo BDP 83 using CD only through the new Arcam AV888 yesterday and it sounded very muddy and not particulary dynamic."

Check the Oppos Dynamic Range function. If it was ON the Oppo was compressing the dynamic range.

Shawn

So the problem was simply that the jumpers were set wrong?

Yes.

Shawn

Sooooo, without wanting to sound contentious, how come it worked for custom HT??

It wouldn't have worked properly. But If whatever material Gary was using to test with isn't within 6dB of 0dBFS he wouldn't have had the digital clipping and he might have missed the channel inversion.

This is why I test specifically with a channel identification track that also gets very close to 0dBFS. (First track of Stereophile Test CD 2) Gary should add a similar track to his testing.

Boring tech details....

All digital audio is carried within 32 bit frames. All the data format does is tell you which of the 24 bits within the 32 are used for the digital audio, the other 8 are preamble/information bits.

24 bit Left Justified means the most significant bit (MSB... or loudest bit is at the very start of the 32 bits of data.)

DDDDDDDDDDDDDDDDDDDDDDDD........

The MSB is the left most data bit above.

24 bit I2S the audio MSB is indented one bit in from Left Justified format.
.DDDDDDDDDDDDDDDDDDDDDDDD.......

When you actually watch these bits on live audio they look just like VU meters that move right to left with level. The louder the material the more bits are active to the left. If the board is set to I2S format and you are feeding it 24bit Left Justified if the music doesn't use the MSB (-6dB from full scale) you don't clip so you won't hear the distortion. You do however still get the channel inversion because the L/R clock being high is 'Left' on one format and it being high is 'Right' for the other format.

End Boring Tech details.

Shawn

Thanks for your efforts Shawn, it's good to get to the bottom of this. I now feel confident in placing my order with Gary.

More out of curiosity more than anything, but how did the jumpers get misplaced? Was it a 'production' (i.e. you or Gary) or an 'operator' (Jim) error?

glad to hear this problem was something simple and my fault

however I am mystified how this could get thru my testing and everything worked well here as I reported twice, I test BD, DVD and CD and all worked perfect, I listen loud so no static will get by me, I will however admit that a inversion or there may get past me

since Jims problems with the Oppo I have started testing the Oppos more thoroughly, which includes checking for inversion and using more test material, Shawn if you have a spare Stereophile test CD would love to have it

thanks Shawn, appreciate it very much and I apologize to Jim for these problems

Gary,

"however I am mystified how this could get thru my testing and everything worked well here as I reported twice, I test BD, DVD and CD and all worked perfect, I listen loud so no static will get by me, I will however admit that a inversion or there may get past me"

It doesn't matter how loud you listen, if the material doesn't get within 6dB of full scale it won't distort and will sound fine. Only on material within 6dB of full scale will you get the distortion in the situation above.

In the case of movies the loud material could be all explosions and such and the distortion could be masked. I have one track which is just a 1kHz sine wave at -20dB then at 0dB. In the situation above the -20dB sine will sound perfectly fine, the sine at 0dB sounds terrible since it is 1kHz with loads of odd order distortion (3kHz,5kHz..etc..etc..).

I'll see if I have a good disc to send you with some good test material.

Shawn

thanks Shawn, that explains it perfectly

would love to have one of those CD's, you can send it with my next order soon and if I owe you anything let me know

BTW, are they 44.1khz usually?

-Gary

You could probably generate a test signal with http://audacity.sourceforge.net/
in 2 minutes and burn it for a test.

Yes...

Generate Tone
1000 hz
Amplitude 1
and however long you want.

If you plot spectrum it shows just the 1kHz peak.

If you then amplify the selection by even 0.1dB (allow clipping) and then plot the spectrum you see all the odd order distortion from the digital clipping.

Bump it up to amplify 6dB and you can really hear the distortion easily.

Shawn

So all you need is the above for the test track.

What you list below is for extra credit to hear and see the effect of clipping 1 bit with in audacity, correct?