COD - Current Output DAC - Page 5

Russ White · 27th January 2008, 02:35 AM

So I took a HD650 cable and modded it for balanced XLR.

I am driving it directly from the ballsie. It does not seem o have any issues driving the 300ohm load. Though, ultimately it will be a new balanced head amp driving the cans.

Cheers!
Russ

scottj · 3rd February 2008, 07:40 AM

Quote:

Originally posted by Russ White
I decided to show the COD with TXD I/V and a Joshua Tree attenuator after each I/V, the output of the attenuator goes to the ballsie where the output is filtered and buffered. From there SE outputs go to my head amp and balanced out to the power amp.

Russ,

Any chance you could list out the order of the chain of modules in that pic?

Thanks!
Scott

BrianDonegan · 3rd February 2008, 12:19 PM

Here you go...

I will be doing more of these for more specific applications.

Russ White · 3rd February 2008, 12:25 PM

Sure.

This is the setup:

WM8804 -(I2S)-> Metronome-(I2S)->COD-(balanced I-OUT)->TXD/IVx2-(balanced V-OUT)->JTx2-(attenuated balanced V out 750R output impedance)-->Ballsie-(LPF single ended and balanced OUT 10R output impedance)--> jacks.

I have been using the metronome at 96khz/24-bit I2S out. The reason is that it just seems to sound better to me than at 192khz. I think its because the chips (both Opus and COD) do better filtering at 96khz than at 192. Also I think the better SNR at that sample rate may play a part.

There is one LCBPS that supplies the ballsie and the pair of TXDs.

There is one LCDPS that supplies the rest. One regulated voltage for the DAC, the other for the metronome and the receiver.

I am using just the basic JT controller which has it own power supply.

I use two dual secondary toroidal trafos. One powers the analog LCBPS on its own. The other powers the JT and the LCDPS. One secondary powers both the JT and one side of the LCDPS. I use this secondary on the same side of the LCDPS that powers the receiver and the metronome. The other secondary is for the other side of the LCDPS, the DAC side.

At some point I will add an OTTO and a USB receiver.

Cheers!
Russ

scottj · 3rd February 2008, 05:23 PM

Quote:

Originally posted by Russ White
I have been using the metronome at 96khz/24-bit I2S out. The reason is that it just seems to sound better to me than at 192khz. I think its because the chips (both Opus and COD) do better filtering at 96khz than at 192. Also I think the better SNR at that sample rate may play a part.

Does the metronome make a very big difference on the sound? How different is it compared with the same setup minus the metronome?

-Scott

Russ White · 3rd February 2008, 05:47 PM

Quote:

Originally posted by scottj

Does the metronome make a very big difference on the sound? How different is it compared with the same setup minus the metronome?

-Scott

Big? Maybe not big, but yes there is a positive difference. The only way I can describe it is that things just seem to sound more clear and liquid. This effect is present accross the board, not just for any particular band. Bass, mids, and treble all seem to sound better to me. More natural, possibly more analog.

Now this is at 96/24. At 192/24 I start to notice a bit of harshness in the mids, but I think this is more from the DAC than anything else. Changing the sample rate changes the way the DAC can apply its digital filters.

I will be trying 192/24 again with Wolfson WM8741 as I think it will do better in this regard than either the WM8740 or the PCM1794. It has a new filtering process that is supposed to significantly reduce pre-ringing. I have been thinking it may well be this pre-ringing I hear at 192/24. The COD, and Opus seem to be effected by this phenomenon in the same way, as I find they both sound better to me at 96/24.

In short, I like it.

You can easily use something like the OTTO to switch the metronome completely in and out. Or simply use the bypass option if you want to retain the master clock of the metronome. Then you can make your own A/B comparisons.

Cheers!
Russ

b-square · 3rd February 2008, 08:27 PM

Russ,

Have you tried either 176.4kHz or upsampling twice, once to 48kHz and from there to 192kHz? I've noticed some upsampling artifacts being amplified when dealing with largish, non-integer multiples.

bb

Russ White · 4th February 2008, 02:24 AM

Quote:

Originally posted by b-square
Russ,

Have you tried either 176.4kHz or upsampling twice, once to 48kHz and from there to 192kHz? I've noticed some upsampling artifacts being amplified when dealing with largish, non-integer multiples.

bb

I have not tried it yet. I have though about changing crystals and trying some unconventional clocks.

glt · 4th February 2008, 02:48 AM

It would nice to try other clocks with Metro. Does this require changing the oscillator?

According to Mr. Wavelength, integer multiples would sound better http://www.audioasylum.com/forums/pc...s/2/28189.html

fierce_freak · 4th February 2008, 03:00 AM

I'd like to try 176.4 sometime. I still need to give 96 a try when I get home (only used 192 so far).

3rd February 2008, 12:25 PM	#44
Russ White diyAudio Member Join Date: Jan 2005 Location: Nashville, TN, USA	Sure. This is the setup: WM8804 -(I2S)-> Metronome-(I2S)->COD-(balanced I-OUT)->TXD/IVx2-(balanced V-OUT)->JTx2-(attenuated balanced V out 750R output impedance)-->Ballsie-(LPF single ended and balanced OUT 10R output impedance)--> jacks. I have been using the metronome at 96khz/24-bit I2S out. The reason is that it just seems to sound better to me than at 192khz. I think its because the chips (both Opus and COD) do better filtering at 96khz than at 192. Also I think the better SNR at that sample rate may play a part. There is one LCBPS that supplies the ballsie and the pair of TXDs. There is one LCDPS that supplies the rest. One regulated voltage for the DAC, the other for the metronome and the receiver. I am using just the basic JT controller which has it own power supply. I use two dual secondary toroidal trafos. One powers the analog LCBPS on its own. The other powers the JT and the LCDPS. One secondary powers both the JT and one side of the LCDPS. I use this secondary on the same side of the LCDPS that powers the receiver and the metronome. The other secondary is for the other side of the LCDPS, the DAC side. At some point I will add an OTTO and a USB receiver. Cheers! Russ __________________ Less pulp more juice Twisted Pear Audio.

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3rd February 2008, 08:27 PM	#47
b-square diyAudio Member Join Date: Feb 2004 Location: Seattle, WA	Russ, Have you tried either 176.4kHz or upsampling twice, once to 48kHz and from there to 192kHz? I've noticed some upsampling artifacts being amplified when dealing with largish, non-integer multiples. bb

4th February 2008, 02:48 AM	#49
glt diyAudio Member Join Date: Oct 2004	It would nice to try other clocks with Metro. Does this require changing the oscillator? According to Mr. Wavelength, integer multiples would sound better http://www.audioasylum.com/forums/pc...s/2/28189.html

4th February 2008, 03:00 AM	#50
fierce_freak diyAudio Member Join Date: Jul 2007	I'd like to try 176.4 sometime. I still need to give 96 a try when I get home (only used 192 so far).