COD - Current Output DAC

[JonPike]

Hmmmm.... after waiting forever and getting teased with promises that never pan out... (for TI's 1794 demo board) this sounds very interesting!

Can you give us some idea when these might be an available product?

[BrianDonegan]

I have about 20 boards that I need to build up. Should be next week. I'll get something up on the site for them.

[Russ White]

I have been listening to the COD now for a few weeks. Mostly with the passive I/V (270R resistor) into the ballsie. This sounds very good. But not really as good as the Opus.

Well I put back in the active I/V stage by putting the cap jumpers in (shorting them) and removing the resistors to GND, so that the DAC is now DC coupled to two TXDs with only THS4141s in them. This is MUCH better. Not just a little. The best way to describe the difference is just simply to say there is an apparent change in resolution. Dynamics just seem more realistic and alive.

Anyway here is how it looks in my test rig with the TXDs as I/V converters right before the ballsie.

Cheers!
Russ

[BrianDonegan]

I have made the remaining beta COD modules and boards available on our site (on the Opus page for now). They are the same as the production boards except for some layout tweaks and we replaced the jumpers with dip switches.

[neb001]

Originally posted by Russ White
Well I put back in the active I/V stage by putting the cap jumpers in (shorting them) and removing the resistors to GND, so that the DAC is now DC coupled to two TXDs with only THS4141s in them. This is MUCH better. Not just a little. The best way to describe the difference is just simply to say there is an apparent change in resolution. Dynamics just seem more realistic and alive.

When you say it's much better, did you mean in comparison to the opus or in comparison to the previous setup with the passive i/v?

[Russ White]

Originally posted by neb001


When you say it's much better, did you mean in comparison to the opus or in comparison to the previous setup with the passive i/v?

I meant better than the passive I/V + Ballsie. Though that setup is still very good!

Cheers!
Russ

[kstagger]

can't offer much on the technical side, but I'm running a PCM1794 via the K&K RAKK DAC using a Lundahl transformer for the IV conversion / outputs. Sounds very good - would like to see your results since the line transformers raised the price of the RAKK considerably.

[Russ White]

Some one one told me this:

Voltage sources like to see a high impedance, and current source like a low impedance.

Well the TXD configured for I/V is about as low as you can get impedance wise. It just in the 10s of milliohms.

At first I was not confident this would make much difference, but it really does. Everything just seems cleaner, not colored.

With passive I/V the sound is still good, but very definitely with a "warm" coloration.

Cheers!
Russ

[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.

Oh yes, there is a metronome in there too.

Cheers!
Russ

[Dougie085]

So with the improvement in the powersupply you think its still not as good as the Opus?