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Buffalo II

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Does the diagram imply that half the dacs of one ESS are in anti-phase mode?

If all the DACs are in-phase, wouldn't it be simpler to just connect both +V and both -V of one DAC together and then use a single IVY?

Sure it would be simpler, sort of, but it would not be symmetrical. It is the symmetry which in part produces the superb dynamic range and low distortion we can achieve.

There is a very good reason the "off-side" is anti-phase and it would not be optimal to use one IVY-III and two DAC modules, but it is certainly still possible, and not hard to do.

The very important reason the DAC is designed to stack with the IVY-III module is that our testing has shown that the signal symmetry and length are key to good performance, and in no small way. It is critical. By keeping the signal lengths exactly the same length and very very short we improve dynamic range.

That said if you *really* wanted to, you could indeed take the anti-phase side and simply wire it in phase to the same side of an IVY-III as the in-phase side. But, that kind of wiring compromise is likely to completely defeat any gains you might have other wise had in dynamic range. You would be surprised what a couple inches of inductance and EMI antennae can do. :)

What I have done is actually a very common way to route dual mono DACs. TI and Wolfson both work this way as well in mono mode, and for very good reason. It is not new territory I am charting here. Take a loof at those data sheets. :)

When I called TI a few years ago about why they designed the PCM1794A this way I did not really get it. Now I do. :)

I am pretty confident if the ES9018 had a hardware mono mode it would also work this way. :)

So now you should have a good idea why it is anti-phase. Of course, how you wire it is completely up to you. :)

Cheers!
Russ
 
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Hi Russ, thanks for the explanation. I have no doubt careful wiring is required to improve on the DNR (I know that's why you designed Buf32s). Just wanted to know how things operate. The data sheet is just bare minimum in comparison to Wolfson or BB data sheets. I wasn't sure if setting the DAC in mono mode you still had the option of setting the phase of the individual DACs,
 
Can we connect the buffalo II to an unbalanced I/V output module such as the Lampizator or the Tubizaotor offered here as a group buy? Thanks.

The Lampizator also shows a balanced circuit based on Voltage out

BuffaloDAC

I am going to try Ron Welborne's Cato module set up as a passive I/V converter for DACs with differential output. This a low voltage unit that I have used with 6GM8s,7308s and 6H(N)6Ps.

DAC Tube Output Stage Kit

Hope it is OK to put this reference. Apologies if not.

Russ - what resistor value should be used for this passive conversion.

Thanks

Bob
 
Why Vout is degraded?

What is the theory behind voltage mode not being as good as current mode?

Is it because the DAC expects a lower impedance at the output? so driving current is "easier" on the DAC?

I also understand that if you add a balanced stage you will filter out a lot of the common mode noise.

That being said, if you are feeding directly to a balanced amplifier, a resistor I/V has some appeal due to its simplicity, linearity and low noise.
 
What is the theory behind voltage mode not being as good as current mode?

Is it because the DAC expects a lower impedance at the output? so driving current is "easier" on the DAC?

I also understand that if you add a balanced stage you will filter out a lot of the common mode noise.

That being said, if you are feeding directly to a balanced amplifier, a resistor I/V has some appeal due to its simplicity, linearity and low noise.

The reason is that the DAC likes to work into a constant voltage.

The only way to achieve that is for the DAC to drive an extremely low impedance. If the voltage the DAC "sees" modulates then it causes distortion. And, you would be surprised how even a seemingly small impedance like 10 ohms can have a pronounced negative effect and increase THD.

So in short you have to keep the voltage at the DAC output from modulating with the analog signal to get the best results.

Is -108db THD+N good enough? Well sure for many it will be, but I much prefer not to have that extra 10-12db of distortion present if I can help it. :)

Cheers!
Russ
 
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I plan on using a single Placid for the Buffalo II and a bipolar Placid for the IVY III. I know you sell 15VA and 30VA transformers, but I'm curious if we could use smaller transformers without compromising performance.

Well, the 15VA is only 9V, so you would have low-ish rails. I do have some 25VA 15V transformers which are a little smaller, if that's what you are looking for.
 
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