[regal]

Really what the Ori and Zapfilter analog stages are doing is simple: differential to single ended buffer.

I am baffled by the lack of info on audio sites on making this basic upgrade to a voltage out DAC

This page describes I think a good method to do this:

http://ultranalog.com/cdenhancer/sac...ancer_evo3.pdf

 

[TzeYang]

are you sure Zapfilters use the same thing?

To me it looks like a very very very simple discrete opamp with single ended output stage

The IV conversion is also done with this circuit too? in anyway, even cetoole's IV converter is much complext than this lol.

 

[Pars]

A voltage-out DAC doesn't need I/V (current-to-voltage) conversion... I haven't studied these at all, but I would assume that it is much simpler than I/V for a current-out DAC. It might basically be just a buffer. The complexity of the zapfilter comes from it being configurable for both v-out and i-out DACs, and both single-ended and balanced (IIRC). As far as its use as a single-ended I/V converter, I would doubt that it would outperform such DIY stage as cetoole's, Jocko's etc.

 

[joe_cool]

Perhaps you don't realize this analog DAC circuit is normally a multi-pole low pass filter. Some commercial DAC chips are single-ended with no need for external differential conversion.

 

[00940]

If it's a differential output, you could easily use a dynalo with only one pair of output transistors to perform the balanced-unbalanced conversion and analog filtering.

 

[majkel]

I guess there are two reasons why DIYers don't care about V-out DACs.
1) Such a DAC is nothing but a linear source, you just need a filter/amplifier stage. There are lots of schematics for active low-pass filters.
2) V-out DACs are inferior to I-out DACs because they have already built-in I/V converter which is of arguable sonic quality for die-hard audiophiles. Some say V-out DAC is a I-out DAC with a mediocre op-amp I/V converter inside.

 

[TzeYang]

Quote:

Originally Posted by Pars /img/forum/go_quote.gif A voltage-out DAC doesn't need I/V (current-to-voltage) conversion... I haven't studied these at all, but I would assume that it is much simpler than I/V for a current-out DAC. It might basically be just a buffer. The complexity of the zapfilter comes from it being configurable for both v-out and i-out DACs, and both single-ended and balanced (IIRC). As far as its use as a single-ended I/V converter, I would doubt that it would outperform such DIY stage as cetoole's, Jocko's etc.

hmmm, but it seems to me that the Zapfilter also mentioned IV conversion in their circuit. I thought we were talking about zhaolu and it's siblings? Those arent voltage DACs are they?

 

[joe_cool]

Quote:

Originally Posted by TzeYang /img/forum/go_quote.gif hmmm, but it seems to me that the Zapfilter also mentioned IV conversion in their circuit. I thought we were talking about zhaolu and it's siblings? Those arent voltage DACs are they?

The Zhaolu DACs use the AD1852 and/or CS4398 DAC chips. These are differential voltage output converters. I believe the Benchmark DAC1 uses an AD1853 which is a current output DAC.

 

[00940]

Quote:

Originally Posted by majkel /img/forum/go_quote.gif I guess there are two reasons why DIYers don't care about V-out DACs. 1) Such a DAC is nothing but a linear source, you just need a filter/amplifier stage. There are lots of schematics for active low-pass filters. 2) V-out DACs are inferior to I-out DACs because they have already built-in I/V converter which is of arguable sonic quality for die-hard audiophiles. Some say V-out DAC is a I-out DAC with a mediocre op-amp I/V converter inside.

The new generation of voltage out DACs (like the wolfson wm8740 or cs4396) isnt' working that way. They use the switched capacitor topology, not an internal opamp like the TDA1547 did.

 

[TzeYang]

Quote:

Originally Posted by joe_cool /img/forum/go_quote.gif The Zhaolu DACs use the AD1852 and/or CS4398 DAC chips. These are differential voltage output converters. I believe the Benchmark DAC1 uses an AD1853 which is a current output DAC.

thanks. So which means if i want to modify the zhaolu's output stage, a buffer that takes differential input will work?

 

[TzeYang]

because the output does not have sufficient current to "turn on" the input transistor bases of the opamps.

 

[Cauhtemoc]

Quote:

Originally Posted by majkel Some say V-out DAC is a I-out DAC with a mediocre op-amp I/V converter inside.

And some say that mankind never really went to the moon, but it doesn't make that true either.

 

[joe_cool]

Quote:

Originally Posted by Shopper /img/forum/go_quote.gif With a DAC like the AD1852 that has differential voltage outputs, do you strictly need low Ib opamps in the analog stage in order not to have DC offset on the line output?

No, the impedances are kept low to control the noise figure. See page 14 in the datasheet for a similar circuit.

AD1852 datasheet

 

[regal]

Quote:

Originally Posted by majkel /img/forum/go_quote.gif I guess there are two reasons why DIYers don't care about V-out DACs. 1) Such a DAC is nothing but a linear source, you just need a filter/amplifier stage. There are lots of schematics for active low-pass filters. 2) V-out DACs are inferior to I-out DACs because they have already built-in I/V converter which is of arguable sonic quality for die-hard audiophiles. Some say V-out DAC is a I-out DAC with a mediocre op-amp I/V converter inside.

Maybe we should care with people making a lot of money installing a few transistors in Zhalou's.

A modern V out DAC is not a I-out DAC with a built in I/V. Study up on Sigma Delta.

To me sharing ideas so people can save a dime is what DIY is all about. People love the OMZ's.

The real trick is the differential to single ended transfer, to be honest I have trouble grasping it and how to adjust the gain to match the different V out p-ps of different chips.

Why not make a project out of it.

Or even better how about a discrete analog stage for the EZDAC. Again the differential to single end and the high p-p current out of the PCM1794 make plugging in a Jocko, Ctool, or D1 difficult for me.

I like this idea better since it is DIY start to finish. I'll start a new thread if people would like to make it a project.

 

[00940]

Quote:

Originally Posted by regal /img/forum/go_quote.gif The real trick is the differential to single ended transfer, to be honest I have trouble grasping it and how to adjust the gain to match the different V out p-ps of different chips.

That's quite easy to understand with opamps (and your discrete stage is just a discrete opamp): http://www.analog.com/library/analog..._Ch2_final.pdf

Quote:

Or even better how about a discrete analog stage for the EZDAC. Again the differential to single end and the high p-p current out of the PCM1794 make plugging in a Jocko, Ctool, or D1 difficult for me

I don't see why you couldn't use those... just change the value of the I/V resistor to get the desired voltage out.