Another interesting r2r dac

[rickmcinnis]

And yet another r2r dac. Less than 500!

http://www.denafrips.com

Wish they offered the boards separately.

Funny how the opening page says they "made" affordable audio products. Guess we are late.

[rickmcinnis]

A diamond buffer suggests push-pull. I'd suggest an SE buffer is more likely to sound transparent than a push-pull.

I do not doubt that is true.

The trade off between ultimate purity and ability to drive the next component effortlessly.

I would think each situation would find a best approach.

I will need to try both

[abraxalito]

We really don't need classAB anywhere but for power. An SE stage biassed for a couple of mA is going to be able to drive a domestic line level signal into loads down to 5k or so without breaking a sweat. Certainly there are plenty of classD amps with input impedances lower than this but they're the exceptions and can be handled by running another couple of mA bias.

Yeah, you gotta try both.

[rickmcinnis]

I will be using some buffers to drive rcrc low pass networks - would stick with the simpler buffer for the output but will try all ways.

Are you going to play with the audio g-d DAC?

[abraxalito]

No, I've been lured away from multibit DACs by the results I've been getting with digital amp chips used as DACs. The dynamics beat off the already excellent results I was getting with my TDA1387 implementations. I'm currently listening to an STA326 (its essentially a PCM -> PWM conversion device) based amp via a 2:1 step-down into my speakers and the dynamics are the best I've had out of any amp. Now imagine how much better the dynamics will get when such a chip isn't used as power amp, but merely a DAC. By which I use a much larger step-down ratio (10:1 say) which puts a much, much lower load on the power supply.

As nige has been discovering, its all about power supplies - either make the PSU very low impedance (which nige has done with his battery approach) or increase the load impedance (step down transformers do this) or both. The dynamics chase for me is mainly about amps now as my PWM-based DACs are far, far from being the weakest link in the chain.

[rickmcinnis]

Well, you think you can write a post like that and not get the dogs of audio salivating?

Any chance of you showing us you set-up?

AS happy as I am with my Nigelized SOEKRIS I do think there is a lack of dynamics.

Would LOVE to give it a try.

[abraxalito]

Well, you think you can write a post like that and not get the dogs of audio salivating?

Ha, quite the opposite the precise aim is to get the interested parties interested and salivating wildly :)

Any chance of you showing us you set-up?

Have you looked at my blog over on DIYA? Here's a post about modding a digital amp into a DAC : http://www.diyaudio.com/forums/blogs/ab ... p-dac.html

And there are pics in the post about modding a digital amp to drive headphones (which is similar to making it into a DAC) : http://www.diyaudio.com/forums/blogs/ab ... c-amp.html

If that isn't enough I'm happy to open a thread on here to talk about progress.

AS happy as I am with my Nigelized SOEKRIS I do think there is a lack of dynamics.

What amp are you currently using?

Would LOVE to give it a try.

There's one aspect which has so far put a fair few people off - the custom wound transformers. But if there's a few people interested perhaps nige could persuade a transformer shop to make some?

[rickmcinnis]

I am using quite a few amplifiers; multi amp horn system.

Main amps are First Watt J2s (made into mono amps) and SIT 1s.

So your scheme is an "all in one" approach? DAC and amplifier?

If I only listened to digitized music that could be neat being able to use digital crossover stuff but I use a phonograph almost as much.

I must admit I do not look at the blogs section very often. Had no idea you had one there.

What you have shown leaves me confused as to how this is used as a DAC alone. (Which is not surprising)

For transformers, there is Dave Slagle over here. He would use nickel laminations. One would think those better than ferrite but I have no real idea. What do you think?

I certainly like the idea of a DAC with plenty of driving power.

Would my situation work with your DAC scheme?

There is nothing about this that scares me off but I know there is much I do not understand about what you are doing. Would not want you to go into detail for just one person.

SO, unless there is a chorus of folks wanting to try this do not start a thread on my account.

Take care,

[abraxalito]

I am using quite a few amplifiers; multi amp horn system.

Main amps are First Watt J2s (made into mono amps) and SIT 1s.

I'll have to investigate them to see if the PSUs are likely impacting their dynamics.

So your scheme is an "all in one" approach? DAC and amplifier?

Not yet, I'm not yet 100% happy with using the FDA chips as digital amps due to not being sure I've fully optimized the PSU. I'm still experimenting on that. But as DACs (digital amp with modified output filter and step-down transformer) they're my reference for D/A.

What you have shown leaves me confused as to how this is used as a DAC alone. (Which is not surprising)

Not surprising as its something a bit different that no-one else has done (rather like nige's output trafo volume controls!). But there might be some interest for those who're looking for the next step up in dynamics.

For transformers, there is Dave Slagle over here. He would use nickel laminations. One would think those better than ferrite but I have no real idea. What do you think?

Nickel is great but fairly costly. Not sure how DIY-able it is in terms of building your own cores. I use ferrite partly because its got lots of options in cores available but mostly because its cheap. It does have an advantage over nickel in that its non-conductive which makes for better isolation between input and output. This is fairly important in a DAC that's fed over a USB from a noisy PC.

I certainly like the idea of a DAC with plenty of driving power.

That is indeed one of the great beauties of this approach - depending on how you do it the driving power can be immense. You can get low output impedances without use of NFB if you think that's important.

Would my situation work with your DAC scheme?

Can't see why not.

There is nothing about this that scares me off but I know there is much I do not understand about what you are doing. Would not want you to go into detail for just one person.

SO, unless there is a chorus of folks wanting to try this do not start a thread on my account.

I'll wait a bit then and see if there's a sign of more interest than just you.

[nige2000]

assume dynamics start at the source and the soekris dac is fairly flat dunno if that is fixable though its x8 oversampling