AK4497 DAC Project

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Ray P
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#1 AK4497 DAC Project

Post by Ray P »

I have a dual-mono AK4497 DAC kit on its way to me;

http://yanasoft.jp/yana/ak4497dm_dac.html

(I use Google Translate)

I will need to derive a single-ended signal from the DAC outputs (voltage output so no I/V required). I have previously had good results using a Broskie BCF on the outputs of a AK4490 DAC (single) and that remains an option (though the BCF has been out of stock for a long time)

However, as this new DAC is dual-mono it is a slightly different scenario as the DAC outputs need to be summed, here's the relevant datasheet schematic;

Image

Instead of using the 100uF cap and 10K/44R resistors, I'm wondering if I can simply connect the relevant DAC outputs together (to sum them) and feed the differential signals into a suitable transformer to derive the SE signal (I'm assuming the roll-off of the transformer will double up with LP filter duties too). Even better would be to use my Silk TVCs as the transformer.

The plan is to pass the SE signal to a 4P1L buffer stage.

Thoughts/comments?

Cheers

Ray
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#2 Re: AK4497 DAC Project

Post by jack »

I wouldn't mess with the internals - just use a balun transformer.

These might do :http://www.ebay.co.uk/itm/4-X-Lundahl-L ... 1905307295 - they're 1:1...
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#3 Re: AK4497 DAC Project

Post by Ray P »

Thanks Nick. I've made an enquiry about suitable Llundahl transformers for both the Diff/SE conversion but also possibilities for performing the summing too?

Having read more about the TVC and the potential loading it would place on the DAC outputs I have discounted using it. I can use the 32bit digital volume control option.

In my mind I have three possibilities for the output stage;

#1 - hook up the summed diff outputs to a Broskie BCF (balanced to SE buffer)

#2 - Use a transformer on the summed diff outputs to convert to SE and hook that into a 4P1L buffer/preamp stage

#3 - Use a transformer with dual primaries to sum the diff outputs straight from the DAC chip and convert to SE and hook into the 4P1L

Let's see what further investigation brings.
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#4 Re: AK4497 DAC Project

Post by Ray P »

I found a couple of other threads where people have done something similar;

http://www.diyaudio.com/forums/digital- ... age-2.html

http://www.diyaudio.com/forums/digital- ... stion.html

so it looks possible to sum and perform diff to SE via a transformer.

I contacted a Lundahl distributer and asked them to recommend a suitable Lundahl transformer and they have suggested either the LL1674 or LL1676 depending on how much stepdown I need (I need stepdown because my power amps have a sensitivity of around 1V and with the DAC output at around 2.5V, which is doubled with diff to SE conversion I may have too much gain). Just asked some supplementary questions but I think I'll act on the suggestions.

http://www.lundahl.se/wp-content/upl...heets/1674.pdf

http://www.lundahl.se/wp-content/upl...heets/1676.pdf
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#5 Re: AK4497 DAC Project

Post by Ray P »

So, I have a pair of Lundahl LL1676 transformers on the way from K&K Audio, following their advice.

The intention is to directly connect a primary to each set of DAC diff outputs, no caps, resistors, etc. The two primary windings will effectively act in parallel, summing the diff outs. The output from the secondary windings, connected in series, will be single ended. Overall ratio should be about 1:1.

Ray
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#6 Re: AK4497 DAC Project

Post by IslandPink »

Try & find a way of running-in those LL1676 off-line. They need a right hammering to open them out , if you don't, they'll sound grey & compressed for ever.
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#7 Re: AK4497 DAC Project

Post by Ray P »

IslandPink wrote:Try & find a way of running-in those LL1676 off-line. They need a right hammering to open them out , if you don't, they'll sound grey & compressed for ever.
Cheers Mark. K&K offered me a choice of new LL1676 @ $130each or used @ $85 each - I took the used ones so should be run in, at least partly.

Ray
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#8 Re: AK4497 DAC Project

Post by IslandPink »

Hopefully but not necessarily . I used mine for several weeks as phase-splitter on the Aurora amps, but then after advice, did something more , like running them off a CD player output or small power amp at controlled levels of several volts ( can't remember - based on their specs ) for a few days continuous - they then got much more transparent.
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#9 Re: AK4497 DAC Project

Post by viper »

status of the project?
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#10 Re: AK4497 DAC Project

Post by Ray P »

viper wrote:status of the project?
Greetings and welcome to Audio-Talk; tell us about your audio interests...

Project is paused for Christmas and while I wait for parts to arrive. I'll post when I have an update.

Ray
Last edited by Ray P on Wed Dec 28, 2016 6:08 am, edited 1 time in total.
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#11 Re: AK4497 DAC Project

Post by viper »

Hello I have a Yamaha 100w+100w amplifier, infinity speaker SM-125, Marantz cd (destroyed). I wanted to replace it with a good DAC I saw the 4497 ​​projects and I wanted to exchange ideas . Ray P have the PM?
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#12 Re: AK4497 DAC Project

Post by Ray P »

viper wrote:Hello I have a Yamaha 100w+100w amplifier, infinity speaker SM-125, Marantz cd (destroyed). I wanted to replace it with a good DAC I saw the 4497 ​​projects and I wanted to exchange ideas . Ray P have the PM?
No PM? I think you may have to post so many times before you can PM?

You need to be aware that my dual-mono AK4497 DAC kit is arriving from Japan courtesy of a friend over there, who purchased it on my behalf. The Japanese supplier will not ship outside of Japan. It is also a true kit in that it consists of a bare PCB and a bag of components; that includes the AK4497 chips, which are not soldered to the PCB.

Ray
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#13 Re: AK4497 DAC Project

Post by Ray P »

I didn't trust myself to solder the two DAC chips and other small ICs for this project so a good friend who is much more experienced and better equipped for such stuff agreed to do the difficult soldering for me; he's just shipped the smd-soldered PCB back to me. Looks like a good job.

Image

I had better move myself and order the through-hole components! I've already received the Lundahl transformers that I plan to use for the output.

Ray
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#14 Re: AK4497 DAC Project

Post by Ray P »

I've hardly touched this project since the New Year - probably spending too much of my spare time sitting on a bike!

It's now time to push on with it though so I'm just ordering the caps I need to finish populating the board.

I plan to try a couple of different output stages, firstly the Lundahl transformers but I'm also leaning towards a Broskie BCF valve balanced to single-ended buffer (which gives the option of a headphone output too).

Ray
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#15 Re: AK4497 DAC Project

Post by simon »

I used a BCF as the output stage of a DAC and the whole sounded wonderful, the best I've had from digital. Then I managed to break the sound somehow as I tweaked and could never get it back. So good luck, it should sound great!
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