Källa DAC

A source of endless thrills

Moderator: Staff

Post Reply
matthias
Very active member
Very active member
Posts: 2108
Joined: 2007-12-25 16:47
Location: Germany

Källa DAC

Post by matthias »

From a Source First POV the DAC is not the most important part of a streamer.
It is very interesting anyway.

Fredrik,
would you care to tell us something about the DAC inside Källa?
Thank you.

Matt
Matt

MBP / Exposure pre + power (both modified) / JBL3677
User avatar
lejonklou
Administrator
Administrator
Posts: 6579
Joined: 2007-01-30 10:38
Location: Sweden
Contact:

Re: Källa DAC

Post by lejonklou »

Sure!

95% of the DAC in Källa is regulators and control systems. They feed and control an AKM AK4358VQ DAC chip, which is an 8-channel DAC on which the two best sounding channels are used and the other six are inactive. The main reason for choosing the apparently simple AK4358VQ is that it sounds fantastic when treated right. Another reason is that it's powered by 5 Volts only and this proved very advantageous when making it work harmoniously with the Tinkerboard.

The AK4358VQ is followed by an analogue output stage, which is a differential input, single-ended output, second-order low-pass MFB filter using one operational amplifier, plus a slow-acting active servo that keeps the output at zero volts DC. The output of nominal 1.57 Volts is connected directly to the RCA connectors, with no degrading output capacitors, muting circuits or relays. This can be heard when switching on Källa as tiny clicks in the speakers when each circuit is activated. When the DAC is fully operational and Källa has established a connection with the local network, a short melody is played in the speakers and Källa will appear as 'Lejonklou' in your control point.

Most of the work spent on tuning the DAC revolved around making Tinkerboard, DAC chip and analogue output stage work together in complete harmony. There are multiple ways in which they can connect and feedback each other and often the tightest and simplest connections are the best - but not always. The only way to find the most harmonious scheme is to build and listen to them all.

By the way, the output level of 1.57 Volts means you can connect Källa directly to a Tundra or a pair of Tundra Mono, in case you like to listen loud. It's a very addictive party set-up.
matthias
Very active member
Very active member
Posts: 2108
Joined: 2007-12-25 16:47
Location: Germany

Re: Källa DAC

Post by matthias »

lejonklou wrote: 2021-07-27 22:46 Most of the work spent on tuning the DAC revolved around making Tinkerboard, DAC chip and analogue output stage work together in complete harmony.
Fredrik,
this sounds very good, but what happens when Asus release a complete new generation of Tinkerboards and the AKM chip becomes obsolete?
Thanks

Matt
Matt

MBP / Exposure pre + power (both modified) / JBL3677
User avatar
lejonklou
Administrator
Administrator
Posts: 6579
Joined: 2007-01-30 10:38
Location: Sweden
Contact:

Re: Källa DAC

Post by lejonklou »

matthias wrote: 2021-07-27 23:47 Fredrik,
this sounds very good, but what happens when Asus release a complete new generation of Tinkerboards and the AKM chip becomes obsolete?
Thanks
Tinkerboard 2 is already here. If we should find it better we can replace it, but it's unlikely that we will. It's performance enhancements (speed, memory, etc) are not needed in Källa.

Obsolete chips can be sourced for many years after they're gone. When we can no longer find it, we'll likely have designed a new DAC.

Electronic components are being discontinued and replaced every day. It's one of my main challenges as a HiFi manufacturer. When I find something that works really well, I gradually stock up on it while I continue to test alternatives.
Sopper
Very active member
Very active member
Posts: 440
Joined: 2017-05-16 14:50
Location: The Netherlands

Re: Källa DAC

Post by Sopper »

lejonklou wrote: 2021-07-27 22:46
By the way, the output level of 1.57 Volts means you can connect Källa directly to a Tundra or a pair of Tundra Mono, in case you like to listen loud. It's a very addictive party set-up.
Hi Fredrik, i noticed a big difference in volume between current source and KÄLLA
2v output vs 1.57v
How do I calculate the difference in db?
I need this to level the volume and be able to compare the KÄLLA with my current source.

And why did you choose 1,57v?
I thought 2v was standard for RCA output of sources?
KÄLLA > Sagatun Mono 1.7 > Tundra Mono 3.0 > Graham LS8/1F
Cables: Trivium Audio Cables
User avatar
ThomasOK
Very active member
Very active member
Posts: 4376
Joined: 2007-02-02 18:41
Location: United States
Contact:

Re: Källa DAC

Post by ThomasOK »

I believe that 2v is the standard output level that was specified for full output on CD players when they were introduced. It was never a standard for anything else as far as I am aware and units like cassette decks and tuners used to be much less than that, often in the range of .8V. The cynical might opine that was done to make CDs sound louder than other sources in the early 80s and hence better to the untrained ear. Over time most modern line level equipment has upped the output level to be around 2V so consumers don't have to deal with the vast differences in volume they did in the early days of CD when changing to other sources. So most streamers and modern tuners, and often phono stages, tend to be at around that 2V level. But there is no actual specified standard that I am aware of.

I'm not sure the exact reason Fredrik set the Källa at 1.57V but I'm sure there is a good reason. As to the volume difference I believe it would be 2dB. This is based on the Sagatuns which with a 2V input put out 1.59V at the 78dB volume level they stop at out of the box and 2V, or unity gain, at an 80dB volume setting. That volume stop on the Sagatuns was put there to help keep from overloading the Tundras which barely start to clip at 1.66V. With an input level that is below 2V you can turn the volume higher without clipping which means it is sometimes beneficial to remove the volume limit on turn on of a Sagatun. This procedure is simple and covered in the manual.
The LP12 Whisperer
Manufacturer, Distributor, Retailer and above all lover of music.
User avatar
lejonklou
Administrator
Administrator
Posts: 6579
Joined: 2007-01-30 10:38
Location: Sweden
Contact:

Re: Källa DAC

Post by lejonklou »

Sopper wrote: 2023-02-24 18:55
lejonklou wrote: 2021-07-27 22:46
By the way, the output level of 1.57 Volts means you can connect Källa directly to a Tundra or a pair of Tundra Mono, in case you like to listen loud. It's a very addictive party set-up.
Hi Fredrik, i noticed a big difference in volume between current source and KÄLLA
2v output vs 1.57v
How do I calculate the difference in db?
I need this to level the volume and be able to compare the KÄLLA with my current source.

And why did you choose 1,57v?
I thought 2v was standard for RCA output of sources?
The difference between 1.57 and 2 Volts is 2 dB. You calculate it by 20*log(A), where A is the output level in Volts.

There is a very specific reason for the 1.57 Volts output level: That’s where it ended up after I had tuned all the parameters of the DAC.

Every sensible manufacturer settles in advance on an output level for their DAC. And then they don’t change that. Just like they decide on a certain gain for their power amp. And for their MC phono preamp.

These decisions are convenient. There are less combinations to try and you don’t have to tell the customer to adjust the volume when comparing with other brands.

I don’t decide on anything in advance. Everything can be varied in the quest for a more intense musical experience. That’s why Entity has such a high gain and Källa ended up a little lower in output level than standard.
Sopper
Very active member
Very active member
Posts: 440
Joined: 2017-05-16 14:50
Location: The Netherlands

Re: Källa DAC

Post by Sopper »

lejonklou wrote: 2023-02-24 20:49
I don’t decide on anything in advance. Everything can be varied in the quest for a more intense musical experience. That’s why Entity has such a high gain and Källa ended up a little lower in output level than standard.
Now I think of it, I could/should have known this. This is your design philosophy and why Lejonklou sounds so natural and real.

I’ll go read about db, dbu and dbr to figure out how I can volume level my 2 setups.
You all sure want some listening clips for comparisons

@Tokenbrit: thanks for the info; 2v for CD player smells like marketing to trick us
KÄLLA > Sagatun Mono 1.7 > Tundra Mono 3.0 > Graham LS8/1F
Cables: Trivium Audio Cables
tokenbrit
Very active member
Very active member
Posts: 2048
Joined: 2012-03-22 19:47
Location: New England

Re: Källa DAC

Post by tokenbrit »

Sopper wrote: 2023-02-25 08:18
...
@Tokenbrit: thanks for the info; 2v for CD player smells like marketing to trick us
That info was from Thomas... but that's OK ;)
User avatar
lejonklou
Administrator
Administrator
Posts: 6579
Joined: 2007-01-30 10:38
Location: Sweden
Contact:

Re: Källa DAC

Post by lejonklou »

And accurate info, as always, so he certainly deserves the credit! :)
Post Reply