Okto Research DAC8 Stereo - Streamer

[Qwin]

This is my latest acquisition and its a cracker.

Apologies for just copying this from my blog, it saved re typing.

https://www.jkwynn.co.uk/Project_Images/Okto/Okto_01.jpg

This is my Okto DAC8 Stereo - Streamer.
It's a high Quality DAC with a built in Raspberry Pi 4B for streaming.
I had a Topping D90 prior to this, a very good DAC in its own right, both in terms of measurements and in its subjective sound quality. I used this with a stand alone RPi4B to great effect, so why change?

The Okto measures slightly better and the built in RPi/PSU makes for fewer boxes on the shelf. It has a large clear display, nice styling and importantly for me, a customer specified output option.
Most modern DAC's have a full scale output of 4 to 4.5v RMS (balanced) and use a digital volume control, to act more like a digital Pre Amp. This is fine if your sources are only digital, but leads to a big imbalance in output if you also have analogue sources, like a Turntable/Phono Stage, working at line level. So I specified 2v RMS balanced output for my unit. I set the digital volume control to maximum, bypassing it and the display shows 0dB. This level of output is a much better match for my Balanced Phono stage. Not withstanding variations in track levels, my digital and analogue sources now give approximately the same output level. The volume is controlled by my Pre Amp.
Sound wise, there is not much in it, the Okto/Topping both give excellent levels of detail, good bass depth and a very Black background. In my set up, the Okto just noses ahead, it's a very slightly smoother/softer sound, so is a bit more forgiving of bright, or harsh recordings. It's a very easy listen, sounding totally effortless, it just disappears.

The Okto Streaming version comes with a RPi4B, having 1or 2GB of RAM, depending on availability at the time of build.
The stand alone RPi I had been using with the Topping has 4GB of RAM and I had installed heat sinks on this unit, so I installed this into the Okto.

https://www.jkwynn.co.uk/Project_Images/Okto/Okto_02.jpg

The top image is the standard RPi 4B and the lower one is after I applied the heat sinks.
I don't think the self adhesive foam strips, that are used on many of these heat sinks, gives a very efficient heat transfer, so I glued them in place, using a thermally conductive adhesive, designed specifically for gluing heat sinks together. It has a high adhesion level, good thermal conductivity and a working temperature of 180 deg C.


The Streaming function of the DAC is meant to be used "Headless" so no monitor/mouse etc. The unit is used as part of your home network and accessed via any networked device with a browser, so using your Phone or Tablet etc.
There is a big downside to this, if you take your unit to a hifi meeting or someone else's house, it won't function, as the network is not available. Even if you plug a USB stick of music into the unit, you can't play it, as the Headless operation requires the network to be in place. I also like to display my music library on my large screen TV via the RPi HDMI output and control it using a wifi "Air Mouse". I think its a mistake not to have exported the RPi's HDMI output to the rear panel of the unit, were you could easily plug in a monitor.

So, how do I modify my unit, to access the HDMI output?
The RPi4B uses Micro HDMI connectors, most monitors/TV's use full size HDMI.
There are not many Micro to HDMI adaptor leads around, even fewer, short enough for this application and I couldn't find a single one for panel mounting at the right length.
So I had to make one.

https://www.jkwynn.co.uk/Project_Images/Okto/Okto_03.jpg

This is what I made. I took a 150mm long Micro HDMI male to HDMI male connector lead and cast a block of JB Weld, a filled epoxy, around the HDMI connector body. I drilled and tapped it M3. The flexible jacket on the connector had a moulded groove around it, which I enlarged with a hot soldering iron. The JB weld flowed into this groove, making a robust fixing.

https://www.jkwynn.co.uk/Project_Images/Okto/Okto_04.jpg

This is the connector in position.



https://www.jkwynn.co.uk/Project_Images/Okto/Okto_05.jpg

I centred the new sockets position with the RPi's USB2 sockets and used CSK screws so as not to foul the Streamers USB output/input jumper strap.
I removed the back panel to make the cut out and screw holes. There are lots of screws to remove, the mains leads, and earth wires can be unscrewed, but you have to de-solder the 12v trigger wires from the back of the socket. There is plenty of access room to do this and I re-applied some heat shrink to the re-soldered joints, so it looks good as new.

I now have my NAS library displayed on my TV via the MoOde music player software I installed on the RPi.

There are measurements/reviews of these excellent Okto and Topping DAC's over at the ASR forum.

[mikeyb]

That's excellent, looks great and I bet it sounds good too [emoji4]

[Qwin]

That's excellent, looks great and I bet it sounds good too [emoji4]

It does Mike, absolutely stunning sound.

[mikeyb]

I use Moode on my Pi system to the main HiFi and I'd like to try a standalone DAC, but this look even more useful to me as I run Logitech Media Server to Squeezelite on Moode to access the streaming services I use.

I'm waiting on an R2R DAC Hat arriving to try on the Pi and see if I like that.

BUT I've also been looking at decent dedicated streamers too [emoji23]

[Qwin]

Based on your previous recommendation Mike, I also now use MoOde/Squeezelite and LMS to access Qobuz.
I have MoOde/LMS installed on the single internal RPi4B in the Okto DAC/Streamer.

I will be selling my Topping D90 shortly.

[mikeyb]

Based on your previous recommendation Mike, I also now use MoOde/Squeezelite and LMS to access Qobuz.
I have MoOde/LMS installed on the single internal RPi4B in the Okto DAC/Streamer.

I will be selling my Topping D90 shortly.Used Moode for years now and light recently started using LMS properly and it gives me everything I want.

[Qwin]

Yeh, me to Mike, though I do prefer the sound of MoOde's MPD player to Squeezelite.

I just balked at Volumio wanting money to access Qobuz, that in effect, made qobuz 50% more expensive for the basic package.

I like the way MoOde auto mounts any USB music stick you plug in to the RPi.
Means you can run demos at HiFi meets without an internet link or network set up.

[mikeyb]

I like Moode, it's been my favourite since I started using the Pi, donated a few times too as I think it's well worth it.

[Qwin]

I just downloaded MoOde 7.0.1
Will be flashing a copy of this when a new SD Card arrives.

I've also been experimenting on my current set up, with the BubbleUPnP App on my Android Phone. I can access Qobuz using this, with MoOde set as the renderer.
Had to switch on MoOdeUPnP in its config menu, but that was all, didn't even need BubbleUPnP Server installed on the network.

[Gazjam]

This looks fascinating as a Roon Endpoint.
Colour me interested!

Any way Ken a PS Audio comparable i2s output can be introduced to the mix?

[Qwin]

This looks fascinating as a Roon Endpoint.
Colour me interested!

Any way Ken a PS Audio comparable i2s output can be introduced to the mix?

No sorry it can't. At least not without some major surgery.
The GPIO socket on the internal Pi is only used for supplying power to the Pi.
Pavel (designer and CEO) at Okto used the asynchronous USB output of the Pi4 for audio.
I asked him and he said it is a very clean signal with no timing issues, on the other hand, the i2s output of the Pi4 is not good and needs re-clocking, it was much more straight forward to use the USB output to achieve good results. The results are spectacular, best measured to date at ASR forum and the subjective sound quality is equally as pleasing.

Note, I found on my PS Audio Stellar GCD that the i2s signal from my CD Transport did not sound as good as its coax SPDIF or AES output. I even bought a fancy (expensive) 300mm long HDMI lead, praised for its audio quality, to try and address this, but it made no difference.

It seems to come down to the quality of the implementation of i2s as to how good the results are. In the case of the Pi, its not done well, Allo do a re-clocking board for the Pi, the Kali, to address this issue, it costs more than than a RPi4B does, think I paid about £70 for one a couple of years back.
Sorry Gaz

[Qwin]

Ooops
I just noticed a typo in my first post.
The lead I modified was a Micro HDMI male to HDMI Female.
:o

[dgolh]

Hi Ken, I'm expecting mine( found 2ndhand) but ufortunately without the Ethernet and the usb interconnect card. I'm waiting for an answer from okto for a possible retrofitting but it will probably take a long time before I can read from them.

Is adding a Rpi4ib an hassle or can a total noob like me handle it? Of course the drill of the back plate might be an issue but I can find somebody to take careof this part of the job.

[ReggieB]

This is top of my DAC wishlist at the moment. There's a very good review of it in Stereophile (https://www.stereophile.com/content/okto-dac8-stereo-da-processor)

[dgolh]

I'm interested in a Soekris 2541 as well, mid-price dacs but very competent.

[Qwin]

Hi Ken, I'm expecting mine( found 2ndhand) but ufortunately without the Ethernet and the usb interconnect card. I'm waiting for an answer from okto for a possible retrofitting but it will probably take a long time before I can read from them.

Is adding a Rpi4ib an hassle or can a total noob like me handle it? Of course the drill of the back plate might be an issue but I can find somebody to take careof this part of the job.

Hi
There is a GPIO socket on the ethernett/usb PCB for the inverted RPi to plug into. Also that you have the SMPS (Black box next to the transformer) this powers the RPi through the GPIO socket. Other than that, cutting the holes is about all you need do. There are a couple of stand offs to locate the RPi.
The main thing is if you have the right power supply, check my picture in the first post, you can see the Black box SMPS above left of the Tranny. If you don't have this on your supply board, you will also need to upgrade to this PSU board.

[dgolh]

Thanks Ken. I can't wait receiving mine !

[Qwin]

You could possibly buy the correct backplate, with all the cut outs from Pavel at Okto.
You will also probably need to change the firmware as well, a friend has the 8 channel version and it definitely uses different firmware.
Have you considered asking Pavel to upgrade it for you?

[dgolh]

Hi Ken

I'm hoping an answer from him on this subject. My fear is that this retrofit could take more or less th esame time than their current lead time. Otherwise, I may take the Soekris way instead.

[Qwin]

Ok
His lead time, at the stated 6-8 weeks, is optimistic at best.
Mine took 15 weeks and my friends 8 channel about 12 weeks.
Mine is a special though, I had the output voltage reduced to 2vrms, to match more normal balanced line level devices, as per my balanced phono stage. I hate huge volume level differences between digital/analogue sources. Mine are now roughly the same, allowing for any mastering differences.
This involved changing resistors that set the gain level, which are SMD and part of the stock PCB's robot pick and place build, so fiddley hand done mods.

With this set up, I don't use the digital volume control, it's set to maximum, which disables it and the display shows 0dB as the output.
I use a separate Pre Amp (Shiit Freya+) for volume. To be honest, once the Okto is fired up, I have the screen auto blank after 5 seconds and it just sits there doing its job. The sound is very neutral using the default filters. My previous DAC, the Topping D90 sounded very slightly cooler, the Okto sounds so natural, you just forget about it being there.
Its a remarkable bit of kit, and for the price a real bargain.

[Qwin]

Thanks for the Stereophile link Rob, I hadn't seen that review.

[dgolh]

Wherever I read, 4 ou 5 months are frequent. Only 2 units are currently for sale 2ndhand, one in UE and the other in the USA. It seems to be the only way to get one on a sensible time limit.

[dgolh]

Finally, the seller has just let me down. So I will take a totally different direction for now and buy a Cocktail Audio X50D and a "small R2R dac" instead. Probalby a discounted Ares 2.

[dgolh]

Hi Qwin,

I've finally found a 2nd hand Dac8 Stereo. I'll use it with Heed PM Blocks which are only fitted with RCAs. What's the rest of your set ? Are you facing the same issue? How did you eventually fix it?

[Qwin]

Hi Didier
You were lucky to find a used unit, well done.
I have a Freya+ Pre Amp, which has two sets of balanced inputs.
The Okto plugs into one set and my Aqvox Balanced Phono stage plugs into the other set.
The Freya+ has one set of balanced and two sets of RCA single ended outputs, all live simultaneously.
I feed the Balanced outputs into a Marchand active x-over (LP 500Hz) and on to a Nord Class D two channel Amp, which services my bass drivers (Full balanced path).
I use one of the single ended sets of outputs on the Freya+ to directly supply a PrimaLuna PL4 Tube Stereo Power amp. This is connected to Troels Grevesen based passive crossovers in my speaker cabinets and supplies my Mids and Twts. This is a completely single ended path, but I swapped out the RCA sockets on both the Freya and the PrimaLuna for XLR connectors, its still Single ended, but now with a separate shield connection. I hate RCA's, my changes mean all my interconnect leads are the same type and interchangeable, regardless of being either balanced or single ended.

This is my set up:

https://www.jkwynn.co.uk/Project_Images/Yam_Rev/YamRev_02.JPG

If you want to see what I did to the Amps etc, find it all here on the bottom row of thumbnails: https://www.jkwynn.co.uk//Projects.html

Ken

[ReggieB]

That's a good find - I don't think they appear 2nb hand very often.

[dgolh]

It comes with the streaming function at a very interested price. It showed on a french Hifi forum at 11:23 and I bought it at 11:25 :lol:

Retirement has some good points :)

[dgolh]

@qwin: what are your findings when used without preamp?

[Qwin]

Never used it without a pre amp.
I have the digital volume control disabled (at max), so it's fixed at 0dB output on the display and runs full scale all the time.
I purchased the optional reduced output level and I had it built to a level that matches my Phono stages output.
So both the Okto and my Phono stage produce approximately the same volume level, track dependant of course.
In general, DAC's output levels have pushed up and up over the years, mine has been set to a more sensible level, similar to other line level devices.
It wasn't just attenuated to achieve this, the gain level was adjusted by Okto, there are parts on the board that set the gain level (output).
The Okto through my Tube pre amp sounds great.

[dgolh]

I can now fully support your opinion on this dac: it's really a winner.

It's worth the wait. It's a -no-brainer -(litterally) compared to the RME which is very good in its own right but with so many possibilities (instructions gave me a headache) :lol: