Review and Measurements of Okto DAC8 8Ch DAC & Amp

[Kal Rubinson]

It is written Input sensitivity 2 V at 8 Ohms.

For the amp, it is not 2v at 8ohms. 8ohms is an output impendance. Input impedance is 10k (balanced) or 100K (unbalanced). Also significant is the specified gain at 23dB. This is about 6db lower than the majority but still OK.

But the dac also operates preamplifier for me..

If you are connecting the DAC to the preamp, the amp specs, except for gain, are irrelevant.

 

[BYRTT]

For the amp, it is not 2v at 8ohms. 8ohms is an output impendance...

Sorry i can be wrong here but If you ask me that was not what chezalfreo said, he listed input sensitivity is 2 V to bring out the full rated specified power 200 watts (1 kHz, 1% THD+N) over 8 ohms loads and then in specified full rated power over 4 ohms loads is nearly a double up listed as 375 watts (1 kHz, 1% THD+N) then input sensitivity for 4 ohms loads should be close to half of that for 8 ohms loads, also 8 ohms is not output impedance number for poweramp section, output impedance is much lower and listed as 0,035 ohms (20Hz-1kHz).

 

[Bliman]

@Bliman, a note is 4 ohms verse 8 ohms load need half the voltage to burn the same wattage and draws double the amps compared to 8 ohms, hope below links can help a bit clear the picture, its some neat calculators (fomula wheels) for electrics plus acoustics, that said you not lost with whatever output level you order for this unit in it can alway be changed down the road solder some other resistor values into unit:

http://www.sengpielaudio.com/calculator-ohm.htm

http://www.sengpielaudio.com/calculator-ak-ohm.htm

And here is main index for all their neat audio calculators at that site:

http://www.sengpielaudio.com/Calculations03.htm

Thanks. I am self-studying (I haven't studied it in school) calculus now and I am 1/3 through it thereafter I would like to try physics. And delve into electronics as well as par for the course. I think I need the calculus to follow the rest of the stuff.
But respect to all the one here that know all these stuff. That is impressive.

 

[Bliman]

I would buy the Dac8 stereo (when I tried it and it works well in my setup), I would connect it with the balanced XLR inputs provided in the Lyngdorf sda 2175 power amplifier I also would connect the dac with the NAD c542 cd player and circumvent the internal dac of the NAD cd player for the stereo dac8 of Okto Research through the optical input. The Lyngdorf would connect to Dynaudio 52Se speakers (4Ohm) and a Q acoustics 2070Si Active subwoofer.
So I would use the stereo dac8 as dac for the cd player and as pre amplifier for the system.
So what number should I take now?
So does the Oktoresearch work the same way as Benchmark? Do you also have to provide the number to Benchmark or does that work automatically?
"
Benchmark DAC1, DAC2, and DAC3 converters are designed to directly drive power amplifiers and speakers. Benchmark converters feature adjustable low-impedance passive attenuators at the XLR outputs that can be used to optimize the interface to the power amplifier (or powered monitor). This unique Benchmark feature optimizes the gain staging between the DAC and the power amplifier. Proper gain staging cannot be overemphasized. When audio stages are properly matched, each component in the audio chain is able to operate at its optimum signal level, and the system performance is significantly improved.
"
And should I then take this number and advice? "
It is written Input sensitivity 2 V at 8 Ohms.
As long as the output level of the DAC is > to the input sensitivity of your amplifier, you will be able to get full output from the amp, therefore you're good to go. "
Because I really don't see me soldering things. That would be a disaster.
Thanks for helping me all.

 

[BYRTT]

...And should I then take this number and advice? "
It is written Input sensitivity 2 V at 8 Ohms.
As long as the output level of the DAC is > to the input sensitivity of your amplifier, you will be able to get full output from the amp, therefore you're good to go. "
Because I really don't see me soldering things. That would be a disaster.
Thanks for helping me all.

If you end up make your mind and place a order suggest take a copy of specification datasheet for power amp plus speakers and send it to OKTO RESEARCH and let them guide what is best output level, a guess from amateur me is they set it 2 V or little less because your speakers is not 8 ohms but 4 ohms, that said don't be nervous if anything need a change down the road say you get a new power amp or set of speakers, then you can hire a local tech company or a friend with good eyes and right solder skills to replace those few resistors for you.

Will also suggest if your computer/head phone setup and player software can output over USB Audio Class 2 that you try out their tour unit to get a pre feel, a reel touch and feel of the 8 channel unit can maybe give peace in mind to order or not one of the stereo channel units.

 

[Bliman]

If you end up make your mind and place a order suggest take a copy of specification datasheet for power amp plus speakers and send it to OKTO RESEARCH and let them guide what is best output level, a guess from amateur me is they set it 2 V or little less because your speakers is not 8 ohms but 4 ohms, that said don't be nervous if anything need a change down the road say you get a new power amp or set of speakers, then you can hire a local tech company or a friend with good eyes and right solder skills to replace those few resistors for you.

Will also suggest if your computer/head phone setup and player software can output over USB Audio Class 2 that you try out their tour unit to get a pre feel, a reel touch and feel of the 8 channel unit can maybe give peace in mind to order or not one of the stereo channel units.

Thank you very much for the advice. Your response is very much appreciated.

 

[Kal Rubinson]

Sorry i can be wrong here but If you ask me that was not what chezalfreo said, he listed input sensitivity is 2 V to bring out the full rated specified power 200 watts (1 kHz, 1% THD+N) over 8 ohms loads and then in specified full rated power over 4 ohms loads is nearly a double up listed as 375 watts (1 kHz, 1% THD+N) then input sensitivity for 4 ohms loads should be close to half of that for 8 ohms loads, also 8 ohms is not output impedance number for poweramp section, output impedance is much lower and listed as 0,035 ohms (20Hz-1kHz).

Of course, your interpretation is correct but my response was to the direct quote of his statement.

It is written Input sensitivity 2 V at 8 Ohms.

 

[HammerSandwich]

...input sensitivity for 4 ohms loads should be close to half of that for 8 ohms loads

Huh? If wattage doubles from 8 ohms to 4, then output voltage is the same. Therefore, input sensitivity for full 4-ohm output will be almost identical, just a fraction of a dB less.

 

[BYRTT]

Huh? If wattage doubles from 8 ohms to 4, then output voltage is the same. Therefore, input sensitivity for full 4-ohm output will be almost identical, just a fraction of a dB less.

Myself have got it wrong then, thanks note.

 

[Okto Research]

Gotcha. I'm assuming this would hardly make an audible difference?

People with high-sensitivity horn tweeters might find themselves fighting noise. Although the noise of DAC8 PRO is just around 2.2 microvolts RMS A-weighted, it gets amplified 20-30x by the power amp. Halving the output RMS noise (increasing the dynamic range twice for a given output voltage) also halves the distance from where it is audible (omitting the noise of the power amplifier itself).

@Okto Research, I am eager to hear from you about the ongoing DAC8 PRO modifications

I would be really interested too @Okto Research

Please stay tuned for the final reveal. We are going to add something extra on top of the specifications on our website.

First DAC8 DSPs about to be delivered. More will follow soon.

 

[pos]

People with high-sensitivity horn tweeters might find themselves fighting noise. Although the noise of DAC8 PRO is just around 2.2 microvolts RMS A-weighted, it gets amplified 20-30x by the power amp. Halving the output RMS noise (increasing the dynamic range twice for a given output voltage) also halves the distance from where it is audible (omitting the noise of the power amplifier itself).

20x4Vrms is a tad hot for a compression driver

Please stay tuned for the final reveal. We are going to add something extra on top of the specifications on our website.

Hope this has to do with directing AES3 inputs to the USB soundcard! finger crossed...

 

[Zog]

Please stay tuned for the final reveal. We are going to add something extra on top of the specifications on our website.

Watching with great interest from New Zealand. Keep up the good work!

 

[escalibur]

People with high-sensitivity horn tweeters might find themselves fighting noise. Although the noise of DAC8 PRO is just around 2.2 microvolts RMS A-weighted, it gets amplified 20-30x by the power amp. Halving the output RMS noise (increasing the dynamic range twice for a given output voltage) also halves the distance from where it is audible (omitting the noise of the power amplifier itself).



Please stay tuned for the final reveal. We are going to add something extra on top of the specifications on our website.

First DAC8 DSPs about to be delivered. More will follow soon.
View attachment 25021

If only we could have a bit cheaper model with pretty much same specs but less connectors and much smaller physical size. Opinions?

 

[trl]

I was having good look inside this extremely good-measuring DAC and I realised that the +/-15V rails are not regulated stabilised on the PSU board, like the two +5V rails, instead there might be couple of power regulators from LT (SO8/SOIC) nearby the +/-15V plug from the audio mainboard. @Okto Research, I wonder if this approach was done on purpose to minimise any possible interferences that might get caught by long cables from the PSU to the audio mainboard, or it was simply a no-reason design.

Also, are those two regulators LT3045? Can't see them very well on the below picture. Thanks!

Also, I guess the multiple halls in the PCB are for cooling, right?

I also see the EMI/RFI filter from the mains, quite small and nice looking.

Thank you!

 

[777]

I don't like the colours of the high voltage wires. Are the same like low voltages wires.

 

[Okto Research]

Please note that this is one of the custom builds we did in the past and it may not be representative of the design of our current products.

I was having good look inside this extremely good-measuring DAC and I realised that the +/-15V rails are not regulated stabilised on the PSU board, like the two +5V rails, instead there might be couple of power regulators from LT (SO8/SOIC) nearby the +/-15V plug from the audio mainboard. @Okto Research, I wonder if this approach was done on purpose to minimise any possible interferences that might get caught by long cables from the PSU to the audio mainboard, or it was simply a no-reason design.

All the power supply rails are regulated both on the PSU side and DAC module side. The reason for that is to suppress the mains ripple close to the source to avoid radiation as well as provide a low-noise, low-impedance power where it is needed.

Also, are those two regulators LT3045? Can't see them very well on the below picture. Thanks!

Yes.

Also, I guess the multiple halls in the PCB are for cooling, right?

Yes.

 

[Ultrasonic]

First DAC8 DSPs about to be delivered. More will follow soon.
View attachment 25021

Will you be sending one of these to @amirm for testing? It's a product I'm very interested in .

 

[trl]

[...]
All the power supply rails are regulated both on the PSU side and DAC module side. The reason for that is to suppress the mains ripple close to the source to avoid radiation as well as provide a low-noise, low-impedance power where it is needed.
[...]

Thank you for the reply. I'm unable to identify what LDO's are you using in the PSU for the +/-15V, from the pics I can only see the two heatsinks for the LDOs for +5V only.

However, given the LT3045 LDOs from the audio mainboard, the OPA1632 opamps, the ES9028/9038PRO DAC chip, then combining all with a very well-engineered PCB, I guess is easy for everyone here to understand why it measures so good. I guess I speak for everyone else here when I say CONGRATS!

 

[Medul]

On the previous picture, I just noticed something interesting on the PCB: pin 1 of XLR output connector is mentioned to be "not connected to the PCB". Thinking about the different possible causes of "ESS IMD hump" discussed on other topics, I'm wondering if this unconnected ground is not "improving" in some ways the sensitivity or impact of common mode disturbances (i.e. including a kind of correlated noise that would appear as a THD/IMD) generated by ESS DACs on the differential outputs. If you don't connect the ground between your 2 devices (DAC and AudioPrecision in the case of Amirm testings) you are floating and it adds a non negligible common mode rejection to the system. Of course, we all know that we wouldn't be totally floating because of different parasitic impedances, and I know this is not the best way to proceed in pure terms of EMC, but be sure that the guys at Okto are well aware about EMC, they know how to work, and if they decide not to connect pin 1, they have good reasons...

An easy way to validate/eliminate this root cause would be to perform a test on an isolated (i.e. on PSU and inputs) DAC with the well known "ESS IMD hump", and to check if the hump is affected when connected using a cable with pin 1 left unconnected.

P.S: Sorry for my poor english skills...

 

[pos]

Hello @Medul, nice to see you here