does the es9023 dac use output capacitors

[arjen]

The title says it all I guess...
I bought a DAC for Raspberry Pi, the Audiophonics Sabre ES9023 V3. Sounds very nice, I use it with Moode Audio on the PI.
I'm in the process of designing a new amplifier for my system, and I was wondering if I need input capacitors on my preamp in combination with this DAC. I looked at the data sheet for the ES9023 and it shows no output capacitors. Since it uses a single power supply this seems strange to me. I do not have an accurate enough voltmeter to see if there is any DC on the outputs, so I'm hoping for someone using the same chip to help me out.

Tnx

 

[Mooly]

Input coupling caps on a preamp are always a good idea imo.

The ES9023 uses a simple 'charge pump' to generate a dual rail supply, so no mystery there

From Wikipedia

A common application for charge-pump circuits is in RS-232 level shifters, where they are used to derive positive and negative voltages (often +10 V and −10 V) from a single 5 V or 3 V power supply rail.

https://en.wikipedia.org/wiki/Charge_pump

 

[arjen]

Thanks, I thought that might be the case but I could not find it in the data-sheet.
Input caps are usually a good idea indeed, but in my setup the DAC will be hardwired to the preamp so no mistakenly plugging a 'wrong' source in the capacitor-less input. I'll put them in anyway, but with the possibility to shortcut them.

Cheers,

Arjen

 

[Mooly]

Fair enough (on the caps ) but you need to be happy that any switch on/off behaviour is well controlled. In other words make sure the DAC output doesn't close in to zero volts (from some higher or lower voltage) at switch on, and that it doesn't wander up or down at power off as the rails collapse. Those scenarios can do unpleasant things in purely DC coupled systems.

If your preamp has correctly implemented muting at power on and off then that should be a non issue.

 

[arjen]

Good point. I did consider to implement a 'speaker-protection' circuit on the power amps, might as well use one to mute the pre-amp. Since the whole set will be controlled by a micro-processor, it should be easy to do a timed 'turn-on-sequence' as well. Pi (with DAC), pre-amp and power amp all have their own power supply so I could set it up so the Pi switches on first, the pre-amp a couple of seconds later, followed by the power amps. Another couple of seconds later the pre-amp can be un-muted. As I hardly ever turn off my set, it seems a bit overkill, but it takes only one spike to kill a tweeter...

 

[jean-paul]

Good idea to mute the preamps output while switching sources. It is precaution as ES9023 does not behave badly at power on.

ES9023 also does not need output capacitors but it does need the filter caps. DC offset is only a few mV, no worries there.

 

[phase]

How about a delay for turning on the preamp?(assuming the two are switched to come on at the same time)
That's how my setup works, dac, preamp sharing a case. The dac has a servo too, but the delay on the amp is a second defense.