Hi there.
I recently received an IMO excellent Gustard A18 (which comes with the AKM AK4499 inside).
The DAC performs really nice of-the-shelve. After applying this or that little tweak - it got me really impressed.
One thing is bugging me big times.
The DAC >> amp integration.
As an amp I am running a Purifi Eval1 @0dB on input stage (resp. overall 12.8dB gain) btw.
The DAC comes with 3/6V on it's output. For a direct DAC-amp coupling this is obviously much too high.
And starting with -20dBFS attenuation, that's what I am looking at, on the digital side is not the best of all options either.
What would you guys suggest to get the level properly in place without jeopardizing the audio performance ?
A fixed inline attenuator? DIY? What about impedances? Quality?
Or even an output stage mod?
Further I could ask myself if it is wise to run the amp at 0dB, which lowers its input impedance. If that'd be the case I'd have to go even lower on
the DAC side!?!?
Proper DAC >> amp integration IMO remains a hot topic. And not just for my setup.
THX
I recently received an IMO excellent Gustard A18 (which comes with the AKM AK4499 inside).
The DAC performs really nice of-the-shelve. After applying this or that little tweak - it got me really impressed.
One thing is bugging me big times.
The DAC >> amp integration.
As an amp I am running a Purifi Eval1 @0dB on input stage (resp. overall 12.8dB gain) btw.
The DAC comes with 3/6V on it's output. For a direct DAC-amp coupling this is obviously much too high.
And starting with -20dBFS attenuation, that's what I am looking at, on the digital side is not the best of all options either.
What would you guys suggest to get the level properly in place without jeopardizing the audio performance ?
A fixed inline attenuator? DIY? What about impedances? Quality?
Or even an output stage mod?
Further I could ask myself if it is wise to run the amp at 0dB, which lowers its input impedance. If that'd be the case I'd have to go even lower on
the DAC side!?!?
Proper DAC >> amp integration IMO remains a hot topic. And not just for my setup.
THX
Last edited:
A stepped attenuator followed by a fet buffer? Or, maybe try it with and without buffering. IME AK4499 sounds best running in direct DSD mode, with no internal volume control. Don't know if Gustard A18 lets it run in that mode or not. Do believe Topping D90 allows direct DSD (volume control bypass) if it is operating in 'dac' mode rather than 'preamp' mode.
Here's some brainstorming I did for planning and calculating an inline-attenuator matching my setup.
Gustard AK18 DAC output impedance - DIFF = 100 Ohm
Purifi Eval1 AMP input impedance - DIFF = 4k4 Ohm
AMP gain = 12.8 dB
Required analog attenuation = 20dB >> factor 10 = 6V >> 0.6V
GND -----------------
..............R1/2
IN+ ----*****--------
...........................|
...........................*
...........................* R2
...........................*
...........................|
IN - ----*****---------
.............R1/2
R2 = 200R R1/2=1000R
The amp sees the 200R impedance. And the DAC is probably not too much loaded, with the 2k2 divider.
Not sure if this would work properly. Any comments?
* 0.25W resistors would do.
* as resistors I could go for e.g. Vishay Metal Film
* the divider gets attached to the amp input
Any thought from you guys? What do I miss? Any improvement proposals ?
THX
Gustard AK18 DAC output impedance - DIFF = 100 Ohm
Purifi Eval1 AMP input impedance - DIFF = 4k4 Ohm
AMP gain = 12.8 dB
Required analog attenuation = 20dB >> factor 10 = 6V >> 0.6V
GND -----------------
..............R1/2
IN+ ----*****--------
...........................|
...........................*
...........................* R2
...........................*
...........................|
IN - ----*****---------
.............R1/2
R2 = 200R R1/2=1000R
The amp sees the 200R impedance. And the DAC is probably not too much loaded, with the 2k2 divider.
Not sure if this would work properly. Any comments?
* 0.25W resistors would do.
* as resistors I could go for e.g. Vishay Metal Film
* the divider gets attached to the amp input
Any thought from you guys? What do I miss? Any improvement proposals ?
THX
If you listen to 24 bits materials (have you many ?), does the 10 db bits left of the dac chip not enough with its internal attenuator or the outrputt will spread always the same outputt voltage level anyway?
Maybe Meldano little Muse kit, less noise contribution ? very transparent and can be remote volume controlled as well if needed...
Maybe Meldano little Muse kit, less noise contribution ? very transparent and can be remote volume controlled as well if needed...
So.
I figured Metal Film would be a bad choice. Bulk Metal Foil is supposedly the much better choice.
Here's a video of a pro audio guy who compared metal film vs. bulk metal foil.
People who spread "the choice of resistors is almost irrelevant" for such an inline-attenuator are simply wrong as it seems.
I figured Metal Film would be a bad choice. Bulk Metal Foil is supposedly the much better choice.
Here's a video of a pro audio guy who compared metal film vs. bulk metal foil.
People who spread "the choice of resistors is almost irrelevant" for such an inline-attenuator are simply wrong as it seems.
I used to use Rhopoint resistors for I/V conversion of my tweaked 1543 DD DACs ~10 years back. Yep. Time flys.
In the end I experienced the same as described in the video. Resistors can make a huge difference if used that way. Nothing new though. There are numerous threads around confirming it.
Thinking about it. That divider would most probably also benefit from such a Rhopoint R.
In the end I experienced the same as described in the video. Resistors can make a huge difference if used that way. Nothing new though. There are numerous threads around confirming it.
Thinking about it. That divider would most probably also benefit from such a Rhopoint R.
The video brought me back on track, a track I left about 10 years ago 
Reminding me of good old Rhopoint times.
And making these people look like fools who're spreading the "it doesn't matter what resistor you choose..." message.
Talking about videos...
Amazing that a pretty cheap youtube video can clearly show the differences in sound.
A hundred times better then endless discussions or fighting audio-trolls.
Talking about videos...
I also already swapped the fuse of the Gustard. I basically bridged it with a silver wire for the time being. It's no secret that fuses can have a pretty solid impact on the audio performance. And to me it made a big difference.
A video that reminded me once more about the fuse topic was this one.
Once more a piece that makes all these "wannabe scientific audiophools" look stupid.
Enjoy.
Reminding me of good old Rhopoint times.
And making these people look like fools who're spreading the "it doesn't matter what resistor you choose..." message.
Talking about videos...
Amazing that a pretty cheap youtube video can clearly show the differences in sound.
A hundred times better then endless discussions or fighting audio-trolls.
Talking about videos...
I also already swapped the fuse of the Gustard. I basically bridged it with a silver wire for the time being. It's no secret that fuses can have a pretty solid impact on the audio performance. And to me it made a big difference.
A video that reminded me once more about the fuse topic was this one.
Once more a piece that makes all these "wannabe scientific audiophools" look stupid.
Enjoy.