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Denafrips Ares II + Topping Pre90 impedance issue

bsas

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Nov 10, 2021
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Hi,

So, I have the Denafrips Ares II DAC that I really like. I used to use it on my Aiyima 07 integrated amp since it has a volume control, but I recently got a VTV Purifi (EVAL1 buffer) amp that I love too, but, now I have to control the volume on the Ares 2. For that I recently got the Topping Pre90 preamp to be able to use it as an XLR preamp with volume control.

But, after that I notice that this combination doesn't sound right. After some reading and digging on the Pre90 review post I learned that it is an impedance mismatch between the Ares 2 and the Pre90. Sorry for my own ignorance, but I barely understand this impedance issues when we talk about line level (RCA or XLR) signal.

So, I don't want another DAC. What should I do? Any recommendation of something that can go between the Ares 2 and the Pre90 to "fix" the impedance issue? Can someone explain to me the reason why the impedance on those have such a huge effect? Can I just use the RCA inputs on the Pre90 with the RCA outs of the Ares 2 instead of the XLR and have no issues?

Thanks!
 
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roderickvd

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Oh wow, the Pre90 only has 10KΩ unbalanced in and 2KΩ balanced in? I think that's poor for a preamp, particulary when it's technically not difficult to have a buffer of 1MΩ. You'd be OK going unbalanced in from the Ares II. Given short enough cables you will probably never notice the drop in noise rejection, but you will notice a drop in volume. I don't know but your Purifi amp should have plenty of headroom?

The electrical and in turn acoustic effects of damping have been discussed at lengths on this forum and elsewhere. Just keep the ratio output impedance to input impedance 1:8 or better (1:10 and on) and you will be fine.
 
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bsas

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Oh wow, the Pre90 only has 10KΩ unbalanced in and 2KΩ balanced in? I think that's poor for a preamp, particulary when it's technically not difficult to have a buffer of 1MΩ. You'd be OK going unbalanced in from the Ares II. Given short enough cables you will probably never notice the drop in noise rejection, but you will notice a drop in volume. I don't know but your Purifi amp should have plenty of headroom?

The electrical and in turn acoustic effects of damping have been discussed at lengths on this forum and elsewhere. Just keep the ratio output impedance to input impedance 1:8 or better (1:10 and on) and you will be fine.

Purifi is fine, the problem is that it doesn't have a volume knob so in my mind I thought about the Pre90 as a volume control (the Purifi is 400W, aka, loud as f**k).
 
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bsas

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The latest firmware for the Ares II has digital volume control, if you fancy that. You can flash your current unit with it.

True… but I am never fully sure how much quality one losses with digital volume control :(
 

gvl

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For starters make sure you only have one set of inputs connected on the Ares, there’s a warning about it in the manual. If the issue is real you can indeed try the RCAs, it may work better due to higher impedance on the Pre90 for single ended. If that fails too you’ll need a different preamp with high input impedance. Or use digital volume control as suggested earlier.
 
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