DAC- Amp input/output impedance and sensitivity - Advice

[jrivask]

Hi there, this is my first post and I apologies in advance in case my question makes no sense because I confess I know nothing about electronics and I'm quite confused with terms like "input sensitivity" "output/input impedance" "Vrms" and "mV"

Now, my question is how to integrate my Violetric V281 headphone amplifier in between the rest of my equipment and how to best utilise some of its features.

My main DAC is an Auralic Vega, my main amplifier is a Luxman L550AX and the speakers are Harbeth Super HL5 Plus.

What I want is to chain the V281 in between the Vega DAC and the Luxman so I don't have to connect/disconnect the cables depending whether I want to listen to headphones or the speakers.

The "issue" is that the Vega DAC has a very "hot" output and the Luxman amp is very sensitive and I'm worried there is an impedance mismatch that will make the amplifier clip. Please check the attachment. The good news is that the Violectric have internal jumpers that will allow me to modify the output signal and I'm wondering if I should switch them to -12db or -6db in order to match better the output level coming from the DAC and the input sensitivity of the Luxman? I'm currently connecting the DAC to the V281 via XLR and then from the V281 to the Luxman also via XLR.

Please let me know if I'm worried about nothing and I should leave the jumpers in the 0 position or if I should lower the output.

Kind regards and thank you in advance!

 

[Blumlein 88]

Welcome to ASR since this is your first post.

Firstly you don't have any impedance issues with what you wish to do. You may have gain (or sensitivity) issues.

If it were me, I'd send the XLR output from the Auralic directly to the power amp. Send the RCA output from the Auralic to the Vioelectric input. So you've got headphones and speakers available without any wire plugging or unplugging. You could even have both speakers and headphones.

The Auralic has 4 volts max output (no word on if it is the same on RCA, it might be only 2 volts on RCA). You'll have to turn it down, but the digital volume control will cause no issues doing that. You'll have a clean signal path to the speakers.

The Auralic is very low noise, so even using RCA for a short distance to the Vioelectric will likely not cause any noise. Make sure your cables have some shielding. I'd start with the Vioelectric pre-gain down at -12 db. If that is too low you can turn it up, but probably will be about right. If there is separate internal gain setting on the Vioelectric I'd start with it also at -12 db, and just see if that is enough or you need less attenuation. You also may or may not benefit from a ground lift in the Vioelectric with single ended RCA cables between it and the Vega.

 

[jrivask]

Welcome to ASR since this is your first post.

Firstly you don't have any impedance issues with what you wish to do. You may have gain (or sensitivity) issues.

If it were me, I'd send the XLR output from the Auralic directly to the power amp. Send the RCA output from the Auralic to the Vioelectric input. So you've got headphones and speakers available without any wire plugging or unplugging. You could even have both speakers and headphones.

The Auralic has 4 volts max output (no word on if it is the same on RCA, it might be only 2 volts on RCA). You'll have to turn it down, but the digital volume control will cause no issues doing that. You'll have a clean signal path to the speakers.

The Auralic is very low noise, so even using RCA for a short distance to the Vioelectric will likely not cause any noise. Make sure your cables have some shielding. I'd start with the Vioelectric pre-gain down at -12 db. If that is too low you can turn it up, but probably will be about right. If there is separate internal gain setting on the Vioelectric I'd start with it also at -12 db, and just see if that is enough or you need less attenuation. You also may or may not benefit from a ground lift in the Vioelectric with single ended RCA cables between it and the Vega.

Hi Blumlein 88, Thank you for the welcome and for your reply.

Let me add a couple of points that I didn't mentioned that may change your advice?

- Both outputs of the Auralic, XLR and RCA, have the same 4Vrms max output.
- Even though other people has suggested me to turn down the signal using the digital volume control in the Aruralic I would rather keep everything in the analog domain, because as far as I know there is always some quality lost when using a Digital volume control ( unless, I'm wrong about this)
- In the Auralic forum and other sites they recommended using the XLR output over the RCA. (They say something about better components and bypassing an opamp in the RCA output?)
- I would also prefer to use XLR in the whole chain. To my ears when listening to headphones in the Violectric, the balance output sounds better and I would rather have a true full balanced input/output. But again I could be wrong...
- And by the way, in case it was not clear. I'm not using the Violectric as a preamp going into the Luxman. But basically just forwarding the input signal (attenuated with the internal DIP switches) but with a fixed volume into the Luxman. (I hope it makes sense)

any more thoughts?

cheers

 

[RayDunzl]

Even though other people has suggested me to turn down the signal using the digital volume control in the Aruralic I would rather keep everything in the analog domain, because as far as I know there is always some quality lost when using a Digital volume control ( unless, I'm wrong about this)

As a practical matter, digital attenuation, used as I may deem necessary, at any of the devices I have that supports it, poses no problem.

The jumpers:

-6dB would reduce the 4 volts to 2 volts
-12dB would reduce the 4 volts to 1 volt - which could be what you want at the Luxman with its 180mv line sensitivity

 

[jrivask]

-12dB would reduce the 4 volts to 1 volt - which could be what you want at the Luxman with its 180mv line sensitivity

This is exactly what I’ve ended up doing today and to my ears it sounds amazing, way better than with the XLR connection coming directly from the Auralic without attenuation. It seems less brittle and more controlled...I don’t know if there is any coloration coming from the Violectric or not, but even if there is I’m OK with it cause I like how it sounds. So, as long as I’m not doing something “wrong” I’m happy with this solution.

Cheers! And thank you