Singxer SA-1 Review (Balanced Headphone Amp)

[Blew]

Let's test power vs distortion+noise using my optimized test for balanced amps at 300 ohm:

View attachment 129584

As I hinted, performance is almost the same in low and high gain. It is also exceptionally good. Powerful and transparent.

Switching to 50 ohm, we get slightly less optimized performance above certain power level:

View attachment 129585

We can see that more clearly as we step through a range of output impedances:

View attachment 129586

Do the math as I have noted to see if you get the amount of power you need at that impedance before distortion rises. There are other high performance amplifiers that don't have this dependency.

Output impedance is shown both for low and high Z.

These measurements appear relevant to headphones. Am I correct in assuming the impedances measured here affect active speakers via XLR too?

I can hear distortion at high gain when I use the SA-1 as a pre-amp outputting to my JBL 305P MKII active speakers over balanced XLR. I also hear some distortion on them when the volume pot on the speakers to around 3/4 of the way. So I run the SA-1 at low gain and Low-Z, and the 305p speakers to +4dBu with the volume pot at 1/2.

The SA-1 input is via a Topping E50, set to DAC mode (ie volume 100%), outputting over balanced TRS to XLR cables. This means the volume pot on the SA-1 needs to be at around 4-5 O'clock for average listening levels in this setup. With the SA-1 volume pot at full, the sound is louder than I would tolerate while sitting at my desk, so the volume is not a huge problem for me but but I have to remember to turn the volume down a lot when switching to headphones! I'm also just interested in why this may be.

I can't find any details on what the impedance of the speakers are to relate to Amir's distortion measurements here. It's not listed in the manual and somewhere I read that input impedance is not relevant to active speakers. Am I on the right path here or could this be caused by poor quality amplification in the speakers, E50 output voltage being too high for the SA-1, or faulty interconnects somewhere in the chain?

 

[roderickvd]

These measurements appear relevant to headphones. Am I correct in assuming the impedances measured here affect active speakers via XLR too?

They should.

I can hear distortion at high gain when I use the SA-1 as a pre-amp outputting to my JBL 305P MKII active speakers over balanced XLR. I also hear some distortion on them when the volume pot on the speakers to around 3/4 of the way. So I run the SA-1 at low gain and Low-Z, and the 305p speakers to +4dBu with the volume pot at 1/2.

In high gain, it probably is due to gain staging.

The SA-1 input is via a Topping E50, set to DAC mode (ie volume 100%), outputting over balanced TRS to XLR cables. This means the volume pot on the SA-1 needs to be at around 4-5 O'clock for average listening levels in this setup. With the SA-1 volume pot at full, the sound is louder than I would tolerate while sitting at my desk, so the volume is not a huge problem for me but but I have to remember to turn the volume down a lot when switching to headphones! I'm also just interested in why this may be.

I can't find any details on what the impedance of the speakers are to relate to Amir's distortion measurements here. It's not listed in the manual and somewhere I read that input impedance is not relevant to active speakers. Am I on the right path here or could this be caused by poor quality amplification in the speakers, E50 output voltage being too high for the SA-1, or faulty interconnects somewhere in the chain?

The input impedance of active speakers, generally, is just like the input impedance of an amp which should be 10K or solidly higher, typically 47/50K or as high as 1M. At such impedances the pre-amp is like a voltage source with very low current and very low power. Now when you switch to headphones, well, they must be actually driven with current and require more power. Here is your reason why you have to change the volume setting.

 

[Blew]

In high gain, it probably is due to gain staging.

What does this mean, and can I prevent it?

The input impedance of active speakers, generally, is just like the input impedance of an amp which should be 10K or solidly higher, typically 47/50K or as high as 1M. At such impedances the pre-amp is like a voltage source with very low current and very low power. Now when you switch to headphones, well, they must be actually driven with current and require more power. Here is your reason why you have to change the volume setting.

If the headphones draw more power than the pre-amp then wouldn't that mean I'd need to increase the volume for headphones out? When I switch to headphones output after using pre-amp out then the volume is far too high, so I need to reduce the volume rather than increase.

 

[roderickvd]

What does this mean, and can I prevent it?

Gain staging is making sure the volume between inputs and outputs are balanced as to maximise SNR. So when you encounter distortion or clipping it is actually the opposite of gain staging, but I think this is what they say on the street Keep the SA-1 in low gain to minimise the chances of that happening.

I don't own that Topping but I think the output is on the hot side?

If the headphones draw more power than the pre-amp then wouldn't that mean I'd need to increase the volume for headphones out? When I switch to headphones output after using pre-amp out then the volume is far too high, so I need to reduce the volume rather than increase.

Ah I see, yes that is counter-intuitive. Might well be due to your active speaker having much more gain than the SA-1's headphone output.

 

[Blew]

Gain staging is making sure the volume between inputs and outputs are balanced as to maximise SNR. So when you encounter distortion or clipping it is actually the opposite of gain staging, but I think this is what they say on the street Keep the SA-1 in low gain to minimise the chances of that happening.

That's what I've been doing, but the volume pot needs to be almost maximum in this mode. It seems odd to have to push the SA-1 so hard to drive active speakers, and means I have to be very careful when switching to headphones output.
I notice it switches from class A to class B by this point and the sound output changes very subtly. However, it then doesn't get as warm. Would that have any effect on the long term durability of it?

I don't own that Topping but I think the output is on the hot side?

The E50 manual specifies 4 volts out on balanced:

But Amir measured the balanced output on the E50 as above 4 volts:
View attachment 150585

AFAIK balanced out should be around 4 volts. Does this mean that the balanced output of the E50 of around 4.25 volts is too "hot" for the SA-1?
Should the E50's volume be below 100% as it's set in "DAC mode"?

Ah I see, yes that is counter-intuitive. Might well be due to your active speaker having much more gain than the SA-1's headphone output.

The manual for the 305P MKII speakers specifies the input level and sensitivity for -10dBV as below:

However I have it set to +4dBu to avoid distortion but it doesn't provide input level details for this setting.
From the manual:
INPUT SENSITIVITY SWITCH – Set this switch to +4dBu to protect from overload when connecting to
professional equipment and sources with high output level capabilities. Set this switch to -10dBV when
connecting to lower-level consumer-grade audio equipment or to the LSR310S subwoofer.

Does any of this have any relevance to Amir's comment from the SA-1 review regarding impedance and distortion quoted below?

Do the math as I have noted to see if you get the amount of power you need at that impedance before distortion rises. There are other high performance amplifiers that don't have this dependency.

 

[roderickvd]

That's what I've been doing, but the volume pot needs to be almost maximum in this mode. It seems odd to have to push the SA-1 so hard to drive active speakers, and means I have to be very careful when switching to headphones output.

Yes that's strange. Something fishy after all?

I notice it switches from class A to class B by this point and the sound output changes very subtly. However, it then doesn't get as warm. Would that have any effect on the long term durability of it?

How can you tell? I think class A going into AB (not B I think) would not be very audible.
Anyway I would not worry about the durability, also in class A warmth it should have a fine long life.

The E50 manual specifies 4 volts out on balanced:

And +4 dBu "expects" 1.228 Vrms so here is definitely a difference.

Should the E50's volume be below 100% as it's set in "DAC mode"?

Either that or you keep turning the volume pots. Doing digital volume control will waste some bits of dynamic range.

Does any of this have any relevance to Amir's comment from the SA-1 review regarding impedance and distortion quoted below?

Maybe I'm missing something (others feel free to chime in) but it's just weird. Preamp out to powered speakers (effectively a plate amp) should draw very little power.

Anyway 4 Vrms is like 14.2 dBu so that's not an ideal match with your active speakers.

 

[Blew]

How can you tell? I think class A going into AB (not B I think) would not be very audible.

It may be subconscious bias but it seems to be slightly less "resonant" if that makes any sense.

Anyway I would not worry about the durability, also in class A warmth it should have a fine long life.

And +4 dBu "expects" 1.228 Vrms so here is definitely a difference.

Does that mean that the -10dBV setting should be used with the balanced XLR input?

Either that or you keep turning the volume pots. Doing digital volume control will waste some bits of dynamic range.

Would setting the Windows USB DAC output to 24 or 32 bit help this at all? I currently have it set to 32 bit output.

Maybe I'm missing something (others feel free to chime in) but it's just weird. Preamp out to powered speakers (effectively a plate amp) should draw very little power.

Anyway 4 Vrms is like 14.2 dBu so that's not an ideal match with your active speakers.

How does this relate to the "Maximum Peak Input Level" of +20.3dBu as shown in the manual?

I don't understand the differences between dBV, dBu, and Vrms Is there an "Amplifier and Speaker Input Sensitivity and Impedance for Dummies" of sorts that would help me understand all this a little better?

 

[roderickvd]

There are plenty of dBu <> Vrms calculators on the net.

If the DAC is operating in 24 or 32 bit you should be fine with digital volume control.

 

[dweeeeb2]

I have a set of HiFiMan edition XS’s running on this. They are 16ohm. These charts suggest this amp performs better with higher impedence HPs. Could this be what the high/low z toggle is for? should I have the toggle on a certain setting to improve clean power out? thanks

 

[roderickvd]

I think the toggle is useless and should always be at low Z regardless op headphones. Low Z is a desirable trait on the output always from an objective standpoint.

In the case of the SA-1, the high Z settings just adds 10 ohms to the output.

 

[dweeeeb2]

I think the toggle is useless and should always be at low Z regardless op headphones. Low Z is a desirable trait on the output always from an objective standpoint.

In the case of the SA-1, the high Z settings just adds 10 ohms to the output.

thank you

 

[IAmAgainst]

I bet a lot of the veil comments about certain sennheisers (and maybe this amp too) are simply not driving them with enough power or hearing soft instruments/or low timbre sound of instruments...when all they had to do was give them more power/switch to high gain/etc...Or they just don't like the frequency response the headphones are putting out, but that's why EQ is a great option.

Mine should be arriving these days and I'm really struggling to make sense of the people that hear a big difference with the mod and those who say that what the former are experiencing is just placebo effect. Could someone please ELI5 what does "more power" mean in this context? The headphones' impedance is a fixed value so I don't see what "more power" could mean besides a different wording for "listen at a higher volume", but I don't think that's what DeckEQMaybe meant since one's preferred listening volume is not something one can really control. Does it mean lowering the input volume and increasing the gain in order to maintain the final volume?

 

[Svperstar]

Can you connect this balanced XLR and then use the single ended connection? If so does it give out as much power as the balanced connection?

That is how my SP200 works.

 

[IAtaman]

Can you connect this balanced XLR and then use the single ended connection? If so does it give out as much power as the balanced connection?

That is how my SP200 works.

If you mean would it work with balanced XLR input and single ended output the answer is yes. And no, SE output does not give as much power as balanced output. That is generally how all headphone amps work.

 

[Roland68]

Can you connect this balanced XLR and then use the single ended connection? If so does it give out as much power as the balanced connection?

That is how my SP200 works.

With the Singxer SA-1 you can use all inputs with all outputs. With the same input voltage (RCA half as high as XLR) there is also no difference in volume, since the RCA input is immediately converted to balanced.
However, your SP200 is not a balanced amp, so it performs the same on SE and Balanced.
The Singxer SA-1 is a "real" balanced amplifier with 4 separate output stages. The power is therefore significantly higher at the balanced output.

 

[Svperstar]

If you mean would it work with balanced XLR input and single ended output the answer is yes. And no, SE output does not give as much power as balanced output. That is generally how all headphone amps work.

With the SP200 the SE output and balanced output give the same amount of power. I know thats rare but its how it works.

 

[IAtaman]

With the SP200 the SE output and balanced output give the same amount of power. I know thats rare but its how it works.

Oh interesting. Did not know that. Thank you for the correction. So it does not have balanced output, just a SE through XLR?

 

[Roland68]

With the SP200 the SE output and balanced output give the same amount of power. I know thats rare but its how it works.

With the SP200 you don't have a balanced output, just a 4-pin XLR socket with the SE output attached.
It's the same output with 2 different sockets. No more.

 

[Svperstar]

Oh interesting. Did not know that. Thank you for the correction. So it does not have balanced output, just a SE through XLR?

Yes. I've done everything in this hobby but go fully balanced and recable everything. I haven't because I like being able to swap stuff between my home, work from home, and office setup without having to detach cables. Also besides raw power there isn't any benefit, so I would be spending a lot of money for nothing. I do have my SMSL SP200 hooked up to my RME ADI-2 via XLR though.

Audio Myth - Balanced Headphone Amplifiers are Better

This Myth Goes Something Like This: "Balanced headphone amplifiers are better." "If balanced line-level connections work well, balanced headphone outputs should also work well." We disagree! Benchmark does not offer voltage-balanced headphone outputs on any of its products. The reason for this...

benchmarkmedia.com

 

[Oukkidoukki]

Yes. I've done everything in this hobby but go fully balanced and recable everything. I haven't because I like being able to swap stuff between my home, work from home, and office setup without having to detach cables. Also besides raw power there isn't any benefit, so I would be spending a lot of money for nothing. I do have my SMSL SP200 hooked up to my RME ADI-2 via XLR though.

Audio Myth - Balanced Headphone Amplifiers are Better

This Myth Goes Something Like This: "Balanced headphone amplifiers are better." "If balanced line-level connections work well, balanced headphone outputs should also work well." We disagree! Benchmark does not offer voltage-balanced headphone outputs on any of its products. The reason for this...

benchmarkmedia.com

Just out of intrest…I have Adi, what more sp200 brings to game? In my mind Adis headamp is pretty much perfect.