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Review and Measurements of Violectric HPA V281 HP Amp


Staff Member
CFO (Chief Fun Officer)
Feb 13, 2016
Seattle Area
This is a review and detailed measurements of the Violectric HPA V281 headphone amplifier and preamplifier. It is on kind loan from a member who has been waiting a while for its review. :) The V281 comes in different versions with the bass unit costing US $1,999. The version I have has remote control with stepped attenuator, raising the cost to US $2,500.

The V281 has a look which would be at home in a recording studio:

Violectric HAP V281 Preamplifier and Headphone Amplifier Audio Review.jpg

I like the massive volume control but it is a bit loose. The rest of the controls all feel good and bring you think you bought a quality product.

The back panel shows fair bit of control and connectivity:

Violectric HAP V281 Preamplifier and Headphone Amplifier Back Panel Connectors Audio Review.jpg
For my testing, I used the XLR connections. I am not a fan of dip switches for gain control. You have to keep messing with them if you use different headphones that require different gain. That said, once you read the measurements you will see that the standard gain (all switches down) provides almost full power and lowering the gain beyond that, does not help with noise level anyway.

There is a DAC option which the test unit does not have.

As is typical of these stepped attenuators using relays, you can often hear glitches as you turn the volume control fast.

Preamplifier Amplifier Measurements
Since there is a provision for analog in and out, I figured I test the unit that way first. Here is our dashboard:

Violectric HAP V281 Preamplifier and Headphone Amplifier Audio Measurements.png

This is very good but not excellent. What was strange and not matching the specifications was the low frequency roll off:

Violectric HAP V281 Preamplifier and Headphone Amplifier Frequency Response Audio Measurements.png

Signal to noise ratio is very good but again, shy of excellence:

Violectric HAP V281 Preamplifier and Headphone SNR Amplifier Audio Measurements.png

Intermodulation distortion versus level shows what we already know:
Violectric HAP V281 Preamplifier and Headphone Amplifier IMD Audio Measurements.png

Headphone Amplifier Audio Measurements
Here is our usual dashboard:

Violectric HAP V281 Preamplifier and Headphone Out Audio Measurements.png

Wow, that is quite a bit better than the pre-amp pipeline. Distortion is solidly in inaudible range placing the V281 in our upper tier of all headphone amplifiers tested:
Best Headphone Amplifiers Measured.png

Noise performance is the same as preamplifier measurements and gets much worse as we lower the output to just 50 millivolts:
Violectric HAP V281 Preamplifier and Headphone Out SNR Audio Measurements.png

Lowest noise headphone amplifier.png

So likely not a good fit for sensitive IEM listening. Searching online, I saw comments about hiss with such devices confirming our measurements here.

Intermodulation distortion versus output power level shows ample amount of latter with higher noise level as we would predict:

Violectric HAP V281 Preamplifier and Headphone Out IMD Audio Measurements.png

Let's look at the THD+N versus output power starting with 300 ohm:

Violectric HAP V281 Preamplifier and Headphone Out Power into 300 Ohm Audio Measurements.png

We an incredible 1.5 watts of power into such a high output impedance. Violectric brags that the internal voltages are as high as 60 volts (likely +- 30 volts) and it shows.

Note that even the baseline gain gets you 366 milliwatts of power so you should really not need other gain settings unless your input signal is very weak.

Switching to the other extreme at 33 ohm we get:

Violectric HAP V281 Preamplifier and Headphone Out Power into 33 Ohm Audio Measurements.png

Since it clipped already, I did not bother to test with higher gains. Once again we have plenty of power at 2 watts and elevated noise levels.

Switching to 50 ohm load and comparing both XLR and 1/4 outputs we get:

Violectric HAP V281 Preamplifier and Headphone Out Power into 50 Ohm Audio Measurements.png

XLR output did not give us more power so I am assuming it is a convenience feature and not differential output. That is fine anyway as there is no benefit other than power there and we already have plenty of power. Some reviewer said the XLR was louder though. I looked but could not decipher the specifications for V281 in this regard. So I am sticking with my measurements. :)

EDIT: Looks like it was current limiting that stopped it from producing more power at 50 ohm. At higher impedances the power should double as shown by the designer later in the thread.

Channel matching was perfect due to stepped attenuator:
Violectric HAP V281 Preamplifier and Headphone Out Channel Balance Audio Measurements.png

Output impedance was very low (and therefore good):
Headphone output impedances measured.png

Headphone Listening Tests
I started with my very low impedance (25 ohm) closed back Drop Mrspeakers Ether CX. To say there was ample power to drive these in baseline gain setting would be an understatement. Bass performance as a result was fantastic as was dynamic range.

Switching to Sennheiser HD650 headphones proved the same with powerful presentation with no hint of distortion whatsoever.

No, there is no magic in its sound with respect to soundstage, etc. There has not been such magic in any headphone amplifier I have tested.

The Violectric HPA V281 sports a serious, professional looking feel and design to headphone amplifiers. Other than higher noise floor than state-of-the-art headphone amplifiers, and rolled off low frequencies, its design is without fault. Clearly great attention has gone into it from start to finish.

The price is of course sky high. With it, you get a unique looking headphone amplifier and preamp with balanced XLRs in and out. You would have to be a judge of these set of trade offs. My job is to look under the hood and tell you if it is sound and the answer is definitely YES. As such, I am going to put the Violectric HPA V281 on my recommended list.

As always, questions, comments, recommendations, etc. are welcome.

I am getting worried about sitting at my desk so much doing these reviews and not getting enough exercise. Fortunately I saw on TV they have a set of wheels you can peddle while sitting at your desk that lets you lose 30 pounds in 30 days. Yippee! Need some money to buy it so please donate using : https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
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Does that low end roll off also present in the amp section? This is a pretty massive downside. Why would anyone design and amp\preamp like this?
It was in the headphone out too. Usually it is caused by using a single voltage power supply and then using a capacitor output to remove the DC.

Maybe there is a setting on the board inside or something?
Thanks @amirm for reviewing this unit. I'm really happy this unit measures pretty well as I'd hoped! My only real issue with it was the loose volume knob as mentioned, but that can hopefully be fixed with a bit of Loctite.
It was in the headphone out too. Usually it is caused by using a single voltage power supply and then using a capacitor output to remove the DC.

Maybe there is a setting on the board inside or something?

Not according to the manual. You can lift the ground connection(s) with jumpers.

It also clearly states the frequency range response:
5 Hz ... 70 kHz (- 0,5 dB)
3 Hz … 200 kHz (-3 dB)
Maybe it's just me, but even considering high end build I can't really see any reason to spend $2,500 for a headphone amplifier. That will get you a very good power amp.

Yes, but pls. consider that - along with the unit, you get a set of 24-bit high-resolution pics of the Bodensee (Lake Constance) ...
Just one sample:

I think it's a bit poor that on a $2000 headphone amp for which the only possible justification would appear to be professional level build quality that the volume knob is loose, I'd not be happy if the knob on my JDS Atom was loose never mind a $2000 alternative which in some respects doesn't measure as well either.
Thanks for the review @amirm , where does DX3 Pro sit on this, I don't recall you measuring this.

@amirm these product photos are a little grainy. Are you using ISO 100, with timer on a tripod? If not, I suggest you try it. I take some product photos myself too. :)
Thanks for the review @amirm , where does DX3 Pro sit on this, I don't recall you measuring this.
I have only maintained this graph for pure headphone amplifiers without DACs.
108db according to the review :)
Just realised, it was presented differently and not in the comparison ;-), only if they hadn't messed up the headphone output impedance of DX3 Pro V2, quoted as < 10 ohms
Glad to see that this actually performs well as a headphone amp. It's seems the trend for "audiophile" products at the price moves further past the $1000 mark is to actually decrease performance into scam territory. This actually performs very well. Having that low end roll off would actually help bass articulation since low end noise and distortion is one of the biggest enemies to dynamics and transient response for lower frequencies. A 2dB dip at 20Hz is not too bad, but the 5dB dip at 10Hz and below is actually helpful when listening to poorly produced music or recordings that may not have those lower frequencies trimmed away. A sharper roll-off that begins at 15Hz instead of 50Hz would have been better, but I think this is acceptable. The price really is not competitive though. This performance is really only worth somewhere around $500 in today's market. I do think the price was ok when this product was released, but the market has just changed so much with the advent of THX amplification technology.
The company is known to be customer-friendly (cost-wise) when it comes to any repair or adding the DAC option, etc., outside the warranty period so this may justify a little the price rocketing. Decent piece of tech, alltough not the excellence I would have expected given it is their flagship.
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Two things to point out
1 Ac coupling: there should be a jumper inside to set the DC coupling or AC coupling.
2 It's fully differential/balanced. No extra power at 50ohm because it's already current limited. If you test with 300ohm you will get tremendous amount of output power.
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