HPA4 is not balanced. Just separate ground. And thx789 isn't balanced all the way through either. Unless what you meant was xlr input.
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Review and Measurements of Benchmark HPA4 Headphone Amp/Pre
- Thread starter amirm
- Start date
Lol then XLR input then
OP
- Thread Starter
- #104
No one has offered one for review.
The specs for the line outs are exactly the same between the HPA4 and LA4 so I wouldn't expect it to perform any better.
I bought the LA4 because I do not use headphone at home.
For resale value, the HPA4 is a better choice.
- Rich
I want one!
I have been waiting for this review for a long time
The main question for me is the added benefit to a Benchmark DAC3 or even goode ole DAC2 digital volume control.
With the internal passive jumpers set to match the amplifier, the digital volume control of the DAC2 and 3 is pretty much perfect.
I have been waiting for this review for a long time
The main question for me is the added benefit to a Benchmark DAC3 or even goode ole DAC2 digital volume control.
With the internal passive jumpers set to match the amplifier, the digital volume control of the DAC2 and 3 is pretty much perfect.
If you are going to buy an HPA4 or LA4, I would recommend the fixed-gain DAC3 B. It is identical to a DAC3 HGC except that it does not have features that would be duplicated in the HPA4. The DAC3 B has no volume control, no headphone amplifier, and now analog inputs (these are all provided by the HPA4). The DAC3 B is built on a DAC3 HGC circuit board and offers identical performance without the extra features. It will save you money too.I want one!
I have been waiting for this review for a long time
The main question for me is the added benefit to a Benchmark DAC3 or even goode ole DAC2 digital volume control.
With the internal passive jumpers set to match the amplifier, the digital volume control of the DAC2 and 3 is pretty much perfect.
Thank you for your answer, I own both the DAC2L and DAC3L since they came out (I have owned every one of your DACs since the 1-USB).
https://www.sunshipaudio.com/p/listening-room.html
So the question is whether I would benefit from adding a HPA4 (On the digital section). With the passive jumpers I have my volume control in the right section, somewhere between 10 and 12 O'clock. With the DAC2 I felt like you had reached some kind of perfect design, runs cool, hybrid volume control, right amount of ins and outs.
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Can you also measure it with a dac connected? I'd like to see if it does what they say it will do.
The HPA4 or LA4 will improve the measured system SNR in an all-Benchmark system by 2 db at most volume settings. This is counter intuitive. How can adding an active component decrease the noise? Here is how:
The HPA4 or LA4 will allow the DAC2 or DAC3 to operate at full output which is +24 dBu at 0 dBFS. This means the D/A converter is always delivering its full rated SNR. Please note that at this calibration, the DAC2 and DAC3 converters still have an additional 3 dB of headroom available for the accurate reproduction of intersample peaks (but this is another topic).
The clip point of the AHB2 power amplifier is reached at an input level of +22 dBu. This was set 2 dB lower than the typical +24 dBu at 0 dBFS calibration used in most studios so that studio D/A converters could drive the AHB2 2 dB into mild clipping. The down side is that this calibration elevates the D/A converter noise by 2 dB. This 2 dB is fully recovered if the HPA4 or LA4 is inserted between the converter and the power amplifier.
If you were to measure the system SNR, you would find that it improves by 2 dB when the HPA4 or LA4 is inserted between a Benchmark D/A and Benchmark power amplifier. This is only possible because the AHB2 and HPA4/LA4 have a greater SNR than the D/A converter. If you use any other power amplifier, the power amp will limit the system SNR. Likewise if you use any other preamplifier, the preamplifier will limit the system SNR. With the combination of the Benchmark AHB2 and HPA4/LA4, the D/A converter will almost always be the limiting SNR factor in the system (the Benchmark power amplifier and preamplifier have higher SNR performance than most D/A converters. The key point is that the Benchmark preamplifier will allow the full use of the D/A converter's SNR.
Another advantage of the HPA4/LA4 is that it optimizes the interface between any D/A converter and any power amplifier. This optimization will produce the highest possible system SNR, given the limitations of the D/A and power amplifier.
The reason that this optimization is possible is that the preamp section of the HPA4/LA4 has a SNR that exceeds 140 dB.
If you are using an AHB2 with a non-Benchmark D/A converter, the HPA4/LA4 preamplifier may yield an improvement of much more than 2 dB. The reason for this is that other D/A converters are not necessarily matched to the gain structure of the amplifier. The insertion of the preamplifer optimizes the gain staging between the D/A and the AHB2.
The system-level SNR improvements can easily be measured.
The HPA4 or LA4 will allow the DAC2 or DAC3 to operate at full output which is +24 dBu at 0 dBFS. This means the D/A converter is always delivering its full rated SNR. Please note that at this calibration, the DAC2 and DAC3 converters still have an additional 3 dB of headroom available for the accurate reproduction of intersample peaks (but this is another topic).
The clip point of the AHB2 power amplifier is reached at an input level of +22 dBu. This was set 2 dB lower than the typical +24 dBu at 0 dBFS calibration used in most studios so that studio D/A converters could drive the AHB2 2 dB into mild clipping. The down side is that this calibration elevates the D/A converter noise by 2 dB. This 2 dB is fully recovered if the HPA4 or LA4 is inserted between the converter and the power amplifier.
If you were to measure the system SNR, you would find that it improves by 2 dB when the HPA4 or LA4 is inserted between a Benchmark D/A and Benchmark power amplifier. This is only possible because the AHB2 and HPA4/LA4 have a greater SNR than the D/A converter. If you use any other power amplifier, the power amp will limit the system SNR. Likewise if you use any other preamplifier, the preamplifier will limit the system SNR. With the combination of the Benchmark AHB2 and HPA4/LA4, the D/A converter will almost always be the limiting SNR factor in the system (the Benchmark power amplifier and preamplifier have higher SNR performance than most D/A converters. The key point is that the Benchmark preamplifier will allow the full use of the D/A converter's SNR.
Another advantage of the HPA4/LA4 is that it optimizes the interface between any D/A converter and any power amplifier. This optimization will produce the highest possible system SNR, given the limitations of the D/A and power amplifier.
The reason that this optimization is possible is that the preamp section of the HPA4/LA4 has a SNR that exceeds 140 dB.
If you are using an AHB2 with a non-Benchmark D/A converter, the HPA4/LA4 preamplifier may yield an improvement of much more than 2 dB. The reason for this is that other D/A converters are not necessarily matched to the gain structure of the amplifier. The insertion of the preamplifer optimizes the gain staging between the D/A and the AHB2.
The system-level SNR improvements can easily be measured.
And that's why I want to see it! Now I want to send my dac in to be connected to this. 
what is going on?
It seems to be a discussion of the review of the HPA4 and also includes its cousin, the LA4 which is an HPA4 without the headphone amp.
- Rich
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DAC3 has 9.2uV noise at max volume. HPA4/LA4 has 1.9uV noise. HPA4/LA4 doesn't have the lowest noise possible. It's easily achievable to have less than 0.3uV noise.
The key point is none of the long paragraphs but "at most volume settings". It's automatically assuming without HPA4/LA4, the system is going digital volume control which is a pretty big assumption.
Let's cut the bullshit first, it doesn't improve SNR. At max volume it's limited by DAC3. Once you start to attenuate using HPA4/LA4 you start to attenuate noise as well as output level. In this case it still doesn't improve SNR over DAC3 itself. It only preserves the SNR. Improved SNR is using digital attenuation as reference assuming noise doesn't get attenuation. Rough calculation indicates that only at higher than. 1.9/9.2 attenuation to before maximum will preserve the SNR of DAC3. Lower than that, HPA4/LA4 will take over the noise. This is happening because they are still active components.
More precisely, we need to take the resistance of attenuator into account. Regular attenuators have max noise at 50% position. For HPA4/LA4 is a little different, it's depending the implementation. But it will introduce some noise at some level.
The key point is none of the long paragraphs but "at most volume settings". It's automatically assuming without HPA4/LA4, the system is going digital volume control which is a pretty big assumption.
Let's cut the bullshit first, it doesn't improve SNR. At max volume it's limited by DAC3. Once you start to attenuate using HPA4/LA4 you start to attenuate noise as well as output level. In this case it still doesn't improve SNR over DAC3 itself. It only preserves the SNR. Improved SNR is using digital attenuation as reference assuming noise doesn't get attenuation. Rough calculation indicates that only at higher than. 1.9/9.2 attenuation to before maximum will preserve the SNR of DAC3. Lower than that, HPA4/LA4 will take over the noise. This is happening because they are still active components.
More precisely, we need to take the resistance of attenuator into account. Regular attenuators have max noise at 50% position. For HPA4/LA4 is a little different, it's depending the implementation. But it will introduce some noise at some level.
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