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Review and Measurements of Benchmark HPA4 Headphone Amp/Pre

I just got my HPA4 with two AHB2.
I see that even with +10db setting the volume is not the high.
I find that I am at almost 90%.
Previously on my Denon PMA-A110 I could not go much above 40% top 50% (depends on the recording dynamic range and mstering).
My souce in from HoloAudio May DAC KTE.
All connections are XLR.
Any idea?
I don’t know what you mean by +10db. The AHB2 has an input level setting on the back with three options, 8.2, 14.2, and 22. Maybe try one step lower on that (lower input level means higher gain).
 
I don’t know what you mean by +10db. The AHB2 has an input level setting on the back with three options, 8.2, 14.2, and 22. Maybe try one step lower on that (lower input level means higher gain).
He is referring to the input gain settings on his hpa4 that can boost input by 10db
 
He is referring to the input gain settings on his hpa4 that can boost input by 10db
The +10db is on the HPA4 per each input and not on the AHB2.
I asked Benchmark and they said that the settings from HPA4 to AHB2 have to be on 22.
They said that for 4vrms XLR I need to add +10db on that input.
 
The +10db is on the HPA4 per each input and not on the AHB2.
I asked Benchmark and they said that the settings from HPA4 to AHB2 have to be on 22.
They said that for 4vrms XLR I need to add +10db on that input.
Yes, customer service with Benchmark is second to none!!! I recalled hopping on to a call to discuss my setup with my 2 subs and the LP4 due to mismatch in output voltage for over an hour.

If you have a dac xlr output at 4v you should add 10db input boost. Not for rca, LPA4 automatically bumped up the input gain on that.

As I mentioned in my earlier post, you will need to be setting your abh2 to high gain, unless you have a dac that outputs 11v xlr like the benchmark dac or my ifi pro idsd
 
Yes, customer service with Benchmark is second to none!!! I recalled hopping on to a call to discuss my setup with my 2 subs and the LP4 due to mismatch in output voltage for over an hour.

If you have a dac xlr output at 4v you should add 10db input boost. Not for rca, LPA4 automatically bumped up the input gain on that.

As I mentioned in my earlier post, you will need to be setting your abh2 to high gain, unless you have a dac that outputs 11v xlr like the benchmark dac or my ifi pro idsd

I don't have RCA connected to my HPA4.
I only have HoloAudio May DAC KTE which outputs 4v on XLR thus I've added +10db on that input.

Rory Rall from Benchmark wrote to me on a that same question:
"The HPA4 is at unity gain at ‘0’ on the dial.

I cannot find a spec sheet on the Holo but my guess is that its XLR output is around 4V. If you have the AHB2’s sensitivity switch in the middle (4V) setting, you’ll not reach full output of the amp until you are at ‘0’ on the volume dial. So if you’re using it at 80-90% of the dial, this is correct. You’re normal listening is about 10-20dB below full output.

Suggestion: Verify the output of the Holo. If 4V, add 10dB of ‘boost’ in the HPA4 setup for that input. Then, set the AHB2 switch all the way down to 9.8. You’ll then reach full output of the amps at about -2. It really doesn’t matter where you are on the volume dial, it will be clean."
 
I don't have RCA connected to my HPA4.
I only have HoloAudio May DAC KTE which outputs 4v on XLR thus I've added +10db on that input.

Rory Rall from Benchmark wrote to me on a that same question:
"The HPA4 is at unity gain at ‘0’ on the dial.

I cannot find a spec sheet on the Holo but my guess is that its XLR output is around 4V. If you have the AHB2’s sensitivity switch in the middle (4V) setting, you’ll not reach full output of the amp until you are at ‘0’ on the volume dial. So if you’re using it at 80-90% of the dial, this is correct. You’re normal listening is about 10-20dB below full output.

Suggestion: Verify the output of the Holo. If 4V, add 10dB of ‘boost’ in the HPA4 setup for that input. Then, set the AHB2 switch all the way down to 9.8. You’ll then reach full output of the amps at about -2. It really doesn’t matter where you are on the volume dial, it will be clean."
For pcm playback, may kte xlr output voltage is 5.8vrms, rca output voltage is 2.9vrms. Take half of that for dsd playback
 

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For pcm playback, may kte xlr output voltage is 5.8vrms, rca output voltage is 2.9vrms. Take half of that for dsd playback

Interesting.
I don’t hear much of a level difference between PCM and DSD.
Maybe I’ll try to sample my PCM to DSD just to see if there’s any difference.
 
Nevertheless, the $150,000 Dan D'Agostino Relentless Preamp is a true work of art. The focus is on unique casework and exotic components, but not on audio performance.

The LA4 cannot compete with the Relentless when both systems are turned off.
I love the last line! :D
 
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