[MacedonianHero]

Different power cord, different outlet, different circuit, same faint hum.

And, as much as I appreciate the help, this is all academic at this point since Benchmark is in the middle of resolving the issue. I don't want anyone wasting their time on a problem that is now moot. You know, unless you find it interesting like I do, then by all means!

I'm an engineer...so yeah, this stuff is fun for me.

 

[phthora]

My DAC3-B makes a micro hum when off. Turn it on and it's gone...FWIW....It's completely unnoticeable unless I place my ear within approximately 10 inches of it.

Turning it on does lessen the hum (that's news to me), but there is still a persistent tone on or off. Playing around with it, I think it would be most accurate to say that there are two tones I am hearing. One very high-pitched and very faint, audible only when I'm withing a foot and actively listening for it. That may be the 'micro hum' you and others are reporting. The other hum is more like a buzzing that has a uneven timbre to it. That one is audible at three feet in moderately quiet room (like with street noise and kids downstairs), and disappears when the unit is turned on. The problem, of course, is that I don't want to leave the unit on 24/7 just so there is no buzz.

 

[nordkapp]

Turning it on does lessen the hum (that's news to me), but there is still a persistent tone on or off. Playing around with it, I think it would be most accurate to say that there are two tones I am hearing. One very high-pitched and very faint, audible only when I'm withing a foot and actively listening for it. That may be the 'micro hum' you and others are reporting. The other hum is more like a buzzing that has a uneven timbre to it. That one is audible at three feet in moderately quiet room (like with street noise and kids downstairs), and disappears when the unit is turned on. The problem, of course, is that I don't want to leave the unit on 24/7 just so there is no buzz.

It sounds to me like Benchmark may have a problem on their hands. If mine gets louder I'm surely going to make an inquiry. Keep us posted as your situation unfolds.

 

[phthora]

Turning it on does lessen the hum (that's news to me), but there is still a persistent tone on or off. Playing around with it, I think it would be most accurate to say that there are two tones I am hearing. One very high-pitched and very faint, audible only when I'm withing a foot and actively listening for it. That may be the 'micro hum' you and others are reporting. The other hum is more like a buzzing that has a uneven timbre to it. That one is audible at three feet in moderately quiet room (like with street noise and kids downstairs), and disappears when the unit is turned on. The problem, of course, is that I don't want to leave the unit on 24/7 just so there is no buzz.

All right, an update is in order. I contacted Benchmark about the situation and they were able to resolve the buzzing issue in my DAC3-B completely and very quickly. I won't go into details because I don't want people to have expectations regarding Benchmark customer service particulars based on my experience. Actions that they were able and willing to take in my case may not be the same in every situation, so I want to respect that there were a variety of factors at play in how this all worked out. But, I can say that they were very prompt with responding to my queries, even when the case got handed off from one person to another. They actually asked me fewer questions than I thought reasonable and my total time spent corresponding with Benchmark was maybe ten minutes. The solution they came up with resulted in about as little inconvenience as I could imagine and zero down time. I have given it a couple of weeks to see if the issue showed up again and, as of now, it has not even once. To be clear, the 'micro-hum' (noted above) is still present when the unit is off, but is only audible inches from the back of the unit and disappears completely when the unit is turned on. The buzz I heard previously is completely gone under all conditions. I am once again very pleased with my purchase, especially now that I know Benchmark customer support is stellar.

On a more HPA4 related note, I was recently able to A/B this amp against the Massdrop THX789, which was my third audition of the 789. I stand by what I said previously: the HPA4 was to my ears a noticeable improvement over the 789 in both musicality and technical prowess. I won't beat a dead horse by repeating what I wrote before, but having more time with the HPA4 has certainly helped those differences to stand out more clearly to me. Still very impressed by the 789 though; that thing is an absolute steal.

 

[nae45ro]

Hello guys. Just received my new Benchmark HPA-4 wich will be linked to a Emm Labs CDSA se player and HD800 headphones. Already tested a demo unit before buying and found it incredibly fast and neutral. My main curiosity now is if it can better or at least equal my Pass Labs XP-10 preamp. If it can, I would use the Benchmark as a preamp for my Pass X-250.5 in order to simplify my chain and make room for a future upgrade of the source to Emm DAC2X or Nagra HD DAC + perhaps an Aurender network player.

 

[Tobes]

My main curiosity now is if it can better or at least equal my Pass Labs XP-10 preamp. If it can, I would use the Benchmark as a preamp for my Pass X-250.5 in order to simplify my chain and make room for a future upgrade of the source to Emm DAC2X or Nagra HD DAC + perhaps an Aurender network player.

That will be an interesting comparison.
I preferred the HPA4 to the Bryston BP-26 I was using previously.

 

[nae45ro]

Ok, so did the 1st comparison to the Pass XP-10 preamp using the Emm Labs CDSA se as source and Pass x250.5 as amp. Music was mainly rock, pop-country, some jazz like America, Harry Chapin, John Mayall, Eagles, Tom Petty, Kate Bush, Jazz from Opus 3 recording, Eric Clapton, Willie Nelson ...

Both were dead quiet to my years but had to set the balance to L2 on Benchmark in order to have a centered stage (slight imbalance between channels ?). However, this setting upset the lower frequency harmony a bit. Now, regarding the sound quality, Pass Labs won easily with more air around instruments, wider and deeper stage, better extension on both ends, simply more musical on all aspects. Benchmark is a precise machine but sounds a bit digital to me and lacks the ultimate musical immersion. Highs are somehow rolled off and on some tracks I’m feeling something weird similar to old Dolby B/C cassette decks that were removing some of the high frequency detail and air along with noise (this was variable along the same song with highs oscillating in intensity). Otherwise, highs were quite delicate and subtle with plenty of detail. Midrange was more “liquid” and a tad warmer on Pass. Bass was heavier on Benchmark but somehow congested as compared to Pass. Both had plenty of dynamics but Benchmark was “muddier” on midbass area.

 

[Tobes]

Pass Labs won easily with more air around instruments, wider and deeper stage, better extension on both ends, simply more musical on all aspects. Benchmark is a precise machine but sounds a bit digital to me and lacks the ultimate musical immersion. Highs are somehow rolled off and on some tracks I’m feeling something weird similar to old Dolby B/C cassette decks that were removing some of the high frequency detail and air along with noise (this was variable along the same song with highs oscillating in intensity). Otherwise, highs were quite delicate and subtle with plenty of detail. Midrange was more “liquid” and a tad warmer on Pass. Bass was heavier on Benchmark but somehow congested as compared to Pass. Both had plenty of dynamics but Benchmark was “muddier” on midbass area.

Interesting impressions, I can't say I really recognise them in my system - except that I'd agree the HPA4 doesn't add any 'warmth'.
Curious what you say about the Pass sounding more extended - since the Pass is 3dB down at 60Khz and the HPA4 is ruler flat to 200Khz (-3dB bandwidth > 0.1Hz to 500Khz !). Something must be giving the impression of 'extension' with the XP-10.
Not that it matters if you prefer the sound of the Pass.
I found the longer I listened the more I appreciated the HPA4's neutral stance. But hey, I listen to my vinyl records with a tube phono amp and love how it sounds with that 'artistic' medium.

 

[nae45ro]

Yes, I was surprised too as I know the specs and measurements. However, used as a headphone amp with the same Emm Labs as a source, the sound is much better and has none of the weaknesses noticed on the speaker setup.

 

[tunes]

We had the HiFiMan Susvara headphones at AXPONA and the HPA4 drove them beautifully! We will be in your backyard at RMAF in October, we will have the HPA4 and a selection of headphones to try out. One of my favorite parts of CanJam is all the major headphones are there and for the most part you can borrow headphones for a quick listening test on different amps.
Hope to see you at RMAF!
October 5-7

Will the HPA4 and Susvara be available at the NYC CanJam in February?????

 

[M Siau]

Will the HPA4 and Susvara be available at the NYC CanJam in February?????

The Susvara and HPA4 will be paired together at CanJam NYC in February as well as at the Florida Audio Expo in Tampa, FL Feb. 7-9

 

[DeepSouth]

@ phthora

Does your house have dimmer switches?
I had a humming Mcintosh amp, I went through great lengths to cure it.
Most power filters don't remove DC power from the line. Some do, but most don't. You could get a low cost single purpose DC filter too.
You can have an electrician to see if DC power is on your AC line. Your electrician won't beleive that DC can be on an AC line, but mine did after he discovered DC on the AC line.
I also had a second electrical panel, and the second one didn't have a dedicated ground, I ran a dedicated ground to that panel and the noise became more quiet.
Eventually, I ran a dedicated 20 amp circuit and line to my Mc theater wall.
I had probably 100 dimmer switches in my home, I never got rid of all of them. But I was able to see that a dimmer switch polluted my AC line with DC on the dimmer switches I own, and everyone I bought from Home Depot and Lowes to test.

 

[MacedonianHero]

The Susvara and HPA4 will be paired together at CanJam NYC in February as well as at the Florida Audio Expo in Tampa, FL Feb. 7-9

I own both the HPA4 and Susvara and absolutely love this combination!

 

[tunes]

I own both the HPA4 and Susvara and absolutely love this combination![/QUOTE
Have you ever compared the Susvara with HPA4 to Susvara with a Benchmark speaker amp like AHB2 since they are the same price?

 

[bimmer100]

I own both ahb2 and hpa4 but personally don’t see needing to try the ahb2 as the hpa4 has plenty of headroom even for those on a mission to destroy your hearing. They sound very full up to well over 100dB if that’s your thing. It’s got grunt power and never sounds thin like many amps commonly are with the susvara due to lack of power.