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March Audio HPA1

March Audio

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Ok thank you.
Sorry for all the questions. And thank you for all the explaining.
I feel you are a passionate person that resembles me as the one I spoke about of the Link audio store. I wish you well in the future and maybe we will meet again.
Thanks

Cheers

Alan
 

March Audio

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Will the HPA1 be safe to used with in-ear monitors?
Not sure what you mean by "safe". :)

Its free from any significant turn on/off pops. Beyond that its up to the user to be responsible with listening levels.

I use Westone 4R IEMs. They are a lot more sensitive than say my HD6xx, but no sign of amp noise hiss and sounds great.
 

DonH56

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Now this is getting out of hand and rather unnecessary!
A few years ago I worked with a guy who was also into the DIY airplane crowd. They got together every weekend to work on and sometimes fly their planes. Some were kits, some from plans, some completely original designs (within the constraints of physics). And yes one of the guys was seriously injured when his engine died a little after take-off and the plane crashed, falling out of the sky.

Google engineering disasters and you'll find plenty of times things went wrong. One of the more famous was the Tacoma Narrows bridge: https://en.wikipedia.org/wiki/Tacoma_Narrows_Bridge_(1940)

DIY audio has had more than its fair share of accidents, often when power supplies go bad or things are wired wrongly. One of my favorites was when someone got the primary and secondary windings of a transformer reversed. Exciting, it was. He has a permanent scar on his cheek from pieces of the main filter caps exploding in his face.
 

March Audio

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Well the HPA is powered from an external CE/FCC approved Wall wart SMPS. 12 V in. This is followed by an internal isolated (to 1500v) supply. I even considered medically approved version to minimise leakage current, but decided it was unnecessary. The unit is all low dc voltage, low power, nothing hot with correctly voltage rated caps. The output circuitry can deal with indefinite short circuit.

Beyond that I suppose you could drop the unit on your foot............ ;)
 
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rebbiputzmaker

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A few years ago I worked with a guy who was also into the DIY airplane crowd. They got together every weekend to work on and sometimes fly their planes. Some were kits, some from plans, some completely original designs (within the constraints of physics). And yes one of the guys was seriously injured when his engine died a little after take-off and the plane crashed, falling out of the sky.

Google engineering disasters and you'll find plenty of times things went wrong. One of the more famous was the Tacoma Narrows bridge: https://en.wikipedia.org/wiki/Tacoma_Narrows_Bridge_(1940)

DIY audio has had more than its fair share of accidents, often when power supplies go bad or things are wired wrongly. One of my favorites was when someone got the primary and secondary windings of a transformer reversed. Exciting, it was. He has a permanent scar on his cheek from pieces of the main filter caps exploding in his face.
Hi Don,

Very familiar with the bridge, and faa safety reg etc, know some pilots.

But a bit??? of a exaggeration to intimate the guy on the Trent line doing audio testing having a bad hair day can bring down an Airbus!! Way too much. Better just to say nothing when you have nothing reasonable to say.
 
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Not sure what you mean by "safe". :)

Its free from any significant turn on/off pops. Beyond that its up to the user to be responsible with listening levels.

I use Westone 4R IEMs. They are a lot more sensitive than say my HD6xx, but no sign of amp noise hiss and sounds great.
I meant safe as in listening levels, I personally use the Ultimate Ears Reference Remastered which is 35 ohms with a 100db sensitivity at 1mw
 

March Audio

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I meant safe as in listening levels, I personally use the Ultimate Ears Reference Remastered which is 35 ohms with a 100db sensitivity at 1mw
Well it could drive them to very high SPL levels, same as any decent amp could. I have blasted myself accidentally in the past by leaving analogue volume controls turned up. One simple way to limit volume is to use your music players limiter. Roon has good functionality in this area.

1548564210432.png


as does J River

1548564335089.png


hope that helps
 

March Audio

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Well, after losing 2 months due to a Chinese manufacturer that didnt deliver :( I finally have some Australian made release candidate PCBs (final prototype) on my bench.

Performance is beyond my measurement capabilities, so need an Audio Precision hooked up to get the final numbers, but its sounding great..........well I would say that :)

So only a month or so to get the cases finished and it should be on sale.

IMG20190319213218.jpg
 

Thomas savage

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Well, after losing 2 months due to a Chinese manufacturer that didnt deliver :( I finally have some Australian made release candidate PCBs (final prototype) on my bench.

Performance is beyond my measurement capabilities, so need an Audio Precision hooked up to get the final numbers, but its sounding great..........well I would say that :)

So only a month or so to get the cases finished and it should be on sale.

View attachment 23849
How's this endeavour going for you Alan ? Are you enjoying it mate ?
 

March Audio

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How's this endeavour going for you Alan ? Are you enjoying it mate ?
Hi Thomas

Things are going well. There are always challenges and complications, but I fully expected that and still thoroughly enjoy it. Sales are increasing. Im just frustrated I cant get all the plannned products out sooner ! :)
 
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restorer-john

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Looks good! How was your experience with the Australian PC board house? I need to find a decent one myself.

What happened to the "D" key on the Lenovo, acetone, super glue or that nice french-tip nail polish wasn't dry? ;)
 

trl

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https://stoneracoustics.com/udxa

This headphone has no volume control. It's been out for a while. Think it's digitally controlled
Hi, just realised this is not a dedicated headphones amplifier, instead is a DAC/headamp combo only. So, there is no way to inject audio signal into. The RCA and XLR plugs from the backside are pure outputs only.

The volume control is realised by the USB DAC chip: https://www.akm.com/akm/en/file/datasheet/AK4497EQ.pdf
"Output Volume (PCM Mode, DSD Mode, EXDF Mode) The AK4497 includes channel independent digital output volumes (ATTL/R) with 256 levels at 0.5dB step including MUTE. When changing output levels, it is executed in soft transition thus no switching noise occurs during these transitions. It can attenuate the input data from 0dB to -127dB and mute when assuming the output signal level is 0dB when ATTL/R[7:0] bits = FFH."

However, given the output buffer used (TPA6120A) I doubt the output impedance would be lower than 10 Ohms.
 

March Audio

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Looks good! How was your experience with the Australian PC board house? I need to find a decent one myself.

What happened to the "D" key on the Lenovo, acetone, super glue or that nice french-tip nail polish wasn't dry? ;)
Hi @restorer-john
Sorry I completely missed your post. I will PM details through.

The laptop is a used one from fleabay, I have no idea what happened to the D key, but yes it does look like it came in contact with some kind of solvent :)
 
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Hi @March Audio (Alan)
I came here when I saw some comments on JDS Labs Atom review and now I'm really interested in your amp.
The only question I have is about single ended input.
As you say, the amp has a "Balanced XLR input design (compatible with single ended RCA)".
As I don't have a balanced DAC (all I have is a Topping D50) I would like to know what am I going to miss if I use the Topping D50 instead of something like SMSL SU-8 or Topping DX7s.
Will I miss any quality or output power when using single ended input?

By the way, the most important question.
Would you ship it to Brazil? :p
 

March Audio

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Hi @March Audio (Alan)
I came here when I saw some comments on JDS Labs Atom review and now I'm really interested in your amp.
The only question I have is about single ended input.
As you say, the amp has a "Balanced XLR input design (compatible with single ended RCA)".
As I don't have a balanced DAC (all I have is a Topping D50) I would like to know what am I going to miss if I use the Topping D50 instead of something like SMSL SU-8 or Topping DX7s.
Will I miss any quality or output power when using single ended input?

By the way, the most important question.
Would you ship it to Brazil? :p
Hi @Mr. Olinad
You can use single ended RCA output Dacs without issue with a balanced input. You lose no quality or power and in fact can still benefit to a degree from the common mode rejection balanced offers. You simply need a correctly wired xlr to rca cable which is available in the webshop.

We ship globally.

The HPA1 is not actually available yet. I am making a final change to the design so it has switchable gain, 0dB (unity) and +6dB, as a potential professional customer requires fixed 0dB gain bur domestic use may still require +6dB to cater for the widest range of headphones.

Regards

Alan
 

JohnYang1997

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Well the HPA is powered from an external CE/FCC approved Wall wart SMPS. 12 V in. This is followed by an internal isolated (to 1500v) supply. I even considered medically approved version to minimise leakage current, but decided it was unnecessary. The unit is all low dc voltage, low power, nothing hot with correctly voltage rated caps. The output circuitry can deal with indefinite short circuit.

Beyond that I suppose you could drop the unit on your foot............ ;)
I was wondering how did you get this low ps noise. Isolated smps, well done.
 

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