March Audio HPA1

[trl]

[...]
With a digital volume only the signal (music) gets attenuated as you turn the volume down, the noise level remains the same. So as the volume goes down the dynamic range / snr goes down.[...]

That's the only bad thing I was thinking myself too, I'm glad you found the perfect words to put it out nicely.
Based on the already published measurements, I see no concern that someone will be actually hearing any noise out of HPA1. Instead, putting a...let's say 2x47KOhm pot in front of HPA1 will add lot of noise when volume's to the max.

P.S.: However, sometimes we need to work backwards from what our customers want, no matter the measurements, so perhaps a volume knob might be added later anyway, who knows?

 

[Kyle / MrHeeHo]

With how that DAC keeps coming up maybe a thread talking about and explaining that there's more to the cost of a device than the bill of materials may be necessary, it's a concept people on the internet seem to really struggle understanding.

As for the amp I think the design will speak for itself but maybe publishing a picture of the PCB close to release might help alleviate some concerns.

 

[March Audio]

That's the only bad thing I was thinking myself too, I'm glad you found the perfect words to put it out nicely.
Based on the already published measurements, I see no concern that someone will be actually hearing any noise out of HPA1. Instead, putting a...let's say 2x47KOhm pot in front of HPA1 will add lot of noise when volume's to the max.

P.S.: However, sometimes we need to work backwards from what our customers want, no matter the measurements, so perhaps a volume knob might be added later anyway, who knows?

Yes it's a theoretical concern but not a significant real world one.

As mentioned elsewhere I have been putting together some test data that shows digital attenuation V analogue with a 100k log Alps pot. I will try and post that later today.

When new the pot in a metal box won't necessarily add significant noise, but will degrade over time and will suffer significant balance tracking issues.

 

[DonH56]

There are a variety of digitally-controlled analog controls these days that might work. Some are essentially integrated stepped attenuators, some are basically MDACs, others use active devices (simple transistors to log amps). No moving (mechanical) parts and many are trimmed and stable over PVT and time.

 

[March Audio]

Yes, aware of, good option. Also looked at some PGAs but they would have reduced performance. Its also about minimising complexity.

 

[rebbiputzmaker]

Yes, aware of, good option. Also looked at some PGAs but they would have reduced performance. Its also about minimising complexity.

Logically amplifiers will have volume controls unless they are a stand alone power amp for use with speakers, and even then some have level controls for system adjustment and balance.

 

[restorer-john]

If it were me, I'd have a fixed and variable pair of inputs, just like several of my power amplifiers. That way everyone gets what they want and the usefulness of an instantly operable conventional volume pot is not lost.

You'd have two inputs which makes it more flexible in any case, a flip/flop and a small signal relay toggling between fixed and variable.

 

[trl]

@restorer-john you took my words out of my mouth, thank you.
One switch on PCB's bottom or on backside, or a relay that switches between "direct-power input" and "volume controlled input" and a regular 2-gang ALPS RK097 volume control potentiometer could be used in the front of the amp, like Neurochrome HPA-1 has...and this measured very well too. This is probably the most cost-effective way and hope it could be easily integrated onto existing PCB's without much re-work needed.

This HPA-1 seems very interesting and after reading so many disputes here I find it more appealing too. I feel like when I first read nwavguy's O2 headamp...a "must have" deja-vu, quite exciting. Now, I'd really like to know what's in the output buffer.

P.S.: Going to stepped attenuator is very expensive and digital volume control is expensive too, also board needs redesigned etc. http://www.ti.com/product/PGA2310 has a dynamic of 120dB, few dB less than the DAC itself, but still a respectful value. In my own "in-house" tests done around Conductor V2's PGA2310 chip I found no added noise coming from the PGA2310 itself until rotary knob gets over 80% when the internal chip's gain becomes higher than 1 (test was done by switching between analogue vs. digital inputs, no music playing, inputs shorted, 16-Ohms IEMs connected to outputs; that's about 6X of gain on 100dB/V IEMs'). If you can program the controller to not pass the volume over 0dB gain it should not add much noise, otherwise entire amplifier needs redesigned, because PGA2310 acts as a voltage-gain too...which kinda sucks in this scenario. https://www.njr.com/MUSES/series/MUSES72320.html should work too, especially if higher voltages are needed, but it's a voltage-gain this chip too. Worth mentioning that I don't have a tool able to measure background noise lower than -115dB, but with my 16 Ohms IEMs at night I can hear the background noise of my 1.5X-gain Objective2 amplifier (around -150dB), so really sensitive indeed.

 

[Veri]

@restorer-johnThis HPA-1 seems very interesting and after reading so many disputes here I find it more appealing too. I feel like when I first read nwavguy's O2 headamp...a "must have" deja-vu, quite exciting. Now, I'd really like to know what's in the output buffer.

Had the same thought !

 

[yummy]

is there 0db gain or -6db gain?

 

[March Audio]

Thank you very much for the reply.
I have a Grace Design m902 in my main system.
I have now ordered an optical cable to test it with my computer to see if I need an amplifier and dac for my headphone and this computer (I have a Beyerdynamic DT 250 250 Ohm).
It is an older amplifier/dac and it was pretty early to come out with usb support. But it performs badly with it. So I am also a little worried because with the March audio I can only connect it with the usb port to the computer
Just so I know how serious are you with this? With that I mean, if I buy it is there a possibility that the warranty would be worthless if you decided to stop inside of three years?
Maybe this isn't the right thread but what is the timeframe for your headphone amplifier and what is your target for pricerange?
Sorry for these questions

Hi @Bliman

The DAC1 is pretty much agnostic to its usb input. I have posted some measurements elsewhere which I will link to that show it operating with various computers and SBCs such as a Raspberry Pi with absolutely no change in output signal quality. With good dacs there is no need to be concerned about USB.

Well, any venture can go out if business, none of us have a crystal ball. I bought some very expensive Tag McLaren AV hifi kit some years ago. They then went out of business. Kit was still going fine 12 years later. Having said that I have invested a lot of time in this venture and I will be expanding the product range with a streamer and speakers. Its all going well so far

The headphone amp Pcb is at manufacture at the moment. It needs to come back, be tested and the enclosure finished/fit tested before I will do a production run. I have been a bit delayed by getting the power amps on the market, but I'm hoping for a month for the headphone amp, but going on experience that may be a bit optimistic.

The HPA1 will have no problem driving your DT250 cans

 

[March Audio]

@Bliman

That link I mentioned testing the DAC1 with multiple different USB sources

https://www.audiosciencereview.com/...end-points-are-they-any-good.5707/post-127194

 

[elira]

@March Audio have you decided the gain of the amp?

 

[March Audio]

@March Audio have you decided the gain of the amp?

I have performed a lot of testing with different cans and my personal view after much deliberation is that unity 0dB was just a bit too quiet for the less sensitive cans. As they are so popular I am using my HD6xx as the base line and with the quieter recordings I think it just needs that bit more.

So we are back to my original setting of +3dB or +6dB. I will be doing some final evaluation/noise level of a +6dB unit next week. Im confident it will be totally silent even with sensitive cans, but its better to keep the gain lower if possible. whichever way it goes someone somewhere wont be happy

 

[Bliman]

@Bliman

That link I mentioned testing the DAC1 with multiple different USB sources

https://www.audiosciencereview.com/...end-points-are-they-any-good.5707/post-127194

First thank you. So I should have no problems connecting it with the computer with optimal quality? I also don't understand it. With the dac, what is your involvement, did you design the board? Did you made it better? I don't understand it. I have someone here where I bought my gear 'link audio' who makes his own speakers and other things. And he is working with audio for I think more then 30 years. He let's make speaker units not the enclosure to his specification and he makes everything around it to his design. It would be nice to hear your story in the audio field, your qualifications and history. What is your work on the dac? Or is it just a case around a board? I do understand you have 3 year warranty but if you buy the board you have I think 2 years warranty for a third of the price. Maybe I am missing something but I would like to know if the extra price is simply for the case and you researching which board to take and also test the board?

 

[March Audio]

First thank you. So I should have no problems connecting it with the computer with optimal quality? I also don't understand it. With the dac, what is your involvement, did you design the board? Did you made it better? I don't understand it. I have someone here where I bought my gear 'link audio' who makes his own speakers and other things. And he is working with audio for I think more then 30 years. He let's make speaker units not the enclosure to his specification and he makes everything around it to his design. It would be nice to hear your story in the audio field, your qualifications and history. What is your work on the dac? Or is it just a case around a board? I do understand you have 3 year warranty but if you buy the board you have I think 2 years warranty for a third of the price. Maybe I am missing something but I would like to know if the extra price is simply for the case and you researching which board to take and also test the board?

Yes. This design does not get adversely affected by the computer it's attached to.

As I said it's a modified Toneboard. OEM supply of electronics is very normal and common place. For example think of Audiolab MDAC or the Project Dac. Designed by 3rd parties and sold under those brands. Hypex amp modules are also used in many products such as NAD and Bel Canto. Any product is a case around a board.

My background is electrical/electronics/signal analysis/test measurement. Much of my career spent at Rolls Royce Aero engines acquiring recording (both analogue and digitally) analysing signals from things like strain guages and vibration transducers. Also acoustic / engine noise measurement (lots of Bruel and Kjaer kit). Whilst at face value you might ask what is the relevance to audio, they are in fact from a technical POV almost identical disciplines - recording engineer. Low level audio frequency range signals that need to be amplified, conditioned, recorded and analysed to the highest accuracy, integrity and lowest distortion. They are analysed in similar ways, I have been staring at FFTs for decades. There is far more discipline and rigour applied to this than audio because the data goes back into and validates aero engine designs. Do it wrong and worst case scenerio a plane could fall out the sky.
As we have seen from Amir's testing some manufacturers, no names mentioned, obviously do not apply any rigour or performance testing of their designs.
I have also spent time working in noise and acoustics, 3d modelling of sound propagation/intensity and also occupational health applications. I have had a life long interest in audio electronics and have designed (non commercially) things like dsp active speakers.

My product range is a mix of self designed and off the shelf components just like many manufacturers. My headphone amp is entirely my design. My speakers will be my design. The streamer will use an off the shelf SBC, unless someone is suggesting I should design and entire computer?

You are buying a product like any other. There appears to be a lot of naivety/ignorance generally regarding product manufacture and some don't appear to understand the difference between buying a high quality, finished and warranted product and DIY. What do you think the cost of the board in any product is? Its A tiny fraction of the overall costs that go into producing and selling a product. Sell price starts at 2.5x BOM and is typically 4.5x. Any less and you don't have a business.


I strongly encourage people to diy, I still do myself. However people rarely actually evaluate the real costs of doing so. Their time, tools, etc etc or compare the finished result to a commercial offering. Frankly very few can achieve professional results. The toneboard is an excellent option for DIY. However if you want a finished professional product, and many are not interested or capable of diy, then the DAC1 is worth considering.

Hope that helps

 

[Bliman]

Yes. This design does not get adversely affected by the computer it's attached to.

As I said it's a modified Toneboard. OEM supply of electronics is very normal and common place. For example think of Audiolab MDAC or the Project Dac. Designed by 3rd parties and sold under those brands. Hypex amp modules are also used in many products such as NAD and Bel Canto. Any product is a case around a board.

My background is electrical/electronics/signal analysis/test measurement. Much of my career spent at Rolls Royce Aero engines acquiring recording (both analogue and digitally) analysing signals from things like strain guages and vibration transducers. Whilst at face value you might ask what is the relevance to audio, they are in fact from a technical POV almost identical disciplines. Low level audio frequency range signals that need to be amplified, conditioned, recorded and analysed to the highest integrity and lowest distortion. They are analysed in similar ways, I have been staring at FFTs for decades. There is more discipline and rigour applied to this because the data goes back into and validates aero engine designs. Do it wrong and worst case scenerio a plane could fall out the sky.
I have also spent time working in noise and acoustics, 3d modelling of sound propagation/intensity and also occupational health applications. I have had a life long interest in audio electronics and have designed (non commercially) things like dsp active speakers.

My product range is a mix of self designed and off the shelf components just like many manufacturers. My headphone amp is entirely my design. My speakers will be my design. The streamer will use an off the shelf SBC, unless someone is suggesting I should design and entire computer?

You are buying a product like any other. There appears to be a lot of naivety/ignorance generally regarding product manufacture and some don't appear to understand the difference between buying a high quality, finished and warranted product and DIY. What do think the cost of the board in any product is? A tiny fraction of the overall costs that go into producing and selling a product.

I strongly encourage people to diy, I still do myself. The toneboard is an excellent option for this. However if you want a finished product, and many are not interested or capable of diy and frankly few can acheive professional results in any case, then the DAC1 is worth considering.

Hope that helps

First I want to thank you for a complete answer.
Also great you worked at Rolls Royce Aero, I have been going to airshows my whole life with my dad (in that way planes are in my blood since I was little).
Now I shall be completely honest with you because what is the point otherwise.
I don't have a technical background and don't know all the tecnical stuff. But I am always searching for new things in my passions.
The way I see it, and I could be wrong, is that those manufactures like NAD and Grace Design, etc... are doing research how they can implement those chips and build a board for it and transformers and such and displays, etc...
So that they do a whole lot more then just buy a board somewhere, put it in a case and just sell it. That's also why I questioned you if you put it basically in a case and case closed. Because otherwise I could buy those same boards make a nice cover and sell it of as my product. Which you can see is a little fishy. With that I don't know what extra I would get if I buy your dac or just buy it here https://www.audiophonics.fr/en/diy-...s-u208-spdif-32bit-768khz-dsd256-p-13062.html and with a cheap case https://www.audiophonics.fr/en/alum...minum-case-for-khadas-tone-board-p-13626.html .
I hope you don't take it the wrong way, I just don't understand.
Like for example here https://www.audiosciencereview.com/...-ject-pre-box-s2-digital-dac.2393/#post-67549 of the Pro Ject Pre box s2 I think that Pro ject designed the board and choose the components and such no?
Or Chord do they just buy a complete board somewhere and put it in a box and that's it?
So If I bought your dac all I would get is a nicer box but nothing that you have really done on it?
And please I don't want to offend you

 

[March Audio]

The value is the way seperior case, its not a just a hobby box like everything else I have seen, the product testing and performance validation, the accessible English speaking customer support, the 3 year warranty. A product that is professionally built and can be resold when later you move on.

Finally you haven't spent time building it. What's the cost of your time per hour?

As I have tried to explain above this comparison of DIY to commercial products is naive in the extreme. Reducing it to component costs is misinformed and erroneous.

It sounds like you may be better off diying . You have to understand that you are not the intended market. A market which BTW is performing within my expectations

I actually do a bit of diy woodwork, the results of the chair I made are not professional. The Ikea alternative chair is frankly better. It costs a lot more than the pile of wood I bought but hey if I had bought that chair I wouldn't have spent hours making an inferior product, even though I can sit on both

BTW John Westlake designed the project dac board. It was just bought in and resold as Project. You might want to compare its performance to the DAC1, or say the more expensive chord mojo

OEM is everywhere.

 

[Bliman]

The value is the way seperior case, the product testing and performance validation, the accessible English speaking customer support, the 3 year warranty. A product that is professionally built and can be resold when later you move on.

Finally you haven't spent time building it. What's the cost of your time per hour?

As I have tried to explain above this comparison of DIY to commercial products is naive in the extreme. Reducing it to component costs is misinformed and erroneous.

It sounds like you would be better off diying you don't appear to understand that you are not the intended market or the value.

I do a bit of diy woodwork, the results of the chair I made are not professional. The IKEA chair is frankly better, it cost more than the pile of wood I bought but hey I didn't spend hours making an inferior product, even though I can sit on both

BTW you are wrong. John Westlake designed the project dac board. It was just bought in and resold as Project. OEM is everywhere.

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.

 

[March Audio]

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