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New DAC and Headphone Amp

DonH56

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Very nice job!

Wish I had my shop set up, and time to piddle in it... I don't really have any electronics test gear anymore, however. My next task is to dig enough of my woodworking tools out to help my son make a shelf for his center speaker. Been in storage for years so I suspect much of the tools may not work (really need my table saw, jointer, and router).
 

Timbo2

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Volume knob. If we are talking only about looks, it doesn't have to be connected :p

Kidding aside I’m assuming this was a conscious decision. I’m not anti software volume control, but computers can be flaky sometimes. I’d feel a lot more comfortable with a switch or something on the back that significantly cut the output until I was comfortable the device was playing properly at and the volume was working.
 
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March Audio

March Audio

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It was a conscious decision. I just don't see the need for analogue volume controls any more. I have been using software control for years without issue.
 

Timbo2

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It was a conscious decision. I just don't see the need for analogue volume controls any more. I have been using software control for years without issue.

More than once I’ve had Windows throw the volume to 100% without me telling it to do so. I’ve also had it decide to output digital noise at 100% volume.

Generally happens with new apps and the like, not as much a concern on stable system.

My issue is practical, not sonic. But I appreciate the desire for simplicity and robustness. Nothing to wear out or add complexity.
 

maverickronin

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It was a conscious decision. I just don't see the need for analogue volume controls any more. I have been using software control for years without issue.

More than once I’ve had Windows throw the volume to 100% without me telling it to do so. I’ve also had it decide to output digital noise at 100% volume.

Generally happens with new apps and the like, not as much a concern on stable system.

I run into that stuff all the time as well. You'd proably need a dedicated music PC or streamer box to make the software volume control reliable.
 

Grave

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IIRC if you change the volume in the digital domain you lose DAC performance so you should have the digital volume at 100% and change the volume in the analog domain.
 
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March Audio

March Audio

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IIRC if you change the volume in the digital domain you lose DAC performance so you should have the digital volume at 100% and change the volume in the analog domain.

No, this is a bit of a myth with volume controls working to 32 or 64 bit resolution. Don't forget that analogue pot volume controls aren't exactly perfect either, balance tracking, noise etc.
 

maverickronin

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What problems are you having? What music player? Zero problems for years with the likes of Roon and J River.

Normally it's with my video player. I have an overly complicated chain of filters for video upscaling and audio DSP purposes which can loose it's marbles and output noise at 0dBfs. I've had occasional trouble with the Windows volume control jumping around or bugs in other random programs causing 0dBfs noise as well.

I use foobar2000 with WASAPI or ASIO as my primary music player and have never had any of those problems with it but I use my headphone setup for all the audio on my computer which opens up a lot more potential problems. That's why I suggested a dedicated music machine but separate sound devices would work just as well as long as you set the primary device to something with it's own volume control or extremely limited output (i.e. built in laptop speakers) and only used the chain with no external volume control with known good programs.

I recently got an RME ADI-2 DAC and I'm loving the digital volume control on it and since it's independent of my PC it will limit the volume of any software glitches as well.

Ultimately I guess it would depend on you usage patterns.
 
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March Audio

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OK, just starting some measurements of my headphone amp with the Virtins MIpro software

hpa2.jpg


I am crudely measuring the SPL (dB(A)

hpa1.jpg


First of all at max output prior to clipping into a 10k load (just the measurement system)

1532956282536.png


This is waaaaaaaaayyyyyy too loud to plug into my Oppo PM1 cans so at a more sensible level.

1532956478946.png


with Oppo PM1 connected - SPL 102db(A) - No difference!

1532956547253.png


I will try and do a full thd sweep tomorrow
 
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March Audio

March Audio

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A bit of an update, a few design changes to the dac including raising the 1.5V RMS output to a more conventional 2 V RMS. Definite improvement to performance including reducing phase noise.

1534574423682.png
 

Timbo2

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A bit of an update, a few design changes to the dac including raising the 1.5V RMS output to a more conventional 2 V RMS. Definite improvement to performance including reducing phase noise.

View attachment 14845

What was your initial reasoning for the lower 1.5V output? More usable volume with the headphone amp?
 

Grave

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A bit of an update, a few design changes to the dac including raising the 1.5V RMS output to a more conventional 2 V RMS. Definite improvement to performance including reducing phase noise.

View attachment 14845

Isn't this basically what I said, that higher DAC volume is better. . .
 
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March Audio

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Isn't this basically what I said, that higher DAC volume is better. . .
?
If distortion remains the same this increase will lead to a marginal increase in SINAD. The main reason to change to 2 v is for comparison purposes. Louder will win in a subjective shoot out.

Your comments above were referring to digital volume controls which if done at high enough resolution (32 or 64 bit) have no discernable impact on quality.
 
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audiobill

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If distortion remains the same this increase will lead to a marginal increase in SINAD. The main reason to change to 2 v is for comparison purposes. Louder will win in a subjective shoot out.

Your comments above were referring to digital volume controls which if done at high enough resolution (32 or 64 bit) have no discernable impact on quality.
I see this is in DIY group. Where is the design kit posted?
 
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March Audio

March Audio

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It's not. :)

However you will be able to purchase a product in the coming months as I have decided to manufacture the designs.
 
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