The Objective2 (O2) Headphone Amp DIY Project - Page 45 - diyAudio
Go Back   Home > Forums > Amplifiers > Headphone Systems

Headphone Systems Everything to do with Headphones

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 22nd September 2011, 04:30 AM   #441
diyAudio Member
 
RocketScientist's Avatar
 
Join Date: Mar 2008
Location: Northwest
@counter culture, I can assure you there's virtually no energy above the audio band, let alone at true RF frequencies, related to the O2's power supply. Ferrites are useless. You have to have sharp corners to create lots of harmonics at RF frequencies, and a linear power supply operating off of 50/60 hz sine waves doesn't have any such sharp corners.

I've looked at the spectrum on the dScope out to 96,000 hz and 99% of the energy is below 121 hz. I've also used a 350 Mhz 2 GS/sec scope and there's even less above 96 Khz. This isn't an RF issue at all. It's just good old fashioned electromagnetic hum. And it's solved.
__________________
http://nwavguy.com - Personal non-commercial audio blog

Last edited by RocketScientist; 22nd September 2011 at 04:47 AM.
  Reply With Quote
Old 22nd September 2011, 07:42 PM   #442
orpheus is offline orpheus  United States
diyAudio Member
 
Join Date: Jul 2004
Location: NYC
Quote:
Originally Posted by RocketScientist View Post
I really believe high-end DAC design is out of reach of most DIYers as they have no way to properly measure the result. Even many popular "commercial" DIY designs, such as those from Twisted Pear and AMB, are never properly measured. So while one can debate the merits of various hi-res audio formats, I think there are bigger problems with many diyDACs and even some commercial ones.
I realize this is off topic, but if I was able to find someone who would send you a Twisted Pear Buffalo DAC, would you be willing to measure it? If you agree, I will see if Russ and Brian might be willing to send one out for measurements. If they aren't, a DIYer might be willing to send one, especially if they bought a new Buffalo III and have a spare II. I only have one and I use it all the time, so I wouldn't want to be without it for the measurement period, but I could contribute an output stage if needed. It would be very interesting to see how a Buffalo measures on your expensive measuring setup.

Thank you for your time.
Aaron.
  Reply With Quote
Old 22nd September 2011, 07:58 PM   #443
diyAudio Member
 
RocketScientist's Avatar
 
Join Date: Mar 2008
Location: Northwest
@orpheus, I would like to get one or more Twisted Pear DACs on my test bench. They might perform great, or they might have one or more problems. I'm just surprised they've never been properly tested.
__________________
http://nwavguy.com - Personal non-commercial audio blog
  Reply With Quote
Old 22nd September 2011, 08:13 PM   #444
orpheus is offline orpheus  United States
diyAudio Member
 
Join Date: Jul 2004
Location: NYC
Quote:
Originally Posted by RocketScientist View Post
@orpheus, I would like to get one or more Twisted Pear DACs on my test bench. They might perform great, or they might have one or more problems. I'm just surprised they've never been properly tested.

Great! I'll ask around and see if anyone is willing to send you one. I'll start with the designers themselves. I doubt they have the measuring equipment you do, and they might be curious to see what you measure.

Hope it works out!

Aaron.
  Reply With Quote
Old 23rd September 2011, 07:58 AM   #445
regal is offline regal  United States
diyAudio Member
 
Join Date: Jan 2004
Location: MD
Quote:
Originally Posted by RocketScientist View Post
@orpheus, I would like to get one or more Twisted Pear DACs on my test bench. They might perform great, or they might have one or more problems. I'm just surprised they've never been properly tested.
DAC's don't need a sweeping THD vs power output measurement. I mean a 24bit ADC in a good soundcard is the worst load you could give a DAC, I guess I don't see how your equipment is going to "properly" measure a DAC any better than a CS ADC that nearly everyone who builds their own DAC owns in their soundcard, are you proclaiming the ability to measure jitter with some NIST standard ? Maybe you should start a new topic in the correct forum
  Reply With Quote
Old 23rd September 2011, 08:29 AM   #446
diyAudio Member
 
abraxalito's Avatar
 
Join Date: Sep 2007
Location: Hangzhou - Marco Polo's 'most beautiful city'. 700yrs is a long time though...
Blog Entries: 101
Send a message via MSN to abraxalito Send a message via Yahoo to abraxalito Send a message via Skype™ to abraxalito
Quote:
Originally Posted by regal View Post
I guess I don't see how your equipment is going to "properly" measure a DAC ...
Yeah I agree. This word in scare quotes "properly" definitely belongs in them because its a weasel word, giving the appearance of being science. Who says what's a "proper" suite of tests for a DAC?

If it were me I'd say a proper test suite would be one that correlated with how it sounds. Does anyone know such? Instead we are more likely to get the currently fashionable tests (multiple averaged FFTs included because they're provided by most equipment vendors) - who's to say they are the "proper" ones?

Many years back Stereophile tried introducing a noise modulation test but that didn't catch on. Its definitely an interesting avenue of measurement for DACs, particularly sigma-delta ones.
__________________
No matter if we meanwhile surrender every value for which we stand, we must strive to cajole the majority into imagining itself on our side - Everett Dean Martin
  Reply With Quote
Old 23rd September 2011, 09:46 AM   #447
Jokener is offline Jokener  Germany
diyAudio Member
 
Join Date: Sep 2010
Location: Good ol' Germany
It will always boil down to the question of "What do you want?".
If you want something that "sounds awesome"... go ahead and buy whatever sounds "awesome".

But I prefer the electrons to my speakers unaltered and as pure as possible.
That means the way the was meant to sound by whomever made it.
And if I want any coloration to my music, there's plenty of opportunity to get it from the speakers.

'Sounded' equipment can only provide a good listening experience if the entire system is matched.
If everything is just a 'wire', you can mix and match anything you'd like.

And don't put every single word like 'properly' on the gold scale.
We should all be able to agree that a DMM and Rightmark are not suitable to measure anything high-end.
__________________
New O2 Amplifier GB: Order Thread, Order Status PDF (Password: diyaudio.com)
Pictures of the GB are in the Gallery: Click me! (User & Password: diyaudio.com)
  Reply With Quote
Old 23rd September 2011, 10:04 AM   #448
regal is offline regal  United States
diyAudio Member
 
Join Date: Jan 2004
Location: MD
Quote:
Originally Posted by Jokener View Post
It will always boil down to the question of "What do you want?".
If you want something that "sounds awesome"... go ahead and buy whatever sounds "awesome".

But I prefer the electrons to my speakers unaltered and as pure as possible.
That means the way the was meant to sound by whomever made it.
And if I want any coloration to my music, there's plenty of opportunity to get it from the speakers.

'Sounded' equipment can only provide a good listening experience if the entire system is matched.
If everything is just a 'wire', you can mix and match anything you'd like.

And don't put every single word like 'properly' on the gold scale.
We should all be able to agree that a DMM and Rightmark are not suitable to measure anything high-end.

But your speaker are an iron core inductore, they are part of the amp! You can't take a cartesian dissection of audio chain, especially when it comes to the temporal membrane of our ears that transfers the physics to perception and consciousness. Your thinking is very, well 17th century Descart. Just about 3 centuries proved wrong by everything from quantum mechanics to the theory of relativity. Anyone who knows even the basics of electrons knows that newtonian physics and cartesian philosophy don't apply.

Measurements are a tool, interpretation of them is completly subjective unless you have have a working model of how perception, the mind , and consiousness work. Let me know when you work that out.

Last edited by regal; 23rd September 2011 at 10:08 AM.
  Reply With Quote
Old 23rd September 2011, 10:42 AM   #449
diyAudio Member
 
xnor's Avatar
 
Join Date: Oct 2010
Jokener's basically right though. Even amb wrote that he uses RMAA just to check if it "works" or something is screwed up. Even for that RMAA is only partly useful.

Quote:
Originally Posted by regal View Post
Maybe you should start a new topic in the correct forum
Maybe you should start a new topic with your attempts to invalidate measurements / objectivity. Good luck.

Last edited by xnor; 23rd September 2011 at 10:48 AM.
  Reply With Quote
Old 23rd September 2011, 03:08 PM   #450
diyAudio Member
 
RocketScientist's Avatar
 
Join Date: Mar 2008
Location: Northwest
I don't use "properly" as a "weasel world" but merely to indicate few audio engineers would consider RMAA "proper". Audio Precision, Prism Sound, AES papers, and even Stereophile have established guidelines for testing DACs. AP, in particular, has some excellent "white papers" on the subject. A lot of those tests cannot be done at all with RMAA, or at least cannot be done properly with RMAA with a high level of confidence in the results. I have written an entire article on the topic. It's a very sketchy bit of free unsupported software.

As for jitter, one of the employees of Prism Sound (makers of the dScope), developed the Jtest signal and test methodology that I use. There's an AES paper on the topic and it's been widely adopted by many others--even their main competitor Audio Precision. RMAA cannot make the measurement.

RMAA also doesn't do low level DAC linearity tests, digital carrier tests (jitter, stability, eye pattern, etc.), test at known output levels, conduct CCIF IMD tests, the noise tests use an unknown bandwidth and unknown weighting, you cannot view distortion residual, you can't create known amounts of jitter on a digital output and measure how well a DAC deals with it, etc. For a partial list of what the dScope performs see: Prism Sound
__________________
http://nwavguy.com - Personal non-commercial audio blog
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Headphone amp project grahamfocal Headphone Systems 7 21st June 2011 05:28 PM
My latest project - DAC + headphone amp gmarsh Digital Line Level 105 13th December 2010 02:31 PM
My headphone amp project trifidmaster Headphone Systems 2 22nd December 2008 03:52 PM
Mini Ipod headphone amp DIY project Nordic Headphone Systems 14 11th March 2007 02:35 PM
Need help for a battery headphone amp project dismalonyx Headphone Systems 1 15th April 2004 11:22 PM


New To Site? Need Help?

All times are GMT. The time now is 08:25 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2