The Objective2 (O2) Headphone Amp DIY Project - Page 160 - 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 21st December 2011, 02:23 PM   #1591
diyAudio Member
 
dirkwright's Avatar
 
Join Date: May 2011
Location: Virginia
Quote:
Originally Posted by Alexium View Post
billyk, my hand is just not steady enough for SMD, it shakes too much. I'd prefer to cut the leads, at least that's possible for me I get your point, though. I think I'm a bit jealous to those who can actually solder SMD
Yeah, I use a clip to hold the part in place while I solder it. I need to get a sharper tip for my Weller though. It's not an easy task and I can't do it without a magnifying glass.
  Reply With Quote
Old 21st December 2011, 07:10 PM   #1592
Alexium is offline Alexium  Ukraine
diyAudio Member
 
Join Date: May 2010
I'm starting to prototype my future DAC, specifically - it's output stage (not much else to prototype once the DAC chip and input receiver is chosen, I guess). It will be plugged in to O2 (obviously ), and my question is: how high a gain can I set without degrading sonical performance? Or, in other words, how low can I push input voltage? Ideally, I'd like to make input voltage as low as 0.1V, which would require gain of ~20. On the other hand, I understand that it would lower S/N ratio significantly, and, I guess, getting input of 300mV and lowering gain to 7-8 might be better. What do you think?
  Reply With Quote
Old 21st December 2011, 07:46 PM   #1593
diyAudio Member
 
RocketScientist's Avatar
 
Join Date: Mar 2008
Location: Northwest
Alexium, I don't see any advantage to having a DAC with a lower than normal output level--especially a maximum output of only 0.1 Vrms. There are only disadvantages to such an approach. Am I missing something?
__________________
http://nwavguy.com - Personal non-commercial audio blog
  Reply With Quote
Old 21st December 2011, 07:57 PM   #1594
diyAudio Member
 
Join Date: Nov 2011
Location: http://binged.it/ukmr5Y
Quote:
Originally Posted by Alexium View Post
I'm starting to prototype my future DAC, specifically - it's output stage (not much else to prototype once the DAC chip and input receiver is chosen, I guess). It will be plugged in to O2 (obviously ), and my question is: how high a gain can I set without degrading sonical performance? Or, in other words, how low can I push input voltage? Ideally, I'd like to make input voltage as low as 0.1V, which would require gain of ~20. On the other hand, I understand that it would lower S/N ratio significantly, and, I guess, getting input of 300mV and lowering gain to 7-8 might be better. What do you think?
That's unconventional. What has influenced your thinking? Are you trying to bypass an I/V stage from your DAC?
  Reply With Quote
Old 21st December 2011, 07:58 PM   #1595
Alexium is offline Alexium  Ukraine
diyAudio Member
 
Join Date: May 2010
Quote:
Originally Posted by RocketScientist View Post
Am I missing something?
At first I want to evaluate the simplest output stage design, which is resistor-based I/U converter. The lower the resistance - the better in terms of DAC linearity, but the lower the output voltage(obviously). Ideally, the resistance should be zero, but upon investigation of some forums I figure I can get 0.1-0.3V (30-100 Ohm) without significant performance degradation.
And I have missed 1 detail - the DAC has differential output, so I'll use an op-amp anyway, and I should choose it's gain, too. So, I'd like an advice on balancing DAC's output gain vs O2's gain. I understand it's a long shot with the amount of information I have on the circuit's characteristics (which is effectively none), but any guess is appreciated.
  Reply With Quote
Old 21st December 2011, 08:18 PM   #1596
diyAudio Member
 
Join Date: Nov 2011
Location: http://binged.it/ukmr5Y
@Alexium, I don't know of a DAC that's not differential output. I'm under the impression that the linearity problems can be solved by a clean I/V stage instead of output resistance. The added noise floor should still be far lower than anything you're going to deal with from extreme amplification of a weak signal. Clean DAC + I/V implementations can approach (maybe exceed) 115dB SNR.

Is this an ESS DAC? It sounds like one.

Even if the DAC had SE output (maybe some do?), since the O2 has 10kΩ input resistence, what does that do to the DAC's output voltage spec?
  Reply With Quote
Old 21st December 2011, 08:44 PM   #1597
Alexium is offline Alexium  Ukraine
diyAudio Member
 
Join Date: May 2010
Quote:
Originally Posted by ethanolson View Post
I don't know of a DAC that's not differential output.
I believe there are all kinds of DACs there - with I and V output, differential and single-ended. I'll try to come up with an example tomorrow.

Quote:
Originally Posted by ethanolson View Post
I'm under the impression that the linearity problems can be solved by a clean I/V stage instead of output resistance.
Of course! But that's not the point. The point is to move from simple to more complex designs to determine the top of my hearing abilities

Quote:
Originally Posted by ethanolson View Post
Is this an ESS DAC? It sounds like one.
Nope. In fact, ESS DACs are not popular or well-known where I live. I have first heard of this manufacturer only few months ago.
I'm prototyping with PCM1798, and when I determine the final design, I'll try to make a nice clean DAC based on PCM1794, perhaps even dual-mono 1794.

Quote:
Originally Posted by ethanolson View Post
since the O2 has 10kΩ input resistence, what does that do to the DAC's output voltage spec?
Nothing at all, except the need to match gains to get sufficiently loud signal on O2's output. I clearly understand this is off-topic, but I think it's a great thread to get valuable advice, so I took the risk
  Reply With Quote
Old 21st December 2011, 09:27 PM   #1598
diyAudio Member
 
Join Date: Nov 2011
Location: http://binged.it/ukmr5Y
The PCM179x chips are great. Isn't it interesting how most all of the modern DACs aren't as good as the ones created 6-12 years ago?

This makes me wonder how the ODAC is coming along. I'm itching for details.

RocketScientist, aren't you expecting some newly minted boards any day now for your next round of testing?
  Reply With Quote
Old 21st December 2011, 09:45 PM   #1599
Limp is offline Limp  Norway
diyAudio Member
 
Limp's Avatar
 
Join Date: Oct 2010
Location: Bergen
I just wanted to say a big thank you to everyone who have posted tips and tricks on how to make a face plate, with only the minimum of tools. I do not think I could have come up with eve half of this on my own.

This is the first time I've tried drilling into aluminium, and I think it proves that as long as you do not expect boutique quality looks and perfect alignment, there's nothing stopping you doing it on your own.

Click the image to open in full size.

Click the image to open in full size.
  Reply With Quote
Old 21st December 2011, 10:23 PM   #1600
billyk is offline billyk  United States
diyAudio Member
 
billyk's Avatar
 
Join Date: Oct 2005
Location: North Central Mass, USA
That face plate looks fantastic! Very nice job, you should be pleased with yourself!
  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 01:07 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