National LME49600 Reference Design Project - Page 11 - 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 9th April 2011, 05:19 PM   #101
IanAS is offline IanAS  England
diyAudio Member
 
Join Date: Dec 2004
Location: London
Thanks, yes I was wondering about how much voltage it takes to run the HD650's as in the manufacturers data it suggests it needs hardly any current or Wattage. I forget now, but it might have been only 1.5mW for 97dB. I'd need to find where I read that again so those are probably not the correct figures.

But I also wondered if people had found that they do sound better with a quite a few volts available so as to not clip transients.

At the moment I driving them from the 26mA max of the LME49710HA chips and through the 200ohm that the sound card comes with. I can't just delete that as there is a muting transistor for each output line that will be pulling too much current. Unless I also delete that. Then there might be some nasty cracks on power up/down.

Last edited by IanAS; 9th April 2011 at 05:27 PM.
  Reply With Quote
Old 9th April 2011, 05:29 PM   #102
diyAudio Member
 
RocketScientist's Avatar
 
Join Date: Mar 2008
Location: Northwest
The HD650's are 300 ohm headphones and relatively efficient. With any music they shouldn't need more than 2 volts RMS which is well within the abilities of any of the designs being discussed here.
__________________
http://nwavguy.com - Personal non-commercial audio blog
  Reply With Quote
Old 9th April 2011, 06:24 PM   #103
IanAS is offline IanAS  England
diyAudio Member
 
Join Date: Dec 2004
Location: London
Thanks.
  Reply With Quote
Old 11th April 2011, 08:52 PM   #104
IanAS is offline IanAS  England
diyAudio Member
 
Join Date: Dec 2004
Location: London
I found this list which concurs with 6V peak to peak for HD650's:

Power Requirements and Amp-Driving Characteristics Popular

Last edited by IanAS; 11th April 2011 at 08:55 PM.
  Reply With Quote
Old 11th April 2011, 10:00 PM   #105
jcx is offline jcx  United States
diyAudio Member
 
Join Date: Feb 2003
Location: ..
the link has some unit inconsistencies and seems to be aiming for 110 dB SPL clipping level - in fact unamplified Classical concert hall levels can reach >120 dB peaks - so if "real life" sound reproduction is a goal then I would recommend higher peak power - at least enough to reach the 120 dB SPL without clipping

many listening scenarios, musical genre could be enjoyed with less - all day listening should be done at less than ~80 dB SPL average level and "good" dynamic range today is +14 dB peak levels, with rare Classical, Jazz recordings sometimes hitting +20-24 dB

reaching the 120 dB SPL level should only be for seconds of the musical performance and requires listening at elevated average levels only allowed for a hr or so a day by OSHA standards
but at headphone drive levels even Class A power is relatively cheap so I like the higher 120 dB SPL clipping free design goal

HeadWize - Article: Preventing Hearing Damage When Listening With Headphones (A HeadWize Headphone Guide)

from the schematic of the QRV09 it looks like connecting a single board for bridged output would be easy so two boards would make a "dual mono" bridged/"balanced output" headphone amp with the headroom to drive a few of the more difficult headphones that would like higher Vdrive
  Reply With Quote
Old 11th April 2011, 11:15 PM   #106
diyAudio Member
 
RocketScientist's Avatar
 
Join Date: Mar 2008
Location: Northwest
Into a high impedance headphone this amp will manage at least double the 6 volt p-p requirement on 9 volt rails. So that alone buys you 6 dB more. So we're already up to 116 dB. And if we bump the rails up to 15 volts, the amp will very likely swing close to 26 v p-p into 300 ohms. And that's 12 - 13 dB more. That gets it up to 122 dB.

On 15 volt rails the amp should manage 9 volts RMS and a whopping 270 mW into 300 ohms. I don't see a maximum power number in the Sennheiser specs, but most headphones I know of start to get very unhappy before 100 mW and that's a common max safe power rating for a lot of full size cans (like the Beyerdynamic models). Above 100 mW you could damage the headphones--either from getting the voice coil to hot, or stressing the excursion limits of the driver and causing physical damage.

The HD650's are spec'd at 103 dB for 1 volt RMS. So 9 volts RMS would give 122 dB if the headphone can even handle that much power.

I know JCX is talking about only short peaks, but the headphone will still distort, compress, and/or could suffer excursion damage if the peak is more than it can handle. But, regardless, you don't need to bridge the amp to get 120+ dB of "headroom".

And, just for anyone who doesn't know, bridging an amp creates other problems--most notably the common ground of the 3 wire plug on nearly all headphones. Bridging also cuts the impedance seen by each amplifier in half. And that can increase power dissipation by a factor of 4 and also typically increases distortion.

Whatever amp I end up building, I'll be evaluating it on many levels including clipping on real world music with real headphones like the HD650's. Anyone with a scope can do the same thing--especially if you use a battery powered portable player to drive the amp eliminating grounding concerns. And you can use any amp capable of similar levels of output swing.

You just set the scope to trigger at whatever the loaded clipping voltage of the amp is, or whatever level you're curious about. Then you listen to your most dynamic music as loud as you dare and see if the scope ever triggers. If it does, you can investigate how often or how realistic that condition is. If it never triggers you know you have plenty of headroom.

I suspect the HD650's will "complain" before the amp does--even on the 9 volt rails. Headphone distortion, like with speakers, rises dramatically as you approach their limits. So even if you can drive them that hard, you might not want to as it may sound rather harsh. Once more people get their QRV09's built in the other thread, and start reporting back, there should be more real-world info.
__________________
http://nwavguy.com - Personal non-commercial audio blog
  Reply With Quote
Old 11th April 2011, 11:44 PM   #107
agdr is offline agdr  United States
diyAudio Member
 
agdr's Avatar
 
Join Date: Sep 2010
Quote:
Originally Posted by RocketScientist View Post
I don't see a maximum power number in the Sennheiser specs, but most headphones I know of start to get very unhappy before 100 mW and that's a common max safe power rating for a lot of full size cans (like the Beyerdynamic models). Above 100 mW you could damage the headphones--either from getting the voice coil to hot, or stressing the excursion limits of the driver and causing physical damage.
The specs on my Shure SRH840s:

Shure Americas | SRH840 Professional Monitoring Headphones

Max. input power (1kHz)
1000 mW
  Reply With Quote
Old 12th April 2011, 12:02 AM   #108
jcx is offline jcx  United States
diyAudio Member
 
Join Date: Feb 2003
Location: ..
you can give several "max power" spec meanings

a max SPL
bottoming the driver against the frame (more common a low frequencies)
melting the glue holding the voice coil/diaphragm together
melting the wire

from the spread of "max power" ratings it appears that different manufacturers use different meanings of maximum


I listen happily to my HD600 from a Sony SACD player with only +/-11 V supply to its headphone output op amp so I'm quite aware the 120 dB+ headroom is practically unnecessary with these headphones - but there are even lower V senisitive headphones out there


bridged drive does require replacing the TRS connector - no good standard exists - the dual 3 pin XLR Headroom uses are very awkward, single 4 pin XLR is still physically big
Ray Samuels is using a camera shutter/focus? "micro" sized 4-pin for portable amps/IEM
  Reply With Quote
Old 12th April 2011, 02:12 AM   #109
diyAudio Member
 
theAnonymous1's Avatar
 
Join Date: Feb 2004
Location: Anonymityville
Quote:
Originally Posted by jcx View Post
bridged drive does require replacing the TRS connector - no good standard exists - the dual 3 pin XLR Headroom uses are very awkward, single 4 pin XLR is still physically big
Ray Samuels is using a camera shutter/focus? "micro" sized 4-pin for portable amps/IEM
I have some neat little 4-pin connectors around here somewhere. I have no idea what they are, but they are very good quality. Let me se if I can find them.

EDIT: OK, I found them. I only have the original part number for the jack, so I had to take a best guess at the plug.

http://search.digikey.com/scripts/Dk...name=HR1607-ND
http://search.digikey.com/scripts/Dk...name=HR1585-ND

I have a couple sets of these I would be willing to let go for a little cheaper than the digi price.

Last edited by theAnonymous1; 12th April 2011 at 02:34 AM.
  Reply With Quote
Old 12th April 2011, 03:41 AM   #110
agdr is offline agdr  United States
diyAudio Member
 
agdr's Avatar
 
Join Date: Sep 2010
Quote:
Originally Posted by jcx View Post
you can give several "max power" spec meanings
True! Just out of curiosity I'm going to shoot Shure tech support an email and see if I can get their take on "max". I'm also assuming that is 500mW a side. I've already pestered them in the past about the ear cups. One of my ears sticks out enough that it rubs against the inside of the cup. I've suggested they have some optional deeper ear cups.

But in general your thoughts on best power levels and RocketScientist's sound really good!

Last edited by agdr; 12th April 2011 at 03:45 AM.
  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
National LME49810TB/LME49830TB UltraHighFidelity HighPower Amplifier Reference Design KLe Chip Amps 75 21st October 2013 12:47 PM
Help with Dayton Reference 2-way Project coldcut Multi-Way 10 23rd May 2010 01:07 PM
How about a 3 inch reference project? type Full Range 52 13th October 2007 04:17 AM


New To Site? Need Help?

All times are GMT. The time now is 10:58 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