So, the Objective2 headphone amp - designed entirely around the measurements? (PLEASE READ RULES BEFORE POSTING)
post-7680605
Post #256 of 1,042

Head Injury

Headphoneus Supremus
Joined
Sep 11, 2009
Messages
5,404
Reaction score
434
Joined
Sep 11, 2009
Posts
5,404
Likes
434
Quote:
kwkarth, if you're not going to provide any objective concerns, I don't think this is the thread for you.
 
Anonanimal, very handy table. Could you add LCD-2 rev.2 to the list for me? Audeze increased impedance to 60 ohms. Thanks 

(I suppose I could just use the K701 and rev.1 as approximations)
 
     Share This Post       
post-7680618
Post #257 of 1,042

Anonanimal

100+ Head-Fier
Joined
Jun 2, 2009
Messages
397
Reaction score
11
Joined
Jun 2, 2009
Posts
397
Likes
11


Quote:
 
Anonanimal, very handy table. Could you add LCD-2 rev.2 to the list for me? Audeze increased impedance to 60 ohms. Thanks 
(I suppose I could just use the K701 and rev.1 as approximations)


Sure.  I've upped the dB requirement to 115 for some additional headroom for quieter recordings.  In practice I've found this to be enough, but again YMMV.
 
I'd attach the .xls file instead of posting screenshots but I seem to have been denied that ability.  Sorry!
 

 
     Share This Post       
post-7680620
Post #258 of 1,042

kwkarth

Electronics guys... we have our plusses and minuses. With advent of digital everything, we're being phased out
Joined
Sep 30, 2001
Messages
10,307
Reaction score
97
Joined
Sep 30, 2001
Posts
10,307
Likes
97


Quote:
Where is your data showing that the amp does not, by spec, have enough output to properly drive the quoted headphones?
 
Actual power specs:
6.25 volts RMS on AC power at < 1% THD into 150 ohms
4.5 volts RMS on DC power at < 1% THD into 150 ohms
 
Compare to this calculations chart using actual headphone specifications.  This is using a Gamma2 as the reference DAC.  YMMV but this should give you an idea.
 

Nice chart!  To answer your question, one word...  headroom.
 
 
     Share This Post       
post-7680637
Post #259 of 1,042

limpidglitch

Headphoneus Supremus
Joined
Oct 29, 2008
Messages
3,389
Reaction score
193
Location
Sandnes
Joined
Oct 29, 2008
Location
Sandnes
Posts
3,389
Likes
193


Quote:
 
I'd attach the .xls file instead of posting screenshots but I seem to have been denied that ability.  Sorry!
 


Why not uploading the file to mediafire, Google Docs or similar, and post a link?
 
     Share This Post       
post-7680644
Post #260 of 1,042

Anonanimal

100+ Head-Fier
Joined
Jun 2, 2009
Messages
397
Reaction score
11
Joined
Jun 2, 2009
Posts
397
Likes
11


Quote:
Why not uploading the file to mediafire, Google Docs or similar, and post a link?


I can do that if there's interest.  It's a series of pretty simple calculations but I've got them packed in a table for quick reference.
 
     Share This Post       
post-7680658
Post #261 of 1,042

kwkarth

Electronics guys... we have our plusses and minuses. With advent of digital everything, we're being phased out
Joined
Sep 30, 2001
Messages
10,307
Reaction score
97
Joined
Sep 30, 2001
Posts
10,307
Likes
97


Quote:
I can do that if there's interest.  It's a series of pretty simple calculations but I've got them packed in a table for quick reference.

I think it's potentially very useful!
 
 
     Share This Post       
post-7680680
Post #262 of 1,042

digger945

Headphoneus Supremus
Joined
Mar 31, 2008
Messages
2,917
Reaction score
14
Joined
Mar 31, 2008
Posts
2,917
Likes
14
Indeed, Google Docs integrates seemlessly for me and works great with Excel, whether uploading or downloading to or from Google Docs.
 
     Share This Post       
post-7680703
Post #263 of 1,042

nikongod

DIY-ku
Joined
Jan 24, 2005
Messages
8,882
Reaction score
119
Joined
Jan 24, 2005
Posts
8,882
Likes
119
 
Quote:
Sure.  I've upped the dB requirement to 115 for some additional headroom for quieter recordings.  In practice I've found this to be enough, but again YMMV.
 
I'd attach the .xls file instead of posting screenshots but I seem to have been denied that ability.  Sorry!
 


Nice chart!
 
Your numbers for Beyer and Sennhesier are off. These companies declare efficiency in "db@1v", except for the HD600 whose efficiency is declared in db/mw. 
 
Im not sure about the AKG K701. it "looks and feels" like the declared efficiency (also given by AKG in db@1vrms) has been converted but Id double check by setting the "target spl" to whatever AKG says the K702 has@1v, and seeing what you get for voltage required :)
 
The gain you give in the far right column assumes that you have a 1v input signal. If you have quiet music you may only have a 0.25v signal or maybe even less with that same DAC. To achieve 115db with Hd800, and a quiet recording it could require boatloads of gain... If you want the amp to play LOUD there is no way around including the gain switch. 
 
     Share This Post       
post-7680726
Post #264 of 1,042

Armaegis

Modern Modder Man of Manitoba
HTML... uphill, both ways!
Joined
Oct 18, 2009
Messages
12,160
Reaction score
1,119
Joined
Oct 18, 2009
Posts
12,160
Likes
1,119
Can anyone provide the formula that converts from sensitivity in V to mW?
 
     Share This Post       
post-7680743
Post #265 of 1,042

The Monkey

Monkey See, Monkey DAC
A really sick dud
Joined
Oct 28, 2004
Messages
8,010
Reaction score
135
Joined
Oct 28, 2004
Posts
8,010
Likes
135
I'm a bit confused why there's a de facto assumption that this is designed to be a portable amp. From what I can glean from the designer's comments, the amp in its initial iteration is small, and therefore portable, but the designer also indicates that the amp also is suitable as a desktop amp (with bigger enclosure if wanted and other options). Regardless of whether the amp is used as a desktop or portable, it does not appear that there are any substantive differences in configuration. In other words, the amp designer appears to suggest that this amp is equally suited to desktop duties as it is to portable. So until someone offers a compelling reason to the contrary, I think limiting assumptions about the types of sources used to portables is inappropriate. Did the designer not use the Benchmark's amp as a comparator?
 
     Share This Post       
post-7680761
Post #266 of 1,042

kwkarth

Electronics guys... we have our plusses and minuses. With advent of digital everything, we're being phased out
Joined
Sep 30, 2001
Messages
10,307
Reaction score
97
Joined
Sep 30, 2001
Posts
10,307
Likes
97


Quote:
Can anyone provide the formula that converts from sensitivity in V to mW?

Watts (W) or milliwatts (W/1000) are the product of Voltage (V) and Current (I) and  R=V(2)/I .  therefore...
 
A sensitivity of 105dB / V is what is published for the AKG K702.  It has a published impedance of 62 ohms, so, our knowns are Voltage and resistance.  Since W=V(2)/R, then 1/62=0.01613, or roughly 16mW required for 105dB output from the AKG K702.
 
 
     Share This Post       
post-7680784
Post #267 of 1,042

fishski13

Member of the Trade: SolderWorksAudio
Joined
Nov 2, 2004
Messages
1,908
Reaction score
40
Joined
Nov 2, 2004
Posts
1,908
Likes
40


Quote:
I'm a bit confused why there's a de facto assumption that this is designed to be a portable amp. From what I can glean from the designer's comments, the amp in its initial iteration is small, and therefore portable, but the designer also indicates that the amp also is suitable as a desktop amp (with bigger enclosure if wanted and other options). Regardless of whether the amp is used as a desktop or portable, it does not appear that there are any substantive differences in configuration. In other words, the amp designer appears to suggest that this amp is equally to desktop duties as it is to portable. So until someone offers a compelling reason to the contrary, I think limiting assumptions about the types of sources used to portables is inappropriate. Did the designer not use the Benchmark's amp as a comparator?

the performance goal posts keep moving to suit a particular line of argument.
 
i generally recommend keeping the gain as reasonably low as possible for improved noise and giving you more play/adjustment with the volume.  also, a lower gain will give you better distortion numbers with increased negative feedback.  while the above table re: HP power requirements is handy, i would caution and reiterate that the source recording may not output enough V to achieve modest volumes, much less silly 115dB, under what i consider to be 'real world'/common playback situations.  choose your source and HPs carefully.
 
 
 
 
     Share This Post       
post-7680792
Post #268 of 1,042

Armaegis

Modern Modder Man of Manitoba
HTML... uphill, both ways!
Joined
Oct 18, 2009
Messages
12,160
Reaction score
1,119
Joined
Oct 18, 2009
Posts
12,160
Likes
1,119


Quote:
Watts (W) or milliwatts (W/1000) are the product of Voltage (V) and Current (I) and  R=V(2)/I .  therefore...
 
A sensitivity of 105dB / V is what is published for the AKG K702.  It has a published impedance of 62 ohms, so, our knowns are Voltage and resistance.  Since W=V(2)/R, then 1/62=0.01613, or roughly 16mW required for 105dB output from the AKG K702.
 

That part I know. I was wondering about the conversion from 1db/V to 1db/mW, which I'm pretty sure has a log or two in there. I could probably do it, but I'm a little too sleep deprived to crunch numbers right now. 
 
... doubling power... roughly 6dB... 2^x... equals P... zzzzzz
 
     Share This Post       
post-7680822
Post #270 of 1,042

bcg27

500+ Head-Fier
Joined
Nov 28, 2010
Messages
563
Reaction score
24
Joined
Nov 28, 2010
Posts
563
Likes
24


Quote:
That part I know. I was wondering about the conversion from 1db/V to 1db/mW, which I'm pretty sure has a log or two in there. I could probably do it, but I'm a little too sleep deprived to crunch numbers right now. 
 
... doubling power... roughly 6dB... 2^x... equals P... zzzzzz
 
Someone should double check this to make sure I didn't make a mistake but:
 
Sensitivity @1mW=sensitivity @1V - 10*log(P(1V in mW))
 
if you want to substitute in the formula to get power from 1 volt you get
Sensitivity @1mW=sensitivity @1V - 10*log(1/R*1000) = sensitivity @1V - (10*log(1/R)+30)
 
logs are base 10 logarithm

 
 
 
     Share This Post       

Users Who Are Viewing This Thread (Users: 0, Guests: 1)

Top