Review: NwAvGuy's O2 DIY Amplifier - Page 70  

Quote:

Originally Posted by Crazy*Carl 

Could you just do your PC sound vs the O2.  I would like to see that one more.

 

Hell i don't even have to do it blind with my pc onboard.

My onboard sound can't make my headphones go as loud as the O2.  They don't sound bad out of the onboard, and I'm not sure if I could pick out which was powering the headphones blind 100% of the time.  If I asked someone to keep increasing the volume I'd know soon enough though.

Thats why the person performing the test sets the volume at a reasonable fixed level before you listen.

I've built mine because I needed more volume and I like having a volume knob.  I don't have to worry about background hiss if I'm using very sensitive headphones/iem.  At <$100 for everything, I have what I want.

Edit:  I'm not trying to be mean, but I never put this amp together to [insert flowery prose about bringing music to life].  I needed something relatively inexpensive that could provide plenty of volume with any of the headphones I own or might consider purchasing in the future.  I could have bought a commercially built amp or a soundcard with a better amp, but I had much more fun and satisfaction building it up myself.

I should have mine O2s this week, I will see how good this is compared to the other cheaper amps I have. :P

Quote:

Originally Posted by Grev 

I should have mine O2s this week, I will see how good this is compared to the other cheaper amps I have. :P

What are the other amps you have?

Quote:

Originally Posted by uelover 

What are the other amps you have?

JDSLabs cmoy, PA2V2, ZO2.

Thinking of buying The Continental too but that would be luxury compared to my existing amps, haha.

I have an O2 (JDS Labs built) and a Violectric V90. Both have output impedance ratings below 1 ohm. My main amp is a Peachtree Nova that I use as a DAC, integrated amp (speakers) and headphone amp.

Since I have not conducted any blind tests, I won't mention the differences that I (think I) hear, but I do want to mention something that I have noticed that surprised me.

It was mentioned way earlier in this thread that the differences between amps, DAC's, etc. are typically blown way out of proportion to the point where newcomers to the hobby can really be convinced that product 'A' is superior to product 'B'. I think this is a real shame.

With my Nova's 30 ohm output impedance, I was convinced that my Denon D7000's (which are rated at 25 ohms impedance) would sound terrible. Well, they don't. In fact, I can barely tell the difference between any of these amps. If damping factor is so important to the performance of dynamic headphones, then how can my Nova drive the Denon's basically as well as the others - with an output impedance that's HIGHER than the headphones impedance?

I'm really at a loss here. Could it be the D7000's were designed with a high output impedance source in mind so the frequency response was purposely engineered to sound "normal" with  the expected FR shifts that that occur with underdamped drivers? I really can't explain it. As I mentioned before, I do hear subtle differences, so perhaps the effects of damping are simply overblown?

My brain wants to hear bloated bass from the Nova so I can replace it with a "properly designed" amp, but my ears just aren't hearing it.

Quote:

Originally Posted by palmfish 

With my Nova's 30 ohm output impedance, I was convinced that my Denon D7000's (which are rated at 25 ohms impedance) would sound terrible. Well, they don't. In fact, I can barely tell the difference between any of these amps. If damping factor is so important to the performance of dynamic headphones, then how can my Nova drive the Denon's basically as well as the others - with an output impedance that's HIGHER than the headphones impedance?

 

I'm really at a loss here. Could it be the D7000's were designed with a high output impedance source in mind so the frequency response was purposely engineered to sound "normal" with  the expected FR shifts that that occur with underdamped drivers? I really can't explain it. As I mentioned before, I do hear subtle differences, so perhaps the effects of damping are simply overblown?

Yeah the effects of electrical damping factor, for many headphones, is probably overblown by many, though maybe you're right about the Denon possibly being tuned that way.  Maybe it is, maybe it's not?  There's an argument about headphone drivers being much smaller than speaker drivers (less momentum, maybe less back EMF I suppose?  it's been a while since I looked at the physics here, and I never did like electromagnetics much) and there being more mechanical damping, but I don't really know enough to comment on that.

The main issue with output impedance is just the change in frequency response if the headphones have impedance that varies over frequency between 20Hz - 20kHz.  You don't get frequency response shifts with more or less constant impedance over frequency that the Denon has.

Quote:

Originally Posted by mikeaj 

 

 

The main issue with output impedance is just the change in frequency response if the headphones have impedance that varies over frequency between 20Hz - 20kHz.  You don't get frequency response shifts with more or less constant impedance over frequency that the Denon has.

Now that is something I didn't consider. I thought all dynamic headphones had "wandering" impedance. I didn't know that the Denons were particularly stable. If that is true, it would explain what I'm hearing.

Quote:

Originally Posted by palmfish 

Now that is something I didn't consider. I thought all dynamic headphones had "wandering" impedance. I didn't know that the Denons were particularly stable. If that is true, it would explain what I'm hearing.

It depends on the model.  See below.  HeadRoom uses a linear scale on the y axis for some reason, so I included a graph from a second source that's probably easier to read.

Quote:

Originally Posted by palmfish 

 

It was mentioned way earlier in this thread that the differences between amps, DAC's, etc. are typically blown way out of proportion to the point where newcomers to the hobby can really be convinced that product 'A' is superior to product 'B'. I think this is a real shame.

 

...

 

My brain wants to hear bloated bass from the Nova so I can replace it with a "properly designed" amp, but my ears just aren't hearing it.

I think you're referring to my post here. But yeah, I'm not surprised at all to read your comment. I think in general the best thing is to be brutally honest to yourself. This can be rather difficult if you just spent another $1K on the next FOTM wunderDAC though. :D

I think a lot of people WANT to hear something and then believe they do instead of actually hearing it. 

Quote:

Originally Posted by Negakinu 

I think you're referring to my post here. But yeah, I'm not surprised at all to read your comment. I think in general the best thing is to be brutally honest to yourself. This can be rather difficult if you just spent another $1K on the next FOTM wunderDAC though. :D

I think a lot of people WANT to hear something and then believe they do instead of actually hearing it. 

 

Exactly 

This is one of the most intresting threads in this forum.

Quote:

Originally Posted by Negakinu 

I think you're referring to my post here. But yeah, I'm not surprised at all to read your comment. I think in general the best thing is to be brutally honest to yourself. This can be rather difficult if you just spent another $1K on the next FOTM wunderDAC though. :D

I think a lot of people WANT to hear something and then believe they do instead of actually hearing it. 

 

Yes, it was your post. I actually only found this discussion yesterday and got through the first 40 pages (phew!) and I remembered yours. Thanks for the impedance charts. I used to own Sennheiser HD600s and I've seen impedance charts for them with a huge rise at 80-100 Hz and I just assumed that all dynamic headphones performed similarly. The Denons impedance does remain remarkably flat - comparable to a planar headphone. Impressive. After learning more about amps and output impedance, I was convinced that my Nova was a POS (as a headphone amp) due to its' 30 ohm output impedance - if the designers did that, what else did they do wrong? Well, it sounds extremely similar to my O2 and Violectric (in sighted A/B listening), so now I know why. I'll just have to stick with Denons and planars!

I think anytime you mix science with emotion (which hi-fi certainly is both), you open the door for "snake oil" sellers. Within the first week of the first Model T Ford rolling off the assembly line, I'm sure someone was selling a silver gas cap to ionize the fuel tank and improve combustion!

Someone else mentioned the 6Moons reviews and I think that not only are they indecipherable, but they are also completely meaningless. Anyone who has taken high school level science knows that in order to prove a hypothesis, you have to test with a large sample, have a baseline, and take measurements - OK, maybe that's not exactly what they teach in high school, but you get my meaning. When I read a review that has lots of flowery prose and lists all the high-end esoteric gear used in the listening room, my bull&*%# meter gets pegged.

I thought the "blanket experiment" referenced on NwAvGuy's blog was a particularly good example of how anyone will hear what they want to hear (or expect to hear).

I agree, great discussion here.

Yeah.  I ordered a $22 ($12 if I get a rebate lol) Asus Xonar DG card with a headphone amp build in.  I will report back with the results later this week.  I assure there will be no placebo effects in my impressions.  I am brutally hard on equipment reviews.

Remember to db match between set ups, otherwise comparisons are pointless. I also find it best to keep a selection of favourite 10 second test segments of music. It's hard to A/B entire songs because each listen you're paying attention to all menner of different things. In a 10 second slot over and over however, comparing specifics is easier.
 

Quote:

Originally Posted by Crazy*Carl 

Yeah.  I ordered a $22 ($12 if I get a rebate lol) Asus Xonar DG card with a headphone amp build in.  I will report back with the results later this week.  I assure there will be no placebo effects in my impressions.  I am brutally hard on equipment reviews.