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Made my first foray into headphone amps finally (C421)

post #1 of 16
Thread Starter 

It's been a long time coming, but I finally purchased my first headphone amp this week, the luck device in question being a JDS C421 with the OPA2227. I didn't really think that I would need a headphone amp considering my current collection is fairly low impedence-wise (highest being 44 ohms), but because I'm at the office for a good portion of my day or on the go, I was left feeling that my cans could benefit from an external amp since my iPod seemed to have great difficulty driving my 440's.

 

Well, finally got the amp in on Friday so I've been putting it through its paces. I immediately noticed the sound open up a lot as opposed to my iPod's amp section. It's really nice finally having my headphones properly driven now! The soundstage seems to have open a lot, and the highs don't seem muffled like before, really helps during busier sections of music. The low end seems to benefit as well, much smoother sounding all around. Even my IEMs get a noticeable boost in sound quality, which was a great surprise.

 

On my desktop setup, I noticed a similar difference in audio quality. The Xonar DX sounded better than any other source I had on hand by far because of its very solid DAC, but it does seem to open up quite a bit when paired with a headphone amp via lineout. I again noticed that busier sections of music (dense parts of rock/metal especially) had greater clarity than before. Maybe it's just placebo, but oh well. I'm going to throw it my signal chain from now on.

 

I did mess around with the bass boost switch a wee bit. I'm not a huge fan of these kinds of eq options, but this one did not seem all that bad compared to some software solutions I've heard. I won't be keeping it on all of the time, but it'll be cool for a change of pace once in awhile.

 

In the end, considering that the C421 benefits my music listening for both portable and home usage, I'm very happy with this investment. It's a bit more expensive than some other options and it doesn't have a DAC, but I decided to invest a bit more in the amp section because that's what I'll be using the most anyway. I'll probably be investing in some higher impedence cans later this year, so it'll be interesting to see how the high gain section can handle those loads. From my research, I think this little guy is up to it.

 

The only issue I've noticed so far is that I'm experiencing a bit of hiss if I were to max the volume out on the amp with my iPod plugged in (no music playing of course!). Though I have a feeling that's more of an issue with my source, since without anything plugged in, I noticed no hiss from the headphone jack. This hiss is noticeable on both my IEMs and full sized cans


Edited by TheChillburger - 8/6/12 at 7:25am
post #2 of 16

Suggestion:  get yourself a LOD (Line Out Dock) cable to connect your iPod to your C421.  Then you are removing the iPod's internal amplifier entirely from the equation.  This will get rid of the hiss you mention, and also increase your sound quality.  There are several to choose from, among the most popular inexpensive ones are the Fiio L9 and L3.  Trust me, it's worth it.
 

post #3 of 16

Agree with above post, if you haven't already done so.

post #4 of 16
Thread Starter 

Yeah, the LOD is something I'm considering. Right now I've set the volume in Rockbox to 0db to get pretty close to a line level signal, since I hear the difference in sound quality is pretty minimal. The hiss really only occurs when I go above half of the volume wheel on the C421, which is far louder than I would ever set it.

post #5 of 16

Yes, you need a LOD.

 

With a mini to mini you are still going through the ipod amp and then the C421 amp. Creating a dirtier sound.

 

An lod will bypass the ipod amp giving you a clean signal.

 

A cheap LOD is Fiio L9.

post #6 of 16
Thread Starter 
Quote:
Originally Posted by ExpatinJapan View Post

Yes, you need a LOD.

 

With a mini to mini you are still going through the ipod amp and then the C421 amp. Creating a dirtier sound.

 

An lod will bypass the ipod amp giving you a clean signal.

 

A cheap LOD is Fiio L9.

I've heard some mixed opinions as to whether the LOD actually bypasses the internal amp, or whether it just sets the output at an un-attenuated 0db. 

 

I may invest in a better cable at some point, though, since a L plug would be pretty handy.

post #7 of 16

An LOD on an iDevice definitely bypasses the internal AMP--that's their entire purpose. It's the DAC that is not bypassed.  Trust me, it's worth it!  And if you want an L-connector, the L9 from Fiio is pretty convenient.  http://www.fiio.com.cn/product/index.aspx?ID=23&MenuID=020303  EDIT: also, it's not expensive, so very little risk to try:  http://www.amazon.com/FiiO-L9-L-Shaped-Cable-iPhone/dp/B004QVNNI0/ref=sr_1_1?ie=UTF8&qid=1344372399&sr=8-1&keywords=fiio+l9

post #8 of 16
Thread Starter 

As an update, I ended up buying a L9, and I still have the same level of hiss that I had with my regular interconnect cable. Not sure if it's just my iPod or an issue with the amp...

post #9 of 16
Quote:
Originally Posted by TheChillburger View Post

As an update, I ended up buying a L9, and I still have the same level of hiss that I had with my regular interconnect cable. Not sure if it's just my iPod or an issue with the amp...

Currently using ipod Classic, C421 and HD600 and no hiss.

post #10 of 16
Thread Starter 
Quote:
Originally Posted by olear View Post

Currently using ipod Classic, C421 and HD600 and no hiss.

Think it might have something to do with the headphones being harder to drive?

post #11 of 16
Quote:
Originally Posted by TheChillburger View Post

Think it might have something to do with the headphones being harder to drive?

 

Perhaps.  Odd thought, in all the reviews I've seen of the C421, no hiss has been reported.  It might be worth sending an email to John to see what he has to say, whether it should be expected or not with your model of IEM.

post #12 of 16
Thread Starter 
Quote:
Originally Posted by Mutnat View Post

 

Perhaps.  Odd thought, in all the reviews I've seen of the C421, no hiss has been reported.  It might be worth sending an email to John to see what he has to say, whether it should be expected or not with your model of IEM.

I bought the amp off a member here at HeadFi, so it's probably not under warranty anymore.

 

I guess to clarify, I get some hiss on my AD700 on high gain mode (I guess that's to be expected? Was just testing for hiss there) but only a little bit in low gain mode. My GR06's also have pretty similar performance.

 

In my soundcard, I haven't really noticed any hiss in regular use, so I'm thinking it has something to do with the iPod. The hissing really only kicks in when I go beyond a volume threshold that is far beyond what I would consider listenable, so I don't really see a big problem yet.

 

EDIT: After further testing, it must be a problem with the iPod. Kind of ticked that the line out didn't really give me anything, but it was worth a try.


Edited by TheChillburger - 8/20/12 at 4:59pm
post #13 of 16
Thread Starter 
Another weird issue: with no source plugged in on the high gain setting, there is a distinct hiss that appears around half of the volume dialed and it tappers off as you max out the dial.... I'm guessing this is a serious issue, since this amp should have a black background. (Tested on my SRH440 to make sure it wasn't an IEM issue.

Sent from my Galaxy Nexus using Tapatalk 2
post #14 of 16
Quote:
Originally Posted by TheChillburger View Post

Another weird issue: with no source plugged in on the high gain setting, there is a distinct hiss that appears around half of the volume dialed and it tappers off as you max out the dial.... I'm guessing this is a serious issue, since this amp should have a black background. (Tested on my SRH440 to make sure it wasn't an IEM issue.
Sent from my Galaxy Nexus using Tapatalk 2

I've never known that to happen. Contact us for support. I'd be glad to have you send it in for inspection, even if you did buy it used.

Reply
post #15 of 16
Thread Starter 
Quote:
Originally Posted by jseaber View Post

I've never known that to happen. Contact us for support. I'd be glad to have you send it in for inspection, even if you did buy it used.

Hey John, got the amp back today! I noticed that there was very significantly reduced hissing with my IEMs using my Xonar DX, so it looks like the TLC worked pretty darn well.

 

From further testing with the iPod Nano, it looks like there is in fact some kind of hardware issue. I did some testing with one of the premium Monoprice 3.5mm to 3.5mm cables in comparison to my Fiio L9 LOD, and noticed that the Monoprice cable produced far less hiss. So either something is wrong with the LOD or there is something wrong with the line out functionality on the iPod.

 

Thanks for the quick response, you certainly live up to your reputation. I know where I'll be going when I decide to buy a new DAC!

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