[miceblue]

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I just noticed a strange thing going on with my C5 today.  This morning when I powered on my Cowon Z2 + C5 setup and hit play, I got silence for about 5-7 seconds, then static and noise started coming in at a gradually increasing volume until it hit the preset volume I left it at before powering down the night before (and left it charging overnight).  I thought it was strange but didn't really give it any thought and chalked it up to a one time fluke.  But when I turned it on again later in the morning, I got the same strange sound.  So I did some testing throughout the day and it seems it's got to do with the bassboost.  If I leave the C5 turned off long enough (not sure exactly how long yet) and turn it on when the bassboost enabled, I will get this strange sound.  If I turned on the C5 with bassboost disabled, then it'll play music and the correct volume right away with no noise or distortion.  It makes sense that it's related to bassboost since I only started using bassboost yesterday.  I was able to record couple clips of the strange noise happening in 2 different instances using my phone and I'm attaching it here (rename to wav for playback).  Did any of you out there experience something similar?
 
 
 
   
 
 
 
   
 

 
I do have to also point out that one of the traces on the PCB had it's soldermask scratched off due to being right under the rail that holds the PCB in place.  The fit is real tight and I had to wiggle the PCB to get it out and I suspect that it got scratched off then.  I emailed John and he said that as long as the anodizing is not scraped off it should work fine.  And if the C5 does short due to metal-to-metal contact, it should just short out one channel and he will replace the enclosure.  I'm attaching a pic of the scratched off area.  Don't know if this has anything to do with the noise issue above though.  Just a heads-up for those of you that are doing mod/dev work.
 

 
I think your .zip files are corrupted or something; I can't open them with 7zip on Windows nor Mac unzippers.
 
My circuit board has no trouble sliding in or out of the aluminum enclosure's rails.

 

[jseaber]

Quote:

I just noticed a strange thing going on with my C5 today.  This morning when I powered on my Cowon Z2 + C5 setup and hit play, I got silence for about 5-7 seconds, then static and noise started coming in at a gradually increasing volume until it hit the preset volume I left it at before powering down the night before (and left it charging overnight).  I thought it was strange but didn't really give it any thought and chalked it up to a one time fluke.  But when I turned it on again later in the morning, I got the same strange sound.  So I did some testing throughout the day and it seems it's got to do with the bassboost.  If I leave the C5 turned off long enough (not sure exactly how long yet) and turn it on when the bassboost enabled, I will get this strange sound.  If I turned on the C5 with bassboost disabled, then it'll play music and the correct volume right away with no noise or distortion.  It makes sense that it's related to bassboost since I only started using bassboost yesterday.  I was able to record couple clips of the strange noise happening in 2 different instances using my phone and I'm attaching it here (rename to wav for playback).  Did any of you out there experience something similar?
 
 
 
   
 
 
 
   
 

 
I do have to also point out that one of the traces on the PCB had it's soldermask scratched off due to being right under the rail that holds the PCB in place.  The fit is real tight and I had to wiggle the PCB to get it out and I suspect that it got scratched off then.  I emailed John and he said that as long as the anodizing is not scraped off it should work fine.  And if the C5 does short due to metal-to-metal contact, it should just short out one channel and he will replace the enclosure.  I'm attaching a pic of the scratched off area.  Don't know if this has anything to do with the noise issue above though.  Just a heads-up for those of you that are doing mod/dev work.
 
 

 
Your files won't open here, could you email them to us? Since you've been removing the board, please check that C602 has not been dislodged (large silver capacitor beneath "R602"). We had once customer jam the battery pack into this capacitor, ripping it from its rightmost solder joint. This caused problems with bass boost. Also make sure your source is paused/muted/off before turning C5 on.

 

[luisdent]

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Also make sure your source is paused/muted/off before turning C5 on.

 
Just out of curiosity, how does that affect the amp?  Also, is it safe to turn the amp off/on with headphones plugged in? (i don't currently)

 

[miceblue]

Quote:

Quote:

Also make sure your source is paused/muted/off before turning C5 on.

 
Just out of curiosity, how does that affect the amp?  Also, is it safe to turn the amp off/on with headphones plugged in? (i don't currently)

I'm assuming yes. I do it all the time.
From the blog post:
Quote:

C5 builds upon c421′s proven power stage by adding cutting edge TPS7A4700 and TPS7A3301 regulators to the supply rails. Hats off to HiFiDuino’s blog post for catching my attention back in September.
 
We wanted to place LDO’s in c421, but there was no way to control them, and without control, unsynchronized LDO’s produce unsafe turn-on transients. C5 is smarter than c421, so its firmware simultaneously enables the positive and negative LDO’s after the rest of the amp has initialized. You hear only a safe turn-on transient with C5, and reap the benefits of ultra-low supply noise.

 

[jseaber]

Quote:

 
Just out of curiosity, how does that affect the amp?  Also, is it safe to turn the amp off/on with headphones plugged in? (i don't currently)

 
No damage is possible (we've tried). The DS1882 has strict startup requirements:
 

1. No input signals
2. Analog supply rails must be applied first
3. Digital 5V rail applied next
4. Apply initialization parameters + short write delay

 
Arduino handles all of this, but cannot prevent the user from playing music before C5 is on. If audio is present before C5 is turned on, the digital potentiometer may not boot properly and audio may be severely distorted, possibly mono, and . No damage, though. Turn the amp off for 5+ seconds to reset. This is all summarized in the instructions:
 
"To ensure proper startup, keep audio player off or paused before turning C5 on."
 
Edit: thor777's description reminds me of the noise I heard when manually booting the DS1882 out of order. It's fairly resistant to small input signals. Larger inputs tend to break the bootup cycle. Toggling bass boost on would possibly push an "okay" signal into "not okay" territory. 

 

[luisdent]

No damage is possible (we've tried). The DS1882 has strict startup requirements:

• No input signals
• Analog supply rails must be applied first
• Digital 5V rail applied next
• Apply initialization parameters + short write delay

Arduino handles all of this, but cannot prevent the user from playing music before C5 is on. If audio is present before C5 is turned on, the digital potentiometer may not boot properly and audio will be severely distorted and possibly mono. No damage, though. Turn the amp off for 5+ seconds to reset. This is all summarized in the instructions:

"To ensure proper startup, keep audio player off or paused before turning C5 on."

Ah. Interesting. I didn't get a manual... But I found the online download. I do all of the proper procedures anyway just out of caution. I was just worried about my er-4s because the only time I accidentally forgot to unplug them before turning the c5 on, it made the typical power popping noise, although not that loud. I just don't want to damage them.

 

[thor777]

C602 capacitor is secure and isn't damaged.  I did not move the battery at all.  Like I noted in my first post, you need to rename the extensions of the 2 audio files to .wav in order to play them.  The attachment tool wouldn't allow .wav files so I changed them to .zip.  I will send the audio files to John for analysis.  Also, the noise happened again on my way back home today.  I was on the metro listening to music (with bassboost enabled) when the last song in my playlist ended and the music stopped.  I just left the Z2 and C5 on playing nothing at all as I was checking email.  After couple minutes I started to play a new album and the noise came back.  So this happens even when the C5 stays on and there's no music for a certain amount of time.
 
Quote:

 
Your files won't open here, could you email them to us? Since you've been removing the board, please check that C602 has not been dislodged (large silver capacitor beneath "R602"). We had once customer jam the battery pack into this capacitor, ripping it from its rightmost solder joint. This caused problems with bass boost. Also make sure your source is paused/muted/off before turning C5 on.

 

[audionewbi]

Any future plans on making an amp based on OPA627? 

 

[jseaber]

Quote:

C602 capacitor is secure and isn't damaged.  I did not move the battery at all.  Like I noted in my first post, you need to rename the extensions of the 2 audio files to .wav in order to play them.  The attachment tool wouldn't allow .wav files so I changed them to .zip.  I will send the audio files to John for analysis.  Also, the noise happened again on my way back home today.  I was on the metro listening to music (with bassboost enabled) when the last song in my playlist ended and the music stopped.  I just left the Z2 and C5 on playing nothing at all as I was checking email.  After couple minutes I started to play a new album and the noise came back.  So this happens even when the C5 stays on and there's no music for a certain amount of time.
 

 
Could there be DC offset from the Z2? We'll be glad to inspect; already replied to your email.
 
 

audionewbi: Not planned 

 

[phrosty]

@jseaber I'm noticing some heavy distortion from my C5 when I've got my ODAC all the way up. Is the C5 not able to handle red book line-level 2Vrms?

 

[audionewbi]

Quote:

@jseaber I'm noticing some heavy distortion from my C5 when I've got my ODAC all the way up. Is the C5 not able to handle red book line-level 2Vrms?

can you upload the track you having issues with here, I haven't encountered anything like that. 

 

[jseaber]

Quote:

@jseaber I'm noticing some heavy distortion from my C5 when I've got my ODAC all the way up. Is the C5 not able to handle red book line-level 2Vrms?

 
C5 handles red book line-level input. I'm listening to C5 and ODAC now, just fine.
 
Supply rails are +/-7V and you can see from benchmarks that max output voltage is above 2VRMS. Try adjusting volume and gain at the amp.

 

[phrosty]

Quote:

 
C5 handles red book line-level input. I'm listening to C5 and ODAC now, just fine.
 
Supply rails are +/-7V and you can see from benchmarks that max output voltage is above 2VRMS. Try adjusting volume and gain at the amp.

 
Apologies, this was complete user error! Some new cans aren't handling the bass boost very well.

 

[audionewbi]

C5 sounds warmer than O2 with bass switch off. I assume lowering the gain might solve that issue. Is there anyway we could have a three gain setup program on C5?

 

[Mannes]

Hm I connected my c3 again now the c5 is burned in it does sound realy good it's more detailed than the iPod touch even I'm double amping now.
I am listening a lot to this setup I think I need a full size headphone now.