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Old 5th December 2011, 10:20 PM   #1221
qusp is offline qusp  Australia
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Originally Posted by cheapskateaudio View Post
Except that the O2 built to spec doesn't sound good with HD650's to my ear, it's kind of thin and harsh sounding. And both amps suffer a change in the character of their sound over time.

HD650's should be a little bassy and lush sounding right? That's what their FR curve would indicate. Most impressions are that the HD650 offer even more of that traditional HD6xx sound (big bass, lush mids, slightly rolled treble) than the HD600's even. To me it sounds like my HD650's are being driven by a lightweight amp. I'm probably being to much of a perfectionist, but then people like yourself hype it up by saying "it sounds as good as anything". I want to hear that, but I don't.
hang on, so it reads like you are not even familiar with the headphone you are using as a 'reference' you only seem to be familiar with the HF cliches including the incorrect notion that they are hard to drive. the difference between hd600 and hd650 is far less pronounced than you seem to think

ahh sorry just noticed its been solved; awesome!!

as you were chaps
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Old 5th December 2011, 10:56 PM   #1222
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This is a filler post so we can get on to page 123... I hope. Why? My screen shows page 123 but for the last hour it's referred me back to page 122... so I'm posting some content to see if it's going into the void or if it'll be just the kick needed to get out of this 123 -> 122 loop.
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Old 5th December 2011, 11:01 PM   #1223
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Default 'Hardcore' use of the O2!

The output level of my DJ mixer was never enough to drive a pair of HD25 headphones to a high enough level to match my PA system. Now, however, boosting it with my O2, there's headroom to spare - certainly need to heed the warnings about being careful to avoid hearing damage by not turning it up too far. What a wonderful sound, clear, clean and powerful. Just as a bonus, the O2 drops neatly into the console's carrying handle, which positions it in exactly the right place...
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Old 5th December 2011, 11:36 PM   #1224
tschuss is offline tschuss  United States
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This is probably my favorite XKCD of all time (and is appropriate for this discussion):
xkcd: Duty Calls


NwAvGuy- Haven't had a lot of opportunity to listen for long periods of time, but I do really enjoy what I've heard thus far in small amounts. Thanks for the design, discussion, and assistance.

Actually, that goes to all of you who have contributed in a positive way. This is a great community!
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Old 6th December 2011, 01:59 AM   #1225
firev1 is offline firev1  Singapore
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Built it right on the first try, gonna build a desktop version after the panels arrive No overheating, running cool. Only gripe is that I can't find a suitable European power supply here that runs 14- 20 VAC. Only found a 12VAC one so far but have no bought it yet so running of batteries for now.
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Old 6th December 2011, 02:30 AM   #1226
nezbleu is offline nezbleu  Canada
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Default Temperature measurements

Wow, there's been a lot of activity here since I last looked...

Anyway, I said I would so I did. I let my batteries discharge fully, to the point where the LED was still on but no output. I connected source and 32-ohm headphones, plugged in the AC (16VAC, 500mA), and cranked 'er up. This was with the board out of the case. So the voltage regs were charging the batteries and powering the amp at uncomfortable levels. I monitored temperatures for a while until they stabilized. Here is what I found (all temperatures Centigrade):

U1 21
U3 28
U4 29
U2 21
Q1 23
Q2 27
R1 24
R2 24
U5 48
U6 45
C2-4 28
C8-9 23

Hmm, I see can insert "table" tags but I can't seem to mark up rows and cells, does anybodu know how to make tables here?

Anyway, you can see that absolutely nothing got warm in any alarming way. I realize now that this topic has been put to bed, but thought I would follow up anyway.

Last edited by nezbleu; 6th December 2011 at 02:38 AM. Reason: messed up table
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Old 6th December 2011, 03:02 AM   #1227
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@Nezbleu, Thanks for taking the time to make the measurements. It always helps to get more hard data out there from someone besides me.

@Greenalien & Tschuss, thanks for sharing your positive experiences so far.

@FireV1, talk to Jokener in Germany and/or Olliver in the UK if you haven't already. Both should have sources for suitable Euro transformers.

A further update on the regulator issue... Konga reported a few pages back his regulator issue was a false alarm. I'm told Mikeaj has done the same on H-F. And I'm not sure the O2 or the regulators were at fault with Cheapskateaudio and Deadlylover. I think Deadlylover may have been commenting on the other 3 failures. He also may have modified or had another problem with his point-to-point wired O2 (no PCB used). So that pretty much concludes the "massive string of regulator problems" which I think was only those four.
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Old 6th December 2011, 03:29 AM   #1228
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qusp, i'm amazed you are still replying csa comments after this previous post:

'CSA really is an insane person. ignore the troll Click the image to open in full size. he changes his story, changes his thoughts, changes his words; all in an effort to gain a reaction'

Last edited by idjoel2000; 6th December 2011 at 03:32 AM.
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Old 6th December 2011, 03:53 AM   #1229
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Originally Posted by ethanolson View Post
We're entering a new era with AKG. They're releasing a new "closed" flagship the K550 with lower impedance and higher sensitivity. Their latest IEMS are 8Ohm 125dB SPL.
Originally Posted by RocketScientist View Post
@ethanolson, interesting. I wasn't aware of some of that. Some of the AKG changes might be the Harman influence. 8 ohm headphones are a bold move. I wonder if they're planning on their own amp/source to go with them?

I can certainly measure the O2 into 8 ohms at those sorts of levels. It might do better than you might think and the 0.5 ohm output impedance is still low enough. But lots of amps, even many expensive ones, are really going to fall on their face with an 8 ohm load.
According to AKG, they rated at 125dB/V and not mW so its not quite as crazy sensitive as it looks at first glance.

There's also the UM Merlin which is rated at 12 ohms.

Interestingly, those are both BA/dynamic driver hybrid designs which seem to be catching on lately. There are one or two other IEMs like that on the market but I can't remember their names or specs anymore.
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Old 6th December 2011, 04:59 AM   #1230
qusp is offline qusp  Australia
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Originally Posted by idjoel2000 View Post
qusp, i'm amazed you are still replying csa comments after this previous post:

'CSA really is an insane person. ignore the troll Click the image to open in full size. he changes his story, changes his thoughts, changes his words; all in an effort to gain a reaction'
fair point, wont happen again hes invisible to me. however I thought the fact that it seems he also bought the hd650 at the same time as the amp and has only spouted cliches in description of their sound, was worth noting. if i didnt know better i'd think he didnt own them either, the difference between 650/600 is VASTLY overstated

Last edited by qusp; 6th December 2011 at 05:08 AM.
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