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
'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...
Photo-0004.jpg
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...
Photo-0004.jpg
Attachments
This is probably my favorite XKCD of all time (and is appropriate for this discussion):
xkcd: Duty Calls
</snark>
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!
xkcd: Duty Calls
</snark>
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!
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.
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.
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):
Ambient 16
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.
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:
@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.
@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.
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.
qusp, i'm amazed you are still replying csa comments after this previous post:
'CSA really is an insane person. ignore the trollhe 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:
One of the O2 mods I looked into was a submini 3PDT toggle or rotary switch to replace the gain pushbutton. I poked around a little but was into "by far the most expensive single component" territory and still hadn't found what I was looking for. The mod would have allowed for unity and 2 other gain settings - maybe helpful for using the O2 with a variety of sources and headphones. Just one of my set-aside-but-not-forgotten mods I'm posting to change the...er, that subject.
UE11 are around 16ohms or less as well and all of the multi BA drivers present far less than their nominal impedance at some frequencies
indeed it is, see this is the fallacy on headfi, headphones like hd600 are presented as hard to drive, but yet people seem to feel that iems should be perfectly fine unamped, when in reality quite the opposite is true. multi BA and hybrid IEMs are about as difficult a load as headphones get, much more difficult to pull off, but still possible with an amp with sufficient damping and capable of driving enough current into the low impedance, pretty much unheard of with the average DAP though, some ipods (or more specifically iphones) pull it off and the clip, but few others, as most will have some sort of resistor on the output to protect the amp
It all depends on sensitivity/efficiency. Many headphones were designed with the dropper resistors on integrated speaker amp in mind. IOW's the voice coil "included" the 120 ohm resistor (that was actually in the receiver.)
With an 8 ohm or 16 ohm voice coil if the sensitivity is high enough it may not draw more current for a given spl than say an AKG272HD (55 ohm/91db/V).
You can't generalize. Some amps can deliver loads of current but only swing 2V's. This is where you get the fallacies on head-fi.
Some amps can swing 7Vrms before clipping but anything over a volt have 1% THD.
Some amps can deliver high current and swing high Volts, but at low voltage have a lot of noise (steep inverse THD+N vs Vrms-out relation before clipping)
Some amps can swing clean 7V rms but clip with more than 40 mA of current, even at 0.2Vrms.
If the new AKGs are 8 ohm 125dB/V, current delivery won't be so much an issue. The issue will be 60hz and 120hz hum.
A lot of headphones sensitivity spec is marketing driven (fudged), did they measure spl at 2cm from the grill or 1 mm? Thats really the thing a lot of folks don't get, used to be the only true spec was max power handling. If it was high like 200mW you could bet your A$$ that the phones were actually -4 to -6dB in sensitivity from what the brochure said.
Its all not as simple as some like to make it out to be. That is why RS's graphs of THD vs Vrms at different loads are so brilliant, never before has the general public had such truthful measurements.
Last edited:
actually yes i can generalise within the limited stated area that i did. multidriver low impedance iems. show me where i said only low impedance? none of them come close to meeting their stated specs across the frequency range and they all give amplifiers, particularly the ones in DAPs a hard time, harder than hd600, given just 4v swing that is. sure some full size headphones are stupidly inefficient, but to be quite honest trying to use such cans portable is a bit dim for the most part and hd600 is not one of them and its often used as some sort of benchmark in this regard
Last edited:
I've been thinking about something similar, only my idea was revolving around a three-position push-button switch. Other than that it's identical to yours, including the "still haven't found what I'm looking for"
Indeed, even the venerable Shure SE530 dips down (just) below 10Ω at 8kHz, despite it being rated 33Ω nominally.
Not meant to start an argument, maybe read my post again?
Lets look at two popular multidriver low impedance iem's.
JH13 Pro - 28 ohms and 116db/mW, so this thing need 1 mw of power. That is 0.167 mA of current. Not hard to drive unless the output impedance is on the level of absurdity.
Unique Melody Miracle - 15.9 ohms and 114db SPL. So another one that need roughly 1 mW of power. Thats 0.126 mA.
So you are saying that IEM's that need <1 mA of current for well over 100db are difficult to drive?
I mean we are seeing this different by an several order of magnitude? I know output impedance could be argued but an amp would have to be at tube output level for this to be an issue I think?
The issue is noise free power, at such low low level of power the SNR is a challenge, not drive. What you want to look for with IEMs like this isn't power but high SNR like the O2, maybe that is where we are our wires are crossed
Edit: even at 10 ohm dips the curent requirement isn't going up that much. I could run the numbers again but believe SNR is the issue you IEM guys are facing.
Last edited:
also if you look at the average opamp datasheet, you will notice that as the load impedance drops, not only is the amount of voltage that can be put into the load limited by ohms law and output impedance, you will also notice that as the supply voltage goes down as with daps and some portable amps, the available swing decreases as they cannot swing as close to the rails with the lower supply, so the effect is compounded. buffers are better in this regard, as are some opamps, but its not the rule.
now if you are going to make a case for some inefficient full size headphones, and i'm guessing you will mention AKG or something, then i will take the same position as RS did and mention that this is so far from the usual that it hardly bares mentioning, i dont tend to include very fringe cases in my general statements.
the vast majority of full size headphones fall within a very manageable 50-300ohms category and are not inefficient either. this is, as a general rule a far easier load than multidriver IEMs.
JH13, which i happen to own, dip considerably lower than 10ohms and some of these hybrids contain single drivers that are less than 10ohms and put them into a multidriver with a series/parallel XO, so the impedance curve in the bass region is nuts. JH13 are NOT an easy load, just ask JCX. the latest ipod touch for example has an outputZ not far off 10ohms and that is not unusual; in fact ipods are thought of as being pretty good in this regard. are you telling me that this is easier?
drive them? yes mostDAPs will drive them, drive them in an anywhere near linear fashion? not so much
not sure what you were doing if not arguing........
now if you are going to make a case for some inefficient full size headphones, and i'm guessing you will mention AKG or something, then i will take the same position as RS did and mention that this is so far from the usual that it hardly bares mentioning, i dont tend to include very fringe cases in my general statements.
the vast majority of full size headphones fall within a very manageable 50-300ohms category and are not inefficient either. this is, as a general rule a far easier load than multidriver IEMs.
JH13, which i happen to own, dip considerably lower than 10ohms and some of these hybrids contain single drivers that are less than 10ohms and put them into a multidriver with a series/parallel XO, so the impedance curve in the bass region is nuts. JH13 are NOT an easy load, just ask JCX. the latest ipod touch for example has an outputZ not far off 10ohms and that is not unusual; in fact ipods are thought of as being pretty good in this regard. are you telling me that this is easier?
drive them? yes mostDAPs will drive them, drive them in an anywhere near linear fashion? not so much
not sure what you were doing if not arguing........
Last edited:
it seems that you based your argument on numbers and thinking that takes the nominal impedance as given, as you had to edit your post after the above numbers for se530 were given. if you had read my posts, you might have picked up that the nominal impedance is pretty arbitrary with this technology and is given at one frequency, often 1khz
anyway i dont want to sidetrack the thread again.
anyway i dont want to sidetrack the thread again.