[headwhacker]

Why would one want to listen at more than 110dB is beyond me. Even 90dB is irritating already. DSD music format prolly needs more than 110dB though.

 
Modern pop/rock records goes very loud at around 90dB. The older mastered rock albums you may need more than that. usually > 100dB. But there are a few classical recordings with a DR of around 30 - 35dB (transients/peaks). The assumption is the average listening level is 85dB. Add 30 - 35 dB and that accounts for 115 - 120dB peak. 
 
If you never listen to those kind of records then 110 dB peak is adequate. But I imagine your volume pot is always near if not close to the maximum position
 
To put things into perspective, I have a few classical and lots of old rock/rock n roll albums (e.g. nut cracker, beatles, eagles). I find myself turning the volume pot of my O2+ODAC @ 3.5x to 1 o'clock position a few times listening to some of these records using my HE-400i  (93dB/mW). HE-6 requires approximately 8 times the power needed by HE-400i to reach the same level of SPL. O2 obviously don't have enough power for these types of records. 

 

[diamondears]

Modern pop/rock records goes very loud at around 90dB. The older mastered rock albums you may need more than that. usually > 100dB. But there are a few classical recordings with a DR of around 30 - 35dB (transients/peaks). The assumption is the average listening level is 85dB. Add 30 - 35 dB and that accounts for 115 - 120dB peak. 

If you never listen to those kind of records then 110 dB peak is adequate. But I imagine your volume pot is always near if not close to the maximum position

To put things into perspective, I have a few classical and lots of old rock/rock n roll albums (e.g. nut cracker, beatles, eagles). I find myself turning the volume pot of my O2+ODAC @ 3.5x to 1 o'clock position a few times listening to some of these records using my HE-400i  (93dB/mW). HE-6 requires approximately 8 times the power needed by HE-400i to reach the same level of SPL. O2 obviously don't have enough power for these types of records. 

Yeah, that's about my experience too. That HE-6 must be one really power hungry HP. 8 times???

 

[headwhacker]

Yeah, that's about my experience too. That HE-6 must be one really power hungry HP. 8 times???

 
every 3dB increase requires approximately 2x the power. 

 

[diamondears]

every 3dB increase requires approximately 2x the power. 

Off topic, but is there any advantage/reason to get the HE-6 SQ-wise? Became interested on the HE-6 because I like the idea of being able to use my speaker amp with it, less gears on the rack, and I have a good extra speaker amp.

 

[headwhacker]

Off topic, but is there any advantage/reason to get the HE-6 SQ-wise? Became interested on the HE-6 because I like the idea of being able to use my speaker amp with it, less gears on the rack, and I have a good extra speaker amp.

 
I'm intrigued as well with HE-6. But the power requirements just puts me off. SQ will always be personal preference. You should go and audition the HE-6 with a capable amp. 
 
I'm actually looking at HE-560. Currently loving the 400i with O2+ODAC. HE-560 will require 2x the power of 400i @ 50ohms which I'm trying to find out if O2 can adequately drive and if there are any spare. 
 
I can't find any measurement online of how much power O2 can deliver @ 50ohm load. 
 
But my calculation is that O2 should be able to drive a 50 Ohm load @ 900mW. My assumption is based on the 33 ohm load measurement (613 mW) in which O2 reach maximum current. As the load increase the current required decreases and the voltage increase. 
 
I was hoping someone with the capability would have done the measurements at 50 ohm load. Violectric includes 50ohms in their amp lineup specs. 

 

 

[diamondears]

I'm intrigued as well with HE-6. But the power requirements just puts me off. SQ will always be personal preference. You should go and audition the HE-6 with a capable amp. 

I'm actually looking at HE-560. Currently loving the 400i with O2+ODAC. HE-560 will require 2x the power of 400i @ 50ohms which I'm trying to find out if O2 can adequately drive and if there are any spare. 

I can't find any measurement online of how much power O2 can deliver @ 50ohm load. 

But my calculation is that O2 should be able to drive a 50 Ohm load @ 900mW. My assumption is based on the 33 ohm load measurement (613 mW) in which O2 reach maximum current. As the load increase the current required decreases and the voltage increase. 

I was hoping someone with the capability would have done the measurements at 50 ohm load. Violectric includes 50ohms in their amp lineup specs. 

 

The LCD-2.2 is 50ohms, and 91dB/mW sensitivity. It only needs tiny bit less than 2Vrms at 110dB.

 

[HotIce]

If these 900mW are meant RMS, then you need about 9.5V peak (19V peak to peak) to get that power on 50 Ohm.
If you look at the 4556 output swing charts, on a 150 Ohm load, the IC already drops a couple of Volts per side, WRT the supply rail. And that is going to get worse on 50 Ohm.
So to get a clean 9.5V peak, you will need at least +/-12V supply. Forget about getting that power under battery supply.
But you have another problem. 9.5V peak, on 50 Ohm, is 190mA peak, divided by the two 4556 buffers, its 95mA each, which exceeds the 70mA max ratings.
This on purely resistive loads. When 'i' becomes non trivial (reactive loads), current figures will get worse.

 

[diamondears]

If these 900mW are meant RMS, then you need about 9.5V peak (19V peak to peak) to get that power on 50 Ohm.
If you look at the 4556 output swing charts, on a 150 Ohm load, the IC already drops a couple of Volts per side, WRT the supply rail. And that is going to get worse on 50 Ohm.
So to get a clean 9.5V peak, you will need at least +/-12V supply. Forget about getting that power under battery supply.
But you have another problem. 9.5V peak, on 50 Ohm, is 190mA peak, divided by the two 4556 buffers, its 95mA each, which exceeds the 70mA max ratings.
This on purely resistive loads. When 'i' becomes non trivial (reactive loads), current figures will get worse.

Wouldn't sensitivity play a huge part? It is a bigger factor than the impedance of the HP, as a matter of fact.

 

[HotIce]

Absolutely. I was just looking at the 900mW power figure.

 

[headwhacker]

The LCD-2.2 is 50ohms, and 91dB/mW sensitivity. It only needs tiny bit less than 2Vrms at 110dB.

 
True but my target is at 118dB to account for all types of music and the peace of mind of making sure clipping would not happen. 

 

 

[headwhacker]

If these 900mW are meant RMS, then you need about 9.5V peak (19V peak to peak) to get that power on 50 Ohm.
If you look at the 4556 output swing charts, on a 150 Ohm load, the IC already drops a couple of Volts per side, WRT the supply rail. And that is going to get worse on 50 Ohm.
So to get a clean 9.5V peak, you will need at least +/-12V supply. Forget about getting that power under battery supply.
But you have another problem. 9.5V peak, on 50 Ohm, is 190mA peak, divided by the two 4556 buffers, its 95mA each, which exceeds the 70mA max ratings.
This on purely resistive loads. When 'i' becomes non trivial (reactive loads), current figures will get worse.

 
I was talking about O2 powered by AC wall adaptor of course. So yes +/-12V into O2 is possible. 613mW is the measured and published output @ 33 Ohms. Should be worse than 50 ohms can manage 190mA peak of current.
 
It's correct the 4556 chip's max current is 70mA. But connected in parallel should double the current available which in theory is 140mA per channel. So 95mA per channel is well within the spec as documented in his blog.
 
Nwavguy guys blog mentioned that O2's current peak limit is around 200mA.

 

[HotIce]

95mA per 4556, which is 25mA over max rating. And this math is resistive load based. Phase makes things more interesting.

 

[headwhacker]

95mA per 4556, which is 25mA over max rating. And this math is resistive load based. Phase makes things more interesting.

 
the 70mA figure is per chip. 2 chips in parallel means each chip only delivers 48mA of current. Planars are resistive load which makes the math more likely to fit here than other types of headphone drivers. 

 

 

[HotIce]

OK, let's get the math back on track
900mW on 50 Ohm (resistive), is ~9.5V peak, and 190mA peak. The O2 has two 4556 current buffers, so each one gets 95mA. But the 4556 has a 70mA maximum rating.

 

[headwhacker]

OK, let's get the math back on track

900mW on 50 Ohm (resistive), is ~9.5V peak, and 190mA peak. The O2 has two 4556 current buffers, so each one gets 95mA. But the 4556 has a 70mA maximum rating.

 
Sorry, I can see where I got myself confused.

 I'm looking at 4556 data sheet now. Are you sure 70mA current limit is peak and not rms? From the maximum voltage vs output current graph it goes all the way to 200mA.