The Qudelix-5K thread

[Tom Brown]

Why would it be so much? The only changes would be a bigger battery and beefier amplification, while not being unreasonably big/heavy. Is there anything else available that could drive planars?

I think the biggest problem will be heat dissipation. 10 Watts at 90% efficiency will leave 1W of heat to get rid of. That's doable. It would have to be class D with Mosfets but that's not such a bad thing.

The larger issue is that Mr. Hypops seems to be under the misapprehension that Qudelix will come into his house while he is sleeping and force him to set fire to his 5K model and buy the Jumbo.

 

[Hypops]

The larger issue is that Mr. Hypops seems to be under the misapprehension that Qudelix will come into his house while he is sleeping and force him to set fire to his 5K model and buy the Jumbo.

Not sure what you're referring to. Whatevs. But I always enjoy tidying up my forum feed by adding folks to my ignore list. Bye.

 

[mtfinny]

Why so much? A mobile device that outputs 8-10W into headphones? I can't even afford a desktop amp that outputs that much power.

Ok, you're right, that might be a bit of a stretch. But 2-3W should be doable for a reasonable price and that would drive most full-sized headphones well.

 

[Safeinthemountains]

Ok, you're right, that might be a bit of a stretch. But 2-3W should be doable for a reasonable price and that would drive most full-sized headphones well.

I'm not into planar headphones, but do they have such bad efficiency/low sensitivity that they need that much power ???

Once I made some measurements at home on my speakers, was just curious... As I had made a 35w stereo amplifier a long time ago, I realized it didn't even had to reach ONE watt in normal listening conditions (40 sqm living room) , and above this value it was far too loud for me...

I have used headphones/earbuds (now iem), almost every day for ~35 years and I'm happy not to be totally deaf at 46...

 

[Hypops]

I'm not into planar headphones, but do they have such bad efficiency/low sensitivity that they need that much power ???

Once I made some measurements at home on my speakers, was just curious... As I had made a 35w stereo amplifier a long time ago, I realized it didn't even had to reach ONE watt in normal listening conditions (40 sqm living room) , and above this value it was far too loud for me...

I have used headphones/earbuds (now iem), almost every day for ~35 years and I'm happy not to be totally deaf at 46...

With planars, it’s not usually power that’s the issue, but current (high power at low impedance). Some planars—like the infamous HE6–need amplification that is both powerful and higher current.

 

[DeJaVu]

it’s not usually power that’s the issue, but current (high power at low impedance)

Power is voltage multiplied by current. For low impedance you need an amp that can provide higher voltage(its what affects the power output, current is decided/limited by the impedance).

 

[Tom Brown]

I'm not into planar headphones, but do they have such bad efficiency/low sensitivity that they need that much power ???

Yes.

10W would be ideal.

3W would be fine for most listening.

 

[Safeinthemountains]

With planars, it’s not usually power that’s the issue, but current (high power at low impedance). Some planars—like the infamous HE6–need amplification that is both powerful and higher current.

OK, I see your point...
The specs say that HE6 V2 is 50 ohms 83dB, the (nominal) impedance seems quite high to me, but the sensitivity is quite low, compared to most of the other planars that are stated ~95-105 dB

Planar design need a flat coil with a rather big surface, so I would expect it to have rather high than low impedance, and most of the ones I found on the market go from 32 to 60 ohms.

But still, 83dB for 1mW (if I'm not wrong) must be loud. With a 50 ohms load you would need ~0.23V and only 4.5mA. Even if you need to add 12dB you need to apply 2^4=16mW instead of 1mW. No need for an amp with ~1W ? I could be wrong but I still don't understand the need for so much power on headphones.

 

[Hypops]

Power is voltage multiplied by current. For low impedance you need an amp that can provide higher voltage(it’s what affects the power output, current is decided/limited by the impedance).

But then you’d have to have lower current (for equal power), so that actually doesn’t make sense to me. The question isn’t whether the 5k has enough power, but enough current.

 

[Hypops]

OK, I see your point...
The specs say that HE6 V2 is 50 ohms 83dB, the (nominal) impedance seems quite high to me, but the sensitivity is quite low, compared to most of the other planars that are stated ~95-105 dB

Planar design need a flat coil with a rather big surface, so I would expect it to have rather high than low impedance, and most of the ones I found on the market go from 32 to 60 ohms.

But still, 83dB for 1mW (if I'm not wrong) must be loud. With a 50 ohms load you would need ~0.23V and only 4.5mA. Even if you need to add 12dB you need to apply 2^4=16mW instead of 1mW. No need for an amp with ~1W ? I could be wrong but I still don't understand the need for so much power on headphones.

Beyond me (I was an English major). I’ve read quite a few competing explanations for why planars need current. Experience confirms that it’s true, but I haven’t a clue why it’s the case. The instant one person explains it, someone else will contradict them. I’ll let the engineers duke it out. One thing I can say from experience is that driving planars usually has little to do with how loud you can get them (sensitivity). It’s about not losing bass or getting other funky FR effects.

If you’re interested, there are a few threads around here that discuss impedance and planars specifically.

 

[XTF1]

Power is voltage multiplied by current. For low impedance you need an amp that can provide higher voltage(it’s what affects the power output, current is decided/limited by the impedance).

Ehmm… no. The first part is absolutely correct. But for a given amount of (electric) power, a low-impedance HP actually requires less voltage than a high-impedance one—as old as it is, the Ohm law, and how it applies to power, is still relevant…
With very low-impedance HP (for example: Moondrop Para planar = 8 Ohm, a speaker-like impedance), current capacity may be the limiting factor, not voltage. @Hypops first statement was correct…

Another potentially important parameter is the amp output impedance. Fortunately, planar HP tend to have flat impedance responses, so not much affected by a high output impedance amp.

And since this above discussion is about the 5K power, whatever power needed to get loud enough is all what you need. If your HP needs 100mW to reach unbearable loud levels, whether your amp is 200mW or 10W wont make any difference… except the later could easily blow out your HP and your tympanic membrane!

 

[Tom Brown]

And since this above discussion is about the 5K power, whatever power needed to get loud enough is all what you need. If your HP needs 100mW to reach unbearable loud levels, whether your amp is 200mW or 10W wont make any difference… except the later could easily blow out your HP and your tympanic membrane!

This isn't the case.

A 200mW amp will have a way smaller power supply than a 10W amp. That will have profound effect on the quality of the output.

The smaller amp will struggle as it gets closer to max output, causing the slew rate to go way up. It may achieve a peak nearly the same as the big amp but it will have triangle distortion.

This is why the best amps have such over built power supplies.

I won't get into control authority that comes from impedance ratio but we can do that dive, if you like.

The exception to the big amp, little amp, rule are amps that use feedback to track a reference signal. They will try hard to track the source signal and this can help a ton but it does come at the cost of a tiny amount of distortion itself and, while it can be done extremely well, it isn't perfect.

 

[XTF1]

The smaller amp will struggle as it gets closer to max output

This is also true for the larger amp!

Some HP amps do have a high wattage, but that’s really a result: you need high voltage and high current to drive any headphones from say 8 to 600 Ohms. It is not because you need 10W for any particular can…

The exception to the big amp, little amp, rule are amps that use feedback to track a reference signal.

What type of amp is used on the 5K?

 

[rlw6534]

This is also true for the larger amp!

Some HP amps do have a high wattage, but that’s really a result: you need high voltage and high current to drive any headphones from say 8 to 600 Ohms. It is not because you need 10W for any particular can…


What type of amp is used on the 5K?

I'm pretty sure the Q5k uses the built-in opamp of the ESS chip. There is no separate amp.

 

[XTF1]

I'm pretty sure the Q5k uses the built-in opamp of the ESS chip. There is no separate amp.

Yes! My question was if the ESS9219 chip is an “amp that uses feedback”, the exception listed by @Tom Brown above. I believe it does, and it’s not an exception at all… but don’t know for sure.