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Headphone and Amp Impedance (2011)

nwavguy.blogspot.com

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Re: Headphone and Amp Impedance (2011)

#61

Post by mckirk »

Aurornis wrote: post #51
dusted wrote: post #44

I find myself guilty of deep-diving into headfi-territory audiophilia once in a while, this time it got to me as well and I started thinking how neat it'd be to finally do it and get some high-end replacement for my 250 ohm dt990 pro cans, and I've heard both the hifman arya and sennheiser hd800s and know they are quite a lot better.. but THEN comes the amp question... and the rabbithole deepens.. and then the DAC an…

> but THEN comes the amp question... and the rabbithole deepens.. and then the DAC and in the end I give up, every time.. Well I have some great news for you! In 2024, you don’t need to spend mega bucks to get a good DAC or amp. You might not need one at all! One of the better performing and measuring DACs out there right now is the $9 Apple USB-C dongle: https://www.audiosciencereview.com/forum/index.php?threads/r..…

I was reading the parent comment and just could feel myself itching to recommend AudioScienceReview, but then was glad to see it was already the top answer. It's such a relief when you finally have some hard data to compare options in that snakeoil-laden field.

I built my stack based on the reviews there, and I've been completely satisfied with my Topping D10 (for DAC) and JDS Atom (for an amp), which cost me like $200 total a few years ago. But of course, there's already a newer model of the Atom that seems to blow the old one out of the water: https://www.audiosciencereview.com/forum/index.php?threads/j...

And btw OP, for headphones I'm using DT1990s, which might also be worth a listen if you are looking to upgrade from the 990s :)

Re: Headphone and Amp Impedance (2011)

#62

Post by kragen »

ahdsr wrote: post #23
geon wrote: post #16

Earlier quoted context omitted.

> i want to use 3.5mm jacks for super simple data communications and power That sounds like an all around bad idea.

ZSA uses this for their keyboards. The moonlander I'm typing this on uses a headphone jack for all of the above [1] [1] https://www.zsa.io/moonlander/

this is pretty cool

Re: Headphone and Amp Impedance (2011)

#63

Post by kragen »

kazinator wrote: post #30

This business of damping or lack thereof, is really just a frequency response change. The concern with the resonance of the speaker is overblown. When you boost a frequency range electronically with an equalizer, that is also resonance (electronic rather than mechanical). Instead of your speaker ringing for a couple of cycles, the circuit is doing it.

a couple of cycles? q=2 isn't much of a resonance

Re: Headphone and Amp Impedance (2011)

#64

Post by BenjiWiebe »

bgnn wrote: post #52
willis936 wrote: post #13

Earlier quoted context omitted.

That's true for RF, but not for DC. Audio is "DC" because transmission lines are well approximated as ideal wires at frequencies below 100s of kHz.

nor fully correct. lumped circuit theory doesn't only depend on the frequency but also the cable length. EM waves travel at around 0.6C in solids (copper). wavelength = V/f where V=0.6C, and frequency is say 20kHz, which is 9km. If you have an audio cable of hundreds of meters you would need impedance matching.

Rule of thumb for RF is that you can ignore impedance matching for <=1/10 WL. So for 20kHz you could ignore impedance matching if your cables are less than 900 meters long. How many audiophiles use cables 900m long? Or anyone else for that matter?

Re: Headphone and Amp Impedance (2011)

#65

Post by kevin_thibedeau »

dusted wrote: post #44

I find myself guilty of deep-diving into headfi-territory audiophilia once in a while, this time it got to me as well and I started thinking how neat it'd be to finally do it and get some high-end replacement for my 250 ohm dt990 pro cans, and I've heard both the hifman arya and sennheiser hd800s and know they are quite a lot better.. but THEN comes the amp question... and the rabbithole deepens.. and then the DAC an…

If you would just commit all the way and get an atomic clock you could save yourself from the tyranny of jitter in the 1MHz audio band and then it'd all be worth it.

Re: Headphone and Amp Impedance (2011)

#66

Post by lelanthran »

kazinator wrote: post #36
michaelrpeskin wrote: post #6

Earlier quoted context omitted.

Digging deep into my memory here, but I always remember that when Zout==Zin that's what you want for maximum power transfer. My guess is that the 1/8 trick is for the typical characteristics of small-speaker headset. Big speakers may have different capacitance and inductance characteristics. I don't know though. That's the first time I heard that approximation, and it doesn't seem to align with anything that I learne…

Unlike what other commenters are saying, this Zout == Zin is applicable to audio. For a fixed Zout much higher than zero, if we want to suck the most power out of the amplifier, we should use a matching Zin indeed. E.g. if an amplifier has 16 ohms output impedance, then we will draw the most power out of it with a 16 ohm load. Loads higher than 16 ohms will result in less current flowing. Loads lower than 16 ohms wil…

> In amplifiers we care about efficiency,

That is at odds with what the blog post says.

I'm now confused - for the best sound quality, are we to maximise efficiency of power usage or maximise accuracy of signal reproduction?

I didn't think you can do both.

Re: Headphone and Amp Impedance (2011)

#67

Post by kazinator »

Aurornis wrote: post #55
kazinator wrote: post #36

Earlier quoted context omitted.

Unlike what other commenters are saying, this Zout == Zin is applicable to audio. For a fixed Zout much higher than zero, if we want to suck the most power out of the amplifier, we should use a matching Zin indeed. E.g. if an amplifier has 16 ohms output impedance, then we will draw the most power out of it with a 16 ohm load. Loads higher than 16 ohms will result in less current flowing. Loads lower than 16 ohms wil…

> Loads lower than 16 ohms will cause power waste in the source impedance. For instance a zero ohm load will mean that all the power is dissipated in the 16 ohm source impedance: the zero ohm load draws current, but no power because it I^2R is zero. Why are you even considering the case of a zero Ohm load with a 16 Ohm source impedance? Modern headphone amps (including really cheap ones) have source impedances in the…

I am not confused. You're engaged with the particulars, whereas my post is mostly about the Zout == Zin, and not specifically about headphones.

> Why are you even considering the case of a zero Ohm load with a 16 Ohm source impedance?

For completeness of the analysis. If we hold Zout constant, and likewise the output voltage of the voltage source, and consider a Zin of zero, in that case, power transfer is mimimal (zero). Likewise power transfer goes to zero for large Zin. In between those is the Zout = Zin point where the maximum transfer is obtained by the load from the source. This is part of explaining of what is Zout = Zin about; what is maximized.

For instance consider a R1 resistor in series with a battery. You may not change the battery or R1. For what value of R2 can you get R2 to dissipate the most power? The solution is R2 = R1.

It is useful to think about what happens if we make R2 zero; why wouldn't we consider it. A certain current will flow through a zero ohm R2, but it will not be dissipating any power. From there as we increase R1, the power dissipation curve rises. At R1 = R2, it turns around, and then converges to zero as R1 grows larger.

Re: Headphone and Amp Impedance (2011)

#69

Post by lagadu »

Aurornis wrote: post #55
kazinator wrote: post #36

Earlier quoted context omitted.

Unlike what other commenters are saying, this Zout == Zin is applicable to audio. For a fixed Zout much higher than zero, if we want to suck the most power out of the amplifier, we should use a matching Zin indeed. E.g. if an amplifier has 16 ohms output impedance, then we will draw the most power out of it with a 16 ohm load. Loads higher than 16 ohms will result in less current flowing. Loads lower than 16 ohms wil…

> Loads lower than 16 ohms will cause power waste in the source impedance. For instance a zero ohm load will mean that all the power is dissipated in the 16 ohm source impedance: the zero ohm load draws current, but no power because it I^2R is zero. Why are you even considering the case of a zero Ohm load with a 16 Ohm source impedance? Modern headphone amps (including really cheap ones) have source impedances in the…

> Why are you even considering the case of a zero Ohm load with a 16 Ohm source impedance? Modern headphone amps (including really cheap ones) have source impedances in the range of 1 Ohm or less while headphones can range from 30-ish to 300 or more.

Modern tube amps (non hybrid) have significantly higher output impedance because they often have no overall negative feedback and a few special snowflake headphones have impedances as low as 0.1r and 2r.

The considerations are definitively relevant for some cases, as well as in general for analysis of the topic.

Re: Headphone and Amp Impedance (2011)

#70

Post by snvzz »

Aurornis wrote: post #51
dusted wrote: post #44

I find myself guilty of deep-diving into headfi-territory audiophilia once in a while, this time it got to me as well and I started thinking how neat it'd be to finally do it and get some high-end replacement for my 250 ohm dt990 pro cans, and I've heard both the hifman arya and sennheiser hd800s and know they are quite a lot better.. but THEN comes the amp question... and the rabbithole deepens.. and then the DAC an…

> but THEN comes the amp question... and the rabbithole deepens.. and then the DAC and in the end I give up, every time.. Well I have some great news for you! In 2024, you don’t need to spend mega bucks to get a good DAC or amp. You might not need one at all! One of the better performing and measuring DACs out there right now is the $9 Apple USB-C dongle: https://www.audiosciencereview.com/forum/index.php?threads/r..…

>One of the better performing and measuring DACs out there right now is the $9 Apple USB-C dongle: https://www.audiosciencereview.com/forum/index.php?threads/r...

Shows how bad the entire industry is. Especially on the DAC side. Lots of snake oil that measures worse than very cheap solutions.

In practice, the amplifier matters more, and there the Apple dongle doesn't do so well.

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