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Headphone and Amp Impedance (2011)

nwavguy.blogspot.com

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Re: Headphone and Amp Impedance (2011)

#101

Post by kristianp »

squarefoot wrote: post #5

I'm very skeptic of that 1/8th rule. Usually output impedance should be as low as possible, so that the resistance added by the cable becomes negligible in comparison, and its intrinsic capacitance won't turn it into a low pass filter. Unless I'm missing something, at least in audio, amplifiers with lower output impedance are always better than those with higher output impedance.

What happened to the rule of thumb that output impedence should equal input impedance? That's just a general rule from antennas IIRC.

Re: Headphone and Amp Impedance (2011)

#102

Post by theK »

dmix wrote: post #48
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…

I went the customcans hifiman route after my open dt 990 pros blew from feedback https://customcans.co.uk/shop/product-category/home/headphon... Not quite the thousand dollar Arya but I like the dampening/venting work and signal testing he did + nice cables + I switched to a balanced xlr setup with my amp as I have grounding issues in my house. I personally find the amp the most interesting part over headphones. I re…

I love how much HD25 stuff that site has. Brilliant piece of kit from Sennheiser, especially when looking at both sound quality and tinkerability.

Re: Headphone and Amp Impedance (2011)

#103

Post by Hamuko »

AlecSchueler wrote: post #85
proto-n wrote: post #47

Earlier quoted context omitted.

Blogspot is google's blogging platform

And Google will happily delete your blog if it's associated with an inactive account: https://support.google.com/blogger/thread/226117604/my-blog-...

If you've bought something using a Google account, it won't be marked as inactive even if you don't log into it. So it could be possible that he died in a car accident or something, but his blog will just keep on trucking along for years and years because he bought an app for his phone from the Google Play Store.

Re: Headphone and Amp Impedance (2011)

#104

Post by bgnn »

BenjiWiebe wrote: post #64
bgnn wrote: post #52

Earlier quoted context omitted.

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?

There are certainly cases in big concert halls etc to run like 100m. 900m should be more a stadiums.

Re: Headphone and Amp Impedance (2011)

#105

Post by kragen »

em3rgent0rdr wrote: post #97
kragen wrote: post #59

Earlier quoted context omitted.

oh hey, that's a pretty good idea, thanks! you can tell i'm a novice it would still probably burn out my earbuds if i put 5 volts at 100 milliamps on the tip connector once the plug was fully inserted

oh ok, I understand your concern now "how do i keep from burning out headphones if someone accidentally plugs them in". I am hesitant to give advice because I don't know a great way, but a possible method of detecting what type of device (a headphone or USB device) is plugged in could work by doing an impedance measurement right after the device is inserted. USB standard specifies that the signal-to-ground impedance…

woww, you have hit upon the solution: data on sleeve (with series resistance), 5 volts on tip, ground on ring. headphones will not provide a current path between tip and ring and so will not burn out. current limiting is still necessary to protect the power source from shorted output. the headphone plug sleeve is necessary for any circuit through the headphones and only ever contacts the sleeve of the jack

thank you!

as for usb, i won't be using it

Re: Headphone and Amp Impedance (2011)

#106

Post by AlecSchueler »

Hamuko wrote: post #103
AlecSchueler wrote: post #85

Earlier quoted context omitted.

And Google will happily delete your blog if it's associated with an inactive account: https://support.google.com/blogger/thread/226117604/my-blog-...

If you've bought something using a Google account, it won't be marked as inactive even if you don't log into it. So it could be possible that he died in a car accident or something, but his blog will just keep on trucking along for years and years because he bought an app for his phone from the Google Play Store.

Yes, you can take measures to avoid your account being marked inactive but A) not as easy as "it's Google, you can trust it" and B) Google could change their minds about this stuff and go on a deletion spree at any moment, or even shut down blogspot entirely, it's not like they haven't shown form previously.

Re: Headphone and Amp Impedance (2011)

#107

Post by lelanthran »

kazinator wrote: post #95
lelanthran wrote: post #66

Earlier quoted context omitted.

> 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.

You are right. Audio amplifiers have not historically been power efficient. In the case of a headphone amplifier on AC power, we don't have to think about efficiency, as long as it isn't ridiculous, like drawing 100W. Class B amplifiers are only efficient when producing no output, or when producing output clipped to the power rails (like a square wave). Due to being almost fully off or fully on. For a sinusoidal sign…

Okay, since you appear to know what you're talking about, if I wanted to maximise signal reproduction (with absolutely zero consideration for efficiency) when matching amplifiers with speakers (for car audio), what numbers should I be looking at when choosing components?

(Yes, I checked a few youtube videos and blogs, but car audiophiles don't really get too scientific and it's hard to tell whether they really know what they are talking about).

Re: Headphone and Amp Impedance (2011)

#108

Post by kragen »

kragen wrote: post #105
em3rgent0rdr wrote: post #97

Earlier quoted context omitted.

oh ok, I understand your concern now "how do i keep from burning out headphones if someone accidentally plugs them in". I am hesitant to give advice because I don't know a great way, but a possible method of detecting what type of device (a headphone or USB device) is plugged in could work by doing an impedance measurement right after the device is inserted. USB standard specifies that the signal-to-ground impedance…

woww, you have hit upon the solution: data on sleeve (with series resistance), 5 volts on tip, ground on ring. headphones will not provide a current path between tip and ring and so will not burn out. current limiting is still necessary to protect the power source from shorted output. the headphone plug sleeve is necessary for any circuit through the headphones and only ever contacts the sleeve of the jack thank you!…

hmm, actually this doesn't help much. because the headphones do provide a current path between tip and ring: through one earspeaker to ground and then through the other one. this does provide more resistance than the alternative, but usually not enough to make a difference; if each earspeaker is 25Ω, 5 volts across it would give you 200mA, and 5 volts across both of them in series will give you 100mA, which is what I was planning to use for the current limit anyway

i think maybe i'll just go with trrs to avoid this problem

Re: Headphone and Amp Impedance (2011)

#109

Post by kragen »

icegreentea2 wrote: post #21
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.

It's not the best idea, but it's not the worst idea either. The original Stripe reader used the 3.5mm jack for example. It's even been used in some power applications ( https://www.amazon.ca/UY-CHAN-Original-Soldering-Replacement... )

i haven't tested this, but i think it is a less bad idea for what i want to use it for, which is 5-volt power at up to 500 milliwatts, than for the ts80 tip. if the ts80 tip is 4.5Ω it needs to carry 3.8 amps, which means 17 volts, which would definitely kill your earphones. but you could imagine that the ts80 uses foldback current limiting or some more elaborate scheme to handle short circuits, which will happen in any case during hotplugging due to the shape of the 3.5mm plug. foldback wouldn't help (the earspeakers are higher resistance than the soldering tip, not lower) but you could design the iron to only turn on the 17 volts if 100 millivolts delivers 20 milliamps or more, say

and, yeah, square. i want to do higher data rates and simpler electronics than an actual audio interface can handle, though

Re: Headphone and Amp Impedance (2011)

#110

Post by kragen »

kazinator wrote: post #98
kragen wrote: post #63

Earlier quoted context omitted.

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

There seems to be this idea circulating among some audiophiles that unless your amplifier has five digit damping factor, the speakers will ring like tympani drums, which is wildly exaggerated.

what's the q of a timpano, maybe 15?
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