Impedances what's it all about.

[Deleted]

If you want to know about output resistances of amplifiers and headphone impedances and how these are related and can affect the sound the pdf below might be of interest.

I have tried to put it into a comprehensive explanation ..

www.mediafire.com/?82kf0r5kdckdcer

revised feb-2012

[Deleted]

Thanks Frans,

The description of what happens with the K701 is pretty much what I was hearing. No more detail, but more 'balanced' in sound.

Interesting that I perceived more bass when in fact it was less treble which gives the impression of more bass!!

Also interesting with the Senns where it actually isn't that easy to hear any difference!!

For me, the K701 changes more with the 120 ohm in place. Also, the Beyers - I wish I hadn't got rid of the DT880 now.

[Deleted]

I had the DT770(hifi ed) and DT880 (2005 ed) and DT990 (old).
The DT770 's bass became annoying as was the emphasis on the highs.
modding it and a filter in place helped but the bass just wasn't quite right for me (to single toned if you know what I mean).
Deep and engaging just not ...
The DT880 was a nice listen but a bit dry and clinical for me (as was the K701).
The DT990 although a bit 'bathtub' like and not as real as the DT880 was a more pleasant listen especially at very low listening levels.
I figure it was made for very low level listening.

The differences between impedances can be subtle but also cut and dry in some cases.
Fun part of the DT990 is I can listen to it with low levels on the 110Ohm setting and for higher levels use the 20 Ohm out and still sounds well.

I always tend to grab the HD681 the most for some serious listening.
For casual and office music nothing beats the KSC75.

I am glad some people read it.
I didn't write it for nothing in this case.

[Deleted]

I always read what people put out Frans. Always interested in what other people say.

Interestingly, I found the K701 dry until I paired it with the Panda which warms it up slightly. Along with 120 out, it sounds just about right for me now. I'm quite happy with its response now, but dread the Panda not working because nothing else sounds the same or close.

The DT770 is a bit one note bass. Better at 120 ohms but the bass stays there, plodding away. That's where the HD250 wins out.

Have you any idea what the Aune output is? I can't find it anywhere, but it's not at all bad with the K701 but I would be interested in getting it right on 120 ohms if it's not already there.

Maybe we don't take enough notice of what the manufacturers recommend?

There's just something 'right' about the balance of the K701 with it set at 120.

being able to adjust the output impedance is definitely a bonus on amps. It's a pity that it's not a built in feature imo.

Of course, you'll always get less sensitive people saying 'no difference' but for me, it makes a very good headphone stunning.

[Deleted]

Nov 14, 2010 16:52:05 GMT @solderdude said:

If you want to know about output resistances of amplifiers and headphone impedances and how these are related and can affect the sound the pdf below might be of interest.

I have tried to put it into a comprehensive explanation ..

www.mediafire.com/?82kf0r5kdckdcer

It's not a complete guide and thrown together rather quick (it only took me a day) but the most important things are discussed.

Even i can get the gist of that Frans.

Thanks for taking the time to explain in a way that the electronically challenged like me can understand.


Mick.

[dicky]

Me too! That has spurred me on to have a go changing the o/p resistors - see what I can do with my DT770s. (Which I think I like :

I plonked in some 75ohm resistors - 'cos that's what Mike did with Panda 1. But now I have a little knowledge mmmwwwahahaha.

Thanks very much for your post

[Deleted]

Try the DT770 with 120. It's even better!!

[dicky]

Thanks, I will - I bought a handfull of different values - just in case.

How do the 701s compare to 702s? SWMBO has bought me a pair for Christmas and you seem to like the Panda/701 combo. Will I get a similar sound from 702s?

[Deleted]

Nov 14, 2010 20:11:01 GMT dicky said:

Thanks, I will - I bought a handfull of different values - just in case.

How do the 701s compare to 702s? SWMBO has bought me a pair for Christmas and you seem to like the Panda/701 combo. Will I get a similar sound from 702s?

I hear that the 702 is much the same with a detachable cable.

There are three headphones I'd like:

The K702 and go balanced.
The HD800
The W1000x.

With the Panda, the AKG is absolutely gorgeous. It's never sounded this way on anything else. Fantastic match.

[elysion]

Thanks for that great explanation, Frans.

Nov 14, 2010 20:36:21 GMT @iancraig10 said:

Nov 14, 2010 20:11:01 GMT dicky said:

Thanks, I will - I bought a handfull of different values - just in case.

How do the 701s compare to 702s? SWMBO has bought me a pair for Christmas and you seem to like the Panda/701 combo. Will I get a similar sound from 702s?

I hear that the 702 is much the same with a detachable cable.

There are three headphones I'd like:

The K702 and go balanced.
The HD800
The W1000x.

With the Panda, the AKG is absolutely gorgeous. It's never sounded this way on anything else. Fantastic match.

K702 to go balanced? Remember that FauDrei has mentioned that K701 is much easier to convert to balanced mode? K701 has four wires and need only a retermination with an other plug, while the K702 has only three wires which makes it more complex to go balanced.

Maybe the new Q701's are also an option (but probably not for balanced operation) if the price is dropping (current price is a rip-off).

[clausdk]

What I do not get, is
Why do amps have different output resistors, they should have none, then the headphone producers could put in the best value in the plug/cans or where evere they wish, thus making all phones sound at their best..with any amp..

[Deleted]

Nov 14, 2010 21:34:42 GMT elysion said:

Thanks for that great explanation, Frans.

Nov 14, 2010 20:36:21 GMT @iancraig10 said:

I hear that the 702 is much the same with a detachable cable.

There are three headphones I'd like:

The K702 and go balanced.
The HD800
The W1000x.

With the Panda, the AKG is absolutely gorgeous. It's never sounded this way on anything else. Fantastic match.

K702 to go balanced? Remember that FauDrei has mentioned that K701 is much easier to convert to balanced mode? K701 has four wires and need only a retermination with an other plug, while the K702 has only three wires which makes it more complex to go balanced.

Maybe the new Q701's are also an option (but probably not for balanced operation) if the price is dropping (current price is a rip-off).

I didn't know about the wiring on the K702. Bugger! You'd think that having a cable that's easily changed would make that an easy option wouldn't you?

[PinkFloyd]

Balanced? Can anybody tell me one good reason why a "use at home" headphone amp needs to be balanced?.... an absolute waste of time / money IMO yet it seems "balanced" is the place to be in this seasons fashion.

I can tell you numerous reasons why "balanced" is a waste of time / money in a home audio setup situation but will await your comments on what you have been led to believe

Over to you..................

[Deleted]

'cos it's compatible with work?

The main reason I thought that was that's a way to avoid other unwanted signals entering the cable?

Just fancied trying it.

[Deleted]

Nov 14, 2010 21:42:54 GMT @clausdk said:

What I do not get, is
Why do amps have different output resistors, they should have none, then the headphone producers could put in the best value in the plug/cans or where evere they wish, thus making all phones sound at their best..with any amp..

High-Ohmic cans do not have to have resistors in the amp.
They will work without the chance of being blown up in all amps.
So one could omit the resistors for these cases.
Since amplifiers that can drive high-Ohmic headphones to full power must also be able to drive low Ohmic headphones without them being blown up and sued by owners they install 120 Ohm (or something close to it) in these amps.
Manufacturers are well aware and use these resistor values (which now is standardized) for high-Ohmic cans because they know it will be used on amps that have high output voltages and thus have to have these value resistors.

For low-Ohmic cans they cannot be inserted in the cans because with low voltage amps the 120 Ohm, that is needed if they should also be able to connect to high output voltage amps would give far too much attenuation and the whole purpose of low Ohmic cans would be out the window because in effect it would have become a high-Ohmic type and would not be able to play loud on low voltage amps anymore.

[PinkFloyd]

Nov 14, 2010 22:10:46 GMT @iancraig10 said:

'cos it's compatible with work?

The main reason I thought that was that's a way to avoid other unwanted signals entering the cable?

Just fancied trying it.

What "unwanted" signals? Signals from Mars maybe?

[Deleted]

;D

Well studios are good at noises. I might pick up Russian radio if I'm lucky. ;D

I do hear odd things on the Bravos. I'm waiting for a Samaritan to come through.

I look forward to hearing Ana there.

[PinkFloyd]

So why do you need "balanced"?

[Deleted]

Just curiosity. Looks like it's a waste of time though.

[Deleted]

and money....

All you 'gain' is more gain and headroom.
The output power of a bridged (balanced) amplifier (when using the same amplifiers) is 400% higher IF you decrease the output resistors of the 2 amps to half that of the original amp if only 1 amp is used.
Otherwise you would be ending up with an amplifier with double the output resistance.

The voltage levels of headphones are relatively high and impedances low that no stray signals can be induced at audible levels even with unscreened wires in a normal setup.
Balanced for microphones.. YES please.
Balanced for line levels with long wires running along side mains cables... YES
Otherwise.. no thank you.

I know a lot of people state they sound much better but you do have to realise the output resistance doubles which alters the sound too. (more bass and top-treble in general)
Also you will be able to blow up your headphones if the output power is quadrupled.
The output voltage will be doubled by the way.
This all means a 6dB gain in SPL.

If you have 2 low voltage amplifiers and want to use these to give more power there are little objections, these have low output impedances any way so doubling those might be a good thing... wouldn't bridge the Panda or SC HA.

[XTRProf]

Yeah, balancing also means we have to have more components just to give a negative half of the positive signal for cancelling noise and distortion. Thru this, it doubles the voltage swing, if I'm not wrong. However, to really cancel noise and distortion, both signal halfs must be really well matched or else there wouldn't be any good cancellation. In other words, both the positive and negative halfs must be a good mirror image of the signal. A perfect amplifier must be built!

Also, more components also means more noise and distortion although they cancels out. So why build something with higher noise and distortion that cancels out instead of building something single ended and having lower noise and distortion? Keep it KISS will always be better sounding. In a home environment do we really run long lengths of signal ICs? No right? So the noise is minimally picked up unless your setup is not connected properly. Balanced is more for the professional AV scene like rock concerts, speeches, discos, DJs, etc with long signal leads that can act like antenae to pick up the noise and distortion.

Correct me if I'm wrong as I'm no expert in this but knowledgeable enough.

[Deleted]

Nov 26, 2010 9:53:36 GMT XTRProf said:

Yeah, balancing also means we have to have more components just to give a negative half of the positive signal for cancelling noise and distortion. Thru this, it doubles the voltage swing, if I'm not wrong. However, to really cancel noise and distortion, both signal halfs must be really well matched or else there wouldn't be any good cancellation. In other words, both the positive and negative halfs must be a good mirror image of the signal. A perfect amplifier must be built!

Also, more components also means more noise and distortion although they cancels out. So why build something with higher noise and distortion that cancels out instead of building something single ended and having lower noise and distortion? Keep it KISS will always be better sounding. In a home environment do we really run long lengths of signal ICs? No right? So the noise is minimally picked up unless your setup is not connected properly. Balanced is more for the professional AV scene like rock concerts, speeches, discos, DJs, etc with long signal leads that can act like antenae to pick up the noise and distortion.

Correct me if I'm wrong as I'm no expert in this but knowledgeable enough.

Driving balanced is effectively using 2 similar amplifiers with opposite signals that both drive the same driver.
For stereo in essence 4 amplifiers are needed instead of 2.
So not positive or negative halves of sinewaves, like in the output stage of an amplifiers complentary output stage, but both amps have the same full signal only turned 180 degrees in phase.
So when the output of one amp goes positive (or negative) the other amplifier goes negative (or positive).

To make it clearer I need pictures but do not have the time for it now.

NO noise and no distortion is cancelled.
In fact distortion caused by the amps is even ADDED instead of cancelled.
The noise generated by the amplifiers don't cancel and doesn't add as noise is random and the noise might be added (if in counterphase) at a certain moment or cancelled (if in phase) at another moment.
Effectively the noise floor of the headphone amplifier itself is hardly any problem (in most SS designs) and well below the hearing treshold unless you have a really crappy design.
The noise floor in the recording which is often several hundreds of times higher (30 to 40 dB) is amplified by both amps and does not cancel out nor add and is reproduced like the music signal in which it is included.

The only thing that is cancelled are COMMON mode induced (unwanted) signals in (very) low level signal lines which would NOT be cancelled/filtered out when induced in unbalanced lines (which a normal RCA cord is).

They also do not have to be in perfect balance for this trick to work.
It works better IF they are closely matched in levels but if not matched exactly it will still work but with a few dB less attenuation of these unwanted COMMON mode signals.

The reduction of COMMON mode induced signals is the ONLY reason balanced lines are used and, indeed, only needed for microphone, instruments and long line level lines to amplifiers on stage or in the studio.

Common mode signals is 50/60Hz hum and their harmonics or Radio Frequency signals that are picked up, like an antenna does, and is in equal phase (and mostly also amplitude, if twisted wires are used) and since these signals are equal in phase and amplitude this does not induce a voltage in the balanced load as this reacts ONLY to signals that are NOT equal in phase (180 degrees).

balanced driving of headphones is mostly used in studios as there are balanced signals there anyway and a lot of equipment with (long) cables lying around in places where they sometimes shouldn't be.
NOT to get the ultimate High-end experience.

[FauDrei]

...so that makes me snobby A-hole with double impedance double "speed" amp...

[Deleted]

Nov 27, 2010 19:12:43 GMT FauDrei said:

...so that makes me snobby A-hole with double impedance double "speed" amp...

Don't agree with double speed as the speed (slew rate = V/us)/bandwidth of the amp remains the same. ;D
Only the output impedance, voltage and distortion is doubled.

Also the snobby and A-hole part are not in my explanation I thought nor do I think such
balanced (bridged) amping works well for low output voltage and low output impedance headphone amps and is great for speaker setups to gain extra headroom (6dB) IF these power amplifiers can deleliver the demanded currents.

[FauDrei]

Hmm... can you elaborate on speed/bandwidth? I'm not sure I understand.

My take is that if you bridge two f.e. 100V/us amps you get a bridged 200V/us amp.