Impedances what's it all about.

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.

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.

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

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?

Thanks for that great explanation, Frans.



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?

'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?

So why do you need "balanced"?

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.

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.

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.