Kameleon portable headphone amplifier

[Solderdude]

I just launched an 'unusual' portable headphone amplifier design.

Maybe it is of interest to some of you guys as well.

The Kameleon is a portable amplifier which doesn't have a volume control.
It only has a 3.5mm stereo jack input socket and 6.3mm stereo jack output socket.



This amplifier must be connected to the headphone output of a portable player/phone/tablet/laptop and cannot be connected to a line-out or line-out dock (unless it has a volume control).
There is an on/off switch and a power indicator as well as an indicator that is lit when the battery needs recharging (the amp switched to standby).
On the rear there is a charger connector and a charging indicator LED.



The Kameleon is intended to drive those headphones that do not perform that well directly from a DAP and can also correct the tonal balance of a several headphones so they sound tonally MORE balanced. While the amplifier is designed to be connected to sources with a headphone out with their own volume control it can be connected to a pre-amp out providing the output resistance of that pre-amp is lower than 100 Ohm and is capable to drive >500 Ohm loads.

Those looking for a (not very small) portable amp for driving higher quality headphones from their low powered DAP headphone out AND have the connected headphone tonally 'corrected' will certainly benefit from this amp.

All headphones need a different correction IF you aim to achieve tonal accuracy. A variable tone control to accommodate for this would be very complex and costly to make. Not really suited for a portable at all with all those variable controls.
For this reason the Kameleon uses filter modules designed for a specific headphone that simply plug into the amplifier board.

Those filter boards can be relatively cheap and small, they are individually configured to compensate the frequency response for a specific headphone.
Headphones that just need that 'nudge' can be corrected in a way that makes them sound more realistic than when connected to a 'standard' amplifier.
One can also make filter boards that lift (or lower) bass levels, or highs or use the amplifier 'flat' like all other amplifiers are.



Several headphones already have a filter made for them and many others can be designed/made.

if you want to know if your favourite headphone can also be driven/corrected with this amplifier please ask in this thread.
http://diyah.boards.net/thread/600/kameleon-portable-headphone-amplifier

Bare PCB's can be ordered by contacting me directly (solderdude)
price of one amplifier board included shipping = € 12,50 included shipping
price of a filter module board included shipping = € 3,70 included shipping
Payments can be made using IBAN/BIC (within Europe) or by PayPal.

Ready made amplifiers and filter modules (after a design for that headphone is made) are sold by Javier via the DIYAH forum.
Contact Javier about prices, shipping, wishes etc in the link above when interested.

For the USA (and Canada) it is possible to contact Garage 1217(Project Ember etc) in the near future as well.

I will not be selling finished amplifiers nor in kit form but will only supply bare boards until stock is exhausted.
After that Javier and Jeremy will be supplying the boards as well.

I will offer any technical support and evaluate if headphones can be corrected and design the filter (consult and design is free of charge).

More info on this amplifier (also specifications etc.) can be found in this article:
http://www.mediafire.com/view/0i2zm9094g7cqly/Kameleon_portable_headphone_amplifier.pdf

[Claus-DK]

You are so Cool Frans...
So from this day forward you will be allowed to sell here in the normal forum, as the only one, mostly because I know the only thing you earn is the gift of helping others..

Yor are still my Hero..

[Daf]

This is quite a unique product. Instead of searching the marked, reading dubious reviews and trying/buying all sorts of different amps to get the best from your headphone of choice, you get the all too familiar issues with frequency response fixed to begin with. It is sort of an advanced dedicated equalizer with an amp to go. Brilliant idea. We all know that an equalizer is the worst enemy of the headphone industry and there are plenty of articles around telling us how bad a solution equalizing is. One thing is to get the right level of equalizing but the most common issue is the story of how degrading an equalizer is to the quality of the signal. The first issue is interesting, the other is trivial because we all know all music already has been equalized while mixing, so it doesn't really make that much of a difference all things being equal.
This Kameleon amp actually ought to be kind of an end-game product for many users that crave to get that last bit of perfection just right with the over all preferred headphone.

[Solderdude]

In most cases a 5 band or even 10 band EQ cannot make what you really would like to as they are fixed bands with fixed bandwidths at fixed frequencies and often only in 'steps'.
Shelving filters only exist in some equalizers (Rockbox for instance).
Often you need to correct a frequency that doesn't exactly match that of the equalizer or cannot create the right shape,
Also digital EQ also shows pre-ringing in these audible band(s).

Here is what the most familiar T50RP (modded) looks like when played by a standard amp and from the Kameleon.
Purple = modified T50RP
Blue = same modified T50RP played from the Kameleon.

[Daf]

Shit! Now we don't have to buy new headphones to accommodate our needs...

[davidsh]

Analog EQ introduces phase distortion as I remember, though?


Sent from my iPhone using Tapatalk

[Daf]

Analog EQ introduces phase distortion as I remember, though?

Maybe, but is it audible? Are the benefits of the Kameleon equalizing bigger than the disadvantages, if there are any?

[Solderdude]

yes, indeed all analog filters cause phase shifts.
I would not call it distortion though as distortion implies a negative impact on the sound.
A tube amp also adds distortion (arguably) but very few people call it distortion but rather feel it is an improvement.
A lot of tube amps also have lots of phase shifts (those without overall feedback) by the way.

In case one is a signal purist (those that do not want anything or as little as possible in the signal path) this amp isn't interesting at all unless perhaps it is used with a 'flat frequency range' plug-in module. The only possible benefit it has then will be a decent output power.
When the amp is used 'flat' the phase shifts are specified in the article.
Can't specify this for filters as they are different in each case.
The whole purpose of this amp is to modify the signal that is applied to the headphone in order to get it closer to the 'ideal'.

Still, correction isn't 100% and can never be either, but at least it will get a number of headphones to sound better.

Also when you look at peaks and dips in the headphone itself they also causes phase shifts and the filter works in the opposite direction of those and thereby reverses those phase shifts for a big part as well.
The phase shifts are on both channels and thus temporal cues (between L and R which hold the spatial cues) are not affected.
For high frequencies turning your head somewhat sideways when listening to speakers is worse.

The headphones I 'corrected' with it all sound much better than without it so to me the audible benefits are much higher than the theoretical downsides (phase shifts being audible).

[Daf]

I am quite sure that the benefits of tuning a headphone this way will be very satisfying, not to mention all the money you will save...

[Solderdude]

To give an idea of how this amp changes the sound here is a 'sample' that can be played on a normal amp.
But ONLY for HD650, T50RP and modified K550 owners (or those headphones that lack bass)

I have compiled an MP3 with excerpts of 3 songs.
Don't expect super-fi as the file was created using 3 MP3 files that were normalized and resampled and converted to MP3 again.

This 'master file' was then played back on FiiO X3 into the Kameleon which was recorded using the SB1240 on 44.1/16
The files created were MP'3 yet again and uploaded.

There are thus 4 files available for download for 7 days ! (http://www.filemail.com/d/vwolzakhaiznckx)
The files will only be available till May 20th.

The recorded files are the same as the original files + FiiO X3 playback + Kameleon (with filter module) + recording + MP3 encoding.
It's thus NOT about sound quality but what the filters used CHANGE.

Also these files are NOT normalized after they have been recorded so do NOT level match with the original.

One called original file and this is the 'source file' that was played back on the X3.
There are 3 other files that have passed through the Kameleon and can give you a preview of HOW your headphones will sound ON the Kameleon from a portable player ON those specific headphones.

Let me be clear... it is pointless to play the HD650 file on another headphone as that other headphone requires a DIFFERENT correction.

For this reason the files available SHOULD only be played back on the 'target' headphone.

I made files for 3 headphones:
Modified T50RP (but you could also try it on standard T50RP's but the correction would not be completely accurate)
Sennheiser HD650
AKG K550 the MODIFIED one that is, won't sound good on the stock K550.
This one (Modified K550) basically is only a 'bass boost' so you can play it on other headphones that are LACKING bass and see if the Kameleon with Bass boost is something you may like.

You can use any normal playback system to 'emulate' the Kameleon's action.

So IF you have a HD650 and want to know what the Kameleon will/can do for it play back the 'original' file and the 'Only for HD650' file.
The latter is how your HD650 will sound when connected to the Kameleon
The HD650 filter is designed for the older black driver version and the silver/white version needs slightly less treble boost)

The same goes for the T50RP.
Compare the 'original' file with the 'Only for T50RP' file and see if that's what you are looking for.
The filter PCB sound different from the Kameleon as the Kameleon cannot fully/exactly compensate but will certainly bring it closer to 'flat'.

I also made a desktop amp from the same PCB.