Post by solderdude on Apr 28, 2014 10:52:29 GMT
NOTE: The Kameleon has been replaced by the (portable Kameleon 2)
The Kameleon is a portable amplifier and 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.
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.
This amplifier is not suited for:
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 will 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.
Bare PCB's can not be ordered anymore, Kameleon 2 PCB's are still available.
I will not be selling finished amplifiers nor in kit form but will only supply bare boards until stock is exhausted.
After that and Jeremy will be supplying the boards as well.
Also shall I 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 ( www.mediafire.com/view/0i2zm9094g7cqly/Kameleon_portable_headphone_amplifier.pdf )
This design originated from THIS THREAD
For those that have built the portable Kameleon amplifier there is a small (easy to do) modification for the battery management section.
This has no influence on the audio quality.
When batteries are brand new or getting older after many many hours of usage the internal resistance of the battery is a bit higher than under optimal conditions.
This causes weird behaviour on start-up. Mostly when batteries are in need of recharging.
During the development a variable power supply was used and this one, of course, did not show this poor behaviour.
It only happens with real batteries.
The modification consists of adding a small electrolytic capacitor (10uF) with a voltage rating of 16V or higher.
HOW to do this is decribed in the latest manual on the last page, but the modification guide alone can also be downloaded HERE.
Do note that this applies to the portable version only so NOT the desktop version nor the inline-Kameleon as these do not run on batteries and thus do not have that circuit.
The same applies to the early portable Kameleon 2 amplifiers (the ones with the volume control).
But as this one has the parts mounted differently another instruction is needed.
The modification guide for the portable Kameleon 2 can be found HERE
The Kameleon is a portable amplifier and 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.
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.
This amplifier is not suited for:
- Those looking for a high powered (desktop) amplifier.
- Those looking for the newest amp they just haven't tried yet.
- Those that believe op-amps cannot sound good.
- An amp to drive their (C)IEM's or high efficiency headphones.
- Those looking for just another cheap C'Moy portable amplifier.
- Those that have never ever been satisfied with ANY (portable) setup period.
- Those that believe only 'guru selected' components will sound good.
- 100 hours of playing time and rechargeable within the hour.
- Those looking for a very small sized pocket amp.
- Those that are afraid of the word 'equalizer'.
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 will 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.
Bare PCB's can not be ordered anymore, Kameleon 2 PCB's are still available.
I will not be selling finished amplifiers nor in kit form but will only supply bare boards until stock is exhausted.
After that and Jeremy will be supplying the boards as well.
Also shall I 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 ( www.mediafire.com/view/0i2zm9094g7cqly/Kameleon_portable_headphone_amplifier.pdf )
This design originated from THIS THREAD
For those that have built the portable Kameleon amplifier there is a small (easy to do) modification for the battery management section.
This has no influence on the audio quality.
When batteries are brand new or getting older after many many hours of usage the internal resistance of the battery is a bit higher than under optimal conditions.
This causes weird behaviour on start-up. Mostly when batteries are in need of recharging.
During the development a variable power supply was used and this one, of course, did not show this poor behaviour.
It only happens with real batteries.
The modification consists of adding a small electrolytic capacitor (10uF) with a voltage rating of 16V or higher.
HOW to do this is decribed in the latest manual on the last page, but the modification guide alone can also be downloaded HERE.
Do note that this applies to the portable version only so NOT the desktop version nor the inline-Kameleon as these do not run on batteries and thus do not have that circuit.
The same applies to the early portable Kameleon 2 amplifiers (the ones with the volume control).
But as this one has the parts mounted differently another instruction is needed.
The modification guide for the portable Kameleon 2 can be found HERE
and it may save a bit on postage. Talking of saving on postage I am also happy to supply and fit the two x 9v rechargeable batteries. My only 'deadline' requirement is that I get my hands on it before mid June if possible please 
.
. I have just had a quick read through of your on-line details and notice that you specify the use of an OPA551 op-amp. From my days of swapping op-amps in my Beresford 7520 DAC I know that major differences can be heard using different op-amps. Is your specifying of OPA551 fixed for good technical reasons or can other op-amps be used to change sound signatures (without defeating the main purpose of the Kameleon and/or filter?) I ask because the OPA551 appears to be soldered in place on the PCB and if op-amp rolling is possible for those that like faffing around with such things I wondered if using a socket to facilitate changing op-amps might have any benefit. 
