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-   -   Distortion problems on my Charlize 2 (http://www.diyaudio.com/forums/class-d/126842-distortion-problems-my-charlize-2-a.html)

Rafoo 23rd July 2008 07:24 PM

Distortion problems on my Charlize 2
 
Hello everyone.

I've got some problems with my brand new charlize.

The power supply is a skynet smps 8080 12V 6A.

I'm using it with a chinese dac (the lampucera) which works perfectly on my rotel amp so my problems do not comes from here.
The first time I tried the charlize, it was without input caps and without volume pot. At high volumes I heard some distortion (it was volume 20 in VLC and at 31 I am supposed to have the same output volume as on my classical cd player, I tested it on the rotel). I was quite disapointed.



Then I made few tests. I put inputs caps (1F PIO 630V) and then an ALPS blue pot. It was the same.

I tried to send a sine signal of 1kHz then 500Hz and finally 100Hz to measure properly at which output voltage it is saturating.

At 1kHz : I've got some noise at 6V (8ohms speakers) so approx 4,5W and if I go a little upper I've got an very nice harmonic !!! The third one I think and it is quite loud !
At 500Hz it is the same but at 5V
At 100Hz it is the same but around 4.8V

So it is harmonic distortion. The TA2020 is not supposed to have such distortion at such output voltages. It is known for its very low THD am I right ?

Then I tried a classical cd player. I put volume down to 0 on the charlize. Something VERY strange happened. The cd player could not read any cd !! it said Error !! I unplugged the charlize and then it was able to read. I tried to plug the charlize inputs while it the cd was playing and then ERROR again !! I measured no DC voltage on the charlize input (there are caps so ...) and no AC voltage neither (I was at volume 0 of the alps).

What is wrong with my Charlize ??!!??

Do I have to separate the input ground of the charlize an the output ground of the source ?

Please help me out because I really don't understand what is going on :(

Pano 23rd July 2008 08:54 PM

May be the power supply. Can you run the Charlize on batteries as a test?

Switch mode power supplies can do some strange things, sometimes....

Rafoo 23rd July 2008 09:05 PM

I never tried it on batteries. What kind of batteries shall I use ?

Lostcause 24th July 2008 09:54 AM

Hi guy's, isn't the Charlize 2 DC coupled? The ground of the charlize is @ 2.4V potential so that's what is probably sending the CD into fits and giving you the distortion?
No expert here but unless I use batteries on either the source or amp I definately get noise on my DC coupled T-amps.

Rafoo 24th July 2008 10:44 AM

That is what I thought first but if it is done like that, that is for a good reason isn't it ? It should not be a problem if they have done it, it was to remove the input caps. Shall I separate the charlize input ground and the output ground of my source ? It's a bit strange no ?

Lostcause 24th July 2008 10:52 AM

HI Rafoo, yes the grounds need to be completely isolated from each other, i.e. no continuity through the power supplies.
Put the amp on 12V batteries and the problem will go away I hope.

Not sure about the CD though....

Rafoo 24th July 2008 12:09 PM

Hi,

I've cut the ground between the rca connctors and the volume pot (so the volume pot ground is connected to the input ground of the charlize.
I've still got the distortion (around 6V at the output at 500 Hz) but now I have a BIG humming = ground problem, so I think it was not the right thing to do. What shall I do ?

Lostcause 24th July 2008 12:44 PM

You just need to isolate the two power supplies.
I don't think cutting the RCA > Pot ground is a good idea at all:bigeyes:
Sorry, but there is no other way, see extract from Yeo's site:

"Downside
After relaying the layout to go "cap-less", there are 2 caveats with the new Charlize.

No feeding her DC voltage okay? Previously there's a cap there for this purpose but there's none now, so don't be daft and feed her some strange DC voltage okay? If you insist, and you get strange noise... brother, what are you thinking? Actually all properly designed gears shouldn't give out any DC voltage at the output but we just said that didn't we, "properly designed gears".

Charlize's power supply has to be STANDALONE. Yup, don't share her power supply with another girl, sorry, component, or ANYTHING at all. Even Monica. Yeah, Charlize is a bit fussy here. She must have her own power supply. I tell you, she'll scream at you if don't heed this advice.
There you go! Just 2 little caveats. If you pay attention to this, Charlize will reward you in spades! [Otherwise I'll come to your house and clobber you with a spade!] "

Rafoo 24th July 2008 02:23 PM

The smps supply is only for the charlize and is not shared at all.
I have put some input caps to get rid of some dc voltage so no problem here.

The thing I don't understand is : when I plug the rca output of my source in the rca input of the charlize, they automaticcally share the same ground right ? I can't separate it ! But the ground of the rca input of the charlize is at 2.5V whereas the output ground of my source is at 0V. How can it work ?
Why it makes this distortion ? well I'm not sure it is that because I haven't tried an other power supply for the charlize.

Lostcause 24th July 2008 02:32 PM

Hi Rafoo, sorry more explanation required....
You need to make sure that the power supply for the Charlize is completely seperate from the others so as not to create a circular or ground loop.
i.e. they cannot both plug into the same mains supply as they would then be connected at the plug.
If the amp is on batteries (or indeed the source) then there is no loop of continuity and the problem is solved.
Try a car or cheap batteries on the Charlize just to test before you go spending lots of mulla on fancy ones and chargers etc.

TTFN


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