It will work because you can set the common mode output voltage to the bias voltage of the Tripath input stage. The input impedance will be low if you ground one of the input resistors for use with a single ended input, and you may benefit from using a buffer between the source and the other input resistor. You could make the OPA134 an OPA2134 and now use both opamps. I would also add the option to use a resistive load between the differential outputs.
I was just about to etch some boards when an idea popped into my head. In the pic above I made a DC trim board, but is it possible to add one to the dc coupling/buffer circuit instead? I would like to kill two birds with one stone if possible.
Something like this......
Something like this......
An externally hosted image should be here but it was not working when we last tested it.
Hmmmmm
OK guy's, time to entertain the novices here please?
When removing the input caps you are saying that there should be no voltage potential between the source/power grounds but I thought that the grounds must be connected at the chip? I thought that the analog ground and source ground were the same thing
Do you need to break any links between these on the board if you are going to convert a T-amp board?
Any further elightenement would be very much appreciated chaps...please
OK guy's, time to entertain the novices here please?
When removing the input caps you are saying that there should be no voltage potential between the source/power grounds but I thought that the grounds must be connected at the chip?
I thought that the analog ground and source ground were the same thingDo you need to break any links between these on the board if you are going to convert a T-amp board?
Any further elightenement would be very much appreciated chaps...please
BWRX said:
Hi there.
Interesting tweak.
I am running my Charlize on batteries. I guess I am floating.
One question from my side:
I connected my DDDAC directly to Charlize. I've thrown out one coupling cap (DAC-output) already.
The DDDAC outputs needs to be DC decoupled. That's taken care of by the Charlize input cap for now.
Can I apply the biascap tweak for above scenario without getting into trouble?
EDIT: I forgot. I am currently using the input cap of Charlize as a 1st order high-pass to filter the low frequencies below 100Hz.
Would there be an alternative to do that differently if considering above. Because I wouldn't really like to drop the benefits achieved with this filter-tweak!
Cheers
Lostcause, normally the power supply and signal ground are the same thing. To get rid of the input caps you have to move the signal ground to the bias cap pin.
Once you do this you have to make sure there is no continuity between the ground of your source and the amplifiers power ground; i.e. back through the mains outlet via the ground prong.
EDIT: A picture is probably better than my explanation. Here is a pic of an AMP3 with the source ground connected to the bias cap.
Once you do this you have to make sure there is no continuity between the ground of your source and the amplifiers power ground; i.e. back through the mains outlet via the ground prong.
EDIT: A picture is probably better than my explanation. Here is a pic of an AMP3 with the source ground connected to the bias cap.
An externally hosted image should be here but it was not working when we last tested it.
theAnonymous1 said:
Ahhhhhhhhhh now I get it, thank you my good man.
What you are saying is do not connect the source ground to anything else BUT the biaspin and leave the bias cap in-place?
My source is floating (PS1) so there should be no continuity after this change.
Is it possible to still have a pot between the two now?
soundcheck said:
Hi soundcheck. Using a coupling cap is the simplest way to take care of filtering and AC coupling.
As far as applying the biascap tweak to your DDDAC/T-amp goes, it all depends on the output of the DDDAC. Since you say the DDDAC needs a coupling cap that normally means the DAC output has a DC bias. The Tripath input stage has a DC bias of about 2.5V, so if the DAC output has a DC bias of 2.5V you could attempt to DC couple the DAC output directly to the Tripath input without connecting the ground of the DAC to the T-amp biascap pin. You would need to make sure the bias voltages are very close or you will end up with a lot of DC offset voltage at the amp's outputs. I would not recommend trying this if you don't know what you're doing. I would recommend using a single coupling cap as you are currently doing because it is simple and takes care of coupling and filtering.
Lostcause said:
Hi Lostcause. Please do me a favor and don't call me sir
You are correct that on T-amps the power ground and the signal ground are connected BUT remember that they are only connected locally. Local means to the T-amp power supply ground. A floating supply (for example a battery or rectified DC from a transformer secondary winding) for the T-amp allows you to connect the biascap pin to the ground of a single ended source. This now means that the ground of the T-amp power supply is -2.5V with respect to the source ground.
Hi,
After many questions on the subject and some disappointing answers, I still want to go Differential from my Dac (with AK4396) to my TA2020 board with the capless tweak.
A transformer is one way to go as Brian pointed out before.
I still got some Sowter transformers from the custom tube output stage of my Pioneer player.
Does any one know if these work for this application?
It would be a shame if they ended up on the shelve.
The transformers are Sowter 8650a with the following specs:
RATIO 9 : 1
MAXIMUM OUTPUT LEVEL 0.5 % THD at 50 Hz +28 dBu
Max dc current per anode 30 mA
Max unbalance current 500 uA
FREQUENCY RESPONSE 8K0 source 100 ohm load +/- 0.5 dB 10Hz to 70KHz
TOTAL DC RESISTANCE referred to secondary 13.5 ohms
EFFECTIVE OUTPUT IMPEDANCE (with 200 ohm secondary resistor) 100 ohms
Greets,
Klaus
After many questions on the subject and some disappointing answers, I still want to go Differential from my Dac (with AK4396) to my TA2020 board with the capless tweak.
A transformer is one way to go as Brian pointed out before.
I still got some Sowter transformers from the custom tube output stage of my Pioneer player.
Does any one know if these work for this application?
It would be a shame if they ended up on the shelve.
The transformers are Sowter 8650a with the following specs:
RATIO 9 : 1
MAXIMUM OUTPUT LEVEL 0.5 % THD at 50 Hz +28 dBu
Max dc current per anode 30 mA
Max unbalance current 500 uA
FREQUENCY RESPONSE 8K0 source 100 ohm load +/- 0.5 dB 10Hz to 70KHz
TOTAL DC RESISTANCE referred to secondary 13.5 ohms
EFFECTIVE OUTPUT IMPEDANCE (with 200 ohm secondary resistor) 100 ohms
Greets,
Klaus
Radian said:
It can be done and sounds nice (great bass), but your 9:1 transfo is going to be way too hot. I've found that even a 2:1 ratio is mega loud. Below 1:1 may even be the ideal ratio, depending on the output of the DAC chip.
Which raises the question, how would you control volume? From a computer you can use software volume control, but most CD/DVD players don't do volume. You can't easily put a pot on the amp side, and I've found series resistance dividers on the DAC side seem to kill the dynamics.
will this work for Charlize 2?
I am electronic illiterate but want to consider the amp.
Will this work for Charlize 2?
http://www.bgmicro.com/index.asp?PageAction=VIEWPROD&ProdID=12293
gychang
I am electronic illiterate but want to consider the amp.
Will this work for Charlize 2?
http://www.bgmicro.com/index.asp?PageAction=VIEWPROD&ProdID=12293
gychang
Attachments
It depends on how your other equipment is earthed. If your source and pre amp use floating supplies (are not connected to earth) it would probably work fine. If this particular SMPS has its ground connected to earth ground (which is likely for safety reasons) and your source and/or pre amp are connected to earth in some way then you would need to open up the SMPS and disconnect the the supply ground from earth ground. I would not recommend doing that though for safety reasons. Usually those types of SMPS bricks can't be sealed after cracking them open and there are very lethal voltages inside when they're plugged into the wall.
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