tripath noise floor.


2008-07-06 10:09 pm
Hi all,
I have a general question that I thought I would post for some input from all those who have tecnical knowledge of the tripath chips-

I own a couple of different amps using the tripath chips (sure, connex, leipai) and I love the sound, but- they all seam to have a inherently slightly high noise floor, the noise doesnt raise with level, its fixed the same with or without signal, and isnt there when i use other amps I have at my disposal.

Is this a avoidable characteristic?- part of the implimientation/grounding etc or inherent and unavoidable aspect of the chips themselves?
As Anonymous pointed out, there is a trade-off between the output noise and amplifier gain. if one needs the minimum noise floor, must use minimum amplifier gain and add a very low noise high gain preamplifier. off course the noise will never be removed completely, the most what can get is to reduce-it to half as it's now, when the amplifier gain will be reduced below 10dB.


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2008-07-06 10:09 pm
Thats a real shame I realy like the sound of all the tripath amps Ive used- especially the connex ones. -Kicks the **** out of my parasound halo a51.

Thankyou Cristi for the link- I see your point.

So what do I do now?
- my next speakers are going to be very efficient (horns), and Im looking for massive dynamic range and minimum power compression, so I would need a very low noise floor and high(ish) power- but I have never found a sound as sweet as the tripath units, and want to keep that.
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I'm working at a new version now which exploit the idea which i mentioned before, of using minimal gain at the amp side and maximum gain at the preamp. if it works, i'll find out soon, and others too. the bad part is that it can't work with less than about 8-10dB gain, simply because the input stage cannot accept too large amplitude signals. don't forget that is supplied from 5V rail.
in your case, the noise could be caused by the wiring as well, as i remember from a previous mentioned issue. you could try to route the input signal using short, shielded wires and reduce the amplifier input impedance by lowering the value of R59 R60, as much as the signal source could afford, but not less than 10K, and also increasing the gain of the amp, by simply connecting in series with the input caps 20-50K resistors.
if you do this, be very careful, and always solder/desolder after the supply caps are discharged completely, and the amp is disconnected completely from mains, signal, and speakers. one of the negative points of the tripath chips is that they are very sensitive to ESD or any over voltage applied to it's pins. by soldering something on the board when is still connected to source, speakers, supply, you have 80% chances to kill the IC, due to leakage currents which can build-up dangerous levels for the IC. i noticed from my experience that if i touch any of the input pins of the ic with the soldering iron and the board is not completely disconnected, i have slight chances to not damage. and the leakage current is at most few mA. i wonder if was too expensive to add simple ESD protection to this ic's or they were designed just as consumables ???