Hi folks.
I read the Trends-Audio T-Amp specs yesterday.
It says that biasing the output DC to 0V, as it is possible with their model, brings
a. cleaner sound
b. smaller switch-on pop
Does anybody have an idea how such a biasing circuit could look like?
Cheers
Klaus
I read the Trends-Audio T-Amp specs yesterday.
It says that biasing the output DC to 0V, as it is possible with their model, brings
a. cleaner sound
b. smaller switch-on pop
Does anybody have an idea how such a biasing circuit could look like?
Cheers
Klaus
The circuit is here:
http://www.tripath.com/downloads/TA2024C.pdf
See page 11.
You can see it in the Trends amp photo below. Look for the trim pots labled Rt.
http://www.tripath.com/downloads/TA2024C.pdf
See page 11.
You can see it in the Trends amp photo below. Look for the trim pots labled Rt.
Attachments
soundcheck said:
Yes.
I am going to add the adjustment circuit to an AMP3 sometime soon. I already made the board, just have to attach it.
I guess you'll share your findings with us. 😉
Looking forward to it.
Tweaking never stops! Amazing!
Looking forward to it.
Tweaking never stops! Amazing!
theAnonymous1 said:
Cool. Sounds like an interesting thing to implement. Do you have a picture of the board by any chance?
soundcheck said:
What's to share? The circuit does exactly what it's supposed to. I implemented it on my Ref-T amp earlier this year and it works fine without negatively affecting the sound. You can easily trim the output offset to below a mV with a multiturn trimpot.
I guess no one uses the search function anymore, eh?
http://www.diyaudio.com/forums/showthread.php?s=&postid=890408&highlight=#post890408
http://www.diyaudio.com/forums/showthread.php?s=&postid=915158&highlight=#post915158
http://www.diyaudio.com/forums/showthread.php?s=&postid=906760&highlight=#post906760
BWRX said:
I just went quickly through the first thread you posted.
To me it's still not clear if the biasing improved the sound!
Why would it improve the sound? All it does is remove the DC from the outputs. You can't hear DC...
A low DC offset is important for drivers with limited xmax because the more DC offset there is on the output the lower the usable excursion you have from your drivers. Any DC offset also causes a quiescent current to flow through the driver's voice coil. The larger the offset the larger the current and the more heat the amplifier's output stage and the driver's voice coil has to dissipate (even though the amount is really very small and is usually considered negligible).
A low DC offset is important for drivers with limited xmax because the more DC offset there is on the output the lower the usable excursion you have from your drivers. Any DC offset also causes a quiescent current to flow through the driver's voice coil. The larger the offset the larger the current and the more heat the amplifier's output stage and the driver's voice coil has to dissipate (even though the amount is really very small and is usually considered negligible).
BWRX said:
That's what I am refering to!!
Are 100mV or whatever offset, respectively the corresponding lower driver excursion, audible.
Or is the main thing to balance both channels offset so the drivers start at the same point.
Or should I better take it that way , as you nicely outlined:
Since DC is not audible.
We shouldn't care about it! 
😉
soundcheck said:
I didn't mean to make it sound like we shouldn't care about, because we should. The point I tried to make was that the DC offset circuit allows you to reduce the DC offset between the speaker terminals without having a negative effect on the sound quality. The circuit does have the potential to increase the noise, but this will be minimal if it is implemented properly. Panomaniac measure the noise floor of the Ref-T and compared it to some other T-amps and found that my Ref-T had about noise floor about 10dB lower than a stock SI T-amp and that a Fenice T-amp had a noise floor about 10dB lower than the Ref-T; the Ref-T was the only amp with the DC offset circuitry. I believe part of the reason the Ref-T had a higher noise floor was due to the DC offset circuitry, even though it still beat out the SI T-amp.
soundcheck said:
How far the voice coil moves from it's equilibrium position depends on a number of driver specific parameters. Theoretically, distortion will be introduced when the voice coil is driven outside the uniform magnetic field between the pole piece and the top plate.
I'll leave it up to you decide whether or not you can hear when that happens 😉
Brian.
Off topic - to get away from biasing the T-amp: 😉
Is the D10.1s still your favourite? I didn't really follow all the ongoing discussions here. Perhaps I can skip the biasing and go for another type of amp? 😉
Are you still selling them?
Klaus
Off topic - to get away from biasing the T-amp: 😉
Is the D10.1s still your favourite? I didn't really follow all the ongoing discussions here. Perhaps I can skip the biasing and go for another type of amp? 😉
Are you still selling them?
Klaus
I just wanted to note that the only reason I'm going to add the adjustment circuit is for my own educational purpose.
I don't really care that the offset is present. I just like to do simple little things like this to help me learn.😀
I don't really care that the offset is present. I just like to do simple little things like this to help me learn.😀
theAnonymous1 said:
Me to.
First thing on my Christmas wish list is a PC based two chanel oscilloscope, to be able to learn more. 😉
soundcheck said:
Hi Klaus. Compared to the Tripath based amps I've heard, I still prefer the sound of the D10.1s.
After I fill all the orders for the TAS5261 project I will do another group buy for D10.1 kits. I'm very busy with a lot of things right now (work and home related) so keep an eye out for something very early this coming year 😉
BWRX said:
How compares TAS5261 vs. D10.1?
Background: I am actually quite happy with my modded Charlize for the time being, I wonder if the D10.1 would kick-in that much.
I have the feeling that 3/4 Watts more headroom wouldn't be that bad on my 98db/SPL 8R system. The D10.1 wouldn't be able to deliver them. The TAS would be overkill I guess.
Undistorted 10-15W (24V max) on 8R is actually that what I am looking for.
Cheers Klaus
I don't have two TAS5261 boards built to listen in stereo so I can't do a worthwhile comparison yet.
The D10.1 can do 7Wrms before clipping into an 8ohm load with +/-12V rails. That's what you can expect from the low power Tripath amps with a 12V rail too. But 98dB @ 1W/1m speakers means just about any amp you use will be operating at very low output power almost all the time anyway, unless you're sitting pretty far away or have a large listening room or like it really loud.
It never hurts to have an amp that has a lot of headroom for a given amp/speaker combo. The D10.1s and low power Tripath amps work very well for near field listening and efficient speakers (both the D10.1s and Tripath amps perform better with an 8ohm load) in small to medium sized rooms (my system falls into this category). But if you have a large room, inefficient speakers, and like to listen loud then you would be better off using a more powerful amplifier.
The D10.1 can do 7Wrms before clipping into an 8ohm load with +/-12V rails. That's what you can expect from the low power Tripath amps with a 12V rail too. But 98dB @ 1W/1m speakers means just about any amp you use will be operating at very low output power almost all the time anyway, unless you're sitting pretty far away or have a large listening room or like it really loud.
It never hurts to have an amp that has a lot of headroom for a given amp/speaker combo. The D10.1s and low power Tripath amps work very well for near field listening and efficient speakers (both the D10.1s and Tripath amps perform better with an 8ohm load) in small to medium sized rooms (my system falls into this category). But if you have a large room, inefficient speakers, and like to listen loud then you would be better off using a more powerful amplifier.
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