Summer is here, and the need for efficient amplification...
So I put together an evaluation board from Tripath, after reading all possible hints & tips on these.
It's a 0103, (ca. 2 x 150W @ 8 ohm), running 53+/-V rails, 90 000uF filtering, Jensen JT-11P-1 input-trafos, one ch. inverted, updated caps...
And it works! have left it on for 30min, I adjusted DC-offset, and installed it for listening-tests.
No problems, no noise, just pure sound.
And now, the critic; it's lacking some "body", very "laid-back", and has no "attack".
Any cure for this?
BTW, measured ideling-switching, both ch. steady at 750kHz.
Heatsink is cold,even after 30 min at ~40% power, module is sligthly warm.
ArneK
So I put together an evaluation board from Tripath, after reading all possible hints & tips on these.
It's a 0103, (ca. 2 x 150W @ 8 ohm), running 53+/-V rails, 90 000uF filtering, Jensen JT-11P-1 input-trafos, one ch. inverted, updated caps...
And it works! have left it on for 30min, I adjusted DC-offset, and installed it for listening-tests.
No problems, no noise, just pure sound.
And now, the critic; it's lacking some "body", very "laid-back", and has no "attack".
Any cure for this?
BTW, measured ideling-switching, both ch. steady at 750kHz.
Heatsink is cold,even after 30 min at ~40% power, module is sligthly warm.
ArneK
I do not think it's the PSU...
I tried a brief moment w. 2 x 15 000uF, and it did not improve, rather got worse.
But I have been tweaking the input circuit a bit, and increased the gain, wich helped a lot. Also tried some different input-caps, (and still think my "secret" RS-bipolars sounds best(10uF100V)).
I also let it run "hard&hot" with a CD on repeat for a couple of hours, into a pair of 8ohm 200W dummy-loads.
The dummys got bloo** hot, the amp/heatsink barely rised to 30-35ºC !
Anyway, things are improving...will also try a new and better filtered 5V supply....
ArneK
I tried a brief moment w. 2 x 15 000uF, and it did not improve, rather got worse.
But I have been tweaking the input circuit a bit, and increased the gain, wich helped a lot. Also tried some different input-caps, (and still think my "secret" RS-bipolars sounds best(10uF100V)).
I also let it run "hard&hot" with a CD on repeat for a couple of hours, into a pair of 8ohm 200W dummy-loads.
The dummys got bloo** hot, the amp/heatsink barely rised to 30-35ºC !
Anyway, things are improving...will also try a new and better filtered 5V supply....
ArneK
The phase-inversion is there to compensate for the supply pumping effect to some extent.
Another positive effect is that you load BOTH halves of your PSU on heavy bass transients (which are often monaural) evenly, giving some additional dynamic headroom. This has already been done with linear amps for exactly that reason years ago.
So this measure should rather improve attack than make it worse.
At the upper end it is the inevitable output filter that is worsening transient behaviour. To what extent is of course debatable.
For bass signals the behaviour of switching amps is usually excellent.
And maybe it is the (positive !) lack of stress that is subjectively perceived as inferior transient behaviour
Regards
Charles
Another positive effect is that you load BOTH halves of your PSU on heavy bass transients (which are often monaural) evenly, giving some additional dynamic headroom. This has already been done with linear amps for exactly that reason years ago.
So this measure should rather improve attack than make it worse.
At the upper end it is the inevitable output filter that is worsening transient behaviour. To what extent is of course debatable.
For bass signals the behaviour of switching amps is usually excellent.
And maybe it is the (positive !) lack of stress that is subjectively perceived as inferior transient behaviour
Regards
Charles
hi.
the idea with inverting one channel is to utilize the power supply charge capacitance better and i dont think it has any negative effects on the sound quality (provided the inversion is made correct)
what amps did you compare to on same speakers/setup?
did you try running the amp without your tweaks?
did you use the 0103 chip from us?
what fets are you using?
rgds karsten madsen - www.cadaudio.dk
ps,
you said in another thread that this board is very different from the small footprint tripath board we sell , can you tell more about this? (i think they are very identical)
on listening tests we made here we didnt get the sound quality you describe, basically we got an open and "forward" type of sound with detail and control , also in the low end, and no lack of attack or transients....
the idea with inverting one channel is to utilize the power supply charge capacitance better and i dont think it has any negative effects on the sound quality (provided the inversion is made correct)
what amps did you compare to on same speakers/setup?
did you try running the amp without your tweaks?
did you use the 0103 chip from us?
what fets are you using?
rgds karsten madsen - www.cadaudio.dk
ps,
you said in another thread that this board is very different from the small footprint tripath board we sell , can you tell more about this? (i think they are very identical)
on listening tests we made here we didnt get the sound quality you describe, basically we got an open and "forward" type of sound with detail and control , also in the low end, and no lack of attack or transients....
Hi!
I just wanted to tell of some interferences the TriPath chips are inducing, according to Thomas Hartwig (www.thel.de), which is why he abandoned his plans on building an amp with them.
First of all, he said that you have a 1 Mhz signal of about 1 V on the loudspeaker cables.
The supply voltage has an interference signal of 1 Mhz / 3 V, and lots of overlaying harmonic waves, which both mean inducing distortion in the mains voltage.
But he also said that this only made the TriPath amps a "no-no" for his commercial offerings, a DIY man might still want to try it, if he disregards those noise considerations...
Bye,
Arndt
I just wanted to tell of some interferences the TriPath chips are inducing, according to Thomas Hartwig (www.thel.de), which is why he abandoned his plans on building an amp with them.
First of all, he said that you have a 1 Mhz signal of about 1 V on the loudspeaker cables.
The supply voltage has an interference signal of 1 Mhz / 3 V, and lots of overlaying harmonic waves, which both mean inducing distortion in the mains voltage.
But he also said that this only made the TriPath amps a "no-no" for his commercial offerings, a DIY man might still want to try it, if he disregards those noise considerations...
Bye,
Arndt
I admit that it's never good to send noise of that kind back into the mains.
But many people are unaware that the main culprits in terms of delivering noise and distortion into the mains are conventional PSUs. Exactly the ones of the type transformer- rectifier - capacitor.
While RF noise can be filtered out with physically small filter components it is not that easily achieved for a conventional PSU.
If someone has no experience with RF circuits it is likely that he will run into trouble when designing switching amplifiers, since these are basically precision RF circuits, used to process audio. So it is best to use a manufacturers design as a starting point.
Regards
Charles
Re: Tripath
Most of the config is described in first post, and all tips from Christopher Brodesen are followed...before I started to tweak...
The board is actually a 0104 eval, been lying around for almost a year, bought from "Profusion", fitted with a 0103 "processor". (Wanted to make it compact, and could not fit larger trafo in this half-size chassi).
I have one more 0104 board, planned for a deep bass/sub project...
Arne K
And, sofar, it has been the best PWM experience! But it cannot beat a good mosfet design...
See also http://www.diyaudio.com/forums/showthread.php?postid=185294#post185294
Most of the config is described in first post, and all tips from Christopher Brodesen are followed...before I started to tweak...
The board is actually a 0104 eval, been lying around for almost a year, bought from "Profusion", fitted with a 0103 "processor". (Wanted to make it compact, and could not fit larger trafo in this half-size chassi).
I have one more 0104 board, planned for a deep bass/sub project...
Arne K
And, sofar, it has been the best PWM experience! But it cannot beat a good mosfet design...
See also http://www.diyaudio.com/forums/showthread.php?postid=185294#post185294
Beware...
I have lent my amp to a friend, and disaster struck...
It took out every second driver in both speakers before fuses burned out :-(
So now I probably have to pay for his custom drivers...bass, mid and tweeter(customized revelator)...*******
A little budget setback...I guess my vacation just got a week shorter...
Arne K
I have lent my amp to a friend, and disaster struck...
It took out every second driver in both speakers before fuses burned out :-(
So now I probably have to pay for his custom drivers...bass, mid and tweeter(customized revelator)...*******
A little budget setback...I guess my vacation just got a week shorter...
Arne K
Re: Beware...
Hi!
Btw., did you measure DC offset at the speaker terminals? Maybe your speakers could handle a high offset, while that of your friends couldn't?
Killed myself a Mid Range WOofer (of course no longer in production) with DC offset, but mine was way too high (12 V
)...
Bye,
Cradle
Hi!
Cobra2 said:
Btw., did you measure DC offset at the speaker terminals? Maybe your speakers could handle a high offset, while that of your friends couldn't?
Killed myself a Mid Range WOofer (of course no longer in production) with DC offset, but mine was way too high (12 V
)...Bye,
Cradle
Hi!
That's learning by painful experience...
Even if the time it takes sumes up, always measure DC offset prior to connecting speakers, even if you only changes the tiniest bit of setup on your amps...
Even 0.5 € dummy speakers can add up to a bigger heap of money (I blew about 10 of them, because I was too lazy to measure DC)...
Bye,
Arndt
That's learning by painful experience...
Even if the time it takes sumes up, always measure DC offset prior to connecting speakers, even if you only changes the tiniest bit of setup on your amps...
Even 0.5 € dummy speakers can add up to a bigger heap of money (I blew about 10 of them, because I was too lazy to measure DC)...
Bye,
Arndt
has anyone tried irf's version of pmw amps? I thought they had a driver IC (2010?) for their pwm implementation but i never heard of reviews on them.
here is the link: http://www.irf.com/product-info/audio/
here is the link: http://www.irf.com/product-info/audio/
Re: Tripath
Hmm, checking the amp, and there is no visible clues on what might have happened.
But I have rail-voltage out, 54V DC...
Even the "mute/reset" seems in order(light).
Guess the mosfets are gone... (?).
Anybody have an explanation on how this can happen, and what I need to do for it not to happen again?
(Can't afford another € 500+ in speaker-drivers).
Arne K
Hmm, checking the amp, and there is no visible clues on what might have happened.
But I have rail-voltage out, 54V DC...
Even the "mute/reset" seems in order(light).
Guess the mosfets are gone... (?).
Anybody have an explanation on how this can happen, and what I need to do for it not to happen again?
(Can't afford another € 500+ in speaker-drivers).
Arne K
Re: Tripath
Have changed all mosfets, as 2 of them had internal short (one channel).
New fets are MTW35N15E powerfets, data is close to the STW34NB20.
And tried again...the dead ch. still did not work. (0103 proc.=kaputt)
Tried with a 0104 "processor", and now both ch.works, but they are running with different frequency???
I can have one running (ideling) at 550kHz, and the other close to 650kHz...
Arne K
Have changed all mosfets, as 2 of them had internal short (one channel).
New fets are MTW35N15E powerfets, data is close to the STW34NB20.
And tried again...the dead ch. still did not work. (0103 proc.=kaputt)
Tried with a 0104 "processor", and now both ch.works, but they are running with different frequency???
I can have one running (ideling) at 550kHz, and the other close to 650kHz...
Arne K
Still running....
As a "long term test", I have left the amp. powered on, no input-signal, loaded by 8ohm-200W resistors, and will hopefully stay this way the next 14 days, while I'm off for work.
But there still was a 90-100kHz difference between channels.
Do these amps also require matched mosfets?
And, can anybody point me in direction to a cheap/simple DC- sense-circuit for the output...(will kill main-power, not speakers).
Arne K
As a "long term test", I have left the amp. powered on, no input-signal, loaded by 8ohm-200W resistors, and will hopefully stay this way the next 14 days, while I'm off for work.
But there still was a 90-100kHz difference between channels.
Do these amps also require matched mosfets?
And, can anybody point me in direction to a cheap/simple DC- sense-circuit for the output...(will kill main-power, not speakers).
Arne K
Cobra...Rod Elliot has a good DC circuit...BUT.... what you want is something that will kill main power. I have given much thought to this and haven't been able to come up with a great solution. Ideally, if a circuit like this senses DC on the speaker output...it'll shut down the amp in time to save the speakers and the amp. However, this isn't readily possible. What you need is a relay between the power supply capacitors and the amp that will essentially disconnect the amp from the power supply. While this is ideal, a high voltage DC relay isn't readily available. DC is not easy to switch because as contacts are opening (switch is switching off) DC just keeps arcing. AC on the other hand, is easy to switch because it goes through a zero point in the voltage. So...what to do? I have some ideas, but I'm in class right now. I'll try to post em later.
-Matthew K. Olson
-Matthew K. Olson
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