Hi,
Is there any specific technical reason why most of Class-T and TDA designs use SMPS power supplies? I know the obvious ones such as probably low cost, size and efficiency.... Other than these?
Or Is there any technical problem in using EI transformers to make power supplies for say an amp based on Tripath TA2024 chip or NXP TDA8930BTH chip?
Thanks,
Ron
P.S:- This question probably have been asked here before, had I located the T-Amp FAQ, I probably could have avoided posting this thread. But the FAQ is nowhere to be seen.
Is there any specific technical reason why most of Class-T and TDA designs use SMPS power supplies? I know the obvious ones such as probably low cost, size and efficiency.... Other than these?
Or Is there any technical problem in using EI transformers to make power supplies for say an amp based on Tripath TA2024 chip or NXP TDA8930BTH chip?
Thanks,
Ron
P.S:- This question probably have been asked here before, had I located the T-Amp FAQ, I probably could have avoided posting this thread. But the FAQ is nowhere to be seen.
Here is a monster I built using EI core transformers.....
http://www.diyaudio.com/forums/class-d/145533-iraudenstein-parts-bin-monster.html
It was built for potential subwoofer duty, but it sounds surprisingly good used as a full range amp. The outputs are almost dead quiet without an input signal.
EI pros:
High input DC immunity
Lower bandwidth = less line noise on the outputs
Low inrush current
EI cons:
Larger size/weight
Higher stray magnetic fields
They like to hum
http://www.diyaudio.com/forums/class-d/145533-iraudenstein-parts-bin-monster.html
It was built for potential subwoofer duty, but it sounds surprisingly good used as a full range amp. The outputs are almost dead quiet without an input signal.
EI pros:
High input DC immunity
Lower bandwidth = less line noise on the outputs
Low inrush current
EI cons:
Larger size/weight
Higher stray magnetic fields
They like to hum
Many Class-D designs have bad PSRR (power supply rejection ratio), even many selfoscillating designs...So it is almost always preferred to use some kind of regulated power supply for class-D amp, I would say...
I have seen KingRex's TA2020 design use a Toroidal transformer for the power. Not sure whether it's just a normal bridge rectifier or a regulated design.
@81bas:- So what do you think about using a EI transformer without a regulated power supply for a TA2024 amp running on Single rail supply? The amp can operate between 10-16v easily I guess...
Thanks,
Ron
DC immunity? How do you mean? On power input? It's not immune, it's very sensitive! On audio input? Why would it be different?
Lower bandwidth? Maybe, but it has only 6 dB/octave slope, while an SMPS has 2 filter stages (12 dB/octave) at least!
Low inrush current? Yes, with soft-start circuit. But SMPS can also has soft-start circuit.
Let me see if I understand this.
Class d amps generally use SMPS PS because they have low PSRR.
Don't SMPS have a reputation for being noisy? Wouldn't that be a bigger problem with a class D?
I thought that people used SMPS with class D for the weight savings + some archaic notion that you need to use "like" with "like". Sort of like the old school tube guys.
Class d amps generally use SMPS PS because they have low PSRR.
Don't SMPS have a reputation for being noisy? Wouldn't that be a bigger problem with a class D?
I thought that people used SMPS with class D for the weight savings + some archaic notion that you need to use "like" with "like". Sort of like the old school tube guys.
What are the power supply current draw characteristics of, for example, a classdaudio module that modulates at 400 kHz? The standard large PS electrolytic typically goes inductive at frequencies a decade lower. Making a large, linear unregulated supply with minimal impedance at modulation frequencies is doable but not trivial.
more on Power supplies
I hope this thread is still "alive" as I find the topic of PS for class D amps very interesting and way too neglected in relation to its importance on audible performance. Measurable it may be a different story, but i care less for that
I have heard big differences between small bypass caps placed across the poles of the large supply caps in linear torodial base power supply for a Hypex UCD amp. I used small jensen P/O caps with values between 0,2uF and 0,0001uF. Different values brought different results. Mixing values brought different results again so I definitely believe that the inductance of the supply caps(or arrangement hereoff) plays a part in how well UCD´s and probably all class D amps operate.
I tried the same on class AB amps (NCC200 and Aussie amp nxV200) and though there were audible differences they appeared to be smaller than on the UCD´s. Although the Aussie amp has a very high PSRR there still was a clear effect of using the small bypass caps, though I actually prefered the sound without on that amp. Quite interesting and difficult to get wise on...
What have I learned then?
high PSRR doesn´t mean that you can disregard the quality of the PS.
There is more to the sound of a PS than just the capacity of the supply caps.
Small bypass caps and their size alter the sound of all the amps I have tried it on, though both for good and bad.
Generally the small caps makes the presentation brighter and tightens the bass. It somehow resembles the effect of altering the air intake on a combustion engine. The torque distribution relates to the way the air moves and resonates.
Using bypass caps I tend to prefer that they are many magnitudes lower in value than the large supply caps; preferably as small as possible as they can in fact smear the sound.
Questions:
-Maybe the resonances caused by different C/L/R attributes of the caps affects each other and thereby the audible effect.
- Maybe the smaller caps thereby even induce distortion that alters the experienced presentation. -Small caps affecting bass is strange and ungraspable but it is known that high frequency distortion artifacts can alter the experience of the entire frequency spectrum -old Krell amps have been accused for this...
Another aspect is the trafos in linear PS´s.
I know many good things are often said about R-cores or C-cores, and I definitely want to try some for my self.
Are there anyone who can explain how they experience the difference from R/C core based supplies opposed to torodial based ones or even SMPS?
The tendency is clearly to go SMPS, but for purely SQ reasons why should one go that way or the R/C core based linear way?
best,
I hope this thread is still "alive" as I find the topic of PS for class D amps very interesting and way too neglected in relation to its importance on audible performance. Measurable it may be a different story, but i care less for that
I have heard big differences between small bypass caps placed across the poles of the large supply caps in linear torodial base power supply for a Hypex UCD amp. I used small jensen P/O caps with values between 0,2uF and 0,0001uF. Different values brought different results. Mixing values brought different results again so I definitely believe that the inductance of the supply caps(or arrangement hereoff) plays a part in how well UCD´s and probably all class D amps operate.
I tried the same on class AB amps (NCC200 and Aussie amp nxV200) and though there were audible differences they appeared to be smaller than on the UCD´s. Although the Aussie amp has a very high PSRR there still was a clear effect of using the small bypass caps, though I actually prefered the sound without on that amp. Quite interesting and difficult to get wise on...
What have I learned then?
high PSRR doesn´t mean that you can disregard the quality of the PS.
There is more to the sound of a PS than just the capacity of the supply caps.
Small bypass caps and their size alter the sound of all the amps I have tried it on, though both for good and bad.
Generally the small caps makes the presentation brighter and tightens the bass. It somehow resembles the effect of altering the air intake on a combustion engine. The torque distribution relates to the way the air moves and resonates.
Using bypass caps I tend to prefer that they are many magnitudes lower in value than the large supply caps; preferably as small as possible as they can in fact smear the sound.
Questions:
-Maybe the resonances caused by different C/L/R attributes of the caps affects each other and thereby the audible effect.
- Maybe the smaller caps thereby even induce distortion that alters the experienced presentation. -Small caps affecting bass is strange and ungraspable but it is known that high frequency distortion artifacts can alter the experience of the entire frequency spectrum -old Krell amps have been accused for this...
Another aspect is the trafos in linear PS´s.
I know many good things are often said about R-cores or C-cores, and I definitely want to try some for my self.
Are there anyone who can explain how they experience the difference from R/C core based supplies opposed to torodial based ones or even SMPS?
The tendency is clearly to go SMPS, but for purely SQ reasons why should one go that way or the R/C core based linear way?
best,
In my case it was only investigated from the perspective of capacitor impedance and the inductance of the wires connecting the last large PS capacitor to the amp. It suggested putting quality electrolytic caps (low Z Panasonic FC, etc.) in the 1000-100 uF range right at the amp's power supply input. If Spice is to be believed, not twisting the plus, minus and ground leads between the main capacitor bank and the terminating caps adds significant power supply rejection at the amp's switching frequency with no impact on the power supply's output Z.
It's easy to do with an SDS-224, two 1000 uF Fc's added as above to the 33,000 uF per rail already in place seemed to bump things up.
It's easy to do with an SDS-224, two 1000 uF Fc's added as above to the 33,000 uF per rail already in place seemed to bump things up.
On the Hypex UCD´s and the aussie amps, there are on board caps very close to the output fets. From the UCD hot-rodding threads back then I remember that those on board caps were a subject that was reported to matter. Also the ST and HG models does use different caps, so it only makes sense that their output R/L values matters a great deal. That said - and considering their sizes (typically between 100-1000uF) - the much much smaller caps that I bypassed the large main filter caps with still yielded big audible differences. I haven´t got a cue about their R/L values, but I guess that being P/O caps, that they are smaller than those on electrolytic caps...
Interesting that you have modeled the supply leads and found that twisting/untwisting should matter. Form my own experience, keeping them straight and spaced typically sounds best (to my ears in my system of course).
Interesting that you have modeled the supply leads and found that twisting/untwisting should matter. Form my own experience, keeping them straight and spaced typically sounds best (to my ears in my system of course).
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.