John you said that these new regulations would wreak havoc on our power supplies. In what way would we have to modify the design of our power supplies?
Or is this hearsay with no factual understanding?
jd
You can do just about any audio or video processing job with custom FPGA's. In fact thats how the ESS guys said they started their DAC project.
Secrecy come with this territory. I love the comment about 150K turntables being a niche market.
I forgot which address I gave you. There is nothing here at work, I will check at home tonight, the mail has piled up lately. 😀
I lost another message. That was the question. It was an answer to Jan. Did 'they' delete it, or did I forget to push a button? That is the question.
C'mon Scott😀 If FPGAs were custom they'd be GA's. Xilinx and Altera are still very much off the shelf parts. Though perhaps by using the scare quotes they really meant to say that "off the shelf" meant no end user-customization. Anyone's guess 🙄
What is the difference to you? It will be very expensive, and they apparently are referencing the analog section for the most part when discussing the digital players. This is a difficult area where integrated circuits are still not held in highest regard. (for some reason). In fact, I was just asked, this week to design a discrete DVD/CD output stage for Parasound.
Almost all of the real professional amplifiers are now smps. A full rack of amplifiers used to weigh just over 1000 pounds. Today the rack is half the size and is about 350 pounds and has a higher rated power. But the bass response is better with the older amplifiers. (Measured and heard.) But that is more a function of designing for available power supply current limits. I have seen amplifiers rated at 6800 watts but then they are connected to a 30 amp 120 volt outlet. So with 6800 watts out from 3600 watts power available they have solved the problems with perpetual motion.
The question as to what power factor is acceptable is more one of standards committees. The IEC as I understand it allows 2 representatives on the committee per national member. Some nations have strong interests in the standards and others may not. So the results get a bit tilted.
The UL these days is tending to follow the IEC to allow more world wide products. That is why the three wire power cord is going away. One of the current standards expires in 2 years and the replacement already available tilts to insulation requirements without a safety ground as many IEC members do not have grounded electrical distribution systems.
For a goal of a .8 power factor there are many approaches. ON Semi has some nice notes on doing it electronically. See http://www.onsemi.com/pub_link/Collateral/AND8394-D.PDF as a typical example.
It can be as simple as having high ripple on your first filter capacitor and a loosely coupled power transformer.
I have tried using a standard transformer with a switched rectifier on the secondary to pull power at a phase angle of 45 degrees instead of 90. This is known as a phase controlled rectifier and is a method of regulating the DC voltage. A nice advantage is that you can use the 90 degree voltage for a higher rail for your driver stage in a power amp.
My favorite method is here http://www.audioxpress.com/magsdirx/ax/addenda/media/simon2944.pdf
But please first read http://www.audioxpress.com/magsdirx/ax/addenda/media/simon2943.pdf
The resonator adjustment in those articles can be automated. This method gives results that actually can be heard, but of course in my test setup the AC line has the power companies distribution transformer feeding 54 feet of cable to my 800 amp power breaker box and then less than 100 feet of 10 gauge cable to my test bench. The AC peaks can still be clipped by 5 to 7 volts.
So the resonator only increases my available power by .36db. Since the device that showed improvement was the CD player, my conclusion was that my CD player has a poor power supply design. (Later confirmed when I took it apart. The basic voltage was 6 volts and it could drop to 5.2 volts depending on the AC supply! With a peak output of 2vrms you can see why.)
Then there is the question of DC on the transformer. I just finished a small theater. An Acentech design. The noise level met NC17. The noise source was not the air handling system, but the power isolation transformer for the sound system. A nice buzz even when the secondary was unloaded! My OPINION is that the feeder voltage is clipped from other loads and that is causing a buzz. (Buzz is not the same as hum! Hum is clean 60hz buzz has lots of harmonics notably 180hz.) I would look at the light dimmer loading for a cause, the consultants will more likely use acoustical isolation.
I've done some experiments with smps's for audio over the last few years.
The important point is to get an smps that has a current limit that doesn't switch the supply off but rather, ehhh, limits the current to some value.
Those smps's will tolerate high value caps at the output. That way you can have large power reserves for those drum beats and other high level, periodic passages.
If you do that, the whole supply works very well. Rather than a traditional xformer-based one, the max current of the smps is available 100% of the time (We all know that in a xformer-based supply the transformer and rectifier is only connected to the cap some 20% or less of the time, which makes the charging cycle short and brutal).
Having, say, 3 or 4A continuously available means that the cap only very rarely has to assist the supply.
I've had good results with two cheap, 60W/32V supplies in a 50W amp followed by 4700uF.
My last try was with a pair of Vicor 1/4 bricks modules which are very, very low on ripple and EMI (they have 0-voltage and 0-current switching), followed by a Vicor RAM (ripple attenuator module). Very clean supply, but more expensive, about $200 for 2*(46V at 4A).
Once one of the mainstream hi-end names embraces smps's and launches a good marketing campaing to convince us that the results are audibly better, they will take off. But the audio industry is very conservative so don't hold your breath...
jd
The important point is to get an smps that has a current limit that doesn't switch the supply off but rather, ehhh, limits the current to some value.
Those smps's will tolerate high value caps at the output. That way you can have large power reserves for those drum beats and other high level, periodic passages.
If you do that, the whole supply works very well. Rather than a traditional xformer-based one, the max current of the smps is available 100% of the time (We all know that in a xformer-based supply the transformer and rectifier is only connected to the cap some 20% or less of the time, which makes the charging cycle short and brutal).
Having, say, 3 or 4A continuously available means that the cap only very rarely has to assist the supply.
I've had good results with two cheap, 60W/32V supplies in a 50W amp followed by 4700uF.
My last try was with a pair of Vicor 1/4 bricks modules which are very, very low on ripple and EMI (they have 0-voltage and 0-current switching), followed by a Vicor RAM (ripple attenuator module). Very clean supply, but more expensive, about $200 for 2*(46V at 4A).
Once one of the mainstream hi-end names embraces smps's and launches a good marketing campaing to convince us that the results are audibly better, they will take off. But the audio industry is very conservative so don't hold your breath...
jd
Jan,
For production use the smps are custom designed. One of the interesting advantages is the the voltage from the supply is regulated and can be allowed to swing following the output voltage.
This is similar to class H design.
So a smaller faster output stage can be used, as there is less heat dissipation.
As to using a larger filter capacitor to hold up the bass note, the spec's on pro amps are now given for 20ms power ratings. Not much bass to be found there.
If you use capacitors after an smps as large as those in a brute force power supply you will have as much bass energy available, but then cannot swing fast enough for semi class H.
I suspect everyone is aware that smps can create noise if not properly handled, but on the up side is that they are unaffected by the AC supply lines losses. If the input voltage drops they will increase the current draw to keep the output voltage stable.
Many pro users had problems with how small the power cords were on the first models. The manufacturer change to a larger gauge cord. Marketing!
So changing to an smps is going to be a learning curve. Bass or fast?
ES
Yes good points.
I know some manufacturers actually see the smps as an integral part of their class-D amp, and even use the actual power supply value as one input to the feedback/control block, getting a theoretical infinite PSRR.
jd
I know some manufacturers actually see the smps as an integral part of their class-D amp, and even use the actual power supply value as one input to the feedback/control block, getting a theoretical infinite PSRR.
jd
Actually not. The results of resistor distortion show two factors. One is the third order distortion which follows thermal levels. Well defined and able to be properly accounted for in design. The interesting effect was the second order harmonic distortion. This was also level dependent, but is better modeled as a fixed level and an amplitude related component. The fixed level is extremely low. As low as -200db re my test level of 15.83 volts. This 1.5nv fixed level on a phono preamp input where the level with a moving magnet cartridge would be around 1mv would be -116 for a really good resistor but -76 for some of the bad ones. With a moving coil cartridge that could be -96 to -56.
The RIAA curve with poles at 50, 500 and 2122hz would greatly tilt the perception of the distortion. If we assume the peak recorded energy is around 200hz - 300hz the second harmonic would be 500hz. Fletcher Munson and others show about a 10 db increase in hearing sensitivity for this change. The eq curve here is at 12db per octave so we have about a 22db increase from these two effects.
That leaves our distortion from our good resistor at -74 and the bad at -34 before we hit our amplifiers! I suspect I can hear the -34 as this is 2% distortion. The -74 is .02% which is above that of a good amplifier.
Now you might argue that at these low levels the measurements have significant uncertainty, and even if you allow for 20db of error, or levels of .002% to .2%. It is still reasonable to allow some resistors will sound better than others.
So yes, the result as surprising as it seems, there actually may be some basis for the claims of being able to hear the difference in cartridge termination resistors besides the actual value of the resistor which is easily explained. As the resistors being compared were within 1%, my OPINION is that the resistance variation is not able to be heard.
As to claims of this level of difference at higher voltage levels and without equalization then I would look to see if the resistor was over stressed.
ES
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Ed, unfortunately, 2'nd harmonic drops directly with level. This will throw off your calculations, BUT not all is lost. When we drop in signal level, other mechanisms of distortion come forth, mainly a form of cross-over distortion. It has been measured, but it is difficult to do so, without specialized test equipment, even beyond you and me, at the moment. Dr. Van den Hul did measure it, however. We should contact him for more details.
Another important mechanism is the relative level of CCIF distortion consisting of difference tones closely spaced at high frequencies. For example, 19KHz and 20KHz then passing through integration type EQ such as RIAA or NAB tape EQ. Please note that the difference tones can be boosted by up to 40dB, by the effect of the EQ.
In any case, resistors have been found to be important in serious design and we take which brands we use into serious consideration when making the best audio equipment that we can.
Another important mechanism is the relative level of CCIF distortion consisting of difference tones closely spaced at high frequencies. For example, 19KHz and 20KHz then passing through integration type EQ such as RIAA or NAB tape EQ. Please note that the difference tones can be boosted by up to 40dB, by the effect of the EQ.
In any case, resistors have been found to be important in serious design and we take which brands we use into serious consideration when making the best audio equipment that we can.
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