Put an RC link between the output terminals and you have fixed the problem of rising speaker impedance. Say 470 nF in series with 10 ohm.
Thorsten
True Thorsten,
An alternative would be to try to modify the speaker impedance.
Which is nothing else.
I dont think that any speaker will profit. Anyway, different speakers will need different impedance correction. So no patented cirquit that is the best.
Put an RC link between the output terminals and you have fixed the problem of rising speaker impedance. Say 470 nF in series with 10 ohm.
Thx Thorsten
Yes i tried this at the TPA3255 amp with 0,33µ and it works ok.
What is wrong with TPA3255?
@FF and Turbo
Yes i know that a lot of speakers need a "ideal" filtering adaptaion and that is not existing. as FF wrote my "compromise" is within one filter to cover the THD in the higher region. without THD measurements its "just" test over hearing and long term listening.
chris
The Vienna Theorem includes no patented matter. It is only the result of solid creative thinking by Chris in response to facts described by ICG. The type of reflection that steadily bring us forward.
Chris may not be the first ever to come to such conclusions but many of us had not given that detail a thought. Thorsten could then add a valid non-patented alternative. When we seek the ultimate sound, all details count and to bother scrutinizing even the marginal effects is a gain.
Let me say it that way: The filter recommendation are based on the calculation of the classical critical damped LC filter. In that case
sqrt(L/C) = Z(out).
With a filter of 10uH/1uF this computes to a "best" impedance of about 3 Ohms. The resonant frequency is
F = 1 / 2*pi*(sqrt(L*C)) = ca 50kHz.
This works fine with a 3 Ohm resistor that has no phase shift at 50kHz. Consequently the frequency plots delivered by the manufacturers a taken with low inductance dummies.
Which does not relate to your reality. There are no speaker drivers with such impedance properties and that means the upper frequency response of your class D amp more likely is the one with no load.
From that point of view it does not make much sense to change the filter for higher impedance speakers - let it as it is.
You may apply a fat RC impedance stabilizing network as proposed here.
Or you go for post filter feedback.
With my TPA3255 RefDesign from 2017 I chosed a special postfilter feedback which yields flat frequency responce no matter the speaker impedance. To illustrate this I append a frequency plot as well as the square wave response without load.
sqrt(L/C) = Z(out).
With a filter of 10uH/1uF this computes to a "best" impedance of about 3 Ohms. The resonant frequency is
F = 1 / 2*pi*(sqrt(L*C)) = ca 50kHz.
This works fine with a 3 Ohm resistor that has no phase shift at 50kHz. Consequently the frequency plots delivered by the manufacturers a taken with low inductance dummies.
Which does not relate to your reality. There are no speaker drivers with such impedance properties and that means the upper frequency response of your class D amp more likely is the one with no load.
From that point of view it does not make much sense to change the filter for higher impedance speakers - let it as it is.
You may apply a fat RC impedance stabilizing network as proposed here.
Or you go for post filter feedback.
With my TPA3255 RefDesign from 2017 I chosed a special postfilter feedback which yields flat frequency responce no matter the speaker impedance. To illustrate this I append a frequency plot as well as the square wave response without load.
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How is the approach to measure the specific speakers impedance, add a correcting network and see how it sounds? The only thing I wanted to point at, it will be the same impedance correction as you would use for a tube amp.
Such an addition to a speakers x-over should have no adverse effect for "normal" amps.
Of course, putting the feedback outside of the HF filter would be much more elegant. Why is it not used?
Such an addition to a speakers x-over should have no adverse effect for "normal" amps.
Of course, putting the feedback outside of the HF filter would be much more elegant. Why is it not used?
The NE5532 is a very good OP-amp. Compared to "usual" cheap OP-amps used in active x-over and many other even good quality audio products, it is very expensive.
For most people there is no other OP-amp, how expensive it might be, that will have a real plug&play impact in a well designed audio product if changed for the NE5532. Well designed means no foreseeable mistakes on power supply and corresponding parts.
In the past there have been intensive OP-amp tests from audiophiles which did not bring out any final result, even after thousends of IC have been rolled.
Indeed it is no easy task to do a objective listening test.
My personal experience is that you can spot a really low quality OP-amp at once, but it is very hard to find a better sounding one in a field of good ones. The differences will be so small, you will not be able to clearly repeat them after the time you need to change the OP-amp in the hard ware. Without a switching system that makes A/B comparison possible in a fraction of a second, you will be lost.
Another problem, thanks to our Chinese friends, are fake OP-amps. No Chinese can resist if you can turn a .2 Cent IC into a 5 or even 20$ one, just by writing another name on it. These fakes have often made their way into even reputable component sellers stock´s in the past and will do so in the future, as long as people wont to make money quick.
So some people might be testing eBay fakes against Amazon ones...
For most people there is no other OP-amp, how expensive it might be, that will have a real plug&play impact in a well designed audio product if changed for the NE5532. Well designed means no foreseeable mistakes on power supply and corresponding parts.
In the past there have been intensive OP-amp tests from audiophiles which did not bring out any final result, even after thousends of IC have been rolled.
Indeed it is no easy task to do a objective listening test.
My personal experience is that you can spot a really low quality OP-amp at once, but it is very hard to find a better sounding one in a field of good ones. The differences will be so small, you will not be able to clearly repeat them after the time you need to change the OP-amp in the hard ware. Without a switching system that makes A/B comparison possible in a fraction of a second, you will be lost.
Another problem, thanks to our Chinese friends, are fake OP-amps. No Chinese can resist if you can turn a .2 Cent IC into a 5 or even 20$ one, just by writing another name on it. These fakes have often made their way into even reputable component sellers stock´s in the past and will do so in the future, as long as people wont to make money quick.
So some people might be testing eBay fakes against Amazon ones...
I got caught out with some 74HC4051 analogue multiplexers.
The first Chinese supplier supplied CD4051's instead and they are 6 times slower. I got a partial refund.
The second Chinese supplier did exactly same trick. I got a full refund this time as I didn't want the items.
I found a slower project for the first batch of CD4051's.
The first time I tested the pcb the 4051 had failed !
So all went in the bin.
In the end I bought in 25 74HC4051's from RS Components at not too much more than the fake devices.
Maybe the main reason for the Chinese to betray at every corner, apart from tradition, is the propaganda of the Chinese Communist Party, that "we", the West, are the enemy. So with ever fake product sold to the West the faker has done good what the Party told him.
Faked electronics have been around for a while, but in "former times" this was a crime and punished by law. Today as soon as the supply chain crosses the border to China, the criminals are save and even celebrated as smart businessmen. Just as China is a save haven for drug dealers, forgers of aircraft spares and financial fraudsters. As long as they hurt the West, they are welcome.
There will be a point where the Chinese economy will get hurt by it´s own politics of faking anything. Even today the same products containing fake parts are sold on the own market as well as they are exported. Not all factory´s run two production lines, as it is often reported, with "A-quality" sold in China and the "B-Grade" for us. This is propaganda too.
I fear the first Chinese commercial airliners that are in development, even as these are Boing and Airbus copies. These are too complex to filter out the "B-grade" parts that will find their way into production of thousand´s of modules. With war planes this is not that much of a problem, as they are not build to survive for long, but Commercial planes are a different story. Here you can´t just don´t tell about an accident.
God have mercy on the poor passengers.
This world has become to complex for any idiot doing what he pleases. They have to learn that in China, too.
Faked electronics have been around for a while, but in "former times" this was a crime and punished by law. Today as soon as the supply chain crosses the border to China, the criminals are save and even celebrated as smart businessmen. Just as China is a save haven for drug dealers, forgers of aircraft spares and financial fraudsters. As long as they hurt the West, they are welcome.
There will be a point where the Chinese economy will get hurt by it´s own politics of faking anything. Even today the same products containing fake parts are sold on the own market as well as they are exported. Not all factory´s run two production lines, as it is often reported, with "A-quality" sold in China and the "B-Grade" for us. This is propaganda too.
I fear the first Chinese commercial airliners that are in development, even as these are Boing and Airbus copies. These are too complex to filter out the "B-grade" parts that will find their way into production of thousand´s of modules. With war planes this is not that much of a problem, as they are not build to survive for long, but Commercial planes are a different story. Here you can´t just don´t tell about an accident.
God have mercy on the poor passengers.
This world has become to complex for any idiot doing what he pleases. They have to learn that in China, too.
I have several choices here, from samples that were sent by manufacturers several years ago. No 5532, of course.
Didn't have the time to look into all of them, but I picked three that I think might be good there: AD712, OPA2604 and OPA2228.
Which one would you think might work better on the Breeze?
If they fit into the board (Data Sheet), just put them in and try to figure out differences.
Depending on the rest of the chain and listening material, maybe you find your preferred one for this board and the way it implements the OP-amp.
The better the speaker and sound samples are, the more you may hear. The tweeter is IMO the most important component. Got to be very good quality. I find it easier to find a favorite DAC than a "better" Op-amp.
You have to be in a perfect mental "Testing Mode" too, the house has to be silent. Often late at night it is much easier to find any differences, maybe the voltage feed is better with less load. Leave the beer in the fridge, even very little alcohol kills any objective acoustical judgement (see: "Party Mode")
Sometimes "better" it is like another dimension, sometimes it might only be a feeling in the gut. It is up to you to find out! Sorry, giving advice on such parts is not very helpful, it depends on your board and it´s components, what sounds best.
Anyway, better parts might not always lead to better sound, but I do not remember any case where they sounded worse.
If you want to know what is imagination and where reality strikes, You have to buy two DUT´s and modify only one. At the end you know where you stand or might give up tuning cheap stuff.
Depending on the rest of the chain and listening material, maybe you find your preferred one for this board and the way it implements the OP-amp.
The better the speaker and sound samples are, the more you may hear. The tweeter is IMO the most important component. Got to be very good quality. I find it easier to find a favorite DAC than a "better" Op-amp.
You have to be in a perfect mental "Testing Mode" too, the house has to be silent. Often late at night it is much easier to find any differences, maybe the voltage feed is better with less load. Leave the beer in the fridge, even very little alcohol kills any objective acoustical judgement (see: "Party Mode")
Sometimes "better" it is like another dimension, sometimes it might only be a feeling in the gut. It is up to you to find out! Sorry, giving advice on such parts is not very helpful, it depends on your board and it´s components, what sounds best.
Anyway, better parts might not always lead to better sound, but I do not remember any case where they sounded worse.
If you want to know what is imagination and where reality strikes, You have to buy two DUT´s and modify only one. At the end you know where you stand or might give up tuning cheap stuff.
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This Zobel network is set to 30kHz (-3dB), so it will not modify speaker impedance in the audible range.
There are two reasonable options: try it or do not try. I made one today for FX502SPro. It looks like complex harmonics come out more detailed, less distorted. I had a feeling it was helping my Polks RT3. Then I played Katie Melua - In Winter, it has a nice choir, but some tracks sound harsh both on FX and Icepower amps. A track Plane Song is recorded with an occasional grating starting at 0:40 for ten seconds. It triggered a low volume purrr purrr purr on the left channel, then it started moving progresively to the middle and disappeared when reaching right channel. I played the same part couple times, it didn't happen again, but now sibilants became stronger than normal and generally transients were overhang.
I initially thought that Zobel network made FX unstable and the controller made an adjustments that didn't work well. This is amazing, it uses series of test pulses sweeping across channels! I powered FX off, checked all connection and found one terminal slightly loose. That was a problem! Now still playing and everything is fine.
Please disregard suspicion about stability of FX502SPro with Zobel network. The same happened with Icepower 125ASX2 and I didn't attach Zobel network yet. This time it was just purr purr purr on the left channel which stopped after 3 seconds. Then it came back after a minute. I quickly played 15 second back, it stopped.
A DAC is Nobsound 8x TDA1387, so it can be responsible USB interface chip (CM108). The chip use isochronous data transfer and a laptop is setup for WASAPI exclusive push. I don't know whether it is right or wrong, please advise.
A DAC is Nobsound 8x TDA1387, so it can be responsible USB interface chip (CM108). The chip use isochronous data transfer and a laptop is setup for WASAPI exclusive push. I don't know whether it is right or wrong, please advise.
Those who don't think this amp sounds fantastic or want's to improve the sound, try a tube preamp. For even better sound some better vacuum tubes
FX Audio 6j1 tube preamp - a $31 wonder | Audiokarma Home Audio Stereo Discussion Forums
Little Dot Tube Amps: Vacuum Tube Rolling Guide | Headphone Reviews and Discussion - Head-Fi.org
FX Audio 6j1 tube preamp - a $31 wonder | Audiokarma Home Audio Stereo Discussion Forums
Little Dot Tube Amps: Vacuum Tube Rolling Guide | Headphone Reviews and Discussion - Head-Fi.org
I know sound of irregular old GSM purr-purr-purr. This is regular one (a single click every 1/4 or half of second - something between). The first time it was spanning from left to right channel, well positioned. But yes, I agree GSM phone can trigger errors in USB transmission. This is not in my case, as I use phone only in emergency, so usually I don't keep it on the desk.
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