Should have used the 888,788 is old NewsChapter 3-1 What exactly is the THX AAA-788+ amp module?
Since the release of FiiO's first module AM3C/AM3D using the THX AAA headphone amplifier technology at the end of 2018, it's been 3 years. During these 3 years, we have been using the THX AAA headphone amplifier technology and gradually expanded it to the Q5s, M11 Pro, and Q3. , M11 Plus Ltd and other products.
Many users have become accustomed to the sound performance of THX AAA amps. After the K9 Pro went on the market, almost all users said that the sound was pretty good.
Why is THX AAA amp technology so amazing, and what other black technologies does it contain? Today, I would like to dig them out with you.
Those who know THX AAA probably know its unique signal amplification and error correction technologies. When coupled with the serious op-amp structure, it has strong audio performance and output efficiency, lower distortion and better sound quality.
There is a picture on the THX official website, which vividly introduces the product line of THX AAA headphone amplifiers.
As you can see from the picture above, the THX AAA-788 is one of the best amps among the entire THX AAA technology, and it is THX's sub-flagship amp.
It is also clearly marked here, the 788 is specially used in desktop amplifiers.
Some users may notice that the above picture does not contain the THX AAA 788+ model used in the K9 Pro. What is the reason?
If you have read my previous articles, you may know the THX AAA technology used in the K9 Pro is an improvement based on the original one.
THX AAA is an amplifier technology, and each of the names is just to distinguish different power consumption and power levels. When applied to specific products, some necessary adjustments will be made according to the actual needs of the products. The AAA 788+ used this time is based on FiiO's previous THX circuit debugging experience and circuit characteristics of the K9 Pro. Therefore, it is an enhanced version based on the THX AAA-788.
The new THX AAA-788+ has lower output impedance, higher heat dissipation efficiency and stronger load capacity. Compared with the original version, its output power is increased by 50%!
Compared with the original version, the THX AAA-788+ has a more unique design, which also went through some twists and turns.
At first, when we were testing the THX AAA-788, we were pleasantly surprised that it can maintain ultra-low distortion and noise under extremely high swings. As we all know, this feature fits perfectly with desktop devices, because desktop devices have a higher supply voltage and high output power while ordinary amplifiers will show nonlinear high noise floor at such a high gain.
However, as we dived into the product design, we found that the 788 actually has some shortcomings. For example, it can maintain 1.8W output power in the single-ended mode, but when two THX AAA-788 amps were combined for balanced output, the output heat exhaustion will quickly raise due to the temperature rise, and it cannot last for a long time at all.
Actually, this problem only occurred in strict test conditions and would not be easily realized by ordinary customers. But it was not permitted in the K9 Pro not only because it was a flagship, but also because of FiiO's strict quality control.
Therefore, we must work with the THX team to find a solution with a stronger load capacity.
After rounds of discussions, back-and-forth email communications, as well as repeated testing and listening experiments by our engineers, we eventually figured out a new rear driver chip, the TPA6120.
This is an ordinary yet well-known chip. It is ordinary because of his low-key presence in many TI products. The keywords introduced on its official website are:
Current feedback ‖ SNR of 128dB ‖ THD of 112.5dB ‖ 0.9µV at Gain = 1 ‖ 1300V/µs Slew Rate
Although it is very common, it is still an outstanding amp chip featuring high-performance audio specifications.
It is well-known because it was used in tons of famous audio brands, such as Sennheiser HDV, SONY DMP-Z1/PHA, and Klipsch Heritage.
Sennheiser HDV:
SONY DMP-Z1/PHA:
Of course, FiiO has also used it on many products, such as the E9 docking amp, the X7 AM5 power-hungry amp module, the K5 Pro, and now the K9 Pro. Experiencing small desktop, portable and large desktop, it has arrived at the fourth generation.
It can be said that we have learned how to make the best use of this chip. You may be confused why there are so many secrets of an amplifier chip?
Indeed, it is. Because the TPA6120 has a current feedback architecture, where a 10Ω resistor is required in series at the output end to prevent self-excitation capacitive loads. However, this output resistance is detrimental to the sound quality of the amp.
In summary, the output impedance of the amplifier will affect the frequency division of multi-driver earphones! We have solved this problem as early as the K5 after research and design improvements on multiple projects. The output impedance of the TPA6120 amplifier is greatly reduced to about 1Ω.
Such output performance not only improves the fidelity of multi-driver earphones, but also improves the damping characteristics of the amplifier, which can drive large dynamic driver earphones with ease.
Since the THX AAA-788 can bring such a large power increase by changing the rear amplification, are other performances equally excellent and qualified to be the THX?
The answer is yes. As mentioned above, THX and FiiO participated in this circuit upgrade together, and the circuit change occupies a large proportion in the development process of the K9 Pro.
While maintaining the circuit architecture of the THX AAA, the characteristics of error correction and multi-level excitation are still maintained. In order to guarantee a very high level when dealing with both low-power amplification and large dynamic output, engineers added multi-level hardware gains to the original circuit, which is a combination of both ability and character.
And the "THX AAA-788+" is also a customized model specially given to us by THX. This small "+" embodies the joint efforts and persistence of both of us.
Now you may understand why our new amp model is called "THX AAA-788+". If you want to learn more about THX AAA amp technology, please pay attention to my next chapter.
[Update completed]FiiO K9 Pro R&D Stories
- Thread starter FiiO
- Start date
-
- Tags
- fiio fiio k9 pro
xtreme4099
Headphoneus Supremus
- Joined
- Apr 10, 2003
- Posts
- 1,665
- Likes
- 50
@FiiO out of curiosity, why was the 888 not workable for this design ? Or is there a K9 Ultra due out in the near future? 
Last edited:
Chapter 3-2 What exactly is the THX AAA-788+ amp module?
This is the second part of chapter 3. We will still talk about the same topic about the THX AAA-788+ amp technology.
A few days ago, I made an introduction to the THX AAA amp technology, which attracted many users' attention. We have received a lot of feedback about the sound performance of the K9 Pro.
As for the THX AAA-788+ headphone amplifier, some users asked what are the differences in specifications compared to the original version?
In fact, compared to the original version, the THX AAA-788+ has increased the continuous output power that the single-ended output has been increased from 1.2W to 1.9W. In addition, the original version has no balanced output, while the new one has up to 2W balanced output.
Here I also attached a detailed comparison table.
"Continuous output" guarantees the long-term working ability of the product under extreme conditions. Although not everyone will be under extreme conditions, this is what we must do as a responsible HiFi brand!
Any technology is no easy access but careful application after repeated debugging, detailed testing and evaluation.
As a decoding headphone amplifier with a fully balanced
architecture, the K9 Pro needs 2 sets of THX headphone amplifiers to form a four-channel amp architecture. When applied to an actual product, this was also a challenge for engineers that they had to spend a lot of time and energy on debugging. Eventually, perseverance and efforts achieved a flagship. Your praise and satisfaction are the best gifts for our hardware engineers and the project team.
By the way, some users are concerned about the amplifier of the M17.
We have made some replies elsewhere. The M17 also uses the THX AAA-788+ amp technology. However, the M17 is much smaller than the K9 Pro because it is a portable product. Therefore, we will slightly reduce the output of some amps used to ensure the overall performance.
Whether we will use the THX AAA-888 is still a question due to its relatively large power. See the table below.
We have also conducted a comprehensive test. However, there is no product that fits it currently. Maybe in the future, there will be. Let's look forward to it.
By the way, you may notice that there was no professional media review of the K9 Pro. This is because we made some adjustments under special situations.
The limited AK4499EQ chip decided the limited number of the K9 Pro. If we distributed some to media review, a supply shortage issue would absolutely occur. Therefore, it will be unfair for those who want to buy one after checking on the reviews. Therefore, we did not arrange media reviews. Hope you can understand.
This is the second part of chapter 3. We will still talk about the same topic about the THX AAA-788+ amp technology.
A few days ago, I made an introduction to the THX AAA amp technology, which attracted many users' attention. We have received a lot of feedback about the sound performance of the K9 Pro.
As for the THX AAA-788+ headphone amplifier, some users asked what are the differences in specifications compared to the original version?
In fact, compared to the original version, the THX AAA-788+ has increased the continuous output power that the single-ended output has been increased from 1.2W to 1.9W. In addition, the original version has no balanced output, while the new one has up to 2W balanced output.
Here I also attached a detailed comparison table.
"Continuous output" guarantees the long-term working ability of the product under extreme conditions. Although not everyone will be under extreme conditions, this is what we must do as a responsible HiFi brand!
Any technology is no easy access but careful application after repeated debugging, detailed testing and evaluation.
As a decoding headphone amplifier with a fully balanced
architecture, the K9 Pro needs 2 sets of THX headphone amplifiers to form a four-channel amp architecture. When applied to an actual product, this was also a challenge for engineers that they had to spend a lot of time and energy on debugging. Eventually, perseverance and efforts achieved a flagship. Your praise and satisfaction are the best gifts for our hardware engineers and the project team.
By the way, some users are concerned about the amplifier of the M17.
We have made some replies elsewhere. The M17 also uses the THX AAA-788+ amp technology. However, the M17 is much smaller than the K9 Pro because it is a portable product. Therefore, we will slightly reduce the output of some amps used to ensure the overall performance.
Whether we will use the THX AAA-888 is still a question due to its relatively large power. See the table below.
We have also conducted a comprehensive test. However, there is no product that fits it currently. Maybe in the future, there will be. Let's look forward to it.
By the way, you may notice that there was no professional media review of the K9 Pro. This is because we made some adjustments under special situations.
The limited AK4499EQ chip decided the limited number of the K9 Pro. If we distributed some to media review, a supply shortage issue would absolutely occur. Therefore, it will be unfair for those who want to buy one after checking on the reviews. Therefore, we did not arrange media reviews. Hope you can understand.
Now you could get the answer for chapter 3-2.@FiiO out of curiosity, why was the 888 not workable for this design ? Or is there a K9 Ultra due out in the near future?
And here is also the answer from the product manger:
Best regards
Last edited:
They had 2 years to figure it out,only two other manufacturers had + designs Drop and Monoprice and those we're made 2 or 3 years ago.@FiiO out of curiosity, why was the 888 not workable for this design ? Or is there a K9 Ultra due out in the near future?
Last edited:
Didn't Wolf at l7 review a prototype?, release the final AP results please.Also since it now in production and for sale send a final product to Wolf,Amir and Jude for measurements, thank youChapter 3-2 What exactly is the THX AAA-788+ amp module?
This is the second part of chapter 3. We will still talk about the same topic about the THX AAA-788+ amp technology.
A few days ago, I made an introduction to the THX AAA amp technology, which attracted many users' attention. We have received a lot of feedback about the sound performance of the K9 Pro.
As for the THX AAA-788+ headphone amplifier, some users asked what are the differences in specifications compared to the original version?
In fact, compared to the original version, the THX AAA-788+ has increased the continuous output power that the single-ended output has been increased from 1.2W to 1.9W. In addition, the original version has no balanced output, while the new one has up to 2W balanced output.
Here I also attached a detailed comparison table.
"Continuous output" guarantees the long-term working ability of the product under extreme conditions. Although not everyone will be under extreme conditions, this is what we must do as a responsible HiFi brand!
Any technology is no easy access but careful application after repeated debugging, detailed testing and evaluation.
As a decoding headphone amplifier with a fully balanced
architecture, the K9 Pro needs 2 sets of THX headphone amplifiers to form a four-channel amp architecture. When applied to an actual product, this was also a challenge for engineers that they had to spend a lot of time and energy on debugging. Eventually, perseverance and efforts achieved a flagship. Your praise and satisfaction are the best gifts for our hardware engineers and the project team.
By the way, some users are concerned about the amplifier of the M17.
We have made some replies elsewhere. The M17 also uses the THX AAA-788+ amp technology. However, the M17 is much smaller than the K9 Pro because it is a portable product. Therefore, we will slightly reduce the output of some amps used to ensure the overall performance.
Whether we will use the THX AAA-888 is still a question due to its relatively large power. See the table below.
We have also conducted a comprehensive test. However, there is no product that fits it currently. Maybe in the future, there will be. Let's look forward to it.
By the way, you may notice that there was no professional media review of the K9 Pro. This is because we made some adjustments under special situations.
The limited AK4499EQ chip decided the limited number of the K9 Pro. If we distributed some to media review, a supply shortage issue would absolutely occur. Therefore, it will be unfair for those who want to buy one after checking on the reviews. Therefore, we did not arrange media reviews. Hope you can understand.
Last edited:
Chapter 4 Why would it take 1~2 months or even longer to change the chip scheme once?
After the K9 Pro stories were shared, some customers questioned that isn't it easy to change the chip? Some brands can get it done in just a week. Why do you need at least one or two months?
I don't know the mobile phone manufacturer, but in the HiFi industry, it may be possible that certain manufacturers may succeed in changing chip schemes in just a week. However, it is under extreme conditions.
For FiiO, chip changing is not as simple as changing clothes, but a rigorous debugging and verification process. As I know, the following procedures are indispensable.
1. Selection and evaluation of the chip and change of PCB
--This process will take at least 1~2 weeks. It is relatively easy for the PIN to PIN chip replacement. But for non-PIN to PIN, it needs several steps, including PCB change, re-sampling, which will take about half a month. Unfortunately, the chip scheme changing of the K9 Pro is a non-PIN to PIN.
2. PCBA testing and debugging
The new PCB should be retested and re-debugged due to the chip and peripheral circuit changes. This is a tortuous and lengthy process, and a big challenge for engineers.
All indicators and important experiments (such as ESD) must be redone, which will last for a week. If problems are found, the time duration will be doubled.
3. Audio parameter adjusting
After changing the DAC, audio products must be assembled into a complete machine before testing the sound, and then we can adjust the audio parameters to ensure its characteristics. This is another one-week job.
In conclusion, the simplest chip change will take about a month.
The above are changes in the development stage. If it is in the trial production or mass production stage, or if the product is already on the market, it will take much more time. Why?
If a problem occurs in mass production, it will cause a large loss. To avoid it, we need a complete quality index test, reliability test and environmental test other than the above 3 tests mentioned, so that we can conduct a 100~500 units trial production.
It takes one and a half months to two months from the trial production of the PCB to the final completion. And then it needs at least 1 week to carry out various tests before mass production. For mass production, it takes another one and a half months to two months.
Therefore, if it is a product that is already on the market, it may take 2 to 3 months or even longer to change the main chip! Every change of every product is almost the same. Persistence and careful execution can ensure fewer mistakes and improve efficiency.
Maybe you think it's too tedious and unnecessary, but it is this attitude that ensures continuous improvement and stable production. What is more, for FiiO, supply shortage is never a hunger marketing approach. We just need more time to organize production.
After the K9 Pro stories were shared, some customers questioned that isn't it easy to change the chip? Some brands can get it done in just a week. Why do you need at least one or two months?
I don't know the mobile phone manufacturer, but in the HiFi industry, it may be possible that certain manufacturers may succeed in changing chip schemes in just a week. However, it is under extreme conditions.
For FiiO, chip changing is not as simple as changing clothes, but a rigorous debugging and verification process. As I know, the following procedures are indispensable.
1. Selection and evaluation of the chip and change of PCB
--This process will take at least 1~2 weeks. It is relatively easy for the PIN to PIN chip replacement. But for non-PIN to PIN, it needs several steps, including PCB change, re-sampling, which will take about half a month. Unfortunately, the chip scheme changing of the K9 Pro is a non-PIN to PIN.
2. PCBA testing and debugging
The new PCB should be retested and re-debugged due to the chip and peripheral circuit changes. This is a tortuous and lengthy process, and a big challenge for engineers.
All indicators and important experiments (such as ESD) must be redone, which will last for a week. If problems are found, the time duration will be doubled.
3. Audio parameter adjusting
After changing the DAC, audio products must be assembled into a complete machine before testing the sound, and then we can adjust the audio parameters to ensure its characteristics. This is another one-week job.
In conclusion, the simplest chip change will take about a month.
The above are changes in the development stage. If it is in the trial production or mass production stage, or if the product is already on the market, it will take much more time. Why?
If a problem occurs in mass production, it will cause a large loss. To avoid it, we need a complete quality index test, reliability test and environmental test other than the above 3 tests mentioned, so that we can conduct a 100~500 units trial production.
It takes one and a half months to two months from the trial production of the PCB to the final completion. And then it needs at least 1 week to carry out various tests before mass production. For mass production, it takes another one and a half months to two months.
Therefore, if it is a product that is already on the market, it may take 2 to 3 months or even longer to change the main chip! Every change of every product is almost the same. Persistence and careful execution can ensure fewer mistakes and improve efficiency.
Maybe you think it's too tedious and unnecessary, but it is this attitude that ensures continuous improvement and stable production. What is more, for FiiO, supply shortage is never a hunger marketing approach. We just need more time to organize production.
Chapter 5 R&D Process of Desktop DAC/Amp-- Power Supply of FiiO K9 Pro
Tips: This chapter was modified based on technical contents written by FiiO's R&D Director Mr. Zhang. From here, you can learn more about the power supply design of our desktop devices. Welcome to join us in the discussion.
The K9 Pro can be said to be FiiO's first true desktop DAC/Amp. What are the main differences between desktop and portable products? Will it decide and influence the design of the product?
1. Different usage scenarios
Due to the built-in audio source and decoding and amplification, portable devices are generally used with earphones or Bluetooth audio transmitters, so the power requirements are not particularly high.
While desktop devices have more abundant connections. They can be connected to sound sources, such as computers, digital audio streamers, game consoles, turntables or CD players, and be connected to terminal devices, such as headphones, active speakers, front-end/rear-end op-amps. Most audiophiles even like a combination of them, so there will be more ways to play with the K9 Pro.
2. Different signal kinds
Unlike portable products, desktop DAC/Amps need to deal with more types of audio signals, involving digital signals, clocks, small analog signals, and large dynamic amplifying drives. Especially when driving large dynamics and large currents for desktop devices, a large amplification is required. Often, a little bit of crosstalk will be amplified and introduced into the amp stage (The magnification times of the K9 Pro goes up to 18).
3. Although it is quite different from portable products, desktop devices have larger internal space for a better design.
Since we knew it was possible, we made it start! How did we do it?
First of all, the usage scenarios are changeable and the collocation is complicated. So the first issue we should solve is "interference at power supply".
In fact, many senior audiophiles are very fond of audio filters, which can filter out the interference and clutter of the power supply through inductance and capacitance.
The linear transformer used in the K9 Pro is a large inductance wound by a coil. It is matched with 4 4700uF Nichicon capacitors, which handle low frequencies and have strong anti-interference ability.
For interference at high frequencies, our engineers designed a circuit at the power input end similar to the power filter on the market to complete the primary power filter.
For some potential differences caused by system connection, the K9 Pro uses a true three-core power socket according to the method of class I electrical appliances, which at the same time enhances the safety of the power supply and anti-interference ability.
Secondly, we managed to prevent the intersection of digital and analog circuits from the source in terms of the design. Because of the large size of the desktop devices, the internal space is also larger. The first point we thought of was how to achieve a divisional design.
In addition, we adopted an isolation transformer to prevent the intersection between digital and analog power supplies.
The isolation transformer separates the digital and analog power and ground electrode, so there is almost no crosstalk between the digital and analog sections. The figure below shows the working principle of an isolation transformer.
Other than the isolated power supply design, special attention was also paid to the power stabilization and filtering within the audio circuit- the first voltage stabilization is performed after DC filtering, and then a second stabilization is added to the power supply of each module circuit.
After the Ti's TPS7A series is used for the first-stage voltage stabilization, the noise and ripple of the power supply have been attenuated by 70dB (1kHz as an example). Generally speaking, it has been reduced by 10 million times.
And then after the second voltage stabilization, it has been attenuated by another 70dB to 140dB. At this time, the output of the power supply is very pure.
We have spent a lot of effort on the K9 Pro, which is sort of FiiO's first desktop device. During the research and development process, we have considered all aspects of the power supply design from various angles, such as the characteristics of desktop products and usage scenarios.
At the same time, we made use of the space advantages of desktop products by designing reasonable partitions for the primary filter, digital-to-analog isolation, signal power and multi-level voltage stabilization. Interpret the concept of "electricity is the mother of sound" in an all-around way.
The knowledge, innovation and accumulation in the middle of the process not only made the K9 Pro live up to FiiO's flagship DAC/Amp, but also laid a solid foundation for our future desktop players and other products.
I believe in the future, we will provide better products for our users.
Tips: This chapter was modified based on technical contents written by FiiO's R&D Director Mr. Zhang. From here, you can learn more about the power supply design of our desktop devices. Welcome to join us in the discussion.
The K9 Pro can be said to be FiiO's first true desktop DAC/Amp. What are the main differences between desktop and portable products? Will it decide and influence the design of the product?
1. Different usage scenarios
Due to the built-in audio source and decoding and amplification, portable devices are generally used with earphones or Bluetooth audio transmitters, so the power requirements are not particularly high.
While desktop devices have more abundant connections. They can be connected to sound sources, such as computers, digital audio streamers, game consoles, turntables or CD players, and be connected to terminal devices, such as headphones, active speakers, front-end/rear-end op-amps. Most audiophiles even like a combination of them, so there will be more ways to play with the K9 Pro.
2. Different signal kinds
Unlike portable products, desktop DAC/Amps need to deal with more types of audio signals, involving digital signals, clocks, small analog signals, and large dynamic amplifying drives. Especially when driving large dynamics and large currents for desktop devices, a large amplification is required. Often, a little bit of crosstalk will be amplified and introduced into the amp stage (The magnification times of the K9 Pro goes up to 18).
3. Although it is quite different from portable products, desktop devices have larger internal space for a better design.
Since we knew it was possible, we made it start! How did we do it?
First of all, the usage scenarios are changeable and the collocation is complicated. So the first issue we should solve is "interference at power supply".
In fact, many senior audiophiles are very fond of audio filters, which can filter out the interference and clutter of the power supply through inductance and capacitance.
The linear transformer used in the K9 Pro is a large inductance wound by a coil. It is matched with 4 4700uF Nichicon capacitors, which handle low frequencies and have strong anti-interference ability.
For interference at high frequencies, our engineers designed a circuit at the power input end similar to the power filter on the market to complete the primary power filter.
For some potential differences caused by system connection, the K9 Pro uses a true three-core power socket according to the method of class I electrical appliances, which at the same time enhances the safety of the power supply and anti-interference ability.
Secondly, we managed to prevent the intersection of digital and analog circuits from the source in terms of the design. Because of the large size of the desktop devices, the internal space is also larger. The first point we thought of was how to achieve a divisional design.
In addition, we adopted an isolation transformer to prevent the intersection between digital and analog power supplies.
The isolation transformer separates the digital and analog power and ground electrode, so there is almost no crosstalk between the digital and analog sections. The figure below shows the working principle of an isolation transformer.
Other than the isolated power supply design, special attention was also paid to the power stabilization and filtering within the audio circuit- the first voltage stabilization is performed after DC filtering, and then a second stabilization is added to the power supply of each module circuit.
After the Ti's TPS7A series is used for the first-stage voltage stabilization, the noise and ripple of the power supply have been attenuated by 70dB (1kHz as an example). Generally speaking, it has been reduced by 10 million times.
And then after the second voltage stabilization, it has been attenuated by another 70dB to 140dB. At this time, the output of the power supply is very pure.
We have spent a lot of effort on the K9 Pro, which is sort of FiiO's first desktop device. During the research and development process, we have considered all aspects of the power supply design from various angles, such as the characteristics of desktop products and usage scenarios.
At the same time, we made use of the space advantages of desktop products by designing reasonable partitions for the primary filter, digital-to-analog isolation, signal power and multi-level voltage stabilization. Interpret the concept of "electricity is the mother of sound" in an all-around way.
The knowledge, innovation and accumulation in the middle of the process not only made the K9 Pro live up to FiiO's flagship DAC/Amp, but also laid a solid foundation for our future desktop players and other products.
I believe in the future, we will provide better products for our users.
END
Last edited:
Hapo
New Head-Fier
...I am intersted in this primarily as a DAC...the head phone amp would not be irrelevent but see little use...I quess I am asking how ell implemented the DAC chip is...I understand and appreciate the R+D that went into the amp and wonder if the same consderation was givin to DAC perfomance...
...how do you feel the sound quality compares to Monoprice Monolith Desktop Headphone Amplifier and DAC with THX AAA Technology (Dual AKM 4493 DACs & Dual AAA-788 Modules) or RME ADI-2 as DAC only...???...
...it is ironic that the DACs I seem most intersted in are consdiered head phone amps...
...please understand that I was excited to discover this product in a thread on ASR...I may purchase this despite having a Monolith in the mail...
...how long have they been available @ Amazon...???...do the ones there have the AKM 4499 chip...???...have you started production of the ESS version...???...is that is what is selling @ Amazon...???...
...how do you feel the sound quality compares to Monoprice Monolith Desktop Headphone Amplifier and DAC with THX AAA Technology (Dual AKM 4493 DACs & Dual AAA-788 Modules) or RME ADI-2 as DAC only...???...
...it is ironic that the DACs I seem most intersted in are consdiered head phone amps...
...please understand that I was excited to discover this product in a thread on ASR...I may purchase this despite having a Monolith in the mail...
...how long have they been available @ Amazon...???...do the ones there have the AKM 4499 chip...???...have you started production of the ESS version...???...is that is what is selling @ Amazon...???...
Last edited:
Dear friend,
The K9Pro ESS version is not available in oversea market yet. And due to individual preferences, you could read the professional reviews and comparisons, as well as try out by yourself.
Best regards
Users who are viewing this thread
