A Closer Look at the Fosi BT20A Pro and Aiyima A07 Amplifiers

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I had the chance to listen to two budget class-D amplifiers, namely the Aiyima A07 and the Fosi BT20A Pro. I'd like to share my thoughts and experiences with these amplifiers, with the hope that it might assist someone who's trying to decide between the two. While I don't claim to be a seasoned audiophile and haven't had the opportunity to audition numerous other amplifiers, I can certainly provide a comparative analysis of these two models.

tempImageddWoBi.jpg

Getting Started
The Fosi Audio BT20A Pro and Aiyima A07 are compact Class D stereo amplifiers, driven by the Texas Instruments TPA3255 chip. They both come with relatively large DC adaptors. The BT20A Pro is accompanied by a 32V 5A adaptor, while the A07 ships with a 36V 6A adaptor. Additionally, the BT20A Pro offers Bluetooth 5.0 connectivity and incorporates tone controls, features that the A07 lacks.

Exterior Design and Appearance
The BT20A Pro's panel design caters to those who appreciate vibrant colors. Its distinctive orange aluminum knob stands out as a striking contrast. However, if your audio setup predominantly features black components, the BT20A Pro's appearance might not blend seamlessly. On the other hand, the A07 boasts a classic black panel that appeals to individuals with more traditional tastes.

Now, about its size. The BT20A pro is a bit on the compact side, especially when compared to the Aiyima A07. But honestly, I'm not entirely convinced that compactness is a major advantage when it comes to amplifiers, at least not in terms of usability. Personally, I'm someone who appreciates a beefier volume knob. The BT20A Pro, with its eye-catching orange knob, does look fantastic, but it's a bit too small for my liking. And let's not forget, they've got those two tone control knobs to fit in there too, making for quite a crowded space.

Image 2.jpeg

One gripe I have is that these knobs lack any markings for minimum or maximum limits. The tone control knobs are nicely centered at the 12 o'clock position, which is great. But here's where it gets tricky – if you assume the same scale for the volume knob, you're in for a surprise. Nope, the 50% volume setting is at 2 o'clock on the knob, not the expected 12 o'clock. A bit more intuitive marking would have been a welcome addition.

Comparatively, the Aiyima A07, without the tone controls, offers a more spacious front panel with ample space for a comfortably-sized volume knob, complete with clear markings indicating the minimum and maximum limits.

image-jpeg.80364


Shifting our focus to the rear panels of both amplifiers, you'll find they both feature standard RCA connectors for input as well as a 3.5mm AUX port that can serve as both input and output. Additionally, they come equipped with two sets of compact speaker binding posts. I would suggest opting for banana plugs when connecting your speakers since dealing with bare wires can be a bit tricky due to the closely placed terminals.

The Aux port provides the flexibility to connect to a powered subwoofer or another amplifier, making it suitable for setting up a separate audio zone. Now, here's where they differ: with the A07, the Aux out functions as a pure bypass. It allows the signal to pass through even if the amplifier is in standby mode. However, please note that there's no volume control for the pre-out on the A07.

On the other hand, the BT20A Pro offers a pre-out with volume control. This means that it's not just a simple bypass; you can adjust the volume. This feature can be quite advantageous for multi-zone audio setups, as you can control the volume for the 2nd zone using the BT20A Pro. Interestingly, when you switch off the BT20A Pro amplifier, the volume controls on the pre-out are bypassed as well.

Lastly, concerning the DC input, both amplifiers can handle a voltage range of 24V to 48V, allowing you to use a compatible adapter within this range depending on how much juice you need for your setup.

Sound Quality
When it comes to sound quality, both amplifiers truly shines, offering an impressive audio experience considering its affordable price point. It delivers clean and detailed sound with a warm signature that suits a wide range of music genres.

To compare its sound quality with the Aiyima A07, I conducted an A/B test using a DIY connector to switch between both amplifiers connected to my Elac Debut B2.6 speakers. The source was an SMSL D6 DAC. It's worth noting that this setup isn't perfect because the Aiyima A07 came with a 36V 6A DC adapter, while the BT20A Pro had a 32V 5A adapter. To level the playing field, I adjusted the Aiyima A07's volume to 50% and the BT20A Pro's to around 75% until they sounded equally loud.

tempImagel6hCqs.jpgtempImageSvak3g.jpg

I even swapped the DC adapters between the amplifiers (with appropriate volume adjustments), and the results remained consistent. In blind A/B testing, the sound from both amplifiers was indistinguishable. However, there was a subtle difference in bass response with the BT20A Pro, which seemed slightly more pronounced compared to the Aiyima A07. I ensured that the tone control knobs were set to neutral positions. It's unclear whether this increase in bass was due to a minor discrepancy in the detents or if the original recording itself contained that extra bass, which the Aiyima A07 wasn't reproducing. This difference was noticeable only during the A/B testing setup, and during normal listening, it's hardly discernible.

Tone Controls on the Fosi BT20A
Now, I know in the audiophile world, some folks frown upon the very idea of having tone controls. But personally, I think having the option to fine-tune your treble and bass is a good thing.

The tone control knobs come with these neat little neutral detents, which are essentially these handy midpoint markers. Setting them to a neutral position is a breeze, and the feedback you get from these detents is pretty satisfying.

And now, the important part – do the tone controls actually work? Yes, they do, and they work well. Cranking up the bass by about 50% really does make a noticeable difference. I mean, you can practically feel the air whooshing out of those speaker ports. If you're into movie nights with some seriously beefed-up bass, this feature is right up your alley.

Now, when we turn our attention to the Aiyima A07, it takes a different approach. You won't find any tone controls here. If you're the kind of listener who believes in experiencing music exactly as the producer intended, this might strike a chord with you. After all, in the budget class, most people aren't obsessing over these details. It all comes down to personal preference, and both amplifiers cater to different tastes in this regard.

Bluetooth on the BT20A Pro

The Bluetooth connectivity is quite convenient, providing reliable performance even at distances of up to 30 feet. However, there's a minor quirk when it comes to Bluetooth functionality. When the amplifier is in pairing mode, it emits a subtle ticking sound through the speakers. This sound is only audible when you're in close proximity to the speakers and actively listening for it.

Additionally, the Bluetooth input takes precedence over the RCA connectors. If a previously paired Bluetooth device comes within range, the input automatically switches to Bluetooth mode. You'll notice this switch when the red LED indicator turns blue, indicating a Bluetooth connection.

To unpair a device, you'll need to perform a long press on the volume knob. However, I found that this long press lasts longer than 5 seconds, which might be a bit cumbersome. Shortening it to around 3 seconds could make the unpairing process more intuitive and efficient.

It is compatible with Bluetooth 5.0, but I would have preferred support for the latest Bluetooth codecs such as aptX and LDAC.

Heating

During a visit to a friend's place, I had the opportunity to experience the heat dissipation from a Class AB amplifier. It was almost like those amplifiers could double up as a stovetop for slow cooking! However, these Class D amplifiers are an entirely different story. I've run them for extended periods, sometimes exceeding 4 hours, at 50% volume, and they remained only slightly warm to the touch.

DC Adaptor Grounding Issue

An interesting point to note is that even though these adaptors have a 3-pin plug that connects to the socket, they only have 2 pins on the adaptor itself. This can result in a slight electrical tingling sensation when touching the amplifier. This "ground leak" issue can manifest as a faint hissing sound when the amplifiers are connected to speakers.

tempImageXcacz2.jpg

A simple solution to this problem is to run an external wire to establish a proper ground connection. In my setup, I utilized an empty coaxial socket on my external DAC to run a wire to the socket's ground. Once this is done, the slight hiss disappears.

Conclusion
For those contemplating between the Aiyima A07 and the Fosi Audio BT20A Pro, it's clear that both offer similar sound quality. Your choice should primarily depend on your specific needs. If you're in search of a straightforward power amplifier, the Aiyima A07 is the way to go. However, if you desire additional features like tone controls and Bluetooth connectivity, then the Fosi Audio BT20A Pro is the obvious choice. Additionally, the volume-controlled pre-out on the BT20A Pro is a valuable feature for multi-zone audio setups.

If you happen to possess either of these amplifiers, I'd love to hear your thoughts and comments regarding their performance.

tempimagehrw3ht-jpg.80368
 

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I had the chance to listen to two budget class-D amplifiers, namely the Aiyima A07 and the Fosi BT20A Pro. I'd like to share my thoughts and experiences with these amplifiers, with the hope that it might assist someone who's trying to decide between the two. While I don't claim to be a seasoned audiophile and haven't had the opportunity to audition numerous other amplifiers, I can certainly provide a comparative analysis of these two models.

View attachment 80362

Getting Started
The Fosi Audio BT20A Pro and Aiyima A07 are compact Class D stereo amplifiers, driven by the Texas Instruments TPA3255 chip. They both come with relatively large DC adaptors. The BT20A Pro is accompanied by a 32V 5A adaptor, while the A07 ships with a 36V 6A adaptor. Additionally, the BT20A Pro offers Bluetooth 5.0 connectivity and incorporates tone controls, features that the A07 lacks.

Exterior Design and Appearance
The BT20A Pro's panel design caters to those who appreciate vibrant colors. Its distinctive orange aluminum knob stands out as a striking contrast. However, if your audio setup predominantly features black components, the BT20A Pro's appearance might not blend seamlessly. On the other hand, the A07 boasts a classic black panel that appeals to individuals with more traditional tastes.

Now, about its size. The BT20A pro is a bit on the compact side, especially when compared to the Aiyima A07. But honestly, I'm not entirely convinced that compactness is a major advantage when it comes to amplifiers, at least not in terms of usability. Personally, I'm someone who appreciates a beefier volume knob. The BT20A Pro, with its eye-catching orange knob, does look fantastic, but it's a bit too small for my liking. And let's not forget, they've got those two tone control knobs to fit in there too, making for quite a crowded space.

View attachment 80363

One gripe I have is that these knobs lack any markings for minimum or maximum limits. The tone control knobs are nicely centered at the 12 o'clock position, which is great. But here's where it gets tricky – if you assume the same scale for the volume knob, you're in for a surprise. Nope, the 50% volume setting is at 2 o'clock on the knob, not the expected 12 o'clock. A bit more intuitive marking would have been a welcome addition.

Comparatively, the Aiyima A07, without the tone controls, offers a more spacious front panel with ample space for a comfortably-sized volume knob, complete with clear markings indicating the minimum and maximum limits.

image-jpeg.80364


Shifting our focus to the rear panels of both amplifiers, you'll find they both feature standard RCA connectors for input as well as a 3.5mm AUX port that can serve as both input and output. Additionally, they come equipped with two sets of compact speaker binding posts. I would suggest opting for banana plugs when connecting your speakers since dealing with bare wires can be a bit tricky due to the closely placed terminals.

The Aux port provides the flexibility to connect to a powered subwoofer or another amplifier, making it suitable for setting up a separate audio zone. Now, here's where they differ: with the A07, the Aux out functions as a pure bypass. It allows the signal to pass through even if the amplifier is in standby mode. However, please note that there's no volume control for the pre-out on the A07.

On the other hand, the BT20A Pro offers a pre-out with volume control. This means that it's not just a simple bypass; you can adjust the volume. This feature can be quite advantageous for multi-zone audio setups, as you can control the volume for the 2nd zone using the BT20A Pro. Interestingly, when you switch off the BT20A Pro amplifier, the volume controls on the pre-out are bypassed as well.

Lastly, concerning the DC input, both amplifiers can handle a voltage range of 24V to 48V, allowing you to use a compatible adapter within this range depending on how much juice you need for your setup.

Sound Quality
When it comes to sound quality, both amplifiers truly shines, offering an impressive audio experience considering its affordable price point. It delivers clean and detailed sound with a warm signature that suits a wide range of music genres.

To compare its sound quality with the Aiyima A07, I conducted an A/B test using a DIY connector to switch between both amplifiers connected to my Elac Debut B2.6 speakers. The source was an SMSL D6 DAC. It's worth noting that this setup isn't perfect because the Aiyima A07 came with a 36V 6A DC adapter, while the BT20A Pro had a 32V 5A adapter. To level the playing field, I adjusted the Aiyima A07's volume to 50% and the BT20A Pro's to around 75% until they sounded equally loud.

View attachment 80365View attachment 80366

I even swapped the DC adapters between the amplifiers (with appropriate volume adjustments), and the results remained consistent. In blind A/B testing, the sound from both amplifiers was indistinguishable. However, there was a subtle difference in bass response with the BT20A Pro, which seemed slightly more pronounced compared to the Aiyima A07. I ensured that the tone control knobs were set to neutral positions. It's unclear whether this increase in bass was due to a minor discrepancy in the detents or if the original recording itself contained that extra bass, which the Aiyima A07 wasn't reproducing. This difference was noticeable only during the A/B testing setup, and during normal listening, it's hardly discernible.

Tone Controls on the Fosi BT20A
Now, I know in the audiophile world, some folks frown upon the very idea of having tone controls. But personally, I think having the option to fine-tune your treble and bass is a good thing.

The tone control knobs come with these neat little neutral detents, which are essentially these handy midpoint markers. Setting them to a neutral position is a breeze, and the feedback you get from these detents is pretty satisfying.

And now, the important part – do the tone controls actually work? Yes, they do, and they work well. Cranking up the bass by about 50% really does make a noticeable difference. I mean, you can practically feel the air whooshing out of those speaker ports. If you're into movie nights with some seriously beefed-up bass, this feature is right up your alley.

Now, when we turn our attention to the Aiyima A07, it takes a different approach. You won't find any tone controls here. If you're the kind of listener who believes in experiencing music exactly as the producer intended, this might strike a chord with you. After all, in the budget class, most people aren't obsessing over these details. It all comes down to personal preference, and both amplifiers cater to different tastes in this regard.

Bluetooth on the BT20A Pro

The Bluetooth connectivity is quite convenient, providing reliable performance even at distances of up to 30 feet. However, there's a minor quirk when it comes to Bluetooth functionality. When the amplifier is in pairing mode, it emits a subtle ticking sound through the speakers. This sound is only audible when you're in close proximity to the speakers and actively listening for it.

Additionally, the Bluetooth input takes precedence over the RCA connectors. If a previously paired Bluetooth device comes within range, the input automatically switches to Bluetooth mode. You'll notice this switch when the red LED indicator turns blue, indicating a Bluetooth connection.

To unpair a device, you'll need to perform a long press on the volume knob. However, I found that this long press lasts longer than 5 seconds, which might be a bit cumbersome. Shortening it to around 3 seconds could make the unpairing process more intuitive and efficient.

It is compatible with Bluetooth 5.0, but I would have preferred support for the latest Bluetooth codecs such as aptX and LDAC.

Heating

During a visit to a friend's place, I had the opportunity to experience the heat dissipation from a Class AB amplifier. It was almost like those amplifiers could double up as a stovetop for slow cooking! However, these Class D amplifiers are an entirely different story. I've run them for extended periods, sometimes exceeding 4 hours, at 50% volume, and they remained only slightly warm to the touch.

DC Adaptor Grounding Issue

An interesting point to note is that even though these adaptors have a 3-pin plug that connects to the socket, they only have 2 pins on the adaptor itself. This can result in a slight electrical tingling sensation when touching the amplifier. This "ground leak" issue can manifest as a faint hissing sound when the amplifiers are connected to speakers.

View attachment 80367

A simple solution to this problem is to run an external wire to establish a proper ground connection. In my setup, I utilized an empty coaxial socket on my external DAC to run a wire to the socket's ground. Once this is done, the slight hiss disappears.

Conclusion
For those contemplating between the Aiyima A07 and the Fosi Audio BT20A Pro, it's clear that both offer similar sound quality. Your choice should primarily depend on your specific needs. If you're in search of a straightforward power amplifier, the Aiyima A07 is the way to go. However, if you desire additional features like tone controls and Bluetooth connectivity, then the Fosi Audio BT20A Pro is the obvious choice. Additionally, the volume-controlled pre-out on the BT20A Pro is a valuable feature for multi-zone audio setups.

If you happen to possess either of these amplifiers, I'd love to hear your thoughts and comments regarding their performance.

tempimagehrw3ht-jpg.80368

Your test has been almost near perfect.

1. You have used a switch to toggle. This is the most important point in a test. Beyond a second it is impossible for the brain to distinguish between two different passage of the same music

2. Don't bother about the 3 point, 2 point on the power supply. These are SMPS and hence your dc output is actually coming from the mains but with very fast switching. All SMPS will have this issue and all SMPS have enough protection to cut off mains in the event the switching stops and you get the full 230 * 1.414 DC out. So there is nothing you can do about the DC ground. Even if you do ground it, you will be doing something which will do nothing as you are using a SMPS.

3. Even with the SMPS, these new CLASS D amps have absolute zero hum. The circuit is such that the hum gets eliminated.

4. The bass really could be the tone control thing in the Fossi. There is no way you can bypass it (setting the knob to mid position is not the same thing as bypassing the tone control). Both use different op amp (Aiyima uses NE5532). Fosi probably uses a different one. The bass difference could be also because of that. NOTE: Aiyima is currently selling two A07 versions. One comes with the NE5532 op amp. The other, a bit more expensive, comes with the LM4562NA op amp. In india you are getting only the NE5532 version.

I too have the Aiyima 07. I don't like the tiny speaker terminals. But at that price one may not care. But it sure beats my valve amp by miles in terms of grunt, bass and HF. Compared to each and every amp, avrs that I have in the house, this one is dead silent. You can't hear your speakers even with the ear next to the speaker cone. Many times I have a hard time knowing if I have switched on the AMP.

But I don't think the power output is as advertized. The Chinese manufacturers are simply stating the power output of the chips from the chip specs of Texas Instruments. But again, for that price who cares?
 
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Thanks for sharing the details about SMPS converters. Honestly, I never really looked into how they work compared to linear power supplies, so your explanation was quite helpful.

Regarding the 3-pin versus 2-pin issue, it's interesting to hear your observations. I've seen laptops with 3-pin power supplies too, and it does make me wonder why these amplifiers use 2-pin plugs.

And, by the way, I appreciate you mentioning the opamps and their potential differences. It's cool that these amps allow for opamp replacement, and I'm curious try that out.
 
Thanks for sharing the details about SMPS converters. Honestly, I never really looked into how they work compared to linear power supplies, so your explanation was quite helpful.

Regarding the 3-pin versus 2-pin issue, it's interesting to hear your observations. I've seen laptops with 3-pin power supplies too, and it does make me wonder why these amplifiers use 2-pin plugs.
The SMPS supplies by design isolate the input and output. They are called class II supplies and don't require the earth connection. These SMPS use a small transformer to isolate the input and output and hence don't require 3 pins


 
The SMPS supplies by design isolate the input and output. They are called class II supplies and don't require the earth connection. These SMPS use a small transformer to isolate the input and output and hence don't require 3 pins


I have three AIYIMA A07's in my three setups purely as a power Amp and they are true value for money each powering the following speakers.
- Topping E30II DAC --> AIYIMA Tube A3 Tube Buffer --> AIYIMA A07 --> Mission QX2
- Fiio BT30Pro DAC --> AIYIMA Tube A3 Tube Buffer --> AIYUIMA A07 --> Elac Debut 5.2
- Fiio BT30Pro DAC --> AIYIMA Tube A3 Tube Buffer --> AIYUIMA A07 -->Old Sony Speakers (part of Mini Hifi System) (Desktop System)

From sound perspective it is as you mentioned, clear and transparent with very good amplification. From a listening point of view (again as it is very subjective), I could experience the sound stage open up slightly better when used with LM4562 NA Op Amps and a 36V 6A as compared to stock Op Amps and 32V 5A supply.

All of my setups have AIYIMA Tube A3 as a tube buffer which also opens up possibilities of both Tube and Op Amp rolling. The Tube Buffers also have been op-Amp rolled to LM4562 NA. For me in terms of listening, I enjoy using GE5654 and 6AK5 tubes in terms of the sound being not too warm and not too bright and for 6J1 tubes if you are looking for the warm sound. The stock tubes 6K4 are a good starting point though.

For someone like me who is quite new to HiFi, I feel owning an AIYIMA A07 represents a very good value / budget proposition.

Good Luck on your Op Amp Rolling journey.

Regards
Sam
 
I had the chance to listen to two budget class-D amplifiers, namely the Aiyima A07 and the Fosi BT20A Pro. I'd like to share my thoughts and experiences with these amplifiers, with the hope that it might assist someone who's trying to decide between the two. While I don't claim to be a seasoned audiophile and haven't had the opportunity to audition numerous other amplifiers, I can certainly provide a comparative analysis of these two models.

View attachment 80362

Getting Started
The Fosi Audio BT20A Pro and Aiyima A07 are compact Class D stereo amplifiers, driven by the Texas Instruments TPA3255 chip. They both come with relatively large DC adaptors. The BT20A Pro is accompanied by a 32V 5A adaptor, while the A07 ships with a 36V 6A adaptor. Additionally, the BT20A Pro offers Bluetooth 5.0 connectivity and incorporates tone controls, features that the A07 lacks.

Exterior Design and Appearance
The BT20A Pro's panel design caters to those who appreciate vibrant colors. Its distinctive orange aluminum knob stands out as a striking contrast. However, if your audio setup predominantly features black components, the BT20A Pro's appearance might not blend seamlessly. On the other hand, the A07 boasts a classic black panel that appeals to individuals with more traditional tastes.

Now, about its size. The BT20A pro is a bit on the compact side, especially when compared to the Aiyima A07. But honestly, I'm not entirely convinced that compactness is a major advantage when it comes to amplifiers, at least not in terms of usability. Personally, I'm someone who appreciates a beefier volume knob. The BT20A Pro, with its eye-catching orange knob, does look fantastic, but it's a bit too small for my liking. And let's not forget, they've got those two tone control knobs to fit in there too, making for quite a crowded space.

View attachment 80363

One gripe I have is that these knobs lack any markings for minimum or maximum limits. The tone control knobs are nicely centered at the 12 o'clock position, which is great. But here's where it gets tricky – if you assume the same scale for the volume knob, you're in for a surprise. Nope, the 50% volume setting is at 2 o'clock on the knob, not the expected 12 o'clock. A bit more intuitive marking would have been a welcome addition.

Comparatively, the Aiyima A07, without the tone controls, offers a more spacious front panel with ample space for a comfortably-sized volume knob, complete with clear markings indicating the minimum and maximum limits.

image-jpeg.80364


Shifting our focus to the rear panels of both amplifiers, you'll find they both feature standard RCA connectors for input as well as a 3.5mm AUX port that can serve as both input and output. Additionally, they come equipped with two sets of compact speaker binding posts. I would suggest opting for banana plugs when connecting your speakers since dealing with bare wires can be a bit tricky due to the closely placed terminals.

The Aux port provides the flexibility to connect to a powered subwoofer or another amplifier, making it suitable for setting up a separate audio zone. Now, here's where they differ: with the A07, the Aux out functions as a pure bypass. It allows the signal to pass through even if the amplifier is in standby mode. However, please note that there's no volume control for the pre-out on the A07.

On the other hand, the BT20A Pro offers a pre-out with volume control. This means that it's not just a simple bypass; you can adjust the volume. This feature can be quite advantageous for multi-zone audio setups, as you can control the volume for the 2nd zone using the BT20A Pro. Interestingly, when you switch off the BT20A Pro amplifier, the volume controls on the pre-out are bypassed as well.

Lastly, concerning the DC input, both amplifiers can handle a voltage range of 24V to 48V, allowing you to use a compatible adapter within this range depending on how much juice you need for your setup.

Sound Quality
When it comes to sound quality, both amplifiers truly shines, offering an impressive audio experience considering its affordable price point. It delivers clean and detailed sound with a warm signature that suits a wide range of music genres.

To compare its sound quality with the Aiyima A07, I conducted an A/B test using a DIY connector to switch between both amplifiers connected to my Elac Debut B2.6 speakers. The source was an SMSL D6 DAC. It's worth noting that this setup isn't perfect because the Aiyima A07 came with a 36V 6A DC adapter, while the BT20A Pro had a 32V 5A adapter. To level the playing field, I adjusted the Aiyima A07's volume to 50% and the BT20A Pro's to around 75% until they sounded equally loud.

View attachment 80365View attachment 80366

I even swapped the DC adapters between the amplifiers (with appropriate volume adjustments), and the results remained consistent. In blind A/B testing, the sound from both amplifiers was indistinguishable. However, there was a subtle difference in bass response with the BT20A Pro, which seemed slightly more pronounced compared to the Aiyima A07. I ensured that the tone control knobs were set to neutral positions. It's unclear whether this increase in bass was due to a minor discrepancy in the detents or if the original recording itself contained that extra bass, which the Aiyima A07 wasn't reproducing. This difference was noticeable only during the A/B testing setup, and during normal listening, it's hardly discernible.

Tone Controls on the Fosi BT20A
Now, I know in the audiophile world, some folks frown upon the very idea of having tone controls. But personally, I think having the option to fine-tune your treble and bass is a good thing.

The tone control knobs come with these neat little neutral detents, which are essentially these handy midpoint markers. Setting them to a neutral position is a breeze, and the feedback you get from these detents is pretty satisfying.

And now, the important part – do the tone controls actually work? Yes, they do, and they work well. Cranking up the bass by about 50% really does make a noticeable difference. I mean, you can practically feel the air whooshing out of those speaker ports. If you're into movie nights with some seriously beefed-up bass, this feature is right up your alley.

Now, when we turn our attention to the Aiyima A07, it takes a different approach. You won't find any tone controls here. If you're the kind of listener who believes in experiencing music exactly as the producer intended, this might strike a chord with you. After all, in the budget class, most people aren't obsessing over these details. It all comes down to personal preference, and both amplifiers cater to different tastes in this regard.

Bluetooth on the BT20A Pro

The Bluetooth connectivity is quite convenient, providing reliable performance even at distances of up to 30 feet. However, there's a minor quirk when it comes to Bluetooth functionality. When the amplifier is in pairing mode, it emits a subtle ticking sound through the speakers. This sound is only audible when you're in close proximity to the speakers and actively listening for it.

Additionally, the Bluetooth input takes precedence over the RCA connectors. If a previously paired Bluetooth device comes within range, the input automatically switches to Bluetooth mode. You'll notice this switch when the red LED indicator turns blue, indicating a Bluetooth connection.

To unpair a device, you'll need to perform a long press on the volume knob. However, I found that this long press lasts longer than 5 seconds, which might be a bit cumbersome. Shortening it to around 3 seconds could make the unpairing process more intuitive and efficient.

It is compatible with Bluetooth 5.0, but I would have preferred support for the latest Bluetooth codecs such as aptX and LDAC.

Heating

During a visit to a friend's place, I had the opportunity to experience the heat dissipation from a Class AB amplifier. It was almost like those amplifiers could double up as a stovetop for slow cooking! However, these Class D amplifiers are an entirely different story. I've run them for extended periods, sometimes exceeding 4 hours, at 50% volume, and they remained only slightly warm to the touch.

DC Adaptor Grounding Issue

An interesting point to note is that even though these adaptors have a 3-pin plug that connects to the socket, they only have 2 pins on the adaptor itself. This can result in a slight electrical tingling sensation when touching the amplifier. This "ground leak" issue can manifest as a faint hissing sound when the amplifiers are connected to speakers.

View attachment 80367

A simple solution to this problem is to run an external wire to establish a proper ground connection. In my setup, I utilized an empty coaxial socket on my external DAC to run a wire to the socket's ground. Once this is done, the slight hiss disappears.

Conclusion
For those contemplating between the Aiyima A07 and the Fosi Audio BT20A Pro, it's clear that both offer similar sound quality. Your choice should primarily depend on your specific needs. If you're in search of a straightforward power amplifier, the Aiyima A07 is the way to go. However, if you desire additional features like tone controls and Bluetooth connectivity, then the Fosi Audio BT20A Pro is the obvious choice. Additionally, the volume-controlled pre-out on the BT20A Pro is a valuable feature for multi-zone audio setups.

If you happen to possess either of these amplifiers, I'd love to hear your thoughts and comments regarding their performance.

tempimagehrw3ht-jpg.80368
I own the fosi bt20a pro and been using since 1 month...
I can say you have pointed out practically everything that I have noticed myself in the BT20A PRO..
Couple of things which you might have noticed but must have missed mentioning is the wobble of the volume knob and when idle if you lower or increase the volume you will hear a faint crackling hiss if you listen closely while being near the speakers...
These are non issue kind of issues tbh, but I have noticed them..

Another strange thing is I used some pretty local kinds of banana connectors and realised that the left channel was not sending any audio but as soon as I used bare wires with the audio out terminals it was fine.. Happened twice or thrice and always with those local connectors.. So since then I have changed them and haven't noticed anything... Any thoughts
 
Another strange thing is I used some pretty local kinds of banana connectors and realised that the left channel was not sending any audio but as soon as I used bare wires with the audio out terminals it was fine.. Happened twice or thrice and always with those local connectors.. So since then I have changed them and haven't noticed anything... Any thoughts
budget connectors usually have thin and uneven circular spring tube with slots having burr from stamping and unknown plating which does not make or makes very little contact. some have no proper screw to hold bare wire. contact may also not reach banana socket if both are low quality. in other words non contact may be the only reason.
regards.
 
I own the fosi bt20a pro and been using since 1 month...
I can say you have pointed out practically everything that I have noticed myself in the BT20A PRO..
Couple of things which you might have noticed but must have missed mentioning is the wobble of the volume knob and when idle if you lower or increase the volume you will hear a faint crackling hiss if you listen closely while being near the speakers...
These are non issue kind of issues tbh, but I have noticed them..

Another strange thing is I used some pretty local kinds of banana connectors and realised that the left channel was not sending any audio but as soon as I used bare wires with the audio out terminals it was fine.. Happened twice or thrice and always with those local connectors.. So since then I have changed them and haven't noticed anything... Any thoughts
Now that you mention it, I did notice a little wobble in the volume knob. Interestingly I've seen the same thing with the SMSL D6 DAC knob. Both of them have this push action, so it might be by design.

As for that faint crackling noise when you turn the volume knob - yep, I hear it too!

About the banana plugs, even though I suggested them in my previous post, I'm still sticking with bare wires because I don't plan on changing my setup all that often. I did spot some banana plugs for just Rs.20 each at a local electronics store, but I'm a bit worried they might mess with the sound quality, so I haven't tried them out. So, I haven't run into the issue of a blank left channel like you mentioned.

Thanks for pointing these things out!
 
There was a query if you folks or the OP could help..

Is this wise to keep the amp powered up all the time.. If yes how to put it in standby mode.. I believe the power switch turns it off completely...

Thanks
 
I also prefer to keep it on all the time for the convenience of playing music whenever I want. Especially with my "separates" setup, I need to switch on all the components and wait for the streamer to boot. My main concern about keeping the amplifier on all the time is the faint hiss from the speakers (power supply noise), and it keeps the speakers always engaged. While this slight hiss doesn't involve any moving parts and isn't expected to result in wear and tear on the speakers, I prefer not to have my speakers "working" continuously, especially since they are the costliest among all the other components.

For dedicated music sessions, I don't mind turning on all the components every time.
I prefer to have always-on system for casual listening. For that purpose, I currently use powered smart speakers. In my home, the Amazon Echo Show is on 24 hours, and I don't hear any hiss from the speakers. I always wonder about the efficiency of the electronic circuitry or its power supply for these speakers.

Regarding your question on how to put it on 'standby,' the toggle switch does the job. Flipping the toggle switch to "off" should cut off the current to the speakers, although the amplifier may still draw a minimal amount of power.

Well, this is just how I see it. I will let the experts share their thoughts.
 
Hi, I was wondering, if there are any budget options {by budget i mean cheapest possible} if one wishes to attach a bluetooth receiver cum dac cum preamp with the fosi bt20a pro...
I am finding the audio to be lacking the high frequencies... Thought of adding a bluetooth preamp with built in dac..
 
Off the top of my head, the Fiio BTA30 Pro at 10k is the most affordable option I know. It supports aptX HD and LDAC Bluetooth codecs with receive and transmit capabilities, but without an IR remote control. If remote volume control is a must, you might need to consider a higher budget. You can search for it on Headphonezone.
 
I have a different set of class d amps (smsl sa98e, fx audio fx1002, fx502, topping tp21) and I've found all of them having very lean bass compared to my class ab vintage amps ( na3020, Kenwood ka 405, Pioneer sa 606)
 
I just did some lookup and found that the iFi Audio ZEN Air Blue priced at 7k. It primarily has Bluetooth inputs. However, considering its features and the value for money, it seems like the Fiio BTA30 Pro offers a more versatile option with additional inputs and outputs.

I also came across the SMSL PS100, priced at 3.5k, but it's limited to the SBC codec, which your existing Fosi amp already supports. However, the PS100 with HDMI ARC functionality is intriguing. I'll create a new discussion thread to see if anyone here has experience with it.
 
Off the top of my head, the Fiio BTA30 Pro at 10k is the most affordable option I know. It supports aptX HD and LDAC Bluetooth codecs with receive and transmit capabilities, but without an IR remote control. If remote volume control is a must, you might need to consider a higher budget. You can search for it on Headphonezone.
Thanks
This is indeed great as a DAC and streamer but it doesn't have tone controls so there is no preamp controls in it...
Without preamp controls (though it's needed) what would you say about this
Xduoo xq50 pro 2
 
@sudikpr and all the other participants of this thread....
I am a bit puzzled.. When the fosi is idle,
I mean no music is playing and no matter if its connected via rca or via Bluetooth the amp is always dissipating heat.. It's always pretty warm to touch....
How is that possible??? When fosi itself says that it consumes extremely low power while idle and according to them there is no need to switch it off hence there is no standby feature...

Care to shed your obserations please.....
Thanks
 
I haven't consistently tried to keep it powered on, but on one occasion, I had it paired with a Bluetooth device for a couple of hours without any music being played. Surprisingly, the device became quite hot, not just warm. This is just my theory, but it's possible that the amplifier is continuously searching for devices to pair since it's not receiving any audio signal through RCA.
 
I haven't consistently tried to keep it powered on, but on one occasion, I had it paired with a Bluetooth device for a couple of hours without any music being played. Surprisingly, the device became quite hot, not just warm. This is just my theory, but it's possible that the amplifier is continuously searching for devices to pair since it's not receiving any audio signal through RCA.
But at my end it's connected to rca via my chromecast audio.. And no music is playing.. Still its a bit warm, wouldn't call it too warm and not at all hot but I am a bit confused, if it's getting warmer in idle state then leaving it on will definitely affect it's life...
 
You might consider starting a new thread to gather input from others regarding the heating issue. Additionally, Fosi has an active community group on Facebook. If you're on Facebook, you could also post your query there to get more insights and advice.

Hi, I was wondering, if there are any budget options {by budget i mean cheapest possible} if one wishes to attach a bluetooth receiver cum dac cum preamp with the fosi bt20a pro...
Fosi is giving us a sneak peek of their upcoming product, the P3, a Bluetooth tube pre-amp featuring tone controls. This pre-amp is designed to complement the V3 amplifier. You might want to check it out.
 
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