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Headphoneus Supremus
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Fosi Audio BT20A Pro Review
Fosi Audio BT20A Pro is a Class D, stereo, speaker amplifier. It has RCA and Bluetooth inputs, Banana Plug (also bare speaker wire) compatible and 3.5mm Pre-Out outputs. It is indicated that Pre-Out can be connected to a powered subwoofer.
Fosi Audio provided this BT20A Pro for my honest review. Thanks for this opportunity.
The customer relations with Fosi Audio company is great. Before this review unit I bought a Fosi Audio T20 Tube Amp with my money from their Aliexpress store and loved the product so much that I write a review in Head-Fi without thinking a minute (T20 Tube Amp Review Link: https://www.head-fi.org/threads/fosi-audio-t20-tube-amp-review-and-thread.968074/). During the review and testing phase of that amp -which became my main desktop/workspace headphone and speaker amp for Tannoy Mercury MX1 speakers and Beyerdynamic DT-150 headphones- I have contacted the technical support team many times and they always replied to me fast and answered my every question kindly. So I was amazed by their customer relations.
Technical Specs of BT20A Pro:
Max Power Output: 300Wx2 @4Ω
SNR: ≥108dB
Terminating Impedance: 2-8Ω
THD: 0.005%
Power Amplifier Chip: TPA3255
Power Supply: 32V 5A
Input Range: DC 24V-48V
Frequency Response Range:
20Hz-20kHz(±1.2dB)
Bluetooth Transmission Range: Up to 50Ft
Bluetooth Codec: AAC/SBC
Audio Input: RCA/Bluetooth
Audio Output: Speaker Output/3.5mm Pre-out
Fosi Audio 30 day return period, 18 month waranty and lifetime technical support claims which are written on the side of the box gives confidence.
What's in The Box?:
The Amp Box Includes These Items:
BT20A Pro Power Amplifier x1
Bluetooth Antenna x1
32V 5A Power Adapter x1
Power Adapter AC Cord x1
User Manual x1
Image: Courtesy of Fosi Audio
Fosi Audio BT20A Pro has an high-end amp chip (TPA3255) integrated in it. This chip is compatible with 24V-48V power supply and delivers premium class-D amplification.
Image: Courtesy of Fosi Audio
The op-amps in BT20A Pro are Texas Instruments NE5532. These op-amps are user replacable and you can replace them with MUSES02, OPA26041P, OPA2134PA, LME49720HA, LM4562 or NJM4556AD. This provides a broad range of sound signature customisation!
Image: Courtesy of Fosi Audio
There is an energy-saving circuit built in to the BT20A Pro which provides a clean shutdown of the unit (and costs no energy).
Image: Courtesy of Fosi Audio
The amp has full aluminum chasis with 4 rubberized feets which do not slip on the surfaces which I have tried; including: glass, raw smooth wood, marble, plastic, smooth concrete, painted metal and varnished wood. Foots supports the amp excellently.
Amp does not feel heavy because it is compact and use of light materials like aluminum (unit weights 547 g). The main chasis is one piece aluminum with front and back aluminum panels are attached to it via the screws on the back. BT20A Pro feels very solid in hand. I feel that it can handle some heavy equipments if paced on top of it which I ceratinly do not recommend because of the heat dissipation and also bluetooth range blockage. Amplifier has an internal heat sink which transfers the heat to the top panel and heat is then distrubuted to the whole aluminum chasis for dissipation.
The bluetooth antenna is on the back left side. It is compact and antenna angle can be adjusted by the user.
Unit does not get very warm like the Fosi Audio T20 Tube Amplifier but feels slightly warm when touched by the hand after extended use. The 32V 5A power adapter does not get warm at all.
BT20A Pro's color is different from most Fosi Audio amps (which are mainly black) and I really love this color which is like bluish-grey (it is so called: space blue).
The amp has on/off switch on the left side followed to the right by: Treble, Bass and Volume control knobs. Volume control knob doubles as a bluetooth unpair switch. You simply long press the knob to unpair your bluetooth device. But you can not get the pairing back by long pressing this knob again. You have to enable pairing again from the source (for example from your phone). Because of the bluetooth unpairing and volume control are carried on the same knob, the volume knob has some wobbling. But once you understand the cause and its 2 different functions you may not care this wobble feeling. Other than this con the volume knob turns very smoothly. I really love the copper color of the volume knob. It should be used as a signature on all Fosi Audio amps volume knobs (or can be used in higher end variants -in my opinion).
The tone controls are must in my using case because my Tannoy Mercury MX1 bookshelf speakers tonality needs some treble boost in order to sound correct to my ears. I feel this boost need with every amp that I connect to these MX1 speakers so there is no problem with the tonality of the Fosi Audio amp. I like that the middle (neutral) position of bass and treble control knobs have a clicky feedback to it so you can be sure when the knobs are in neutral position. The power On/Off/Bluetooth On led indicator is located on the lower left side of the power switch. I normally do not like shiny (producing strong light) power leds but this BT20A Pro led is very tiny for my taste. It is very difficult to see if the amp is on or off from a distance in day time (or night time from an angle). But I can understand why it is very tiny (or very recessed to the body). Just wanted to mention that I prefer to see the light in day time as well (or from an angle at night) and the light must be dim enough to not to disturb me at the night time.
On the front panel upper left side, you can see the brand and model name. I wish that the letters were slightly larger because in a normal sitting position many people can not even notice which brand and model amp this is. Also there is another con for the lettering: On / off switch have only one mark on the bottom part. So one can not be sure if it is on or off if the red 'on' indicator dies (Yes I know I am getting analytical here and I can understand if the designers like to prefer a clean look). The bass, treble and volume knobs letters are written below them. This approach is very rare and for my experience you have to bend your head to see which knob is which each time you try to adjust the tone (unless you place the amp over your head position). After getting used to the placement of bass and treble knobs there is no problem but I wish that all the letters were written above the knobs not below them. After using another Fosi Audio brand amp (T20 Tube Amp) for 4 months I did get used to the placement of the bass and treble knobs of that model amp. When I have the BT20A Pro I thought the right knob were treble so adjusted it without even noticing the tiny letters below the knobs. To my surprise it appeared to be bass knob this time. I advise Fosi Audio to not to change some main control knob placements between different models (in respect to designers; whenever possible and if the main design allows it). Because there is user experience and when a user choses a brand in the long term he/she wants to see some similar/old user experience friendly controls. We are talking about only two knob placements here but consistency is important in my opinion. I have to add in the end that these are not big cons and can be overcomed by user experience over time. I am just getting very analytical sometimes. May be another user would not care about these cons at all ! Or may be prefer the clean look of the face panel!
This review is based on three different usage scenarios; 1st: as a desktop amp connected with Tannoy Mercury MX1 bookshelf speakers. 2nd: as a stereo speaker connected with Dali Zensor 7 (White) floor standing speakers. 3rd: as a stereo and 2+1 setup with Pioneer S-H509V floor standing speakers and Pioneer S-W 110 Powered Subwoofer.
I always connect my amps to my speakers through banana connectors. I use RCA to 3.5mm stereo pure copper wires to connect the amp to my sources which are Mac Mini M2 and Macbook Air M1. I did not use any DAC or CD-DVD player intentionally in order to keep my review of speaker amps in-line. Power source of the amp is Fosi Audio's own 32V 5A power adapter which was connected to a power regulated 220V socket. Bluetooth connection were tested with an LG V30+ cellphone.
Comparisons with other amps included Yamaha RX-V663 (tested on Pure Direct mode disabling all equiliser and effects) and Fosi Audio BT20 Tube Amp.
Listening BT20A Pro through Tannoy Mercury MX1 Bookshelf Speakers:
Tannoy Mercury MX-1 are very old but well respected set of bookshelf speakers which incorporates ceramic coated paper cones and soft dome tweeters. I love their sound as a desktop stereo and monitoring set-up. I use them while video editing, music mixing and for general use on the workspace. Only drawback is: they lack some treble energy so I have to boost treble on every amp that I have tried with these speakers. Luckily BT20A Pro has tone controls so I can adjust the treble for the correct amount. I keep the bass on the neutral position because there is no need. BT20A Pro delivers clean, smooth and well defined sound with MX1's.
(BT20A Pro AMP on the left, T20 Tube AMP on the right)
After A-B'ing it with T20 Tube Amp I have concluded that only on this setup I will keep the T20 Tube Amp connected with it because T20 delivered more lively, more clear and musical sound. But with other speaker sets the situation changes so please keep reading. I have tried Yamaha RX-V663 previously with Tannoy's and prefer T20 Tube Amp at that time as well.
Tannoy Mercury MX1 Specs:
Enclosure Type: 2 way bass reflex (2 speaker units)
Max SPL: 100 Watts
FQ Response: 55Hz - 20kHz
Sensitivity: 87dB
Impedance: 8 Ohms
Drivers: 1 x 25mm High frequency soft textile dome
1 x 130mm Ceramic Coated Paper cone
Listening BT20A Pro through Dali Zensor 7 Floor Standing Speakers:
Before beginning this part I have to mention: I have a special interest and love with Dali brand speakers. I love the sound of Zensor 7 and it is the main component of my home theater and stereo set-up in my living room. The wood-fibre cones and soft dome tweeters of the Zensor 7 brings incredibly natural tones. Treble energy and clarity of Zensor 7's are already excellent so there is no need to adjust the tone control knobs with BT20A Pro. All I hear is clean, clear sound with wide soundstage and well defined bass. Midtone reproduction is excellent. Vocals and strings sounds amazing with this setup.
I have compared my home theater and stereo listening amp Yamaha RX-V663 's pure direct out to the BT20A Pro and they were so close that I could not decide which one to prefer. You can compare the size of the units and RX-V663 do not have bluetooth connection so it is less versatile option for stereo listening. But for movies, there is no competition because RX-V663 supports DTS-HD and 7+2 speaker setup. Main amp chip of RX-V663 is produced by Burr Brown company and with its *Pure Direct mode you get Hi-Fi reproduction from this amp. So Fosi Audio really brought smiles to my face while listening and comparing to Yamaha. You do not expect this kind of quality from such a small amp like BT20A Pro.
(*Pure Direct mode on Yamaha receivers disables all equaliser and digital effects)
I have included T20 Tube Amp to the comparisons and it was not a good match with Zensor 7's. The sound were not refined as the BT20A Pro and highs do have less natural reproduction. T20 Tube Amp adds some coloring to the sound and sounds less hi-fi in comparison.
While connected with BT20A Pro the background was dead silent as well. No audible hissing or buzzing sounds.
Dali Zensor 7 Floor Standing Speaker Specs:
Enclosure Type: 2 way bass reflex (3 speaker units)
Frequency Range: 40Hz - 26.5kHz
Sensitivity: 90 dB
Impedance: 6 Ohms
Max SPL: 110 Watts
Drivers: 1 x 25mm High frequency soft textile dome
2 x 7inch Low frequency Wood Fibre cone
Listening BT20A Pro through Pioneer S-H509V Floor Standing Speakers:
(My SUP Boards are excellent for decoration and acts like a sound absorber to cut unwanted reflections from a bare wall)
BT20A Pro sounds excellent with this 8 Ohm speakers. Although the Pioneer's tweeters do produce some hissing (background sounds when music is not playing) this is not native to the Fosi Audio amp, this speaker produces this kind of sound with every amp that I have tried and I believe it is because of the crossover unit implementation or tweeter sensitivity. Some amps exaggerate this and some amps do not.
When I play the music I hear clean, clear sound with good defined mid range and bass. Highs are smooth and never gets sibilant. Bass hits if the recording calls for it. When I connect Pioneer SUB Woofer (powered) to the pre-out I get great sub bass in addition to the other frequencsies. But I prefer to listen these speakers in stereo mode. So in a 2+1 scenario the BT20A pro can deliver the needed sub bass. But in order to obtain best results you have to adjust the frequency, phase, crossover and volume from the sub bass units control panel. Also I have to mention that in this usage scenario the amp is not acting like a real 2+1 amp, it only sends the pre-out signals and your powered subbas only delivers the bass frequency from there (from my understanding). I especially like the mid-range when paired with this Pioneers. Vocals and strings sounds amazing. Reproduction is life-like and without any sensible coloration to the sound. I crank the volume nearly all the way up with these speakers and luckily they did not blew up. All I hear were non-distorted, clean and powerful sound which was not ideal for a 35 square meter living room. So I have no doubt that the amp can deliver more than enough volume with 8 Ohm speaker units even with the 32V power adapter. If you have larger room or use open space and do not have any body in fear of disturbing you can prefer 48V power adapter to obtain the full volume potential of the BT20A Pro.
In comparison to the Fosi Audio T20 Tube Amp, BT20A Pro delivered smoother sound with well defined and layered instruments. T20 Tube Amp's only strength compared to BT20A Pro with this speaker that it sound slightly more lively. I feel and prefer BT20A Pro is more true to the source and less colored so prefered it over T20 for this setup.
Pioneer S-H509V Floor Standing Speaker Specs:
Enclosure Type: 2 way bass reflex (4 speaker units)
Frequency Range: 30Hz - 35kHz
Sensitivity: 90 dB
Impedance: 8 Ohms
Max SPL: 100 Watts
Drivers: 1 x 25mm High frequency soft textile dome
3 x 14cm Low frequency Paper Fibre cone
Bluetooth:
I have tested the range and it was approximately 15 meters. Inside the house reception range depends on the variables like walls and furniture. So it may be lesser. But I have no complaints for the range inside the biggest place of my house (which is my living room) and when I go to the kitchen with my phone and return, bluetooth were still delivering the data (without any cuts). I really wanted to see APTX-HD implementation with the amp but after comparing the sound quality with the APTX-HD supported T20 Tube Amp the bluetooth sound quality on the BT20A Pro is not bad at all and even very good.
Bluetooth connection requires enabling the pairing from the phone (or any other bluetooth compatible source) with the amp. There is no on/off Bluetooth switch on the amp. Bluetooth is always on unless you unpair your device fom the amp. The bluetooth connection time is around 3-5 seconds after pairing the 2 devices once. With my phone, sometimes the amp did not connect automaically so I have to open the bluetooth settings on my phone to see and connect the BT20A Pro. To unpair you can simply long press the volume knob. Bluetooth connection can be monitored through the power led color which turns from red to blue when a device is connected.
Conclusion of The Review:
Pros:
Powerful, smooth, clean, well defined sound
Bass and treble tone controls with clicky middle (0) position
Bluetooth input which have a good range and good enough audio quality
Upgradeable op-amps for future upgrades
Small footprint
Strong aluminum chasis
Rubber feet
Good implementation of quality audio components and heat sink
Pre-out support (can also be used for a powered subwoofer connection in a 2+1 scenario)
Plated connections (speaker outs supports banana and dirct cable connection)
Scales well with better quality speakers
No popping sounds while on/off switch operation
Very very low audible background noise (even if you if you crank the volume all the way up; speaker dependent)
Very high price/performance ratio
Cons:
No support for Bluetooth aptX-HD (unlike its smaller tube brother T20 Tube Amp)
Slightly wobbly volume control knob
Text size on the front panel are small and text can be written above the control knobs
You need to purchase 48V power adapter with the amp in order to get full sound potential (volume) which adds extra cost
I'd like to see a slightly more visible led indicator (for on/off/Bluetooth)
PS: BT20A Pro sounds better with higher end speakers (as expected) so this may be a 'Con' for someone but 'Pro' for another...
Fosi Audio BT20A Pro is a Class D, stereo, speaker amplifier. It has RCA and Bluetooth inputs, Banana Plug (also bare speaker wire) compatible and 3.5mm Pre-Out outputs. It is indicated that Pre-Out can be connected to a powered subwoofer.
Fosi Audio provided this BT20A Pro for my honest review. Thanks for this opportunity.
The customer relations with Fosi Audio company is great. Before this review unit I bought a Fosi Audio T20 Tube Amp with my money from their Aliexpress store and loved the product so much that I write a review in Head-Fi without thinking a minute (T20 Tube Amp Review Link: https://www.head-fi.org/threads/fosi-audio-t20-tube-amp-review-and-thread.968074/). During the review and testing phase of that amp -which became my main desktop/workspace headphone and speaker amp for Tannoy Mercury MX1 speakers and Beyerdynamic DT-150 headphones- I have contacted the technical support team many times and they always replied to me fast and answered my every question kindly. So I was amazed by their customer relations.
Technical Specs of BT20A Pro:
Max Power Output: 300Wx2 @4Ω
SNR: ≥108dB
Terminating Impedance: 2-8Ω
THD: 0.005%
Power Amplifier Chip: TPA3255
Power Supply: 32V 5A
Input Range: DC 24V-48V
Frequency Response Range:
20Hz-20kHz(±1.2dB)
Bluetooth Transmission Range: Up to 50Ft
Bluetooth Codec: AAC/SBC
Audio Input: RCA/Bluetooth
Audio Output: Speaker Output/3.5mm Pre-out
Fosi Audio 30 day return period, 18 month waranty and lifetime technical support claims which are written on the side of the box gives confidence.
What's in The Box?:
The Amp Box Includes These Items:
BT20A Pro Power Amplifier x1
Bluetooth Antenna x1
32V 5A Power Adapter x1
Power Adapter AC Cord x1
User Manual x1
Image: Courtesy of Fosi Audio
Fosi Audio BT20A Pro has an high-end amp chip (TPA3255) integrated in it. This chip is compatible with 24V-48V power supply and delivers premium class-D amplification.
Image: Courtesy of Fosi Audio
The op-amps in BT20A Pro are Texas Instruments NE5532. These op-amps are user replacable and you can replace them with MUSES02, OPA26041P, OPA2134PA, LME49720HA, LM4562 or NJM4556AD. This provides a broad range of sound signature customisation!
Image: Courtesy of Fosi Audio
There is an energy-saving circuit built in to the BT20A Pro which provides a clean shutdown of the unit (and costs no energy).
Image: Courtesy of Fosi Audio
The amp has full aluminum chasis with 4 rubberized feets which do not slip on the surfaces which I have tried; including: glass, raw smooth wood, marble, plastic, smooth concrete, painted metal and varnished wood. Foots supports the amp excellently.
Amp does not feel heavy because it is compact and use of light materials like aluminum (unit weights 547 g). The main chasis is one piece aluminum with front and back aluminum panels are attached to it via the screws on the back. BT20A Pro feels very solid in hand. I feel that it can handle some heavy equipments if paced on top of it which I ceratinly do not recommend because of the heat dissipation and also bluetooth range blockage. Amplifier has an internal heat sink which transfers the heat to the top panel and heat is then distrubuted to the whole aluminum chasis for dissipation.
The bluetooth antenna is on the back left side. It is compact and antenna angle can be adjusted by the user.
Unit does not get very warm like the Fosi Audio T20 Tube Amplifier but feels slightly warm when touched by the hand after extended use. The 32V 5A power adapter does not get warm at all.
BT20A Pro's color is different from most Fosi Audio amps (which are mainly black) and I really love this color which is like bluish-grey (it is so called: space blue).
The amp has on/off switch on the left side followed to the right by: Treble, Bass and Volume control knobs. Volume control knob doubles as a bluetooth unpair switch. You simply long press the knob to unpair your bluetooth device. But you can not get the pairing back by long pressing this knob again. You have to enable pairing again from the source (for example from your phone). Because of the bluetooth unpairing and volume control are carried on the same knob, the volume knob has some wobbling. But once you understand the cause and its 2 different functions you may not care this wobble feeling. Other than this con the volume knob turns very smoothly. I really love the copper color of the volume knob. It should be used as a signature on all Fosi Audio amps volume knobs (or can be used in higher end variants -in my opinion).
The tone controls are must in my using case because my Tannoy Mercury MX1 bookshelf speakers tonality needs some treble boost in order to sound correct to my ears. I feel this boost need with every amp that I connect to these MX1 speakers so there is no problem with the tonality of the Fosi Audio amp. I like that the middle (neutral) position of bass and treble control knobs have a clicky feedback to it so you can be sure when the knobs are in neutral position. The power On/Off/Bluetooth On led indicator is located on the lower left side of the power switch. I normally do not like shiny (producing strong light) power leds but this BT20A Pro led is very tiny for my taste. It is very difficult to see if the amp is on or off from a distance in day time (or night time from an angle). But I can understand why it is very tiny (or very recessed to the body). Just wanted to mention that I prefer to see the light in day time as well (or from an angle at night) and the light must be dim enough to not to disturb me at the night time.
On the front panel upper left side, you can see the brand and model name. I wish that the letters were slightly larger because in a normal sitting position many people can not even notice which brand and model amp this is. Also there is another con for the lettering: On / off switch have only one mark on the bottom part. So one can not be sure if it is on or off if the red 'on' indicator dies (Yes I know I am getting analytical here and I can understand if the designers like to prefer a clean look). The bass, treble and volume knobs letters are written below them. This approach is very rare and for my experience you have to bend your head to see which knob is which each time you try to adjust the tone (unless you place the amp over your head position). After getting used to the placement of bass and treble knobs there is no problem but I wish that all the letters were written above the knobs not below them. After using another Fosi Audio brand amp (T20 Tube Amp) for 4 months I did get used to the placement of the bass and treble knobs of that model amp. When I have the BT20A Pro I thought the right knob were treble so adjusted it without even noticing the tiny letters below the knobs. To my surprise it appeared to be bass knob this time. I advise Fosi Audio to not to change some main control knob placements between different models (in respect to designers; whenever possible and if the main design allows it). Because there is user experience and when a user choses a brand in the long term he/she wants to see some similar/old user experience friendly controls. We are talking about only two knob placements here but consistency is important in my opinion. I have to add in the end that these are not big cons and can be overcomed by user experience over time. I am just getting very analytical sometimes. May be another user would not care about these cons at all ! Or may be prefer the clean look of the face panel!
This review is based on three different usage scenarios; 1st: as a desktop amp connected with Tannoy Mercury MX1 bookshelf speakers. 2nd: as a stereo speaker connected with Dali Zensor 7 (White) floor standing speakers. 3rd: as a stereo and 2+1 setup with Pioneer S-H509V floor standing speakers and Pioneer S-W 110 Powered Subwoofer.
I always connect my amps to my speakers through banana connectors. I use RCA to 3.5mm stereo pure copper wires to connect the amp to my sources which are Mac Mini M2 and Macbook Air M1. I did not use any DAC or CD-DVD player intentionally in order to keep my review of speaker amps in-line. Power source of the amp is Fosi Audio's own 32V 5A power adapter which was connected to a power regulated 220V socket. Bluetooth connection were tested with an LG V30+ cellphone.
Comparisons with other amps included Yamaha RX-V663 (tested on Pure Direct mode disabling all equiliser and effects) and Fosi Audio BT20 Tube Amp.
Listening BT20A Pro through Tannoy Mercury MX1 Bookshelf Speakers:
Tannoy Mercury MX-1 are very old but well respected set of bookshelf speakers which incorporates ceramic coated paper cones and soft dome tweeters. I love their sound as a desktop stereo and monitoring set-up. I use them while video editing, music mixing and for general use on the workspace. Only drawback is: they lack some treble energy so I have to boost treble on every amp that I have tried with these speakers. Luckily BT20A Pro has tone controls so I can adjust the treble for the correct amount. I keep the bass on the neutral position because there is no need. BT20A Pro delivers clean, smooth and well defined sound with MX1's.
(BT20A Pro AMP on the left, T20 Tube AMP on the right)
After A-B'ing it with T20 Tube Amp I have concluded that only on this setup I will keep the T20 Tube Amp connected with it because T20 delivered more lively, more clear and musical sound. But with other speaker sets the situation changes so please keep reading. I have tried Yamaha RX-V663 previously with Tannoy's and prefer T20 Tube Amp at that time as well.
Tannoy Mercury MX1 Specs:
Enclosure Type: 2 way bass reflex (2 speaker units)
Max SPL: 100 Watts
FQ Response: 55Hz - 20kHz
Sensitivity: 87dB
Impedance: 8 Ohms
Drivers: 1 x 25mm High frequency soft textile dome
1 x 130mm Ceramic Coated Paper cone
Listening BT20A Pro through Dali Zensor 7 Floor Standing Speakers:
Before beginning this part I have to mention: I have a special interest and love with Dali brand speakers. I love the sound of Zensor 7 and it is the main component of my home theater and stereo set-up in my living room. The wood-fibre cones and soft dome tweeters of the Zensor 7 brings incredibly natural tones. Treble energy and clarity of Zensor 7's are already excellent so there is no need to adjust the tone control knobs with BT20A Pro. All I hear is clean, clear sound with wide soundstage and well defined bass. Midtone reproduction is excellent. Vocals and strings sounds amazing with this setup.
I have compared my home theater and stereo listening amp Yamaha RX-V663 's pure direct out to the BT20A Pro and they were so close that I could not decide which one to prefer. You can compare the size of the units and RX-V663 do not have bluetooth connection so it is less versatile option for stereo listening. But for movies, there is no competition because RX-V663 supports DTS-HD and 7+2 speaker setup. Main amp chip of RX-V663 is produced by Burr Brown company and with its *Pure Direct mode you get Hi-Fi reproduction from this amp. So Fosi Audio really brought smiles to my face while listening and comparing to Yamaha. You do not expect this kind of quality from such a small amp like BT20A Pro.
(*Pure Direct mode on Yamaha receivers disables all equaliser and digital effects)
I have included T20 Tube Amp to the comparisons and it was not a good match with Zensor 7's. The sound were not refined as the BT20A Pro and highs do have less natural reproduction. T20 Tube Amp adds some coloring to the sound and sounds less hi-fi in comparison.
While connected with BT20A Pro the background was dead silent as well. No audible hissing or buzzing sounds.
Dali Zensor 7 Floor Standing Speaker Specs:
Enclosure Type: 2 way bass reflex (3 speaker units)
Frequency Range: 40Hz - 26.5kHz
Sensitivity: 90 dB
Impedance: 6 Ohms
Max SPL: 110 Watts
Drivers: 1 x 25mm High frequency soft textile dome
2 x 7inch Low frequency Wood Fibre cone
Listening BT20A Pro through Pioneer S-H509V Floor Standing Speakers:
(My SUP Boards are excellent for decoration and acts like a sound absorber to cut unwanted reflections from a bare wall)
BT20A Pro sounds excellent with this 8 Ohm speakers. Although the Pioneer's tweeters do produce some hissing (background sounds when music is not playing) this is not native to the Fosi Audio amp, this speaker produces this kind of sound with every amp that I have tried and I believe it is because of the crossover unit implementation or tweeter sensitivity. Some amps exaggerate this and some amps do not.
When I play the music I hear clean, clear sound with good defined mid range and bass. Highs are smooth and never gets sibilant. Bass hits if the recording calls for it. When I connect Pioneer SUB Woofer (powered) to the pre-out I get great sub bass in addition to the other frequencsies. But I prefer to listen these speakers in stereo mode. So in a 2+1 scenario the BT20A pro can deliver the needed sub bass. But in order to obtain best results you have to adjust the frequency, phase, crossover and volume from the sub bass units control panel. Also I have to mention that in this usage scenario the amp is not acting like a real 2+1 amp, it only sends the pre-out signals and your powered subbas only delivers the bass frequency from there (from my understanding). I especially like the mid-range when paired with this Pioneers. Vocals and strings sounds amazing. Reproduction is life-like and without any sensible coloration to the sound. I crank the volume nearly all the way up with these speakers and luckily they did not blew up. All I hear were non-distorted, clean and powerful sound which was not ideal for a 35 square meter living room. So I have no doubt that the amp can deliver more than enough volume with 8 Ohm speaker units even with the 32V power adapter. If you have larger room or use open space and do not have any body in fear of disturbing you can prefer 48V power adapter to obtain the full volume potential of the BT20A Pro.
In comparison to the Fosi Audio T20 Tube Amp, BT20A Pro delivered smoother sound with well defined and layered instruments. T20 Tube Amp's only strength compared to BT20A Pro with this speaker that it sound slightly more lively. I feel and prefer BT20A Pro is more true to the source and less colored so prefered it over T20 for this setup.
Pioneer S-H509V Floor Standing Speaker Specs:
Enclosure Type: 2 way bass reflex (4 speaker units)
Frequency Range: 30Hz - 35kHz
Sensitivity: 90 dB
Impedance: 8 Ohms
Max SPL: 100 Watts
Drivers: 1 x 25mm High frequency soft textile dome
3 x 14cm Low frequency Paper Fibre cone
Bluetooth:
I have tested the range and it was approximately 15 meters. Inside the house reception range depends on the variables like walls and furniture. So it may be lesser. But I have no complaints for the range inside the biggest place of my house (which is my living room) and when I go to the kitchen with my phone and return, bluetooth were still delivering the data (without any cuts). I really wanted to see APTX-HD implementation with the amp but after comparing the sound quality with the APTX-HD supported T20 Tube Amp the bluetooth sound quality on the BT20A Pro is not bad at all and even very good.
Bluetooth connection requires enabling the pairing from the phone (or any other bluetooth compatible source) with the amp. There is no on/off Bluetooth switch on the amp. Bluetooth is always on unless you unpair your device fom the amp. The bluetooth connection time is around 3-5 seconds after pairing the 2 devices once. With my phone, sometimes the amp did not connect automaically so I have to open the bluetooth settings on my phone to see and connect the BT20A Pro. To unpair you can simply long press the volume knob. Bluetooth connection can be monitored through the power led color which turns from red to blue when a device is connected.
Conclusion of The Review:
Pros:
Powerful, smooth, clean, well defined sound
Bass and treble tone controls with clicky middle (0) position
Bluetooth input which have a good range and good enough audio quality
Upgradeable op-amps for future upgrades
Small footprint
Strong aluminum chasis
Rubber feet
Good implementation of quality audio components and heat sink
Pre-out support (can also be used for a powered subwoofer connection in a 2+1 scenario)
Plated connections (speaker outs supports banana and dirct cable connection)
Scales well with better quality speakers
No popping sounds while on/off switch operation
Very very low audible background noise (even if you if you crank the volume all the way up; speaker dependent)
Very high price/performance ratio
Cons:
No support for Bluetooth aptX-HD (unlike its smaller tube brother T20 Tube Amp)
Slightly wobbly volume control knob
Text size on the front panel are small and text can be written above the control knobs
You need to purchase 48V power adapter with the amp in order to get full sound potential (volume) which adds extra cost
I'd like to see a slightly more visible led indicator (for on/off/Bluetooth)
PS: BT20A Pro sounds better with higher end speakers (as expected) so this may be a 'Con' for someone but 'Pro' for another...
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