linuxslate
Well-Known Member
I normally hang out on the Tube Audio Forum, but I just bought a couple of inexpensive Solid State Chinese amplifiers, and I thought I would do a mini-review of there here.
Why did I buy these amps? -- Well, first of all, I have been obsessed with audio, HiFi, and PA since I was a small child. I buy and build audio stuff obsessively, and I don't think I will stop until the circle of life inevitably causes me to stop. Secondly, I have a specific application in mind. More on that later if there is interest.
My specific application aside, the Sunbuck AV-660BT, seems to be at least a usable small utility amp, so I wanted to provide a little of my experience with this and similar amps here.
The first question many people ask about an audio amp is "How many Watts" ... Well the short answer is that I (and thus any consumer) have no idea. The eBay listing calls it "2000W", and then says "Rated power: 1200W Peak: 2000W" -- Uh -- Yeah -- if you think this tiny amp does anything near that, there is no point in continuing to read this. For context, this thread shows a "real" 500W amplifier that I have experience with. The box is far more honest about the output power -- I doesn't mention any output power at all. Nor do any markings on the unit itself.
If one assumes that energy cannot be created nor destroyed, one can set an upper limit on the output power buy considering the input power. This amplifier can run on 110VAC, 220VAC or 12VDC. The AC inputs have no wattage rating, and there is no accessible fuse, but the 12VDC input is rated at 5A. 12 x 5 = 60, so if the amp was 100% efficient, like -- you know -- absolutely nothing is -- it would have a maximum possible output of 60 watts - 30 WPC - continuous. The AC line cord is also very thin. It would never (safely) handle the power required to produce 1200 watts even assuming a very efficient class D amp.
To determine the actual power, one would have to open the amp, look at the output chips, and research the manufactures rated power -- and that would assume the amp contains genuine parts, and not Chinese counterfeits -- which I would not consider a valid assumption.
So how many watts is it really? Well, I connected it to my Realistic APM-500 TRMS watt meter, and it would solidly light the 11.5W LEDs with the volume all of the way up (regardless of source). The next LED on the 200W scale is 22.5W, so giving the amp the benefit of the doubt (lack of resolution), I'm going to give the amp credit for 15-20WPC TRMS, although one must expect at least some noticeable distortion anywhere near full power.
So this "2000 W" amplifier is really good for maybe a little over 20W total without significant distortion. What's 2 orders of magnitude in eBay advertising?!
That said, 10 WPC TRMS is actually plenty for even a fairly large room if connected to a pair of decent speakers. In addition to the Realistic TRMS watt meter, the AV-660BT was connected to a pair of Sony 3-way bookshelf speakers. It actually sounds very nice playing from the line in or from the internal USB mp3 player.
The analog tone controls work well, and the overall frequency response seems to be good. It is capable of producing crisp highs, and as much bass as is reasonable to expect from a small amp and bookshelf speakers. Mids and vocals remain present and clear.
It doesn't have the "presence", "depth", or clarity that I have come expect from a tube amplifier. In fact a "benefit" of this amp could be its use to demonstrate (by contrast) "tube sound", since it is about the same power as a P-P EL84 or similar tube amp.
As mentioned the amp can run from 110VAC or 220VAC -- switch selectable. The fact that there is a switch indicates to me that it is applying the AC input to different taps or windings in an actual power transformer. Switchmode power supplies (SMPS's) typically auto adjust for input voltage, and don't have a switch. The power switch also switches the actual incoming AC -- the unit will work from 12VDC with the main power switch off. I believe it utilizes a toroidal transformer for the AC power input. What does all this mean? A lot of audio purists don't like SMPS's in audio equipment, and toroidal transformers are small and efficient, so this is good news for the typical user.
The AV-660BT includes a basic player module that provides FM Radio, Bluetooth, USB, and SD card support. The player is very basic, but works adequately. Hitting the auto button in FM mode found lots of local stations even indoors and surrounded by lots of interference from a nearby PC, test equipment, lights, etc. The player module controls all input selection, including the AUX (Line) input. While there are 2 sets of RCA connectors on the back, there is really only one AUX (Line) input. I'm pretty sure the 2 pairs of RCA connectors are just shorted together. Connecting 2 inputs is not really correct, and there is no switching between them. The box also mentions a 3.5mm AUX input, but I see no such connector on this unit. The digital player buttons are soft, which gives at least a little bit of a "quality" feel.
I suspect that the case is the same for the 2 mic connectors on the front panel. There is only one mic level control. The Echo control only applies to the mic, as it should. The mic input is not wired through the input selector, so you can talk over the sound no matter what source input is in use.
Interestingly, the MP3 player module has it's own (digital) volume control. This volume applies to all inputs, and is not remembered after a power cycle. In other words, if you turn the digital volume down (e.g. with the provided remote), and then physically turn the amp off, you could get an unpleasant blast of audio the next time you power it on with the switch.
It also means that if you plan to control the volume with the input device (for example using a TV's remote), then the sounds for bluetooth connection can come through unpleasantly loud.
The speaker terminals are the push-to-insert type, and have strong springs to hold speaker wires securely. Again, typical of Chinese goods, the actual unit is marked as 4 -16 ohms near the speaker terminals, but the box says "Load Impeckance" 4 to 8 hms" [all spelling is intentionally copied]
I should also note that the box says "Frequency Response 20Hz to 20KHz (+/-10) dB". -- Who caught that? Even if true, that does not mean the unit has a frequency response of 20Hz to 20KHz. Frequency response is normally measured at the -3 dB points. If it is already 10 dB down at the indicated points, we know the true frequency response is actually much worse.
So while I might seem pretty down on these Chinese amps, and it is very important that the buyer knows how to read past the -- I'm going to say it in a public forum -- false advertising, these amps can be useful, good sounding, and an inexpensive solution to many applications. Many of the Sunbuck amps are also nice looking units, and this model is available in white or black.
The observant may also note that the box says "Home Theater Amplifier", and the unit itself is marked "Karaoke Audio Amplifier" -- so which is it? It really just a stereo utility amplifier with a rather obnoxious digital input module, and a single mic input (with 2 jacks). This means it has lots of uses. With the 12V input and Bluetooth, it can be used as a hidden stereo system in a car or RV. It can also be used for PA in either a vehicle or in a restaurant or other business. Yes, it could be used -- for example -- to run rear speakers in a home theater system. Also as advertised, it can be used with passive speakers as a Karaoke system, and the result will probably be cheaper and sound much better than most self-powered integrated Karaoke speakers. Add a pair of passive speakers from the local thrift store, and you have a good sounding and inexpensive "on demand" system for backyard parties or for use in the workshop.
So while I understand that most AK'ers know what to expect from such an amp, my intention here was to introduce these devices to less experienced readers. IMHO, Such amps do have a place in the audio world. When shopping for one, use common sense -- if it doesn't look like a 2000W amp (or even a 500W amp) -- it ain't. Drop the power rating by a factor of 100 to get the actual mostly distortion-free power capability. Built-in players work, but are not sophisticated or refined. I should also note that many such units are intended for use in Europe, Russia, China and other countries that have 220VAC "mains" voltage. Make sure the unit supports the voltage used in your country. If you have dropped your expectations accordingly, you can get a nice looking product at a fair price.
Why did I buy these amps? -- Well, first of all, I have been obsessed with audio, HiFi, and PA since I was a small child. I buy and build audio stuff obsessively, and I don't think I will stop until the circle of life inevitably causes me to stop. Secondly, I have a specific application in mind. More on that later if there is interest.
My specific application aside, the Sunbuck AV-660BT, seems to be at least a usable small utility amp, so I wanted to provide a little of my experience with this and similar amps here.
The first question many people ask about an audio amp is "How many Watts" ... Well the short answer is that I (and thus any consumer) have no idea. The eBay listing calls it "2000W", and then says "Rated power: 1200W Peak: 2000W" -- Uh -- Yeah -- if you think this tiny amp does anything near that, there is no point in continuing to read this. For context, this thread shows a "real" 500W amplifier that I have experience with. The box is far more honest about the output power -- I doesn't mention any output power at all. Nor do any markings on the unit itself.
If one assumes that energy cannot be created nor destroyed, one can set an upper limit on the output power buy considering the input power. This amplifier can run on 110VAC, 220VAC or 12VDC. The AC inputs have no wattage rating, and there is no accessible fuse, but the 12VDC input is rated at 5A. 12 x 5 = 60, so if the amp was 100% efficient, like -- you know -- absolutely nothing is -- it would have a maximum possible output of 60 watts - 30 WPC - continuous. The AC line cord is also very thin. It would never (safely) handle the power required to produce 1200 watts even assuming a very efficient class D amp.
To determine the actual power, one would have to open the amp, look at the output chips, and research the manufactures rated power -- and that would assume the amp contains genuine parts, and not Chinese counterfeits -- which I would not consider a valid assumption.
So how many watts is it really? Well, I connected it to my Realistic APM-500 TRMS watt meter, and it would solidly light the 11.5W LEDs with the volume all of the way up (regardless of source). The next LED on the 200W scale is 22.5W, so giving the amp the benefit of the doubt (lack of resolution), I'm going to give the amp credit for 15-20WPC TRMS, although one must expect at least some noticeable distortion anywhere near full power.
So this "2000 W" amplifier is really good for maybe a little over 20W total without significant distortion. What's 2 orders of magnitude in eBay advertising?!
That said, 10 WPC TRMS is actually plenty for even a fairly large room if connected to a pair of decent speakers. In addition to the Realistic TRMS watt meter, the AV-660BT was connected to a pair of Sony 3-way bookshelf speakers. It actually sounds very nice playing from the line in or from the internal USB mp3 player.
The analog tone controls work well, and the overall frequency response seems to be good. It is capable of producing crisp highs, and as much bass as is reasonable to expect from a small amp and bookshelf speakers. Mids and vocals remain present and clear.
It doesn't have the "presence", "depth", or clarity that I have come expect from a tube amplifier. In fact a "benefit" of this amp could be its use to demonstrate (by contrast) "tube sound", since it is about the same power as a P-P EL84 or similar tube amp.
As mentioned the amp can run from 110VAC or 220VAC -- switch selectable. The fact that there is a switch indicates to me that it is applying the AC input to different taps or windings in an actual power transformer. Switchmode power supplies (SMPS's) typically auto adjust for input voltage, and don't have a switch. The power switch also switches the actual incoming AC -- the unit will work from 12VDC with the main power switch off. I believe it utilizes a toroidal transformer for the AC power input. What does all this mean? A lot of audio purists don't like SMPS's in audio equipment, and toroidal transformers are small and efficient, so this is good news for the typical user.
The AV-660BT includes a basic player module that provides FM Radio, Bluetooth, USB, and SD card support. The player is very basic, but works adequately. Hitting the auto button in FM mode found lots of local stations even indoors and surrounded by lots of interference from a nearby PC, test equipment, lights, etc. The player module controls all input selection, including the AUX (Line) input. While there are 2 sets of RCA connectors on the back, there is really only one AUX (Line) input. I'm pretty sure the 2 pairs of RCA connectors are just shorted together. Connecting 2 inputs is not really correct, and there is no switching between them. The box also mentions a 3.5mm AUX input, but I see no such connector on this unit. The digital player buttons are soft, which gives at least a little bit of a "quality" feel.
I suspect that the case is the same for the 2 mic connectors on the front panel. There is only one mic level control. The Echo control only applies to the mic, as it should. The mic input is not wired through the input selector, so you can talk over the sound no matter what source input is in use.
Interestingly, the MP3 player module has it's own (digital) volume control. This volume applies to all inputs, and is not remembered after a power cycle. In other words, if you turn the digital volume down (e.g. with the provided remote), and then physically turn the amp off, you could get an unpleasant blast of audio the next time you power it on with the switch.
It also means that if you plan to control the volume with the input device (for example using a TV's remote), then the sounds for bluetooth connection can come through unpleasantly loud.
The speaker terminals are the push-to-insert type, and have strong springs to hold speaker wires securely. Again, typical of Chinese goods, the actual unit is marked as 4 -16 ohms near the speaker terminals, but the box says "Load Impeckance" 4 to 8 hms" [all spelling is intentionally copied]
I should also note that the box says "Frequency Response 20Hz to 20KHz (+/-10) dB". -- Who caught that? Even if true, that does not mean the unit has a frequency response of 20Hz to 20KHz. Frequency response is normally measured at the -3 dB points. If it is already 10 dB down at the indicated points, we know the true frequency response is actually much worse.
So while I might seem pretty down on these Chinese amps, and it is very important that the buyer knows how to read past the -- I'm going to say it in a public forum -- false advertising, these amps can be useful, good sounding, and an inexpensive solution to many applications. Many of the Sunbuck amps are also nice looking units, and this model is available in white or black.
The observant may also note that the box says "Home Theater Amplifier", and the unit itself is marked "Karaoke Audio Amplifier" -- so which is it? It really just a stereo utility amplifier with a rather obnoxious digital input module, and a single mic input (with 2 jacks). This means it has lots of uses. With the 12V input and Bluetooth, it can be used as a hidden stereo system in a car or RV. It can also be used for PA in either a vehicle or in a restaurant or other business. Yes, it could be used -- for example -- to run rear speakers in a home theater system. Also as advertised, it can be used with passive speakers as a Karaoke system, and the result will probably be cheaper and sound much better than most self-powered integrated Karaoke speakers. Add a pair of passive speakers from the local thrift store, and you have a good sounding and inexpensive "on demand" system for backyard parties or for use in the workshop.
So while I understand that most AK'ers know what to expect from such an amp, my intention here was to introduce these devices to less experienced readers. IMHO, Such amps do have a place in the audio world. When shopping for one, use common sense -- if it doesn't look like a 2000W amp (or even a 500W amp) -- it ain't. Drop the power rating by a factor of 100 to get the actual mostly distortion-free power capability. Built-in players work, but are not sophisticated or refined. I should also note that many such units are intended for use in Europe, Russia, China and other countries that have 220VAC "mains" voltage. Make sure the unit supports the voltage used in your country. If you have dropped your expectations accordingly, you can get a nice looking product at a fair price.
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