Class D amplifier boards.
I've noticed many mixed reviews of such boards both being great and bad. And there's reasons why some will find these little amplifier boards bad. Other than that they're tiny and made in China. But consider th is, The chips that are the heart of these boards are made in the great USA. MAGA!! The Chinese folks just put them on pcbs with some additional components to make a functioning amplifier. Let's get one thing understood about audio amplifiers. They amplify whatever it is that is put into them. What ever that may be.
As we hobbyists to audiophiles like to tinker with our electronics, not everyone has the whole understanding of audio components. There's voltage and current, and the different sources of that. Some AC derived sources are "dirty". Meaning that they output a lot of unfiltered or poorly rectified ac noise into your circiut. Then there's the wiring. Some of the wires can and do pick up noise, just like an antenna. That can be fixed too. I've even read that a guy heard his refridgerator in his kitchen cycling through his class D amp board. Well, old cars used to have alternator whine. Next is distortion.
Most of us are familiar with the figures of 1% and 10% THD +N @ a number of watts @ ? ohms. But not to many takes into the consideration of what we are using to source our tunes with. And they are all different. Phones both Android and Iphones- different, and the different brands. Pocket mp3 players both quality ones and cheaper ones. Different even more. Desktop pc's and laptop pc's and then different brands. An old tape deck with or without a preamp. Note that I said preamp. Both home and professional equipment- different output levels. Said again- different output levels. They all vary from item to item. and the inputs of many different class D amplifier board differ. Here what some folks miss.
The input gain. Not enough, music is low, noise is more noticable. Sounds like a weak toy. Too much gain, lots of noise and distortion. Sounds like ****. Now if you knew how to get it right, it sounds wonderful. Question is do you need a preamp. Or is your source too heavy for your inputs. Now lets get to the good stuff.
As I have been tinkering with audio components for litterally decades, I've come to know a quite of bit. I also have a small collection of these Cheap little class D amp boards. The TDA's, TPA's and the PAM's too. They all have different gain inputs. Some of the OEP (tiniest) boards other than the PAM's have choosable gain inputs by just bridge soldering two tiny pads. 20DB, 32DB. ETC. And if you are going to use a powered preamp board. Some of them have tone and volume pots on them. Some are the BBE types. I just got one that has both BBE and Stereo Widener on it. There are some tone controllers that are passive. So here's some help. Don't chuck a board cause it don't sound right at your first try. Try another source or two. Try a different board. The only bad amp board is one that smokes as soon as you apply voltage to it. I've never had one of them. Here's some source and board combinations to consider.
The PAM boards, Their gain is good with phones and some pocket mp3 players. No good in cars, some tape decks and definitely not professional audio. Unless you change the gain. The TDA's and the TPA's vary board model to model but, they are best suited with a preamp. Can be use in vehicles and pro pa systems. Them tiny minimalist OEP are TDA's and TPA's with minimal components. They're the red tiny boards and they have the bridge solder tabs for different gain. So if you have loud distortion and loud noise, reduce your gain at the inputs. Ifyou have not enough volume and some noise, you best bet to need a preamp to increase your gain at the inputs. Then there are some combinations of source and amps that seem to be made for each other.
Have you seen them FM radio, bluetooth, usb, SD card module boards, usually black in color, Cheap plastic with the remote. Ebay, Amazon, Aliexpress, Thanksbuyer, etc. They go practically perfect with the PAM's. I use a passive tone volume board with them at the most. Some of the Bluetooth only boards work with the PAM's but some need a preamp. Some need reduction. I've found that I put a small resistor in series of the negative wire of the input works. I've used 1k, 5k and 10k as well as trim pots. Just try different resistors.
To conclude, I wish I had these little Class D amp boards back in the 80's when I was strapping old heavy car batteries, 20 expensive Duracell D batteries to my bicycle just to have cruise tunes. And back then. Even the cheapest car stereos were expensive. And them expensive D cells didn't last long and the car batteries were heavy on a bike. Even speakers are better. 3 inchers, 4 inchers. I remember the 6x9's I had on my chopper bike. And them little 1 watt 4 incher blew if I turned it up. And my first Boombox build. That was nice but, it was restricted to my shelf Ac-dc power supply. My first PAM 8610 sounded a lot better than my old Pioneer receiver did. It died years ago. I was thinking about ripping out them heatsinks and putting in a pair of TDA 8932's in. But something else may die in it. Best to build one from scratch.
I hope this help you with your builds and projects. Build large boomboxes and play it loud. Pedal in stereo. Put some tunes on your backpack while hiking. Phones and pocket players are nice, just like walkmans were. But nothings like bass in everyone's face. And also, efficient speakers make it just much more louder and better. My current build is a pam board 2.1 that has two pam chips putting out 30w sub and 2x15w left and right. Got that from Parts Espress. A efficient vintage 15 inch woofer and two vintage efficient 10 woofers, some planars and piezo's all (Ebay, Amazon, Junk in alley) three 26650 li ions. Sounds like my old Pioneer system with a shoulder strap. I do use lightweight boards and ABS sheets. Almost forgot. Another practice I do is to braid my input wires, speaker wires and power wires. And a loop or two through a ferrite donut cannot hurt either. Kill the noise. An extra capacitor on the power inputs too (Proper voltage). I also make my own led vu meters but you can find some prebuilt from China. Google LM 3914, 3915 and 3916. Look up Youtube for these too. Lots of choices and info. I also use the hard to find UAA180 (a2770) for led vu meters too. Learn how to etch pcb's or least use perf boards. I build just about anything, but you can too.
I've noticed many mixed reviews of such boards both being great and bad. And there's reasons why some will find these little amplifier boards bad. Other than that they're tiny and made in China. But consider th is, The chips that are the heart of these boards are made in the great USA. MAGA!! The Chinese folks just put them on pcbs with some additional components to make a functioning amplifier. Let's get one thing understood about audio amplifiers. They amplify whatever it is that is put into them. What ever that may be.
As we hobbyists to audiophiles like to tinker with our electronics, not everyone has the whole understanding of audio components. There's voltage and current, and the different sources of that. Some AC derived sources are "dirty". Meaning that they output a lot of unfiltered or poorly rectified ac noise into your circiut. Then there's the wiring. Some of the wires can and do pick up noise, just like an antenna. That can be fixed too. I've even read that a guy heard his refridgerator in his kitchen cycling through his class D amp board. Well, old cars used to have alternator whine. Next is distortion.
Most of us are familiar with the figures of 1% and 10% THD +N @ a number of watts @ ? ohms. But not to many takes into the consideration of what we are using to source our tunes with. And they are all different. Phones both Android and Iphones- different, and the different brands. Pocket mp3 players both quality ones and cheaper ones. Different even more. Desktop pc's and laptop pc's and then different brands. An old tape deck with or without a preamp. Note that I said preamp. Both home and professional equipment- different output levels. Said again- different output levels. They all vary from item to item. and the inputs of many different class D amplifier board differ. Here what some folks miss.
The input gain. Not enough, music is low, noise is more noticable. Sounds like a weak toy. Too much gain, lots of noise and distortion. Sounds like ****. Now if you knew how to get it right, it sounds wonderful. Question is do you need a preamp. Or is your source too heavy for your inputs. Now lets get to the good stuff.
As I have been tinkering with audio components for litterally decades, I've come to know a quite of bit. I also have a small collection of these Cheap little class D amp boards. The TDA's, TPA's and the PAM's too. They all have different gain inputs. Some of the OEP (tiniest) boards other than the PAM's have choosable gain inputs by just bridge soldering two tiny pads. 20DB, 32DB. ETC. And if you are going to use a powered preamp board. Some of them have tone and volume pots on them. Some are the BBE types. I just got one that has both BBE and Stereo Widener on it. There are some tone controllers that are passive. So here's some help. Don't chuck a board cause it don't sound right at your first try. Try another source or two. Try a different board. The only bad amp board is one that smokes as soon as you apply voltage to it. I've never had one of them. Here's some source and board combinations to consider.
The PAM boards, Their gain is good with phones and some pocket mp3 players. No good in cars, some tape decks and definitely not professional audio. Unless you change the gain. The TDA's and the TPA's vary board model to model but, they are best suited with a preamp. Can be use in vehicles and pro pa systems. Them tiny minimalist OEP are TDA's and TPA's with minimal components. They're the red tiny boards and they have the bridge solder tabs for different gain. So if you have loud distortion and loud noise, reduce your gain at the inputs. Ifyou have not enough volume and some noise, you best bet to need a preamp to increase your gain at the inputs. Then there are some combinations of source and amps that seem to be made for each other.
Have you seen them FM radio, bluetooth, usb, SD card module boards, usually black in color, Cheap plastic with the remote. Ebay, Amazon, Aliexpress, Thanksbuyer, etc. They go practically perfect with the PAM's. I use a passive tone volume board with them at the most. Some of the Bluetooth only boards work with the PAM's but some need a preamp. Some need reduction. I've found that I put a small resistor in series of the negative wire of the input works. I've used 1k, 5k and 10k as well as trim pots. Just try different resistors.
To conclude, I wish I had these little Class D amp boards back in the 80's when I was strapping old heavy car batteries, 20 expensive Duracell D batteries to my bicycle just to have cruise tunes. And back then. Even the cheapest car stereos were expensive. And them expensive D cells didn't last long and the car batteries were heavy on a bike. Even speakers are better. 3 inchers, 4 inchers. I remember the 6x9's I had on my chopper bike. And them little 1 watt 4 incher blew if I turned it up. And my first Boombox build. That was nice but, it was restricted to my shelf Ac-dc power supply. My first PAM 8610 sounded a lot better than my old Pioneer receiver did. It died years ago. I was thinking about ripping out them heatsinks and putting in a pair of TDA 8932's in. But something else may die in it. Best to build one from scratch.
I hope this help you with your builds and projects. Build large boomboxes and play it loud. Pedal in stereo. Put some tunes on your backpack while hiking. Phones and pocket players are nice, just like walkmans were. But nothings like bass in everyone's face. And also, efficient speakers make it just much more louder and better. My current build is a pam board 2.1 that has two pam chips putting out 30w sub and 2x15w left and right. Got that from Parts Espress. A efficient vintage 15 inch woofer and two vintage efficient 10 woofers, some planars and piezo's all (Ebay, Amazon, Junk in alley) three 26650 li ions. Sounds like my old Pioneer system with a shoulder strap. I do use lightweight boards and ABS sheets. Almost forgot. Another practice I do is to braid my input wires, speaker wires and power wires. And a loop or two through a ferrite donut cannot hurt either. Kill the noise. An extra capacitor on the power inputs too (Proper voltage). I also make my own led vu meters but you can find some prebuilt from China. Google LM 3914, 3915 and 3916. Look up Youtube for these too. Lots of choices and info. I also use the hard to find UAA180 (a2770) for led vu meters too. Learn how to etch pcb's or least use perf boards. I build just about anything, but you can too.
Sound like great ****.
Which one?
For me, they use manufacturers PCB design.
I'd look into an ICEpower 50ASX2SE. Better than most performance, and almost absurdly easy to get working, as the power supply is built onto the board, and no heat sinks need to be dealt with. AC line power in, speaker audio out.
ICEpower 50ASX2SE Class D Audio Amplifier with Power Supply Module 2 x 50W
ICEpower 50ASX2SE Class D Audio Amplifier with Power Supply Module 2 x 50W
I have to second the IcePower recommendation as they have come down in price and sound very good. As mentioned they come complete as to power supply and all of the connections. The only quirk can be how low the output impedance of your preamp stage is. If it's very low then you will be fine without an input buffer stage, but if it's a higher output impedance preamp then you might need a buffer. The buffer stage is essentially what differentiates the use of these modules by different OEMs, and each has their own secret sauce.
The IcePower ASX modules have an input impedance of 5000 to 8000 ohms depending upon the model, and your preamp's output impedance must be less than 1/10th of that amount or the sound will be unpredictable. More typical power amplifiers have a higher input impedance of around 47,000 ohms, making them forgiving of connection to a wider range of preamp driving impedances.
The IcePower ASX modules have an input impedance of 5000 to 8000 ohms depending upon the model, and your preamp's output impedance must be less than 1/10th of that amount or the sound will be unpredictable. More typical power amplifiers have a higher input impedance of around 47,000 ohms, making them forgiving of connection to a wider range of preamp driving impedances.
TDA8932 for me delivers excellent sound. Just needs a couple of extra caps adding to the stock modules, between VDDA (pin8) and GND (pin9).
I think it really depends on whether you need the buffer or not. For example, I have driven IcePower ASX modules directly from preamps with 200 ohms output impedance and they sounded just fine. There is no need to add a buffer if one isn't needed as it just represents another stage of electronics and a possible loss of transparency.
OTOH I was working on someone's tube preamp recently that had over 1000 ohms output impedance and would need a buffer to drive an IcePower ASX module.
Interesting. Passive preamps have varying impedance at different attenuation right? Are there any good, technically sound articles on this impedance matching I can read up about?
Good Point! In tests that I ran, passive preamps using a switched attenuator, an LDR, and an Alps potentiometer operating at typical listening volumes had output impedances of around 3500 ohms. This is obviously a huge mismatch with the input impedance of a basic IcePower module, but would still work fine with a typical power amplifier with a 47,000 ohm input impedance. It's also why some of the better passive preamps are now including an output buffer stage (making them not so passive anymore) - in that it makes their integration more forgiving for different applications. I believe the high output impedance of typical passive preamps is what makes them a generally substandard solution, well that and no gain at all.
The bottom line is that you want at least a 10X relationship between input and output impedance.
About any modern solid state preamps (or most modern non-tweaky tube types), or DACs, or pre-out from receivers will have low enough impedance. A "passive" preamp wouldn't do so well though.
Adding a buffer to the ICE module would be equivalent to putting a buffer at the output of the "passive", making it into an "active" preamp. So put the buffer in either location if a passive is all you have.
Adding a buffer to the ICE module would be equivalent to putting a buffer at the output of the "passive", making it into an "active" preamp. So put the buffer in either location if a passive is all you have.
The way I look at it the item with the "defect" is the passive preamp and its 3500 ohm output impedance at typical listening volumes. That's really quite higher than the vast majority of preamps, so I think is where the buffer should be placed.
I have a half dozen of my own operating stereo systems and switch components around between them, and also loan components to local friends who want to try something. In that the IcePower based amp will work perfectly fine with the vast majority of preamps I don't feel compelled to place the buffer there - UNLESS there is a good reason to do so (specific application). For example, one amp I built around the 125ASX2 module I used a tube buffer on its input, despite knowing I would use it with a very low impedance solid state preamp which would have been a perfectly fine impedance matchup, because I wanted to try and impart a little tube sound to that system. Another one I built around a 50ASX2 I used no buffer at all and it has worked great with a vintage tube CJ preamp and also with a Classe Audio preamp. In retrospect the tube buffer on the 125ASX2 ended up a little brighter than I would have liked, which then necessitated tone controls.
I am using a 125ASX2 amp with no input buffer on the output of an Infinity IRS Bass Module Servo Controller, and it's driving two Infinity IRS Bass Columns very well.
OTOH, if I were a lover of passive preamps, which I am not, I might think differently about where the impedance defect lies. Passive preamps are weird in my view in that that have a varying output impedance, their output impedance is unusually high at normal listening volumes (you can measure that easily enough with an ohmmeter to be sure), and unless there is a whole lot of source output level preceding them they seem to rob some dynamics from the music. I would lump them in the same defective impedance category as "wonky tube preamps" with thousands of ohms of output impedance - but that's just my opinion and the next person may feel that a power amp with 5000 - 8000 ohms input impedance is defective. Different strokes, and really the difference of where you place the buffer comes into play someday in the future when you move the components around.
Here's a picture of the 125ASX2 amp with the tube input buffer:
BO 125 acrylic lid by antennaguru uda, on FlickrI got some 50ASX2SE boards from PE that I'm DIY'ing into a 1RU rack shelf to make a 12 channel amp for my surround/Atmos speakers. I plan on trying out the yet-to-be-released Monoprice Monolith 16 channel pre-pro (HTP-1, I think.)
Concerning the input signal cables, included in the cable set, do I need to connect the shielding of the cable to ground? It appears the shielding is already grounded at the board, but I wonder about if and where I should ground the other end. Ground to chassis? Ground to the signal ground of the RCA connector?
I read through the manuals available on the PE website, but this wasn't addressed.
Concerning the input signal cables, included in the cable set, do I need to connect the shielding of the cable to ground? It appears the shielding is already grounded at the board, but I wonder about if and where I should ground the other end. Ground to chassis? Ground to the signal ground of the RCA connector?
I read through the manuals available on the PE website, but this wasn't addressed.
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It is normal practice to isolate chassis ground from signal ground, which is why the RCA connectors come with plastic isolation washers. Look above through the lid on mine that is pictured and note the RCA connectors on plastic isolation washers.
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