Kitty is so cute. I'm trying to put together a guitar amp using the TDA7294 chip on a board that is sold on Ebay. Unfortunately, I was taken in by the low reduced price, ordered it and didn't pay attention that it requires a AC input from a transformer (100 to150VA) around 24vac to 36 vac with a centre tap. These transformers are getting expensive these days when looking at supplierss such as Mouser. I haven't ordered at transformer for it yet, but instead found another circuit board , almost identical, that accepts a bipolar rail supply of 50volts to develop the 100 watts rms claimed. The heatsinking has to be external on this one. I ended up buying a +/- 35volt swithching power supply from China and also the other DC input version of the TDA7294 `100 watt amp to go with the switching power supply. Problem with these Ebay sellers from China is that there is no technical information other than the pictures for the pc cards and components on them.
I once bench-tested my Fender Super Reverb and my VOX AC-100 Super Beatle head. Clipping with a 1K sine wave occured at 18 watts on the Super and about 35 watts on the AC-100.
Similar but not exactly the same as class D pdf.datasheetcatalog.com/datasheet/Tripath/mXyzxwwt.pdf c/p from another review Class T? What's That? Those who have been paying attention so far have surely noticed the “Class T” designation on the DTA-1 amplifier. You might be wondering what that means. The following is a simplified explanation. A “Class T” amplifier is a single integrated circuit (a “chip”) audio amplifier produced by the defunct Tripath Semiconductor company. Class T amplifiers are closely related to class D amplifiers, which operate in a switching mode. A switching amplifier operates on the concept that its amplification components (the transistors) are either fully turned on or fully turned off. In the case of a Class D amplifier, the input is "blended" with a wave generator to produce a squarewave, which is amplified by the transistors. This is then low-pass filtered to remove the switching frequency from the audio, theoretically leaving behind only an amplified version of the input signal. Switchmode power supplies (as frequently found in computers) work in a similar fashion--a controller IC varies the switching frequency of one or more transistors. When switching, the transistors are either fully on or fully off for a certain length of time. If you adjust the duty cycle (ratio of "on" time to "off" time) the output voltage and current can be controlled. The switching pulses are then filtered out with a capacitor to "smooth" the output. This method of design leads to a very high efficiency amplifier. Efficiencies approaching or even exceeding 90% are possible in high quality designs. The only drawback is the distortion of the input signal during the amplification process. Sometimes the switching frequency (or a harmonic) can leak through the filter and may be audible. I have noticed this behavior from the Tripath amplifiers used in some Apple computers. (It seems that Apple was aware of this and something deactivates the amplifier when it is not in use.) The "Class T" design adds to this a digital signal processor that is used to manage the power systems in the amplifier IC. Also included are thermal, overload, and short circuit protection. The small package size, high power output, relatively good audio quality and efficiency made these amplifiers a popular choice for many different applications--computers (Apple Computer used them in the Quicksilver Macintosh G4 systems, as well as the iMac G4 and probably others), home theater in a box setups and compact stereo systems. Despite the technological advantage of their parts and their popularity, the Tripath company ended up failing. So far as I know, after the company failed, the supply of new Class T amplifier ICs came to an end. I'm not aware of anything having bought the remains of the company or the rights to its products, which are patented. (If you have further information on this, I'd appreciate being contacted so as to set the record straight here.) Anyway, that's what a Class T amplifier is. Onward to... greyghost.mooo.com/dayton-review/
I am guessing that the 'high power instability' you are seeing is that PWM over-powering the low pass filter. That's the trouble with class D. Since you are using high-frequence PWM to modulate voltage the class d depends on a LPF to eliminate the PWM frequencies from the audio output. So it's expensive to design a good LPF that works both well at both high output and low output.
I don't terribly get it. I mean, why is eliminating PWM even important? It's not like you're gonna hear the 400 KHz carrier wave, plus the response of your speakers around those frequencies is likely to be nil. But i can see the fault that can lead to issues with high power, saturation in the filter inductor, which is a source of nonlinearity. For this reason, i think Tripath is specified to be used with a 3-10uH air core inductor, which is honestly not all that big of an issue, just a handful of turns of 0.8mm wire in air and a handful of .47uF film capacitors, no big deal at all, pennies. But chances are, whatever factory churns this out just stuck in whatever they had at hand, whatever was cheap.
I guess Im randomly asking but does any of you know a trick to log back into an instagram account? I was dumb forgot the password. I love any help you can give me.
@Preston Dominik thanks for your reply. I found the site through google and im in the hacking process now. Takes a while so I will get back to you later with my results.
70% efficiency at 30 watts = 9 watts peak power dissipation = 6.36 watts of heat you need to dissipate. You have to take the RMS value of the peak wattage being lost to get the actual wattage wasted to heat, but outfitting the heatsinking to handle the unrealistic peak wattage is an overbuild I can stand behind :P
Yeah, that osculation is probably ultrasonic, but it would hetrodyne with the audio, producing difference frequencies that might be audible. So I'd rate it with no oscillation, which would give an even lower result on the power test. So I share your preference for AB over D, though if this was to be a battery powered application the D would be worthwhile.
***** The frequency of the oscillation appeared to be several hundred KHz, so any inter-modulation products and associated harmonics would be well out of the audio band, otherwise it would have showed as a blip on the blue spectrum wave on the scope.
JohnAudioTech Yeah, notice that the spectrum readout was pretty clean. Still, music is much more complex than a 1kHz test tone. Noticed your using a player with a recorded tone for less distortion. Too bad low distortion sine wave oscillators remain expensive. Would like to see two or more clean tones at once, pulsed tones, other variants, though that would be one long video!
Anton's Workbench Amplifiers "see" only a changing voltage level. Doesn't matter if the signal is complex music or a pure sine wave. As long as the signal doesn't change too fast (fast slew) the amp will handle it. The amp can be amplifying 1 tone or 100. As long it has reasonable low distortion, the amp will product no audible inter-modulation products. See: sound.westhost.com/articles/myths.html sections 5.3, 5.6, 5.7 (whole article is a good read, btw). The THD of that music player plus my computer's sound input is around .002%, so it works great for these tests. I've played around with dual tones to check the sum and different inter modulation signals but any good amp with low distortion will produce low IM because it is mathematically impossible to have IM without nonlinearity which also causes harmonic distortion.
Very informative video you got here. Just want to ask the published wattage per channel of the tda1558q. Also, why do you think most "audiophiles" think that most class T or D amps sounds more anlaog or tube like compared to class AB amps. Can your test show harmonic differences?
Carlos Mergulhão I performed a heat transfer test of several materials and found epoxy works quite well. It is in fact better than Sil-Pads and nearly as good as greased mica washers. It wasn't even the thermal conductive type epoxy.
I fucked around a bit with maths and according to the results I got, AB amps get the hottest when the signal amplitude is 0.707 times the supply voltage (this means half power), but the most interesting thing is the graph of the efficiency is linear (X/1.41, where X is output/supply), so they are most efficient at full power. And my homemade AB amp proves this. (I don't have an oscilloscope btw, but at half power I can't touch the output transistors, whereas on full power they are just a bit warm).
Most modern class D amps don't produce quite as fuzzy of an output as they used to. They use to have lower frequencies limiting how much could filter and those same lower frequencies increasing aliasing when sampling to PWM and back to analog.
Great video, and while class D amps have pretty much the same audio quality, I find them boring, I mean, just one chip? xD. I like normal linear amps but I would go class D any day just due to their efficiency.
If memory says me right, output cascade of TDA1558q is biased to be in class B, even though quiescent current doesn't say so. But in datasheet it says that this is class B
MrJohhhnnnyyy I see that a lot on datasheets, yet the ones that show an internal schematic clearly show a biasing scheme used. It wouldn't make a lot of sense to develop an audio power chip and not bias the outputs. I think they call it class B because most AB amps are really close to B which is a true amplifier class rather than an "in between" or subset.
JohnAudioTech I agree, I usually set quiescent current just enough to eliminate crossover distortion, not more. Class A amps can draw few amperes of quiescent current, so indeed class AB is closer to B.
Dover gerold Thanks Dover. Even though I'm a few miles away, I stopped going many years ago. Parking and admission costs offset the good deals. I find a lot of things I need online now. I'm also trying to cut down on stockpiling stuff I'll likely never use.
A bridged amplifier is always, even in class D, less efficient compared to a half bridged amplifier, because you have have the losses of the doubled amount of active transistors. I don't understand why the people make bridged class D amplifiers, because the only reason to make them is efficiency. It makes no sense to operate a class D amplifier with a non-symmetric power supply because you lose immediately a big portion of its only advantage compared to class AB amplifiers.
Hi John. I'm a noob in electronics here, but what are the speakers watt you are using? For instance, can i use a 2way 50W speaker (25w rms) 4ohm, with any of these amplifiers? Or i must choose other speakers, like 15w 4ohm?
You can use 4 or 8 ohm speakers with most of these amp boards. Check the instructions with the amp board to be sure (some may not be safe with 4 ohm speakers). Speaker wattage can be the same or greater. You can even use lower wattage speakers than the amp is rated but you must be careful that you don't crank the volume too high that you damage the speaker.
you did your measurements with that 1 KHz signal, I wonder if the highth of the output relates to the kind of signal and waveform - basically the same way a base sounds more voluminous too
I have a high-end Pioneer amp, but my two 12" woofers, connected via crossover units, are not too "deep-throated". Lower noted from cellos, tubas etc. just don't make it. Double bass and bass drums are fine, as my 15" sub deals with this area very well. Can I 'slip a D class amp in-line to boost the 12" delinquents?
+Michael Denning Don't connect two amps to the same speakers unless you really know what you're doing, bi wiring and all that. Running more amps in one system is no problem as long as you keep the loads separated.
Michael Denning No you cannot do that. If your subs aren't performing either design a new enclosure that works with the power available or get new subs that work better with the power you have. Your final option would be to get new amps AND subs.
@@Assimilator702 I've strapped 2 2k rms mono block class D amplifiers to 1 15" sub before , it can be tricky but it's totally doable . And why you might ask? Well I have a 4k rms sub but my amps are only 2k so strapped I get 4k rms 👍 it's a common thing to do in the car audio world when you have a big boy 90lb subwoofer that can eat a small towns worth of power
Is that the dirt cheap ta2024 off ebay that it looks like? Am about to build some very sensitive horns andthink my TA2022 45wpc might be a bit powerful, was looking at those cheapies tofix that and to sample ta2024 sound
Praise, great work. If we could explain in more detail about the amplifier used by jbl extrem 2. As far as I can see, jbl works at 7.2 V? Amplifiers TPA .TDA ... require 20V.... to work .Which amplifier uses JBL? Thank you
To measure efficiency accurately you cannot use sine signals. You must use a white or pink noise signal with a crest factor that simulates music. What you're measuring here is just circuit specific deviance from optimal efficiency. The theoretical peak efficiency of class AB and class D are 71% and 100% respectively. If you measure on sine signals before clipping that number should be about 80% of that for both amps which is what your numbers show. It is important to understand that class D amplifiers are designed to play music. The average level in music is far lower than a sine wave. Usually 10-12dB lower (or 10-16 times). It is at an 10% average output (-10dB average) you measure the efficiency. A class AB amp will show about 15-18% efficiency and a typical class D amp will show about 70-80% efficiency at 10% average output level. Everything in class D chips and amps is designed for the purpose of musical playback. Heat sinking, component dimensioning, etc etc. Using sine waves as test signals for class D amps is wrong from an engineering point of view as it will not show the actual performance when in use.
SaturnusDK I see that a lot of amplifiers are designed for playing music, for if it played a continuous sine wave tone at max power, the amplifier could get too hot since, as you said, average level of music is much lower. This is common with consumer products because an extra large heatsink and power supply would be costly. The companies making this stuff want to be competitive and profitable. Of course, this may not apply to boutique gear. I don't agree at all with your last line about using sine wave as being wrong from the engineering standpoint. Sine wave signals are what every amplifier designer or EE I know of would use. Once the amp is built, tested and stable, it is time for the musical listening test.
@Steve Foudray Exactly what I'm arguing. These are audio amplifiers, they are advertised as such and sold as such. Many places that sell these even stipulate they are for audio playback only. So when you measure them you must use audio signals, or internationally recognised approximations of audio signal but never pure sine waves, or at least never pure sine waves used as the only metric, as that gives a completely false picture of the performance.
+a133m210 I used a 16v cap since my voltage was under 15 and regulated. Adding a second cap my be of some advantage if your amp has long power supply leads.
+Peter Pan Good point. While I didn't perform a blind listening test or an extended listening test with good speakers, I really could not tell the difference between them. Put it this way: Nothing ugly stood out with either amp when I performed the quick listening test.
+JohnAudioTech not to mention a lot of the way it sounds in the end depends on the implementation of the board, the components used, the power supply, and the chip not being fake
love your videos,,,if u can only make 1 amp (around 15 to 50w) what chip would you use?,,,(very clean bass and high ) any recommendations on diy boards on ebay? thanks
dulasha1 I'd use the LM1875 for the lower end of that scale and the LM3886 for the upper end. I don't trust the stuff sold on ebay. Chipamp.com sells kits or boards for both of these ICs.
I'm looking for a very efficient amp to power a set of speakers for a cosplay suit. It has to be able to run off of a battery pack (probably one used for large RC vehicles) for a few hours. I want it to be fairly powerful, loud enough for people to hear and understand what I say in a noisy environment Speakers will include a midbass woofer and a full range driver. Is there an amp you would recommend for this purpose?
+Daniel Miller Parts Express has a selection of class D amp modules that should work. If you're using a microphone, you will need a preamp before the power amp. Knowing the amount of decibels you need and the sensitivity of the finished speaker would be a big help in figuring the power needed. Sounds like yo need a mono unit. Most kits and modules are stereo but you could use each channel to drive the proper speaker and use a filter before the preamp to direct frequencies to the correct driver so extra power is not wasted.
If I were to make a stereo system using amp boards like this, where would you place a headphone jack in the signal line? (the kind that would mute the speakers when plugged) .. I would guess after the preamp?
+Kyle Comeaux You would need a headphone amp if you insert between the preamp and power amp. Preamps don't normally have enough current to drive the headphones. You would need a manual switch or an auto disconnecting headphone jack to turn off the speaker amp when using the phones.
Class D it self is really efficient - but - a BIG *BUT* : They are mostly used when something needs to be built down to a price and/or efficiency and thermal limits are important. So very often you will see rather poor Class-D Amps just cause no other design would really work for those designs. At the very highend you can get pretty much every design to sound perfect. I personally rather like Class D cause you can even make them your self really cheap and still have a great performance. And with a bit of knowhow you can use it to drive some bigger Mosfets to get high amplifications and the ability to drive big loads even with a really cheap Amp.
I think if you call this a test, you have to talk about the low and high-pass filters that you have on the breadboard, as well as other components. Not a scientific test without that info?
that's an incredibly terrible example of a class D amp. You should try ones built on TPA3116D2. I have one and I'm liking it. It actually works better than my TDA2050 when supplied with 20 volts of switched-mode power.
I had a question that relates to Class D. I'm thinking about buying a Class D solid state guitar amplifier, but I heard that Class D amps lose a lot of their power (more than Class A or A/B amps do) when they drive speakers above 4 ohms, and my speaker happens to be 8 ohms. Is this so? If it is, the high watts the amp manufacturer claims for the amp don't seem as impressive.
No, your ears are just fine. It is because there really isn't any audible differences. Most properly functioning solid state amplifiers will have distortion under 1% or even far less and that has been shown to be inaudible with music. Frequency response is usually pretty flat and damping factor high which is all good for fidelity. However, some of the class D boards I've tried have background hiss a little higher than I'd like.
Does this amplifier gives distortion for low frequency less than 2hz as i want very low frequency sound generation in my project..Suggest any audio amplifier circuit..
You don't hear any distortion? Well, I guess it's a subjective thing you're doing, but the music sounds like it was being played through a tin can instead of a HiFi speaker of any decent type.
Class "D" is a single channel, it's a mono sub woofer amp. You are calling a 2 channel stereo amp class "D" class "AB" amps amplify the signal as it comes into the amp. Class "D" amps filters out the mids and highs, then only amplifies what is left, the lows, that's why people say it's more efficient. To get the same effect with a class "AB" amp you need to run a crossover. Class "D" is typically smaller and does not need to take signal from a crossover. Therefore it's a space saver.
I'm friends with a dozen DJs and around age 35, they're well on their way to be declared legally deaf. One is actually deaf on one ear. The rest have around 20db-30db worse hearing than myself. The profession isn't particularly kind to one organ it relies upon.
+DVXCine I think it is important to show the "trash" as it could be instability or core saturation of the filter chokes. It really shouldn't be there in a properly operating circuit.
:) that is one of the worst types of boxes ive heard , philips "bass" unit sounds a bit like taht as well but that is the worst ive heard , even that small amp is way better then da boxes , no rant intended bu really
Lets compare a regular amplifier vs a "premium entry level" class amplifier, lets put the video on youtube and let everyone that most likely use some kind of class D amplifier on their computers "hear" the difference :P
My speaker quality + My room acoustics + my camera's weak, compressed audio quality + video editor's audio compression + RU-vid's audio compression + viewer's computer, amplifier and speakers/headphones = Not a reliable way to judge sound. However people jump up and down and pitch a fit if I don't play a sample of music through the amplifier.
lol sorry it was not a mean to offend, i just think it is crazy to say that the difference is clear on the vid. I have no doubts that there is difference, just hard to tell through here.
John, are you having some breathing problems? You sounded out of breath during a lot of your discourse. Also, shut off the camera and feed the cat. Then get back to the video. Everyone will bee less tense. 😎
