Are T amps just over hyped Distorting noise boxes? Or am I doing it wrong?

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That won't work. It'll reduce the impedance to the amp, but it won't increase power to the speaker, which is why the amp works better with lower impedances.

12V bridged amp maximum power into:
4ohm = 36W
8ohm = 18W
15ohm = 9.6W

And those are nowhere near the actual, once you take circuit efficiencies etc into account. You are likely only able to get around 3W of clean power into 15ohm speakers.

I have been looking at Pano's, How much voltage (power) do your speakers need? and according to his formula a 15 Ohm speaker requires less power than 4 Ohm speakers. I am accepting this as being correct because my old 15 Ohm Tannoys require less gain than the 8 & 4 Ohm speakers I have when connected to my T2020.
I had guessed that the Tannoys were drawing less than 3 watts but tomorrow, when the wife is at work, I'll set up for Pano's test, it should be interesting.
 
Yes indeed. You just won't get much out of a 12V amp, no matter what the topology. 7 watts RMS into 8 ohms is about all you can expect from the amp running 12 volts on the power supply. 10 watts RMS if you push the supply voltage a bit. That's plenty for my speakers (Altec VOTT), but not for low efficiency speakers.

Clipping sounds nasty on these, so you can't really push it hard like you can a 7 watt tube amp.

Well, I have conducted your test and the voltage requirements for my old speakers is 0.4vac. Doing the math for 15Ohm I'm only drawing .085 watts and thats on Baroque music!
I guess this is why I love my little inexpensive Chinese chip amp so much.
 
That won't work. It'll reduce the impedance to the amp, but it won't increase power to the speaker, which is why the amp works better with lower impedances.

12V bridged amp maximum power into:
4ohm = 36W
8ohm = 18W
15ohm = 9.6W

And those are nowhere near the actual, once you take circuit efficiencies etc into account. You are likely only able to get around 3W of clean power into 15ohm speakers.

Of course it will not increase the power to the speaker, but I understood that the sound would be the issue, not the power.

And now after your answer I am wondering why the power to the speaker should be the thing which makes the amp working better.
How should the amp notice when a 4 Ohms load is not a speaker but a combination of speaker and resistor?
Of course speakers are not purely resistive, but I strongly doubt the filter of the amp is optimized for the particular complex speaker impedance of any speaker. It is most likely designed to serve the range of 4 Ohms to 8 Ohms in a more or less acceptable way.
 
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Thanks for taking me to school guys.

Wow Well thanks guys for schooling me. I just about agree with all said. The very same amp I had on the fe103 needle excelled on lower impedance and efficiency now that I think about it cheap little 4 inch woofer and tweeter 2 ways.. The other 2020 I have enjoyed is a pretty extreme implementation. I wish I still has a pick but they are all sold out off ebay. I never have seen such a beautiful board lay out. Phillips blue ten uf Polly's. The ones in the nagras. A board designed to tweak endlessly like a breadboard almost with large spacings on important caps and a grid of holes and large spaced gold plated tracks. And what I find most interesting and unique is they hand wound output inductors on plastic nuts and bolts(about ten mill rather then the usual ferrite). This could be a flaw as well as an advantage as inductance would probably would be less then most ferrite based inductors inviting instability. I found using this amp with high capacitance cable into 8 ohm coral coaxes running a large sla to be a lush warm and quiet enjoyable. Perhaps a lucky combination. But I allso have had it driving a multiway altec 288 on jabo 350hz cutt off ev horn set up playing great now that I recal too! As much as mum is scared of the sla's it is the obvious supply test allso.(She doesnt wanna charge them and I scared her telling her about my RC car lipo battery's bad habits lol)

I agree about tripath chip probably being fake or having quality issues as the older they get too. Thanks Guys aw some schooling.

I agree out at mums power supply's very much most likely have to be reassessed and also I am running one of those digital remote preamps off china ebay out there too. So that could be a factor. I Thought also to up my game and try build a neat Little el84pp for her lounge and give it a shot with the little digital preamp also. I will persevere with the 2020's a little longer having 5 of these 4 of still rapped up but I think I will leave the hypex go for a while until I can have a go at trying to talk her into a el84. I have all the parts already tens time over unlike the hypex.
 
Hmmm I will check. I don't need that much power or to spend so much on a power supply to feed it. There was also A guy on ebay claiming a tiny little Yamaha chip and I mean "tiny" little chip was better then 2020. Here is a google DIY TUBE excerpt "There's a Yamaha class-D chip that may be better for some purposes, the YDA148. Similar power to the TA2020/TA20204, but with the bonus of built-in clipping protection. There's a "Y148" amp board on eBay for about $14 shipped, but I found a cheaper one at Dealextreme (which I ordered a few days ago). " I would like to try it too. """ i do wonder now how easy all these chips may be partially damaged by abuse""""

My hifi - YouTube I run into this Utube Funny Iam listening to this chip amp through my joey Roth chip and and usb dac and trans and techinics sb-f2 trying to figure out if it sounds better lol. Honestly No offense to ever it is. I couldn't live with that set up for half en hour. It seems to shriek like all low end fostecs to me that contain whizzers of the few different ones I have bought or heard so far. I do look foward to trying a really good set of hiend fostecs one day even there horn drivers.

The tinyier chip the more they appeal to me from Zen perspective. If I ever really new what that meant not being Asian Maybe they are just cute. :)
 
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Regarding the Y148 boards on DealExtreme: From the picture, the output filter inductors appear to be small ferrites, so they are probably subject to inductance change due to temperature rise if played loud for awhile. The output capacitors are surface mount types, probably ceramic, so the will be subject to the distortion mechanisms mentioned in Understanding output filters for Class-D amplifiers and Trevor Marshall - Class D Audio Amplifier Design - TDA7498 Output filters . But hey, for $9.50, what do you expect? You won't get premium inductors and caps for that price.

Regarding driving 15 ohm speakers: The problem is that the output filter is designed for 8 ohm speakers. The purpose of that filter is to suppress the class-D switching frequency which is in the 50 kHz range. The optimum L and C values for class-D output filters depend on the load impedance. The inductors shown in the photo are 22 uH, which is the correct value for 8 ohm speakers. If you connect a speaker with a different impedance, the output filter will still operate, but its damping factor factor will be wrong. For 15 ohm speakers, the "Q" of the filter would be too high, which is the same as saying that it is "underdamped". What that means is that the filter will "ring", and more of the 50 kHz signal will be present on the output. That could cause the chip to see transient voltages or currents in excess of those it can easily handle. That could result in distortion or damage to the chip.

Class-d (and class-t) amps thus work best when the speaker impedance matches the design point for the output filter circuit. As a rule of thumb, if the filter was designed for 8 ohms but you want to use a 4 ohm speaker, you halve the output inductor values (2 inductors per channel) and double the capacitor values (2 or 3 capacitors per channel). To go from 8 ohms to 16 ohms, double the inductors and halve the capacitors. That's the rule of thumb - to really do it right you need to consider the speaker inductance, and you may also need to add an additional "snubber network" to deal with currents flowing in the circuit when the output transistors are turned off. The two links cited above give the gory details.
 
Can the above be verified with ones ears? That is, could could an "expert" say to me, "You have the wrong inductors in your amp for those speakers, I can tell by the sound"?
The reason I ask is that I have several sets of still highly regarded speakers and they all sound great hooked up to my T2020 amp. They range from 4ohm to 15ohm and very small to huge.
The best are my huge old 15ohm jobs, they just purr along drawing just under 1 watt.
 
Wouldn't it be way easier to put an 8ohm (10W+ rated) resistor in parallel to an 8ohm speaker, so it will count as a 4 ohm load for the entire output filter. Of course you "waste" half of the power on that resistor.
But: the ta2020 has almost double the power on 4ohm than on 8ohms. So in the end the power to the 8ohm speakers will stay the same, just the ta2020 will be running hotter (4ohm has lower efficiency and you will put out double the wattage).
 
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It's mostly the top end of the response that is affected by the output filter. See my measurements here:
Super-T Response
Sonic Impact Response
Sonic Tripath


Putting a parallel resistor across the terminals is a crude approach. Better to tailer the impedance of your tweeter, or the values of the output filter. It's the response above 8-10Khz that really changes with speaker impedance.
 
The upper frequency band still seems fine though. 1-2db variance in the last 1/3rd octave of your upper hearing range seems insignificant. Same goes to the sub 50hz band, seeing as that you aren't listening on a free field and your room has so many modes in that region which can easily reach > +-10db.

I would rather be concerned about possible distortion or other artifacts, than some attenuation in the most upper and lower frequency ranges. Because those could be very audible.
 
Regarding the audibility of output filter mis-damping: I suspect that it is not directly audible in and of itself, but I could imagine situations where it caused amplifier instability that would be audible. It probably depends on several factors including the supply voltage (if close to the maximum, the chip would be more susceptible to overvoltage induced by filter ringing). Other factors could include the inductance and capacitance of the cables and the presence of RF interference or other noise coupled back into the circuit. A well-tuned output circuit will be less susceptible to such problems - but if those problems don't exist, maybe the mis-tuning itself is benign. If, as you say, the system sounds good to your ears in your setup, you win.

I once connected a 2-ohm load (four 8-ohm speakers in parallel) to one channel of a Sure 4x100 T-amp and it sounded just awful, even at low volumes. The amp was clearly freaking out. It sounded fine at 4 ohms. The problem mechanisms for too-high impedance are rather different - overvoltage for too-high impedance vs. overcurrent for too-low - but it is clear that, in some circumstances, impedance does matter.

Regarding a parallel resistor: If the output circuit is turned for 8 ohms - as appears to be the case for the two T-amps that I have (HLLY 20 and Sure 4x100) - dropping it to 4 ohms will make things worse (albeit overdamped instead of underdamped). But paralleling a 16 ohm resistor across a 15 ohm speaker to bring it down to 8-ish ohms would indeed do the right thing for an 8-ohm-tuned output filter. It would not change the amount of power instantaneously available to the speaker, because the voltage across the speaker would be the same in either case. The amplifier would still be operating within its rated I-V conditions. The only possibly-audible downside might be a reduction in the reserve power available for extended bass passages. I doubt that would be a problem if the power supply is decent.

The resistor power rating would not need to be all that high for normal listening. For music, you want to listen at average power levels lower than about 1/10 the rated amp power. At higher average levels, the musical transients will exceed the amp power and clip, and that is definitely audible. For a low-power T-amp, a 5W resistor would be more than adequate. Full-power bench testing is obviously a different story.
 
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But paralleling a 16 ohm resistor across a 15 ohm speaker to bring it down to 8-ish ohms would indeed do the right thing for an 8-ohm-tuned output filter. It would not change the amount of power instantaneously available to the speaker, because the voltage across the speaker would be the same in either case.

If the output impedance of the amp is low enough, yes. In this case it mostly is.
 
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