Yeah but it's not 100% foolproof... I've had a TDA7294 shoot itself into orbit when I "tested" the short circuit protection during full power sinewave testing at high frequency...
There are always limits! 😀. Not the sort of thing an ordinary consumer is going to try while his fancy speakers are hooked up ... and, this delves into the whole highly debated arena of what, and how precisely, to "protect" of the bits of a system ...
Its telling peufeu that you used scare quotes around 'tested'. ISTM your 'test' fell into the HHGTTG 'Ultimate question' trap. What precisely was the question you were testing your TDA7294 with? 'Can you drive a 20VRMS 20kHz sinewave into a short circuit without exploding?'. And if that was the question, why ask that particular one when as Frank points out, its not particularly relevant to everyday usage?
Actually I put quotes because the "test" wasn't really voluntary... something slipped, and poof. I did test it (voluntarily) at reasonable power with music and it didn't seem to pose problems.
As for "limits", the only limit I will concede to are the power rails. That is the one limit which truly cannot be exceeded. For all other than that situations, a failing chip is junk chip.
As for what are the limits in everyday use, excuse me, Frank and Abraxalito, but you are not the judges of that. What if someone has an awkward load of a speaker? That too is not "everyday use", if that someone wants the full blast he was promised?
Sorry gents, but protection is by its nature diguital, it either sleeps (0) or works (1). The only art in it is making sure it doesn't trip too soon (needs a delay) and that it was designed to make full use of the available facilities, no matter what they are, on a case to case basis.
The overvoltage part should act only when one is dangerously near the supply line limits, since a slightly reduced dynamic volume is far more preferable to a clipped sine wave. The part about current must act only when the amp is in serious proximity of overreaching its limits, or the limits of the power devices in terms of voltage to current relationship.
If I can do that, there's no way any big manufacturer cannot. And if it doesn't quite work out, well, back to the drawing board.
All the last few posts have told me is that chip power amps are not nearly as safe as discrete ones. Thank you for a wonderful sound of a short fuse bomb.
As for what are the limits in everyday use, excuse me, Frank and Abraxalito, but you are not the judges of that. What if someone has an awkward load of a speaker? That too is not "everyday use", if that someone wants the full blast he was promised?
Sorry gents, but protection is by its nature diguital, it either sleeps (0) or works (1). The only art in it is making sure it doesn't trip too soon (needs a delay) and that it was designed to make full use of the available facilities, no matter what they are, on a case to case basis.
The overvoltage part should act only when one is dangerously near the supply line limits, since a slightly reduced dynamic volume is far more preferable to a clipped sine wave. The part about current must act only when the amp is in serious proximity of overreaching its limits, or the limits of the power devices in terms of voltage to current relationship.
If I can do that, there's no way any big manufacturer cannot. And if it doesn't quite work out, well, back to the drawing board.
All the last few posts have told me is that chip power amps are not nearly as safe as discrete ones. Thank you for a wonderful sound of a short fuse bomb.
Some time ago I built a H-bridge and I wanted it to have bomb-proof protection against shorts between outputs and to ground. A fast current comparator connected to the PWM controller hardware fault input does the trick. The whole thing takes much less than 1 µs to react (the MOSFETs switch in ~10-20ns) and the track inductance limits the current rise to something reasonable for SO8 dual MOSFETs. This one I tested by putting a screwdriver across the output terminals. I felt sorry for the poor MOSFET sitting between the big capacitors and a screwdriver. It worked.
Actually any wire going out of this board can be shorted to any other wire without burning stuff. The uC may crash but not burn... That was an interesting challenge...
I'd be tempted to transpose this to an audio amp : current sense the output or the rails, tweak the value to provide max current versus time settings (by integrating, for example), and switch the ouput or the power rails using MOSFETs.
Another simple idea to protect speakers : put a small resistor on the output of the amp, in parallel with the speaker, sense its temperature, trip when the resistor is too hot.
Short circuit protection needs to be very very fast ; for the rest, unless the output SOA is a problem, slow is OK.
Actually any wire going out of this board can be shorted to any other wire without burning stuff. The uC may crash but not burn... That was an interesting challenge...
I'd be tempted to transpose this to an audio amp : current sense the output or the rails, tweak the value to provide max current versus time settings (by integrating, for example), and switch the ouput or the power rails using MOSFETs.
Another simple idea to protect speakers : put a small resistor on the output of the amp, in parallel with the speaker, sense its temperature, trip when the resistor is too hot.
Short circuit protection needs to be very very fast ; for the rest, unless the output SOA is a problem, slow is OK.
You should build one and get off the paper guessing ..🙄
😀
Yes frank limited, to 100 db @5M listening distance 🙄 as to quality amplifier, have you ever heard one? you should try and get one to listen for your own edification, it will arm you when in conversation.
Now put the pen down and put your amazing pie in the sky 32amp capable chipamp together,
OK theory captain..................
I have short circuit protection, it welds anything in short time, that's how you make amplifier protection...
🙂
To be realistic, Wayne, your own views are higly coloured by your, I daresay, almost unique system. Please don't quote a few other, literally astronomically priced systems, I am not too sure they are hard to drive because they have to be, but because they purposely made them so, pushing you towards behemoth amplification. Just like every new generation of Windows needs a new PC platform.
I can easily see Frank's chip power amps as being quite sufficient for like 90% of home users - note I say "sufficient", not ideal. A home system typically has a speaker system of 8 or 4 Ohms, and much as yourself, hardly even goes beyond 17 Vpeak; that's like 5-6 Amps in short term peaks, and as Frank says, the chip amp will deliver up to 8 Amps in peaks.
But, cheap loudspeakers tend to be shouty, implying greater than your speakers' efficiency, so even 17 Vpeak is suspect, most will probably never go that after after a tryout when they first buy it.
Besides, those chip amps were never intended to be, or are sold as, anything even approaching higest quality of reproduction; they are simple and cheap solutions to the audio industry's need for cheap multichannel HT devices.
No my own views are from experience and never owning dinky toy amps, always bought big amplifiers , overbuilt and with loads of power. Even when i was into tubes , no dinky toy tube amp , i went with mc3500's, then my first S amp was a custom fully regulated amp with huge current capability, this is 1978.
I have never liked nor owned dinky toy amps ..........Never
I have never liked nor owned dinky toy amps ..........Never
Ohh,
Chip amps have no sound , so less forget about it, one day Frank will come out of the clouds ..
😀
A Pilot?s View: Queenstown, New Zealand
Chip amps have no sound , so less forget about it, one day Frank will come out of the clouds ..
😀
A Pilot?s View: Queenstown, New Zealand
Good. We finally have something to work with, so now can we get some sort of sensitivity figure, on the panels? - if the maximum voltage swing is only 17V, then either these panels are amazingly efficient, or you're talking about what the bass drivers are doing. So, forgetting the latter, at 1 metre distance from the panels what dB does a midrange sine do?
Efficient, you mean sensitive and 17Volts? where are you getting these numbers from Frank, i never set a limit on anything , these are your sky numbers for your dream chip amp, my min target is 25v, 25-30v is preferable .. 🙄
As to sensitivity , I had already stated this and if you weren't aware , sensitivity ratings based on point source speakers are different for linesource dipoles. I will wait for DVV to chime in , you seem to hear him better ..
anechoic is 79db/2M/2.83V +/- 3db 28-22K, knock yourself out ...🙂
As to sensitivity , I had already stated this and if you weren't aware , sensitivity ratings based on point source speakers are different for linesource dipoles. I will wait for DVV to chime in , you seem to hear him better ..
anechoic is 79db/2M/2.83V +/- 3db 28-22K, knock yourself out ...🙂
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Methinks master a.wayne doth protest a little too much ... I've only heard one system setup in 10 years of hearing other people's mega expensive gear that clearly had the goods on what I normally experience and look for - this was obviously the Bryston combo, and what it clearly was capable of was going outrageously loud, by normal home audio standards, while remaining 100% clean. I've had my fill of pretentious systems bellowing fit to bust, not interested in hearing more of the same ...
hearing voices again Frank , what are you talking about and we dont do loud Frankie, we do real and musical, loud is only an expression, so when someone describe a system by telling me how loud it goes,
Well ...🙄
Run ..................
Well ...🙄
Run ..................
The Perreaux had 90V rails, my DIY chip amp had 42V ones, and the latter was pushed to next to overload levels regularly - so, giving 35V or so swings.
Simple test. I want a DB level, 1 metre away, I'm not interested in room and configuration enhancements - because neither is the amp. How much do the panels rattle back and forth, for a certain voltage input?
I'm still running your responses thru Google translate, I'm not following , less do one at a time ,
what is this 17volt bit ...? and i already gave you all the sensitivity specs you need, unless you still want efficiency 🙂
Rattle..? not plastic Frank no rattling ,Now what does this have to do with anything apart from eating bandwidth ....
Perreaux's are donkey dodo ...🙁
what is this 17volt bit ...? and i already gave you all the sensitivity specs you need, unless you still want efficiency 🙂
Rattle..? not plastic Frank no rattling ,Now what does this have to do with anything apart from eating bandwidth ....
Perreaux's are donkey dodo ...🙁
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Need to get out and about more, my dear chap. Real instruments go loud, really loud, effortlessly - that's why they sound, well, "real" ... 🙂hearing voices again Frank , what are you talking about and we dont do loud Frankie, we do real and musical, loud is only an expression, so when someone describe a system by telling me how loud it goes,
Well ...🙄
Run ..................
I normally would like to use the term "intense", it captures the essence of the subjective experience better. Conventional hifi, no matter how expensive, is usually pathetic at creating that sense of intensity - and that's what I'm looking for - the Bryston did the intense, just like the real deal ...
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