I was reading the specs for the Technics Network CD Receiver SA-C600 and in the specs it is rated from 4 Ohms to 16 Ohms speakers. 16 Ohms is a bit before my time and I am wondering what happens if this rating is exceeded.
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What happens if more than a 16 Ohms speaker is used on a 4-16 Ohm rated amplifier?
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Generally power drops at a given voltage as impedance goes up. So 16 ohms will be half the power of 8 ohms so on and so forth. For lower impedances at some point an amp's power supply is unable to supply enough current and that can limit power in the other direction. In this case from their one power spec, I would imagine 30 watts at 8 ohms, 15 watts at 16 ohms and 7.5 watts at 32 ohms. Other than power reduction at the higher impedances nothing untoward will happen.
PMA's comment is worth noting. For some class D amps like the old TriPath class D, the higher impedance will cause a peak in the treble and low ultrasonic. With enough of an increase things might go awry.
PMA's comment is worth noting. For some class D amps like the old TriPath class D, the higher impedance will cause a peak in the treble and low ultrasonic. With enough of an increase things might go awry.
Think of this: What happens to an amp when you have no speakers connected at all? That is equivalent to having really, really high impedance speakers connected, right? And nothing at all bad happens to the amp. The voltages are right there on the terminals but no current flows.
Even more important from my point of view is the fact that we have an interaction of the output LC resonant circuit of most cheap class D amplifiers with the complex impedance of the speaker. Pure resistor load 4 - 16 ohm does not tell the whole story, it only speaks about damping factor of the LC Q, which is usually tuned to make flat response with 4 ohm resistor. Higher resistance leads to FR peaking. Complex impedance load may transfer the peak as low as to 10 kHz. Unfortunately, this remains untested here.
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Yes. As you said with Hypex or Purifi we don't need to worry. I think the Tact amps I have which are Tripath based, they were optimized for 6 ohms. Stereophile does show measurements of FR with 2,4 and 8 ohms along with their simulated load. ICE Power amps don't seem horribly misbehaved this way. Though not as well behaved as Hypex or Purifi.
mhardy6647
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Less power delivered into the higher impedance. At the limit of infinite impedance, zero power. 
PS Some of us use 16 ohm loudspeakers all day long.
PS Some of us use 16 ohm loudspeakers all day long.
you get more deviation in the FR > 10KHz
mhardy6647
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Class D + High impedance loudspeaker...
And that's playin' Little Girl with Guitar music! Play something like Fanfare for the Common Man and it's game over, ol' son.
ahem.
back in the good ol', bad ol' days of output transformers -- and with apologies @atmasphere and others who espoused other approaches -- there were several companies who went a slightly different route. Philips was probably the better known, but Stephens Trusonic did it, too.
source: http://hifilit.com/Stephens/Stephens.htm
I have a single 106AX... but, for better worse, not one of the 500 ohm variants.
And that's playin' Little Girl with Guitar music!
Play something like Fanfare for the Common Man and it's game over, ol' son.ahem.
back in the good ol', bad ol' days of output transformers -- and with apologies @atmasphere and others who espoused other approaches
-- there were several companies who went a slightly different route. Philips was probably the better known, but Stephens Trusonic did it, too. source: http://hifilit.com/Stephens/Stephens.htm
I have a single 106AX... but, for better worse, not one of the 500 ohm variants.
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Nonsense.Class D + High impedance loudspeaker...
View attachment 403252
And that's playin' Little Girl with Guitar music!
ahem.
back in the good ol', bad ol' days of output transformers -- and with apologies @atmasphere and others who espoused other approaches
View attachment 403253
source: http://hifilit.com/Stephens/Stephens.htm
I have a single 106AX... but, for better worse, not one of the 500 ohm variants.
If the class D is properly designed then a high impedance load won't be any problem at all.
Exactly! If there was a problem you'd see class D powered subwoofers failing all the time. A subwoofer impedance can be greater than 100 ohms as it approaches Fs
mhardy6647
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I was just joshing around -- in fact, riffing off of the post I quoted.
Given your OTL heritage, I wouldn't think you'd be interested in building amplifiers that would mind a high impedance load.
Some tube power amps though may die, AFAIK due to overvoltage in the output transformer.
Barrelhouse Solly
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I startedout with a mono system. Fisher tuner preamp and Brociner power amp. I got a pair of headphones and an adapter. The adapter was made for use with a stereo amp so I ran the speaker leads in parallel to the 8 ohm tap on the amp. The power tubes blew out every two or 3 months.
Wonder how many people got electrocuted? 20 watts into to 500 ohms takes 100V RMS.Class D + High impedance loudspeaker...
View attachment 403252
And that's playin' Little Girl with Guitar music!
ahem.
back in the good ol', bad ol' days of output transformers -- and with apologies @atmasphere and others who espoused other approaches
View attachment 403253
source: http://hifilit.com/Stephens/Stephens.htm
I have a single 106AX... but, for better worse, not one of the 500 ohm variants.
Your down to 15 watts, thats the only problem.
I know practically nothing about tubes or tube amps, so you might be right. I didn't even consider them.
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Actually the problem in a tube amp might be arcing if the load is removed while the amp is playing. With no load otherwise its a different story, as the tubes will see a very high load impedance as well (so will not be able to make much power) since the transformer always reflects the load in either direction. I've never seen an amp damaged by no load, although I did hear of one design that could oscillate with no load. But that's more a design flaw than anything else.
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