Class T-amps

[MartinT]

Looks like the standard modulation frequency is 400KHz which is pretty high indeed.

Wow, those devices must be fast as the heatsinking doesn't look sufficient otherwise at that switching frequency.

[Reid Malenfant]

One device but two power mosfets on a single die Martin, looking at the specification the gate charge is very low indeed for a device with that voltage rating & RDS on It's fast alright

[MartinT]

Concur: 6.6ns rise time

[Reid Malenfant]

Concur: 6.6ns rise time

Ah, you must take into account the test generator resistance, that in this case can supply what looks like 4Amps or so charging current to the gate. The IRS2092 can only supply just over 1Amp, but as the circuit is feeding the filter inductor on the output stage i'd actually expect it to be even faster as in no way will full current be drawn instantly due to this.

Also the 6.6ns rise time is with a non inductive resistive load, so full current is drawn instantly which certainly doesn't help things

So yes, the mosfet is lightning fast.. In fact it might be fast enough to modulate at 1MHz with less than 1% dead time

[John]

I have no idea what you 2 are talking about but sounds like you found a bargain capable of very fast dynamics?

[Reid Malenfant]

I have no idea what you 2 are talking about but sounds like you found a bargain capable of very fast dynamics?

I'll see if i can explain John

Class T amplifiers are similar to class D except for one thing. At low output levels the mosfets that do the switching are switched at up to 1.5MHz or 1,500,000 times a second, this improves the sound quality as the carrier frequency is way above the audio frequency being produced. If you like you get many more & more accurate samples per second which are fed into the filter on the output of the amplifier which hopefully smooths things out & you get a nice sound in your speaker (hopefully ). At higher output powers class T amps switch to a lower switching frequency to improve efficiency because there are losses in the mosfet switches (nothing is totally instantaneous).

A class D amp (generally) uses a fixed frequency to switch the mosfets so at lower volume levels they may well not be quite as clean as a class T amp.. Of course all this depends on the switching frequency of the mosfets, if you can switch them very fast then it's quite possible that a class D amp will out perform a T nearer full power but not be quite so good at low volume levels..

These things i bought look interesting, i only saw them today but as soon as i did i went into research mode.. As i have a pretty decent understanding of the subject i came to the conclusion that these were extremely good value for money with the possibility of very good performance indeed

For £37 delivered i'm more than willing to take the chance seeing as i understand how they work A little calculation reveals they should be good for 200W RMS into 8 ohm & heading for 400W RMS into a 4 ohm speaker load with a +/- 60V supply Of if they were bridged 800W RMS 8 ohm

They'll be getting bigger heatsinks all the same The control IC is good for +/- 100V though, so if the correct mosfets were used for switching each amp module could be good for well over 500W RMS 8 ohms as long as certain other components were upgraded, that'd be 2KW RMS bridged into 8 ohms with both amplifiers

[Welder]

Keep us posted please Mark and get on with it

[John]

I'll see if i can explain John

Class T amplifiers are similar to class D except for one thing. At low output levels the mosfets that do the switching are switched at up to 1.5MHz or 1,500,000 times a second, this improves the sound quality as the carrier frequency is way above the audio frequency being produced. If you like you get many more & more accurate samples per second which are fed into the filter on the output of the amplifier which hopefully smooths things out & you get a nice sound in your speaker (hopefully ). At higher output powers class T amps switch to a lower switching frequency to improve efficiency because there are losses in the mosfet switches (nothing is totally instantaneous).

A class D amp (generally) uses a fixed frequency to switch the mosfets so at lower volume levels they may well not be quite as clean as a class T amp.. Of course all this depends on the switching frequency of the mosfets, if you can switch them very fast then it's quite possible that a class D amp will out perform a T nearer full power but not be quite so good at low volume levels..

These things i bought look interesting, i only saw them today but as soon as i did i went into research mode.. As i have a pretty decent understanding of the subject i came to the conclusion that these were extremely good value for money with the possibility of very good performance indeed

For £37 delivered i'm more than willing to take the chance seeing as i understand how they work A little calculation reveals they should be good for 200W RMS into 8 ohm & heading for 400W RMS into a 4 ohm speaker load with a +/- 60V supply Of if they were bridged 800W RMS 8 ohm

They'll be getting bigger heatsinks all the same The control IC is good for +/- 100V though, so if the correct mosfets were used for switching each amp module could be good for well over 500W RMS 8 ohms as long as certain other components were upgraded, that'd be 2KW RMS bridged into 8 ohms with both amplifiers

Cheers Mark I look forward to hearing how they perform I finally might of found a DIY project to try fot myself

[Reid Malenfant]

They have to get here first John I find most stuff from Hong Kong takes about a fortnight or so, but i'll keep you up to date as i'm interested in the outcome myself Just hope they are sent registered like everything else i have bought recently appears to have been

[Jonboy]

They look interesting Mark, after my Mini T purchase i have got a hankering for a 2050 chip amp, anybody tried one?