Maybe it is just my experience but I have never met anyone willing to spend subtantial efforts in getting good sound that have been saying that efficiency of a power amplifier is of any great importance, on the contrary I see more interest in inefficient class A amplifiers with high output power now then before.
For boomboxes I can agree that class D with its current limitations is a good choice for economical and efficiency reasons.
As I wrote earlier, it is anyway probably more whortwhile spending efforts in improving speaker efficiency making it possible to use lower power amplifiers than to make the amplifier more efficient, but also in this area modern speakers are if anything less efficient then before.
I dont think I am defensive against new technology but I am carefully investigating if the new technology has something better to offer, if I am critical it is probably something that I learned from my work, I also usually don't fall for sales talk be it technical or otherwise.
BTW it is good to read about all more or less crasy ideas in this forum, many ideas are not new but has been earlier considered to be unrealistic, that is the same with innovations in other parts of industry, take car technology where very old ideas suddenly gets new life beacuse it is easier to implement them today.
If I should design a class D amp I would probably try to use something efficient as a switch and therefore give up the idea using tubes, I am sure that class D amps will continue to be improved and maybe one day all amplifiers are built using this tecnology, who knows?
Regards Hans
old hat!
If someone wants to combine tubes and switching, its already been done and on the market too (although not using class D), the David Berning switching impedance converter. Reviewed in Glass Audio Vol. 12, No. 1, 2000 page 22-30 and the following issue also. The Berning design eliminates the HV xfmr. and the output xfmr., making for a lightweight amplifier.
For DIY implimentation, I would suggest modifying the Berning scheme to use two 90 degree overlapping phases (diode commutated), instead of one, and slowing the square wave transition times to prevent generation of EMI (like Linear Technology Inc. does in its ultra-quiet PWM switcher designs). (requires the two phases in order to do this in the Berning design.)
Don
If someone wants to combine tubes and switching, its already been done and on the market too (although not using class D), the David Berning switching impedance converter. Reviewed in Glass Audio Vol. 12, No. 1, 2000 page 22-30 and the following issue also. The Berning design eliminates the HV xfmr. and the output xfmr., making for a lightweight amplifier.
For DIY implimentation, I would suggest modifying the Berning scheme to use two 90 degree overlapping phases (diode commutated), instead of one, and slowing the square wave transition times to prevent generation of EMI (like Linear Technology Inc. does in its ultra-quiet PWM switcher designs). (requires the two phases in order to do this in the Berning design.)
Don
A friend of mine is a tube-o-phile. He once mentioned that class-d has been done with tubes (maybe just for modualtor stages in AM transmitters). I will ask him for more info.
Those who want to try: don't forget a fast antiparallel rectifier tube, for each switcing tube, that deals with the output filter's freewheeling current.
I by myself I wouldn't even bother to try a tube class-d amp.
Regards
Charles
Those who want to try: don't forget a fast antiparallel rectifier tube, for each switcing tube, that deals with the output filter's freewheeling current.
I by myself I wouldn't even bother to try a tube class-d amp.
Regards
Charles
class d tube amp
i am building a class d tube amp, and was thinking about using cold-cathode switching tubes for the output stage. i know they can switch up to 100k, which is almost 5x faster than i need, but am not sure about output power. has anyone worked with cold-cathode switching tubes before? any thoughts or suggestions?
thanks.
i am building a class d tube amp, and was thinking about using cold-cathode switching tubes for the output stage. i know they can switch up to 100k, which is almost 5x faster than i need, but am not sure about output power. has anyone worked with cold-cathode switching tubes before? any thoughts or suggestions?
thanks.
Class D with tubes benefits?
Hi all
Just my 2 cents:
A supposedly sonic advantage wiyh Class D is there is NO crossover distortion. Only class A can claim this as well.
Tubes in D:
One of the main factors of distortion in D is the nessesary deadtime you have to introduce to avoid shootthru in the MOSFet's ... If shootthru happens, the MOSFet's are history! So you have to operate with a certain safty margin.
Tubes on the other hand will be more tolerate to shootthru, so you can operate with almost no deadtime.
Perhaps there are other benefits, but these are enough for me to play with the thought..
2 x 2 PL509/6kg6 would probably do the trick..
koldby
Hi all
Just my 2 cents:
A supposedly sonic advantage wiyh Class D is there is NO crossover distortion. Only class A can claim this as well.
Tubes in D:
One of the main factors of distortion in D is the nessesary deadtime you have to introduce to avoid shootthru in the MOSFet's ... If shootthru happens, the MOSFet's are history! So you have to operate with a certain safty margin.
Tubes on the other hand will be more tolerate to shootthru, so you can operate with almost no deadtime.
Perhaps there are other benefits, but these are enough for me to play with the thought..
2 x 2 PL509/6kg6 would probably do the trick..
koldby
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