In this moment the load will be resistive, I have no idea of what is in the chief mind, the only thing I know in that this is a first experiment to see if tubes is more resistent than mosfet when peak overloaded so I think that the output stage will be driven with a squarewave and also the load will be lowered to create stress.
It is not about tubes versus solid states, it is about how the topology reacts on overloads! Some solid state designs are intrinsicly immune to overload, while tubes in others can overheat and run off with red anodes.
it costs money to hide the real requirements from the engineers
yes splitting the amp output xmfr by frequency bands, allowing switching is more practical, cheaper
combining 2 output xfmr wtih a XO needs a better load definition, and a frequency response flatness tolerance
the Real product requirements are really, really helpful for design recommendations
yes splitting the amp output xmfr by frequency bands, allowing switching is more practical, cheaper
combining 2 output xfmr wtih a XO needs a better load definition, and a frequency response flatness tolerance
the Real product requirements are really, really helpful for design recommendations
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the Real product requirements are really, really helpful for design recommendations
"You design for me a product, but I will keep from you details". It does not work such a way. 😀
"You design for me a product, but I will keep from you details". It does not work such a way."
Oroville dam is proof!
Oroville dam is proof!
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It is well known that OTL output level is very much load dependent.
This is sim result of my 6 pairs 6c33c.
RL(Ohm)/Pout(W) @1Khz
2/650
4/550
8/820
16/500
32/275
64/150
100/100
How to get Pout 600W into 96 ohms?
This is sim result of my 6 pairs 6c33c.
RL(Ohm)/Pout(W) @1Khz
2/650
4/550
8/820
16/500
32/275
64/150
100/100
How to get Pout 600W into 96 ohms?
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a 2 ohm to 96 ohm matching traffo.....
20hz-20khz is ok for transformer. Anyway there is upper limit for inductive type of load, say 20 khz, that should be ok. It's very possible to configure to connect directly other type of (resistive) low load and run higher than 20khz.
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the iron in the audio traffo is good only for the lower frequencies, above 400 hz, it is air coupling....i hope Bud Purvine chimes in....
You need pentodes to get real power out. 6C33 (triode) is too constrained on max B+ and minimum voltage drop. They will just make a lot of heat.
300 KHz, full power, on a steel core will make for smoking hot laminations. Nano-crystalline, amorphous core or ferrite needed. Ferrite won't work reasonably for the LF end however (too low Bsat).
To get 20 Hz to 300 KHz bandwidth will require a toroid big enough for the primary winding to be single layer progressive wound. (and Circlotron to reduce # turns by 1/2)
300 KHz, full power, on a steel core will make for smoking hot laminations. Nano-crystalline, amorphous core or ferrite needed. Ferrite won't work reasonably for the LF end however (too low Bsat).
To get 20 Hz to 300 KHz bandwidth will require a toroid big enough for the primary winding to be single layer progressive wound. (and Circlotron to reduce # turns by 1/2)
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The efficiency of tube OTL is also very much load dependent, the higher the load the more efficient it gets, maybe < 10% @2 ohms 11%@8 ohms to 20%@100 ohms or more with specific design and use.
So if matching transformer is 2/100 ohms for max power 600W, how you account for efficiency? If a particular tube like pentode you may get 600W at 100 ohms, how about low load 2-8 ohms, how many watts you can get? I believe the final product is not only for 96 ohms, it would have limit use. So I suppose if pentode can do 100/(2-100) matching to cater for 2-100 ohms load that is more realistic, IMO. Is there such a pentode otl out there? For 6 pairs of power pentode mean 1.2k each rather than 100R or less for triode.
Edit: the sch I post earlier post no.4 class ab amp efficiency of 80%, this OTL output 200W more than that, but same operating points and supply. What do think the efficiency is?
So if matching transformer is 2/100 ohms for max power 600W, how you account for efficiency? If a particular tube like pentode you may get 600W at 100 ohms, how about low load 2-8 ohms, how many watts you can get? I believe the final product is not only for 96 ohms, it would have limit use. So I suppose if pentode can do 100/(2-100) matching to cater for 2-100 ohms load that is more realistic, IMO. Is there such a pentode otl out there? For 6 pairs of power pentode mean 1.2k each rather than 100R or less for triode.
Edit: the sch I post earlier post no.4 class ab amp efficiency of 80%, this OTL output 200W more than that, but same operating points and supply. What do think the efficiency is?
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don't want it to work like a kitchen grinder,,,not for continuous duty. 8 ohms is 16A from PSU, efficiency is too low hardly a trade off to me.it is a trade off....what is your priority? output power at any cost?
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ya, OP looks pretty frustrated with solid state, now maybe more frustrated with these "bad news". As far as efficiency go, everyone knows switching is way forwards.only the OP can really answer that.....were are just speculating, no biggie...
ya, OP looks pretty frustrated with solid state, now maybe more frustrated with these "bad news". As far as efficiency go, everyone knows switching is way forwards.
Sure.
$59.90
Sure Electronics AA-AB31241 1x600W TAS5630 Class-D Amplifier Board
$124.88 for the power supply:
http://www.parts-express.com/mean-well-mw-se-600-48-48-vdc-125a-600w-regulated-power-supply--320-317
yes, when it comes to efficiency class d is king.....then couple it with an smps psu...winner...
I just come across this 10 years old drawing by David Berning:
http://www.montagar.com/~patj/tubeamp-pwm.gif
http://www.montagar.com/~patj/tubeamp-pwm.gif
An OTL configuration has been suggested, and this may be possible, but you state that you want to use "current production tubes." Most OTL's bump up against, or violate the output tube's peak cathode current rating. This may be possible with music since the peaks are seldom seen, but the amp will fail if operated contiguously at full power into the minimum specified load impedance. The tubes that I use with an OPT are rated for 1.4 amps of peak cathode current. You will need a lot more current handling capability to drive an unspecified load impedance without an OPT. I am not aware of any current production tubes with a peak current capability even near 1 amp.
Thank you very much for your suggestions and congratulation for your power amp! It looks great!
So, I'm thinking about an OTL mixed transistor driver/output tubes, I need +-300V B+ power supply (or 350 to stay safe) because power pentode or tetrode usually have a minimum of 50V Vak when Vg=0V.
The only tube that I have in mind for this kind of amp is the EL509, rated for 1.4A max but dissipation is about 40W, calculating a 500W dissipation I need at least 12 tubes (six couples).
I think it is also possible to use two or more transformer with different frequency bands.
I found the Shuguang 805 tubes, with 1.5kV and four or six of this tubes I can obtain about 600W, anyone know how reliable are they?
This is only an experiment to see if tubes can be useful today, I know that I can design the same with MOSFET (I don't know if SiC can be used for linear applications) but we want to see if tubes have some advantages, I know that transistor is a better choice but the chief want to experiment with tubes, for me is an occasion to get fun.
Maybe after experimentation phase all the stuff will be throw in the rubbish.
"The only tube that I have in mind for this kind of amp is the EL509, rated for 1.4A max but dissipation is about 40W, calculating a 500W dissipation I need at least 12 tubes (six couples)."
If psu is +-300v, 1.4A each for 12 tubes this is 16.8A peak, total power in=300x16.8=5KW, minus 600W output still 4.4KW tot tubes dissipation, not 500W.
If psu is +-300v, 1.4A each for 12 tubes this is 16.8A peak, total power in=300x16.8=5KW, minus 600W output still 4.4KW tot tubes dissipation, not 500W.
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