Jacco,
Nee, nie bedoel om te spot nie. Dit het maar uitgeglip!
Eintlik het jy 'n punt.
Actually Jacco has a point, in that multiple power transistors distributes heat over the heatsink instead of creating a point source. Handy to keep a stabilising transistor from lagging behind in T.
Anders,
That circuit would certainly give up to 80 - 90W. I do not know the 2SC../2SA.. power transistors, but presume they are adequate. The Vce max for the BDs under these conditions is 100V.
There are minor component values here that I wonder about (e.g. the rather high value of C4 and C6; I would rather also phase-correct by having a phase-lead cap over R5) but let us not nit-pick. If you have no way out, 7 - 10 BDs a side should do it, and would also decrease the net value of the temperature compensating resistors. (It would appear that few people realise that these give rise to some high order harmonic distortion.)
Hope you come right - regards.
Nee, nie bedoel om te spot nie. Dit het maar uitgeglip!
Eintlik het jy 'n punt.
Actually Jacco has a point, in that multiple power transistors distributes heat over the heatsink instead of creating a point source. Handy to keep a stabilising transistor from lagging behind in T.
Anders,
That circuit would certainly give up to 80 - 90W. I do not know the 2SC../2SA.. power transistors, but presume they are adequate. The Vce max for the BDs under these conditions is 100V.
There are minor component values here that I wonder about (e.g. the rather high value of C4 and C6; I would rather also phase-correct by having a phase-lead cap over R5) but let us not nit-pick. If you have no way out, 7 - 10 BDs a side should do it, and would also decrease the net value of the temperature compensating resistors. (It would appear that few people realise that these give rise to some high order harmonic distortion.)
Hope you come right - regards.
Johan,
baie meer mense begryp dat nie.
I did't mean to say that someone as Blunt should try to do a 60 watt in 8 output stage with BD139/140, i'm just trying to defend the little critters.
Doing a board layout for that many devices in parallel requires a lot of practice and/or start all over again.
If Blunt can not make the distinction between an 8 watt TO-126 and a 200 watt T0-247 he should try something a lot easier first, imo.
My 20 BD139/140 per channel amps are based on the Elektor Class A headphone amp design to drive an AKG K1000, btw. Fully regulated and separate rails for front end and output stage, <1% 1 Ohm metalfilm emitter resistors, BDs mounted without insulators, does 20 watts/8 in Class A.
Not that i still use them, there are much better front end designs nowadays. But they beat Mr Lang's 20 watt/A design by a mile.
baie meer mense begryp dat nie.
I did't mean to say that someone as Blunt should try to do a 60 watt in 8 output stage with BD139/140, i'm just trying to defend the little critters.
Doing a board layout for that many devices in parallel requires a lot of practice and/or start all over again.
If Blunt can not make the distinction between an 8 watt TO-126 and a 200 watt T0-247 he should try something a lot easier first, imo.
My 20 BD139/140 per channel amps are based on the Elektor Class A headphone amp design to drive an AKG K1000, btw. Fully regulated and separate rails for front end and output stage, <1% 1 Ohm metalfilm emitter resistors, BDs mounted without insulators, does 20 watts/8 in Class A.
Not that i still use them, there are much better front end designs nowadays. But they beat Mr Lang's 20 watt/A design by a mile.
jacco vermeulen said:
i'm not saying 'it won't work', but this solution is 'a little bit crazy', i think better to use 2pair good transistors in output stage than 64, 120Mhz Ft, hmm is that usefull in audio ? and what bandwidth has got that amp ? have you got a link to it ?
blunt said:
the basic solution to make amp give more power is incrase supplying voltage, (what voltage you have?), but if you incrase voltage you must instert transistors that hold a higher voltage and higher current
and you should change a value of some resistors
say what you use transistors as q1, q2, q3, q4, q5, q6, q7, q8 ?
www.arrayaudio.nl/reviews.html
I built a KSA50 with 12 Sanken devices per channel, two of them dissipate 700 watts.
Some say that is a little bit crazy.
I've got about 1000 output devices with an Ft of 30 to 80 MHz more to play with, not counting mosfets.
Ever constructed an A-75 ? i'll show you a few hundred TO-220 mosfets if you like.
I built a KSA50 with 12 Sanken devices per channel, two of them dissipate 700 watts.
Some say that is a little bit crazy.
I've got about 1000 output devices with an Ft of 30 to 80 MHz more to play with, not counting mosfets.
Ever constructed an A-75 ? i'll show you a few hundred TO-220 mosfets if you like.
Re: schematics..
What worries me more is that it seems your teacher should do the same reading too...
Didn't do a very good job of stealing either
In a power amplifier, transistors get progressively bigger as you go from the input to the output, as the signal is amplified in stages. In your schematic, the rightmost transistors, top and bottom, are the output transistors, the ones immediately to the left of them are their drivers, and the sole one marked BD140 is the so called voltage amplification stage. Now, to give you an idea how (in)adequate BD139/140 are for the output stage, let's compare transistor sizes: take a BD139 and then multiply it's size about 3 times in each direction - this is how big a MJL type output transistor is - why do you think this is so?
So, I have a question for you - and feel free to ask your teacher the same question: would it be a good idea to fix wheels to a car with screws from a watch, instead of the rather big ones used normally used?
What worries me more is that it seems your teacher should do the same reading too...
Didn't do a very good job of stealing either
In a power amplifier, transistors get progressively bigger as you go from the input to the output, as the signal is amplified in stages. In your schematic, the rightmost transistors, top and bottom, are the output transistors, the ones immediately to the left of them are their drivers, and the sole one marked BD140 is the so called voltage amplification stage. Now, to give you an idea how (in)adequate BD139/140 are for the output stage, let's compare transistor sizes: take a BD139 and then multiply it's size about 3 times in each direction - this is how big a MJL type output transistor is - why do you think this is so?
So, I have a question for you - and feel free to ask your teacher the same question: would it be a good idea to fix wheels to a car with screws from a watch, instead of the rather big ones used normally used?
Bonsai said:
Ek es nog verslaaf aan die Fritz boeke
Anders,
if you want something good between 100 and 150 watts i suggest you build a Leach amp.
You can download everything you need from ACD and Jens, the designer of the Leach boards: HERE
Plenty of people present who can help you while you're building it.
(ek moet praat nie soveel nie
)ok parts list...
Transistors.
Q1,Q2,Q3,Q9 = NPN BC546
Q5 = NPN BD139
Q4,Q6 = PNP BD140
Q7 = TIP 2955
Q8 = TIP 3055.
thats all the transistors..
32v i think we have from the trafo..
hmm leach amp sound like a good idea.. whats the average cost price and what benefits do it have over the one i allready have built.
Transistors.
Q1,Q2,Q3,Q9 = NPN BC546
Q5 = NPN BD139
Q4,Q6 = PNP BD140
Q7 = TIP 2955
Q8 = TIP 3055.
thats all the transistors..
32v i think we have from the trafo..
hmm leach amp sound like a good idea.. whats the average cost price and what benefits do it have over the one i allready have built.
blunt said:
It's a complete and matured design, a great many have constructed it.
There's a quadratic rule for amplifiers as well, twice the amp will cost four times as much.
In the 100 to 150 watt range, the Leach amp offers a great deal for the money and time you invest.
Tomahauk is smart, but he is 16 and offering ill advice to upscale Rod's Project 3 oldy to a higher wattage level. Stick to the 60w P3 if you favor economics, otherwise pick a different design.
Less can be more.
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