Carlos, do not get me wrong, i think this amp is fine for what it is... but it is a kit that is made to be as easy to assemble and as cheap as it can be, and i think they cut a lot of corners on this. Those TIP142/147 darlingtons are not very good for audio use, which is why they need big 680pF miller capacitors around them.
I feel that, rather than modify this, especially as you would then need to make a new PCB anyway, it would be better to build a better circuit, such as one of your own amps, or Sixtek's "ST151" that you see on here (which uses cheap and easy to get parts).
I feel that, rather than modify this, especially as you would then need to make a new PCB anyway, it would be better to build a better circuit, such as one of your own amps, or Sixtek's "ST151" that you see on here (which uses cheap and easy to get parts).
he he he
exactly ...those caps over there is the safety fuse of the ticking bomb ..... remove them and you got your shelf a very nice oscilator ( beyond that death of sonics is a fact with this topology )
The only device that i ve seen working properly with 142-147 and also parallel pairs is the nelson pass a40 4 x outs biased at 200 ma per divice i thing
perfect specs, no caps needed in the base of the darligton and performance is zouper
( i have constructed the blody thing used any tip 142-147 found in my shop , diferent brands , diferent batch , and the thing is working perfectly )
i put it on hold since i wasnt able to find semis of a reasonable quality yet .and never try that in long term for stability
my asumption is that when tip 142-147 are biassed that high ( 200ma ) are too busy to oscilate ...please notice that the rest of the circuit is not space technology ...on the contrary its very simple
explosive regards sakis
exactly ...those caps over there is the safety fuse of the ticking bomb ..... remove them and you got your shelf a very nice oscilator ( beyond that death of sonics is a fact with this topology )
The only device that i ve seen working properly with 142-147 and also parallel pairs is the nelson pass a40 4 x outs biased at 200 ma per divice i thing
perfect specs, no caps needed in the base of the darligton and performance is zouper
( i have constructed the blody thing used any tip 142-147 found in my shop , diferent brands , diferent batch , and the thing is working perfectly )
i put it on hold since i wasnt able to find semis of a reasonable quality yet .and never try that in long term for stability
my asumption is that when tip 142-147 are biassed that high ( 200ma ) are too busy to oscilate ...please notice that the rest of the circuit is not space technology ...on the contrary its very simple
explosive regards sakis
I guess i did not really say enough in the first post, it was just a quick comment. Simple circuit is OK as long as the limits are understood, and if you want to go past those limits, then it is time for a more advanced one.
Hi Orcad2010,
I have followed your thread with interest and although many comments have some value, I do not agree totally. I have a little experience and some of the logic presented does not make total sense, but I stand to be corrected.
These transistors are used all over in motor drives which in my opinion is a lot more difficult load than a loudspeaker. The TIP142/147 can safely pass 10 amps at Vce of 12VDC.
Firstly, these devices are rated 100V which is more than twice the voltage that the amp is designed for and that is safe.
At a supply of +-40VDC with a 4 ohm load connected, just before the onset of clipping, a device will pass about 8 amps, and this is well within its safe operating area since Vce will only be 3V and you should not experience any problems with the device "exploding". These transistors being "boms" are simply untrue.
The fact that these transistors have very high gain (1000 @ 5amp) could be a cause of oscillation in a poorly compensated designs. In fact too much compensation can be as bad as no compensation. Velleman must have chosen the values from practical experience.
The destruction of TIP140 - 147 range are almost always due to oscillation and thermal runnaway in uncompensated designs. In a well designed circuit they can take a lot of punnishment.
If Velleman designs were so awful and prone to explosion he would not sell any and would be a poor man having to return everyones money.
Personally I think that you are safe with this product provided you follow Velleman's instructions.
Besides, you have a commercial recourse should the amplifier fail.
Kindest regards
Nico
Nico... read it once again..he had troubles with the amplifier while using less than
50 volts...do you want him to burn more transistors?
You are good, skilled and very competent..but send me some of this grass or this white powder that you have used.
Maybe i will have fun too!... will suggest Orcad to install plus and minus 100 volts.
hehehehe.
regards,
Carlos
50 volts...do you want him to burn more transistors?
You are good, skilled and very competent..but send me some of this grass or this white powder that you have used.
Maybe i will have fun too!... will suggest Orcad to install plus and minus 100 volts.
hehehehe.
regards,
Carlos
For sure i have over reacted Nico..i was trying to edit the text to make it less
agressive...the way you deserve, as you use to be kind and very well educated, but i was impeached.... repair folks decide to move the internet radio antenna and i was out from the air.... so...the post was keept the way it is.
I am sorry.... over reacted...you do not deserve to be kicked that way... even not agreeing....you deserve a lot of respect..you are kind, competente, has beautifull amplifiers, a very nice home page and you are a veteran in this forum, a skilled man and and a very good, and respectable, forum member.
Sorry,
Carlos
agressive...the way you deserve, as you use to be kind and very well educated, but i was impeached.... repair folks decide to move the internet radio antenna and i was out from the air.... so...the post was keept the way it is.
I am sorry.... over reacted...you do not deserve to be kicked that way... even not agreeing....you deserve a lot of respect..you are kind, competente, has beautifull amplifiers, a very nice home page and you are a veteran in this forum, a skilled man and and a very good, and respectable, forum member.
Sorry,
Carlos
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Hi Carlos,
No appologies needed. I said I stand to be corrected. This is a forum for sharing experience, not to say bad things. But I believe that looking at the SOA of the TIP142/147 it would quite easily comply to what Mr Velleman says.
I mean no disrespect with this statement at all.
If you have a look at the SOA graph we note that if Vce is 2 V (This is under severe clipping) the current can be 10 A and it is for DC conditions. Now the only time when you will be dissipating much power is during the rise and fall of the signal since it takes time, of course half VDC would indicate worst case.
I do not believe that Mr Velleman protection will work too well though, because the point where it will cut the base is far too high, thus this circuit can be omitted, it is not of much use as a protection.
Kindest regards
Nico
Carlos,
I would agree with you that this particular design is thermally not stable since the total gain of the output stage is far higher than that of the Vbe multiplier and one could expect that it will surely run away. Besides there will be quite some lag between the case temperature of the Vbe multiplier and that of the output devices.
You are right that at some stage the amplifier will die, but I am not convinced that the reason is SOA, it is thermal and oscillation may be contributing factor.
I would agree with you that this particular design is thermally not stable since the total gain of the output stage is far higher than that of the Vbe multiplier and one could expect that it will surely run away. Besides there will be quite some lag between the case temperature of the Vbe multiplier and that of the output devices.
You are right that at some stage the amplifier will die, but I am not convinced that the reason is SOA, it is thermal and oscillation may be contributing factor.
There are only two individuals in this forum that I have absolute repect for. Simply because their hard earned knowledge through experience paid off better that pure theoretical hogwash.
My first most favourite person is "Hugie Baby" Dean and the second is ...ahahahahah you of course you old fart.
Damit John Patchwork, how could I have had you slipped throug my fingers!
My first most favourite person is "Hugie Baby" Dean and the second is ...ahahahahah you of course you old fart.
Damit John Patchwork, how could I have had you slipped throug my fingers!
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Carlos, Hugh,
Here is my suggestion for a new thread: Carlos and other magicians pooling their experience especially to create a state of the art newby amplifier?
We throw in three simple base designs and you (Carlos) can quickly knock them up to evaluate the one with the most potential to become this amp. We then add some effort squeesing the best performance from it. How about that. Lets do something for our young community.
Others are welcome to joint but the base design we selected is all that can be worked on and we run with it start to finish so that every person in DIY can have the opportunity to build his own amp.
Kindest regards
Nico
Here is my suggestion for a new thread: Carlos and other magicians pooling their experience especially to create a state of the art newby amplifier?
We throw in three simple base designs and you (Carlos) can quickly knock them up to evaluate the one with the most potential to become this amp. We then add some effort squeesing the best performance from it. How about that. Lets do something for our young community.
Others are welcome to joint but the base design we selected is all that can be worked on and we run with it start to finish so that every person in DIY can have the opportunity to build his own amp.
Kindest regards
Nico
They are saturated off my simple ideas dear Nico
they're searching for something sophisticated, they want complexity, several stages and many surrounded auxiliary sub circuits.
No one will try.... i have tried something nice and old, the Trust, i said was the best sounding, despite the worse in measurements and no one had interest.
We already gave them several amplifiers Nico, i made that, and you too...yours are good and great, same philosophy, same idea..basically the same high quality sonics in amplifiers.
But this is considered old, ancient, stone aged...people wants modern parts, some Fets, the mixing of tubes, fets, bgts, lateral mosfets with a little bit of super condensers, using some unobtanium powder.
We had selected and attracted the ones loves to try simple things, old designs, tuned by year... they built..they did.... we cannot control time..we have not the time machine... they want more exotic things...they want to believe in the "big magic" they suppose will find into high tech or mixing technologies.
We are old bastards... we already had a lot of attention from them...we have cooperated a lot...i think it is enougth to me dear Nico....maybe it's your time.
I will give you all my support, but i want to be a supporting guy, a helping hand, not the responsable, not the designer...just someone to help.
There are time to work and time to rest..i worked very hard..watch how many threads i have opened, how many amplifiers i have build..how many pages written...it is time to rest and enjoy young folks sweting a little.
regards,
Carlos
they're searching for something sophisticated, they want complexity, several stages and many surrounded auxiliary sub circuits.
No one will try.... i have tried something nice and old, the Trust, i said was the best sounding, despite the worse in measurements and no one had interest.
We already gave them several amplifiers Nico, i made that, and you too...yours are good and great, same philosophy, same idea..basically the same high quality sonics in amplifiers.
But this is considered old, ancient, stone aged...people wants modern parts, some Fets, the mixing of tubes, fets, bgts, lateral mosfets with a little bit of super condensers, using some unobtanium powder.
We had selected and attracted the ones loves to try simple things, old designs, tuned by year... they built..they did.... we cannot control time..we have not the time machine... they want more exotic things...they want to believe in the "big magic" they suppose will find into high tech or mixing technologies.
We are old bastards... we already had a lot of attention from them...we have cooperated a lot...i think it is enougth to me dear Nico....maybe it's your time.
I will give you all my support, but i want to be a supporting guy, a helping hand, not the responsable, not the designer...just someone to help.
There are time to work and time to rest..i worked very hard..watch how many threads i have opened, how many amplifiers i have build..how many pages written...it is time to rest and enjoy young folks sweting a little.
regards,
Carlos
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