No I don't think so - reason follows
The output power is related to the output voltage and current, and the current is related to the voltage and load. No powersupply is going to be big enough to sustain the current into 2 ohms. But testing have shown 300W + into 8 ohm and 450W+ into 4 ohm (both resistive), but this will depend heavily on the supply capabilities. I have not yet tested into 2 ohms, and prefer to wait until I have a proper heatsink, the rail voltage must be lowered below 60V (again not tested) if the amp is going to be used into 2 ohms continues operation.
The ability to double the power will depend on the size of power supply, and the protection circuit of the amp. I don’t recommend anyone to use 2 ohm loads unless they really know that the amp is up to it. I will post the result of the 2 ohm test when I have it.
\Jens
The output power is related to the output voltage and current, and the current is related to the voltage and load. No powersupply is going to be big enough to sustain the current into 2 ohms. But testing have shown 300W + into 8 ohm and 450W+ into 4 ohm (both resistive), but this will depend heavily on the supply capabilities. I have not yet tested into 2 ohms, and prefer to wait until I have a proper heatsink, the rail voltage must be lowered below 60V (again not tested) if the amp is going to be used into 2 ohms continues operation.
The ability to double the power will depend on the size of power supply, and the protection circuit of the amp. I don’t recommend anyone to use 2 ohm loads unless they really know that the amp is up to it. I will post the result of the 2 ohm test when I have it.
\Jens
Well if this can do a 450 w on 4 ohms who needs the super leach amp?
How can you use such high voltages for the gain and driver stages anyway when the small leach amp is working on a lot less than the ones you mention (70 or 75 rail v)? Have you made any changes there and can the driver section sustain output of such wattage?
How can you use such high voltages for the gain and driver stages anyway when the small leach amp is working on a lot less than the ones you mention (70 or 75 rail v)? Have you made any changes there and can the driver section sustain output of such wattage?
Villaw said:
I have chosen transistors that have high enough Vce ratings.
I have had no problems with the driver stage running out of current, but then again 4 ohms is not a really hard load to drive.
I change some resistor values a bit, to closest standard value 300 ohm => 330 ohm etc.
I also changed the short circuit protection to fit 5 parallel devises and a higher railvoltage.
\Jens
rajeev,
It depends on if you ask for maximum power out (peak) or the avarage power during one cycle. Or maybe the maximum power dissapated in the output transistors.
Peak power out is easy:
Rails = 70V
Output_peak = 60V
Vce_peak = Rails-Output_peak = 10V
Ic= Output_peak/(RL*5) (5 parallel devises) = 60/(4*5) = 60/20 = 3A @ Vce = 10V well inside the SOA curve.
The other ones I will have to look into tonight when I return home.
\Jens
It depends on if you ask for maximum power out (peak) or the avarage power during one cycle. Or maybe the maximum power dissapated in the output transistors.
Peak power out is easy:
Rails = 70V
Output_peak = 60V
Vce_peak = Rails-Output_peak = 10V
Ic= Output_peak/(RL*5) (5 parallel devises) = 60/(4*5) = 60/20 = 3A @ Vce = 10V well inside the SOA curve.
The other ones I will have to look into tonight when I return home.
\Jens
Regarding the numbers....
Please be patient, I'm very busy with my "non-diyaudio" life at the moment. I have started a transistor analyses to compare some of the most used ONSEMI transistors. I will be part of the manual I make for the Leach amp pcb, and will include calculations for 5 parallel and 3 parallel transistors.
All calculations are show in the manual, so other DIY folks can use them to find out how many transistors to use in a new amp design.
I will update the manual this weekend I hope, and then there will probably be very little news the next couple of months, as I’m in the process of moving.
\Jens
Please be patient, I'm very busy with my "non-diyaudio" life at the moment. I have started a transistor analyses to compare some of the most used ONSEMI transistors. I will be part of the manual I make for the Leach amp pcb, and will include calculations for 5 parallel and 3 parallel transistors.
All calculations are show in the manual, so other DIY folks can use them to find out how many transistors to use in a new amp design.
I will update the manual this weekend I hope, and then there will probably be very little news the next couple of months, as I’m in the process of moving.
\Jens
Hello Jens,
I went through your mannual , very interesting and informative , learnt
much on SOA , power loss in output stage & heatsinking , good work .
Regarding the use of MJ21193/94, MJ21195/96 your comment is that
thay are too slow and you would not use these devices though they are
very rugged .
You suggest MJL3281A/1302A & MJL4281A/4302A for medium power
fullrange amplifiers between 200w - 450w . But you do not recomend
them for subwoofer or other applications where high - long term power is
needed .
Now like this there is some or other problem in all your tested devices ,
what device do you recommend for PRO SOUND applications .
A friend has commented as follows , :
"SOA at high voltages is not all that important in audio amp design. That
is because when a transistor is exposed to the highest voltages, it is not
conducting at all. For example, consider the device connected between
the load and the positive rail. When the output signal swings negative,
this device is turned off and conducts nothing. Al long as the device can
handle the voltage, you are fine. It is only when the signal goes positive
does the transistor conduct. And in this case, as the output voltage rises
and the current rises, the voltage across the transistor falls. Thus, the
SOA requirements are not as stringent as many believe.
We have used the Toshiba devices with great success with rails as high
at +/-100V. "
what do you have to say above ,
Please also post a SOA chart of Toshiba 5200/1943's ,
as you know I was going to use 11 pairs 5200/1943's at +/- 87v for an
speaker load upto 2 ohms and the same was turned down by K-Amps
also it is not possible as per Quasi,s graph ,
will these 11pairs 5200/1943's be 0k at +/- 87v and load 4ohms pro
sound use .
You reccomend the 10 ms SOA curve for audio use , if I see this curve of
the 5200/1943's at 10ms without derating it is not bad , it is 2A at 100v ,
4A at 80v the devices should be safe at +/-87v and 4 ohm loads with
enough margin for the protection circuit to come into acton , also the
supply would fall to 70v or lower on load , thus increasing the SOA .
Your Comments please!!
I went through your mannual , very interesting and informative , learnt
much on SOA , power loss in output stage & heatsinking , good work .
Regarding the use of MJ21193/94, MJ21195/96 your comment is that
thay are too slow and you would not use these devices though they are
very rugged .
You suggest MJL3281A/1302A & MJL4281A/4302A for medium power
fullrange amplifiers between 200w - 450w . But you do not recomend
them for subwoofer or other applications where high - long term power is
needed .
Now like this there is some or other problem in all your tested devices ,
what device do you recommend for PRO SOUND applications .
A friend has commented as follows , :
"SOA at high voltages is not all that important in audio amp design. That
is because when a transistor is exposed to the highest voltages, it is not
conducting at all. For example, consider the device connected between
the load and the positive rail. When the output signal swings negative,
this device is turned off and conducts nothing. Al long as the device can
handle the voltage, you are fine. It is only when the signal goes positive
does the transistor conduct. And in this case, as the output voltage rises
and the current rises, the voltage across the transistor falls. Thus, the
SOA requirements are not as stringent as many believe.
We have used the Toshiba devices with great success with rails as high
at +/-100V. "
what do you have to say above ,
Please also post a SOA chart of Toshiba 5200/1943's ,
as you know I was going to use 11 pairs 5200/1943's at +/- 87v for an
speaker load upto 2 ohms and the same was turned down by K-Amps
also it is not possible as per Quasi,s graph ,
will these 11pairs 5200/1943's be 0k at +/- 87v and load 4ohms pro
sound use .
You reccomend the 10 ms SOA curve for audio use , if I see this curve of
the 5200/1943's at 10ms without derating it is not bad , it is 2A at 100v ,
4A at 80v the devices should be safe at +/-87v and 4 ohm loads with
enough margin for the protection circuit to come into acton , also the
supply would fall to 70v or lower on load , thus increasing the SOA .
Your Comments please!!
You seem to be on track rajeev with your pulse assessment. The SOAR's at high voltage are very necessary consideration for reactive loads as only resistive loads switch the output half off at zero crossing and the amp need deliver NO current at zero volts but real reactive loads are more demanding.
My rule of thumb is to deliver full 8 ohm load current at zero volts satisfies medium duty needs eloquently.
My rule of thumb is to deliver full 8 ohm load current at zero volts satisfies medium duty needs eloquently.
I think it depends on where you put the emphasis on.
If sound quality is the supreme goal, linearity of the output signal is of great importance, which legislates the use of extreme high bandwidth output devices.
If very high power output is the primary goal, linearity at 20 KHz should not be that vital.
A subwoofer puts even lower demands on frequency behavior of output stages.
Many who build amplifiers want the best out of the first couple of watts.
Only some desire the most of the last watts, as you, Rajeev.
If you wish the most power you can get i would not be concerned with bandwidth specs of 4 or 30 MHz for different devices but go for the ones most affordable and most sturdy.
For a hefty subwoofer amplifier or a stage amplifier that delivers the most reliable, i'd opt for high power TO3 Motorola's instead of sota very high bandwidth Japanese devices.
"Nothing beats cubic inches" applies to Pro amplifier gear too.
Seems to me that K-amps recommended some good ones.
Why you need all that excessive power is still a puzzle.
If sound quality is the supreme goal, linearity of the output signal is of great importance, which legislates the use of extreme high bandwidth output devices.
If very high power output is the primary goal, linearity at 20 KHz should not be that vital.
A subwoofer puts even lower demands on frequency behavior of output stages.
Many who build amplifiers want the best out of the first couple of watts.
Only some desire the most of the last watts, as you, Rajeev.
If you wish the most power you can get i would not be concerned with bandwidth specs of 4 or 30 MHz for different devices but go for the ones most affordable and most sturdy.
For a hefty subwoofer amplifier or a stage amplifier that delivers the most reliable, i'd opt for high power TO3 Motorola's instead of sota very high bandwidth Japanese devices.
"Nothing beats cubic inches" applies to Pro amplifier gear too.
Seems to me that K-amps recommended some good ones.
Why you need all that excessive power is still a puzzle.
Jacco
you write "Why you need all that excessive power is still a puzzle." the answer to your puzzle is that I am a small touring pro sound operator , and high power amps are the requirement of my sound system .
You will find this interesting ,
I just did a survey and found out that most of the branded pro amps of today like Crest , Crown , QSE , Yamaha , Pavey , Behringer etc are nowadays only using TO-264 case devices in the output stages.
you write "Why you need all that excessive power is still a puzzle." the answer to your puzzle is that I am a small touring pro sound operator , and high power amps are the requirement of my sound system .
You will find this interesting ,
I just did a survey and found out that most of the branded pro amps of today like Crest , Crown , QSE , Yamaha , Pavey , Behringer etc are nowadays only using TO-264 case devices in the output stages.
most commercial pro amps are usually using those
plastic packages because of thier convinience
since they only require a single mounting screw
and perhaps when designing the PCB lay outs
these packages are even very easy to include in,
thus hardwiring is practically deminished,
one more thing, designing amps with plastic packages
looks more elegant to look at.....
plastic packages because of thier convinience
since they only require a single mounting screw
and perhaps when designing the PCB lay outs
these packages are even very easy to include in,
thus hardwiring is practically deminished,
one more thing, designing amps with plastic packages
looks more elegant to look at.....
I was interested in the facts of Pro amplifiers for a few years and subscribed to a "professional sound" magazine.
A common thing with pro gear seemed to be that they all had very tight protection circuitry, and below 4 Ohms the max output was restricted by the protection limit.
Most of the PA amplifiers i saw pictures of had plastics, and that fase of mine was 10 years ago.
A common thing with pro gear seemed to be that they all had very tight protection circuitry, and below 4 Ohms the max output was restricted by the protection limit.
Most of the PA amplifiers i saw pictures of had plastics, and that fase of mine was 10 years ago.
Reactive loads changes this.
I plan these transistors:
I will use 5 parallel MJL21195/96 or MJL21193/94 for my subs.
I will use 5 parallel MJL4281A/4302A for my upper bass or in a full range system.
I will use 3 parallel MJL4281A/4302A for my midrange.
I will use 2 parallel MJL4281A/4302A for my tweeter.
\Jens
As far as i got the story right Vce level is of major importance in the high frequency range, where very fast transients occur.
At lower frequencies the output changes much slower from positive to negative, theoretically at zero crossing there is no output current.
Which implies that in most cases voltage level over an output device's collector and emitter is no higher than the PS voltage.
Vce at 50v or 100v makes quite a difference on the soa sheet.
A tweeter has to battle for every 1/10th of a dB, because there is very little energy in high frequencies.
In return the power handling of tweeters is not high, when Vce reaches the maximum there will be very little current going to the tweeters.
imo, at low frequencies the 1st thermal breakdown of the soa line is important, that is where high voltage levels and high currents are needed constantly.
Calculating the integral[1/2*Rho(air)*square(Sin (Vair))] for a 20Hz tone is nice to get a grip on the energy that goes into these low frequencies.
For the higher frequencies its the 2nd thermal breakdown part of the soa that applies.
if you look at half cycle:
Everything above 500Hz is in the 1mS and shorter range.
Signals above 50 Hz are inbetween 1mS and 10mS.
Signals above 20 Hz from 25mS to 10mS.
If electrostats are skipped the highest phase shift generally occurs in the upper frequency zone too.
Ribbon tweeters have both high phase shifting and require relatively high currents, for those i'd think setting up an output stage for enough current at high Vce is sensible.
If not, then i tend to agree with Rajeev's friend.
At lower frequencies the output changes much slower from positive to negative, theoretically at zero crossing there is no output current.
Which implies that in most cases voltage level over an output device's collector and emitter is no higher than the PS voltage.
Vce at 50v or 100v makes quite a difference on the soa sheet.
A tweeter has to battle for every 1/10th of a dB, because there is very little energy in high frequencies.
In return the power handling of tweeters is not high, when Vce reaches the maximum there will be very little current going to the tweeters.
imo, at low frequencies the 1st thermal breakdown of the soa line is important, that is where high voltage levels and high currents are needed constantly.
Calculating the integral[1/2*Rho(air)*square(Sin (Vair))] for a 20Hz tone is nice to get a grip on the energy that goes into these low frequencies.
For the higher frequencies its the 2nd thermal breakdown part of the soa that applies.
if you look at half cycle:
Everything above 500Hz is in the 1mS and shorter range.
Signals above 50 Hz are inbetween 1mS and 10mS.
Signals above 20 Hz from 25mS to 10mS.
If electrostats are skipped the highest phase shift generally occurs in the upper frequency zone too.
Ribbon tweeters have both high phase shifting and require relatively high currents, for those i'd think setting up an output stage for enough current at high Vce is sensible.
If not, then i tend to agree with Rajeev's friend.
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