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Old 31st January 2007, 09:00 PM   #1
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Default ESP P3A with higher supply rails

hi everybody...
is possible to use this amplifier with a 40+40 Vac transformer(56+56Vdc)???

i think that a transistor change is needed...

i want to change all the bc546 with MPSA42, and the output transistors with MJ21193/4

in place of the MJE15034/35 i allready have some pairs of MJE15030/31

do you think that these mods are possible, and with this power supply, the amp can work correctly???

thanks....

http://sound.westhost.com/project3a.htm
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Old 31st January 2007, 09:27 PM   #2
AndrewT is online now AndrewT  Scotland
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Hi,
Quote:
40+40 Vac transformer(56+56Vdc)....with this power supply, the amp can work correctly
no.
It's an SOA limitation.
Do you realise that the MJL and the MJ are different packages?
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Old 31st January 2007, 09:31 PM   #3
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yes, i know... but isn't a problem because i have to design my own pcb...

but you say that let work the amp with this voltage isn't a good thing..:why?
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Old 31st January 2007, 11:55 PM   #4
lineup is offline lineup  Sweden
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Default Re: ESP P3A with higher supply rails

Quote:
Originally posted by Flavio88
hi everybody...
is possible to use this amplifier with a 40+40 Vac transformer(56+56Vdc)???

i think that a transistor change is needed...

i want to change all the bc546 with MPSA42, and the output transistors with MJ21193/4

in place of the MJE15034/35 i allready have some pairs of MJE15030/31

do you think that these mods are possible, and with this power supply, the amp can work correctly???

thanks....

http://sound.westhost.com/project3a.htm

As Elliot write in his description MJL21193 / MJL21194 is a good replacement.
And MJE15030 / MJE15031 is the same as MJE15034 / 35.
So no problem with this.
Also replace BC546 with MPSA42 is good!

MJL21194 can take: +/- 125 V
MJE15030 can take: +/- 75 V
MPSA42 can take : +/- 150 V

====================================

But Elliot says:
Quote:
For use into 4 ohms do not exceed 35V (from a 25-0-25V transformer).
Most applications will be satisfied with the lower voltage, and the reliability of the amp is assured with almost any load.

In bridge mode, this amp will happily produce 200W into 8 ohms, and will do so reliably even for continuous high power levels.

Never attempt to operate the amp in bridge mode into 4 ohms, as this represents an equivalent load to each amp of 2 ohms. The amp was not designed to handle this, and will fail.

42V is the absolute maximum voltage, and should only be used where 4 ohm loads will never be applied.

# Operation into 4 ohm loads is not recommended with the 42V supplies.
Peak dissipation will exceed 110W in each output transistor, leaving no safety margin with typical inductive loads.
All supply voltages are nominal, at no load - your transformer may not be capable of maintaining regulation, so power may be slightly less than shown.

In short, if you want to use higher voltage than 42V
do not use any speakers with lower imp than 8 Ohm!

You should be aware, that using ONLY 1 PAIR of output transistors
and try to have too high Supply voltage (=much more power)
will make it too heavy for those 2 devices.
They will destroy.


MJL21193 MJL21194 are good.
But they can not do too much.
They will simply get too hot.
Does not help if you use 100 kg of heatsinks.
They will will smoke

============================================

Advice.
If you want to make more power,there is other projects
with many output transistor pairs.

Have a look at Nelson Pass high power amplifier, for example.
He uses here 24 big output transistors!
He does not do this because he likes to - he does it because he must ....

http://passlabs.com/np/400a-4000.tif


You can come a long way with +/- 56 V
if using two MJL21193 and two MJL21194.
There are several good amplifiers at forum, for higher Watt
that parallel several output transistors.
2 + 2 would be good for this.

But I don't think you should try this with P3A.
You need to change many other things in the amplifier to get this to work.

=========================================

Maybe someone at our forum already have built a higher power version of P3A?
I do not know?


Regards
lineup

--------------------------------
http://www.onsemi.com/pub/Collateral/MJL21193-D.PDF
MJL21193 / MJL21194
Max 15 Ampere
Temperature Range, Max: 150 degrees C
Thermal Resistance, Junction−to−Case: 0.7
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Old 1st February 2007, 11:25 AM   #5
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To get the p3a to operate on higher supply rails you will most definately have to go with an emitter follower output stage which can easily be implemented into the original design with few parts changes. To try and build a high power psa utilizing the sziklai pair will take much more effort to stabalize.


Colin
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Old 1st February 2007, 04:23 PM   #6
AndrewT is online now AndrewT  Scotland
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Hi,
ESP say <=+-35Vdc for 4ohm speakers, and <=+-42Vdc for 8ohms speakers.
If you want to use more than +-42Vdc as a supply then you MUST use speakers with a higher impedance than 8ohm.
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Old 1st February 2007, 04:48 PM   #7
jaycee is offline jaycee  United Kingdom
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Trying to use a Sziklai output stage when you need to add on more than one power device is a total pain. It can be done, but you end up adding compensation and current sharing resistors everywhere.

Don't bother. Build the Leach Low TIM or so. You should be able to use MJL21193/4 with this.
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Old 1st February 2007, 06:00 PM   #8
paulb is offline paulb  Canada
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Why not use Rod's other amp, specifically for higher voltages?
http://sound.westhost.com/project68.htm
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Old 1st February 2007, 06:29 PM   #9
lineup is offline lineup  Sweden
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Quote:
Originally posted by paulb

Why not use Rod's other amp, specifically for higher voltages?

http://sound.westhost.com/project68.htm

.

I think the first question friend Flavio should ask himself
is:
Do I really need more power??

P3A is giving a lot of power.
All needed for 90% of all audio sound systems.

----------------------
It is my firm believe, that many of these 'power wattage hungry' guys, often the young ones,
fool themselves.

----------------------
It is a bit like young men:
They drive their cars like they were chased by something to escape.
Most persons killed in automobile crashes are 16-25 years old.

Maybe they are trying to impress other guys
- show manhood or something or impress on girls ...

When you are an older lady or and older man
you have learnt, that you will get where you are going
even if drive in nice and proper speed.
No need to risk to kill yourself, just to save 10 minutes or so!
When the use of these 10 minutes will be wasted anyway,
just watching TV, reading a paper or plain doing nothing

----------------------
These Power Hungry Maniacs:
I think,
They have no idea of how much power they would have use for.
Because they can not do a proper math, calculation and estimation
of the power requirements for their speakers.

----------------------
If I build a 150-300 Watt amplifier I know for sure
I would never have any use for, in extreme loudness playing,
more than 20-50 Watt.
Because I have speakers with good efficiency: decibel / Watt
I need for example only like 10 Watt RMS to reach 100 dB SPL, Sound Pressure Level
here in my small room.
And I live in a house with many apartments = neighbours behind my walls.
They would call The Police Force upon me, if misbehaving.


***
with 'good efficiency in my case, I mean,
my regular speakers used, have a sound output of:
90-92 dB SPL per watt
.... this means at 10 Watt = 100-102 dB Sound Pressure



Regards
lineup - wants to remain in good relation with his close neighbours
.... and stay free from The Local Police and out of jail
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Old 1st February 2007, 08:07 PM   #10
CBS240 is offline CBS240  United States
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Hi

I agree with Colin, the output impeadance of an emitter follower is inherently less than that of the common emitter or CFP, consequently there is no voltage gain from the emitter follower circuit. CFP or sziklai circuit is much more load dependent than an emitter follower, and this is important when driving a reactive load like a speaker.



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