Am building an amp using readily available pcb of ETI480 amplifier, and i wish to substitute 2N3055/MJE2955 as i understand these are not audio specific devices ...what options i have..can i use MJE15001/MJE15002 or MJE15003/MJE15004 or even with MJ11032/ MJ11033 with better Ft, IC and Pd ?
ETI480 schematic:
ETI480 schematic:
Given the nature of the design I would try to stick to transistors that are quite similar to the old 2N2955 and 2N3055. TIP series devices from TI come immediately to mind. (or modern versions in TO-3P packages)
Making unstudied changes to this design may result in an oscillator.
Compensation cap values would probably have to be tweaked for proper sq wave response and good stability.
Beta and ft are important in this design as is no doubt cob and a few other parameters.
Get yourself free LTspiceIV from the linear website and find the appropriate transistor models and model the amplifier.
Making unstudied changes to this design may result in an oscillator.
Compensation cap values would probably have to be tweaked for proper sq wave response and good stability.
Beta and ft are important in this design as is no doubt cob and a few other parameters.
Get yourself free LTspiceIV from the linear website and find the appropriate transistor models and model the amplifier.
Useful information about this amp can be found here:
http://home.alphalink.com.au/~cambie/ETI480/ETI480.zip
regards
http://home.alphalink.com.au/~cambie/ETI480/ETI480.zip
regards
Looks like another incarnation of the Tiger (Tiger, Tiger, burning bright....). That output stage is finicky to say the least. Substituting output trannies may or may not work. Even with modern 3055's it may still be troublesome. I would probably try to build it with MJ15015/15016, which are upgraded 2N3055/2955's. Similar characteristics, higher voltage.
MJ11032/33? 50 amp darlingtons??? No way would I ever go there.
MJ11032/33? 50 amp darlingtons??? No way would I ever go there.
this is
another wonderfull sziklai ....
out stage that has some gain on his own.....
a few plus :
----more eficient than emmiter followers
----drives strange loads eazier
---- simple to make
----sziklai tents to be more "musical" than other topology but also this depents on the rest of the circuit and semis
a few minus ....
----it is pcb depending
---- it is unstable if abused
---- vbe multiplier has a god on his own ( thermal runaway)
---- Network arround drivers work as a sonic killer (there are better design ideas arround that )
---- modern transistors or faster and oscilation is arround the corner
----- the particular circuit will produce turn on thump i think
----- especially R15- 17 are the sonic killers but also keep the amp stable ...
----- the paricular amp has a reputation of
you may choose now
i love sziklai circuits ...but not the particular one ...there are more ....by far better than this one
if youre building something for casual listening go for a DX amplifier it is by far more acurate sharp and precise than this one only probably with a bit less drive abilty .... soundwise will outperform this one for breakfast and also can work with modern and powerfull semis
if your conquest is power this one will not do any way .....
if you allready have the pcb you might consider your shelf mods that will make the amp a typical ammiter follower and you are done !!!!!
happy sziklai regards
sakis
another wonderfull sziklai ....
out stage that has some gain on his own.....
a few plus :
----more eficient than emmiter followers
----drives strange loads eazier
---- simple to make
----sziklai tents to be more "musical" than other topology but also this depents on the rest of the circuit and semis
a few minus ....
----it is pcb depending
---- it is unstable if abused
---- vbe multiplier has a god on his own ( thermal runaway)
---- Network arround drivers work as a sonic killer (there are better design ideas arround that )
---- modern transistors or faster and oscilation is arround the corner
----- the particular circuit will produce turn on thump i think
----- especially R15- 17 are the sonic killers but also keep the amp stable ...
----- the paricular amp has a reputation of
you may choose now
i love sziklai circuits ...but not the particular one ...there are more ....by far better than this one
if youre building something for casual listening go for a DX amplifier it is by far more acurate sharp and precise than this one only probably with a bit less drive abilty .... soundwise will outperform this one for breakfast and also can work with modern and powerfull semis
if your conquest is power this one will not do any way .....
if you allready have the pcb you might consider your shelf mods that will make the amp a typical ammiter follower and you are done !!!!!
happy sziklai regards
sakis
There is little wrong with 2n3055 and mj2955.
Maplin electronics did a kit in the 1980's which was very similar in design and it was 225WRMS and it was very loud. I used one for my disco and was always getting asked to turn it down !
I have to echo what others have said and be careful of stability problems if you put in different output transistors.
If the design is tried and proved then stick to it.
There is an endless stream of threads on here from people who tried updating amps only to find they have a good oscilator !
Maplin electronics did a kit in the 1980's which was very similar in design and it was 225WRMS and it was very loud. I used one for my disco and was always getting asked to turn it down !
I have to echo what others have said and be careful of stability problems if you put in different output transistors.
If the design is tried and proved then stick to it.
There is an endless stream of threads on here from people who tried updating amps only to find they have a good oscilator !
@ Sakis:
I would be interested to hear your thoughts on a well-implemented Sziklai output stage. I like the concept of it for many reasons but I'm struggling to actually design an output stage that will do what I want.
Particularly regarding the connection of parallel output devices. Which side of the output devices emitter resistor do you connect the driver if you have multiple output devices?
Can you suggest some examples of good Sziklai's to look at please?
Chris
I would be interested to hear your thoughts on a well-implemented Sziklai output stage. I like the concept of it for many reasons but I'm struggling to actually design an output stage that will do what I want.
Particularly regarding the connection of parallel output devices. Which side of the output devices emitter resistor do you connect the driver if you have multiple output devices?
Can you suggest some examples of good Sziklai's to look at please?
Chris
yea yea yea
-----fast transistors will make this amp oscilate
----- the particular amp performance is allready limited
----- altering the performance by playing with more modern devices or feedbak networks will result instability
finally ....waveburn there are extensive threads and discusions in the forum abut this amp having a """" burning down the house" reputation
Wavebourn said:
-----fast transistors will make this amp oscilate
----- the particular amp performance is allready limited
----- altering the performance by playing with more modern devices or feedbak networks will result instability
finally ....waveburn there are extensive threads and discusions in the forum abut this amp having a """" burning down the house" reputation
Small Example
OF A SERIOUS DRAWBACK ....
there is a similar amp in the forum that shares more or less the same topology ....but !!! features an individual driver for every outpout transistor .... eventhough it doesnt share the same topology on the drivers regarding outpouts of the drivers driven partially to ground through resistors to keep the drivers kinda safe ....
the above comment proofs how essential is the drive .... meaning if you safe guard the amp then the drive is not enough .... ( for an sziklai that has gain on the out stage on its own may this is not that importand ) BUT IT ALL ENDS UP TO HOW CLEAR IS THE SOUND AND HOW GOOD ARE YOUR SONICS ....
my dear friend wavebourn ....
the sziklai that is made with four drivers with modern transistors like1943-5200 to make stable requiered the astronimical figure of 680 PF arround the drivers and another 100pf in the vas stage to keep stable ...
under these rules i will never produce an amplifier like that
OF A SERIOUS DRAWBACK ....
there is a similar amp in the forum that shares more or less the same topology ....but !!! features an individual driver for every outpout transistor .... eventhough it doesnt share the same topology on the drivers regarding outpouts of the drivers driven partially to ground through resistors to keep the drivers kinda safe ....
the above comment proofs how essential is the drive .... meaning if you safe guard the amp then the drive is not enough .... ( for an sziklai that has gain on the out stage on its own may this is not that importand ) BUT IT ALL ENDS UP TO HOW CLEAR IS THE SOUND AND HOW GOOD ARE YOUR SONICS ....
my dear friend wavebourn ....
the sziklai that is made with four drivers with modern transistors like1943-5200 to make stable requiered the astronimical figure of 680 PF arround the drivers and another 100pf in the vas stage to keep stable ...
under these rules i will never produce an amplifier like that
Lets focus on my current project for the time being then. I'm building some largish biamp studio monitors and need an amp channel of about 300W @ 8R so I'm looking at about 75V rails and 3 output devices (probably OnSemi MJL1302/3281). At the moment I'm running an output triple with the drivers in a Sziklai arrangement but not the output devices.
Something a bit like http://www.chaudio.co.uk/AmpDesign/TestAmp2Sch4.pdf.
Now, could I use a 'nested' sziklai and use the current MJE340/MJE15033 arrangement to drive MJL1302 output devices? Or, should I arrange the MJE15033 and MJL1302 as the Sziklai, driven by an MJE340 in darlington arrangement.
Or are there other clever options I haven't considered. I'm trying to minimise the number of Vbe drops between the VAS and the output for both bias stability and output swing.
I WOULD NEVER
mess up with this topology to produce 300W ..... 75 volt rails ???? that is totally out of the question....
i would go for a prooven design sziklai or not but no way i ma pushing this 300 years old schematic to 75+75 volts ...it will not end up well
if you go for bi amp and you need something simple and effective go to the ESP pages look at a prooven design like P68 for low end and if 75 watt is enough you may go fro P3A for the high end .....
all others will not work .... this a ticking bomb in this rail voltage
mess up with this topology to produce 300W ..... 75 volt rails ???? that is totally out of the question....
i would go for a prooven design sziklai or not but no way i ma pushing this 300 years old schematic to 75+75 volts ...it will not end up well
if you go for bi amp and you need something simple and effective go to the ESP pages look at a prooven design like P68 for low end and if 75 watt is enough you may go fro P3A for the high end .....
all others will not work .... this a ticking bomb in this rail voltage
Ah, a downside of thread hi-jacking.
I'm not referring to the original antique amplifier, I just thought since the subject had got round to Sziklai's, this would be a good place to start a discussion on them. I'm talking about designing a new output stage using the benefits of Sziklai's.
Or are you saying that you can't use them at all for high power designs? I'm fairly sure QSC use the topology for their big power amps but their schematics aren't the easiest to follow.
I'm not referring to the original antique amplifier, I just thought since the subject had got round to Sziklai's, this would be a good place to start a discussion on them. I'm talking about designing a new output stage using the benefits of Sziklai's.
Or are you saying that you can't use them at all for high power designs? I'm fairly sure QSC use the topology for their big power amps but their schematics aren't the easiest to follow.
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