Substitute 2N3055/2955

[sivan_and]

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:

[kevinkr]

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.

[taj]

That circuit is strange to my newbie/inexperienced eyes. What's the purpose of taking the output from the collectors on that output section?

..Todd

[Greg Erskine]

Useful information about this amp can be found here:

http://home.alphalink.com.au/~cambie/ETI480/ETI480.zip

regards

[wg_ski]

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.

[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

[nigelwright7557]

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 !

[ceharden]

@ 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

[kuldeepsingh]

whats the Wattage of this amp

[sakis]

Originally posted by ceharden
@ 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

it would be wise to know your power figures .... whta do you expect ???? what is your needs ....

tell me that and i will let you know what i have in mind