Substitute 2N3055/2955

[wg_ski]

Originally posted by ceharden
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.

Sakis is right. The old Qsc circuit is completely different. And it's limited on what kind of result you can actually get - if you're looking for studio-reference quality forget it. Two current gain stages is not really enough at 75V rails. Adding a third will work, but you'll end up with new problems to solve.

If you're looking for something sziklai-ish with better performance and high current capability, look at the QSC PLX circuit. It's a four-stage sziklai with voltage gain, and quite thermally stable. The "output" is a darlington, and the driver is cascode. That output stage could be married to a standard Self-type front end if you don't like op-amps. Then it would look a lot like the OP's topology, but on steroids. I would use 6 pair of outputs on +/-75V rails if you don't go class H.

[Wavebourn]

Originally posted by sakis


everybody has a right to his own opinion .... construct listen and let us know my friend

Did already, 30 years ago. Very similar to this one, except weird compensations. Sounds much better than with symmetrical emitter follower output.

[sakis]

Originally posted by Wavebourn


Did already, 30 years ago. Very similar to this one, except weird compensations. Sounds much better than with symmetrical emitter follower output.

this what i thought so in the first place wavebourn ( but i was afraid to say ).....that you constructed the thing some 30 years ago since i also thing that you must be a bit older than i am ....

30years ago i was 13 .... i was constructing quasi kits with 2x2N3055 and 40 volts of single rail at the time and it sounded god to my ears .... but from then till now way too many things are changed ,,,,,,both in amps but also to our brain ( mine at least )

i try to work with data when it comes to sound memories and feelings play some role also but its not the biggest ....

best regards sakis

[Wavebourn]

A first, such outputs have more linear input and output resistances than Darlingtons, especially when crossing zero, loaded on complex load which a speaker is. Second, it has gain, so less voltage swing and voltage amplification factor is required from VAS stage that may be more linear due to relatively big emitter resistor, and loaded on very linear Zobel for compensation.

[sakis]

so continue having an argument with you has no longer meaning to me ...

let as agree to some point at least ....

----i like generaly sziklai also
---- i am only against the way the drivers are working

i rest my case

thanks for your atention so far

[sivan_and]

thanks "Greg Erskine" for ur link,i will settle with this,

BC557>>>>>>2SA1123
BD139/140>>>MJE340/350
2N3055/2955 >>>>>MJE15003/MJE15004


Using (dual)50~55Vdc supply rails
100W into 8W(one pair of MJE15003/MJE15004)
150W into 4W (2 pairs)

[sakis]

Originally posted by sivan_and
thanks "Greg Erskine" for ur link,i will settle with this,

BC557>>>>>>2SA1123
BD139/140>>>MJE340/350
2N3055/2955 >>>>>MJE15003/MJE15004


Using (dual)50~55Vdc supply rails
100W into 8W(one pair of MJE15003/MJE15004)
150W into 4W (2 pairs)

dont count on this ....50-55 volt will produce more power than 100 dont expect it to remain stable at this rail voltage