Your opinion about this schematics?

[Pigy]

Please, tell me your opinion,about this old schematics.
I know that this schematics is old,low hi-fi,but easy to building, and cheaping.
Yours experience?

[hollow_man]

Power Supply Rejection Ratio (PSRR) looks like is going to be really poor, so you may end up having considerable hum. Ii may be cheap, but it be worth the trouble?

[richie00boy]

It is a typical old AC coupled design. Build it if you have a PCB for it, otherwise choose another amp with a PCB that is known good. That amp is no simpler or easy to build than may other amps.

[Mooly]

Old it may be but you may be surprised just how good it may sound. Look at the feedback factor.
It's ideal as a first project IMO, you have no worries about DC problems damaging speakers and the PSU will be simple.
It will work with just about any suitably rated transistors too...

Do you have the full construction details ? showing how to set up the bias etc and having T3 in thermal contact with the output transistors to keep it from thermal runaway.

[destroyer X]

Do not bother with modern and fashion circuits.... an enormous ammount of them sounds awfull.

You know when something sounds bad when you go tweaking tone controls and never feel satisfied..then you go to tweak your speakers, and then you replace speaker and speaker crossovers.. and then you tweak your home acoustics ..and continue not happy.... this happens when sound is no good.

When the amplifier is good you do not even need tone controls, all musics sounds good, nothing to tweak...it is easy that way.

regards,

Carlos

[Bonsai]

"Old it may be but you may be surprised just how good it may sound. Look at the feedback factor.
It's ideal as a first project IMO, you have no worries about DC problems damaging speakers and the PSU will be simple.
It will work with just about any suitably rated transistors too...

Do you have the full construction details ? showing how to set up the bias etc and having T3 in thermal contact with the output transistors to keep it from thermal runaway. "

Solid Advice.

[Lumba Ogir]

Howdy,
this is great sounding topology with scope for further refinements.
No thermal runaway.

[Pigy]

Dear frends, T3 is bias control, this transistor shold be to put in to heatsink with outputs transistors,think in same place(heatsink, because good termal stabilty) .
About hum,yes that is probably problems,but with BC550,and metal films resistors,maybe hum to be low.
This is kit,and I get(buy) a PCB with parts and manual instruction,my job is only conclude.
This kit is in circulation but ten years.

I wanted to build later in bridge mode,but speaker shold be 8 ohm's,

[richie00boy]

Sounds like a good project for you then, although I think 1/2 watt for R16 and R17 is far too small. Maybe it is a mistake and it should say 2W.

[tiefbassuebertr]

Originally Posted by Pigy

Please, tell me your opinion,about this old schematics.
I know that this schematics is old,low hi-fi,but easy to building, and cheaping.
Yours experience?

This circuit is one of my prefer topology for Class AB mode (20-30mA idle current through the output devices). If there are 10-15 mA idle current for T1 and 30 - 50mA for T2, so as additional jFET input buffer and high quality capacitors/transformers, then such an amplifier is very hard to beat (except nessecary concepts with pure class A in the output).
There are also some commercial amplifiers, that have inside this topology, e. g. the no longer exist U.K. brand "Nytech", model No CA202 (CA-202), have a look to http://images.deep-resonance.net/image/85.jpg
http://i36.tinypic.com/2chxelx.jpg
and the pdf file: