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Old 5th November 2009, 04:03 PM   #1
Pigy is offline Pigy  Serbia
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Question Your opinion about this schematics?

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?
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File Type: jpg RK3760 sema.jpg (138.3 KB, 982 views)
File Type: jpg RK3760 delovi.jpg (161.6 KB, 961 views)
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Old 5th November 2009, 05:14 PM   #2
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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?
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Old 5th November 2009, 05:25 PM   #3
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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.
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Old 5th November 2009, 06:22 PM   #4
Mooly is offline Mooly  United Kingdom
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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.
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Old 5th November 2009, 06:40 PM   #5
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Default It is very good...you gonna be happy with it.

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
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Old 5th November 2009, 11:58 PM   #6
Bonsai is offline Bonsai  Taiwan
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"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.
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Old 6th November 2009, 08:26 AM   #7
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Howdy,
this is great sounding topology with scope for further refinements.
No thermal runaway.
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Old 6th November 2009, 01:35 PM   #8
Pigy is offline Pigy  Serbia
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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,
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Old 6th November 2009, 02:41 PM   #9
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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.
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Last edited by richie00boy; 6th November 2009 at 02:43 PM.
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Old 6th November 2009, 06:30 PM   #10
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Quote:
Originally Posted by Pigy View Post
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:
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File Type: jpg Nytech CA202 Front.JPG (17.6 KB, 643 views)
File Type: jpg Nytech CA202 Rückfront.JPG (17.2 KB, 597 views)
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File Type: pdf C_tmp_Nytech CA202_ckt.pdf (17.3 KB, 216 views)
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