2SC5200 Power Amplifier

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i found this amp when i googled for 2SC5200 schematics. did anyone tried this amplifier? i want to try this simple amp becoz all the components are easily available. any suggestions? i've 27-0-27/5A transformer, hope it will run smoothly.


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how can i set the Vbais?
Hi Reji,
wow it is 150W is identical to OCL150W that so many building here in my country.
I guess it is 150W stereo anyway (75+75).

To set V bias you must change 3 diode strings with VBE multiplier you can see what AndrewT want you to compare, don't you?

From the OCL 150W that very popular here there is no VBE multiplier,
only 3 diode 1N4148 + one 100 ohm resistor just like your schematic.
And that OCL 150 very easy to built with standard parts & no need to set anything it is work quite fine ;), so many built it include me :)
First time I build it using 2N3055+MJ2955 (fake one) & smoke everywhere, so be aware of your parts selection.
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A lot - too many compromises there :Pumpkin:. It seems aimed at lowest parts count which doesn't make sense when that also means compromised performance and taking needless hits to the safe and low distortion working limits. If that is driven at full output into 4 ohms, it will not only sound mediocre but have a short life. A bias scheme like that, without specific details for construction is going to be disaster for control with a Quasi-comp. design.

OTOH, using the smaller transformer for ~40V power rails would probably save it from an early binning. For the cost of 2 or three more cheap transistors and maybe 5 resistors, you could have a great, stable amplifier that really kicks at good, safe power. Visit The Avondale Audio site for a schematic and details of what a Quasi of this size can really do.....;)
i built this yesterday and i connected power (DC 35+/-), speakers, ipod and start to play music but sound is distorted and T5, T7 gettin hot. output transistors are warm. :confused::confused::confused:


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First time I build it using 2N3055+MJ2955 (fake one) & smoke everywhere, so be aware of your parts selection.[/QUOTE]

It's difficulty to see smoke in transistor amp. blown fuse first.
On earth, how can we get good transistors, most of them are FAKE, even you want to pay higher, Fck'n China is the most and large FAKE manufacturer, You guys heard about Fake eggs and salt. even this cheap stuff, they still make FAKE, few years ago, the "double deer" milk powder makes the head of the baby becomes big and bigger. You can check this on globe news, they put the baby's father in prison due to him appeal this case.

The word out of me is truth, Nothing but the truth.:):):):smash:

This amplifier is based on the Digi125 designed by Graeme Dicker and published in the Australian version of ETI magazine as project ETI1430. There are changes to the choice of some components, most notably the transistors and the 5W resistors. The capacitor across the power rails has been omitted so a well filtered supply would benefit.

I have built a number of the original version and the results are surprisingly good. Output transistors included 2N3055/2955, MJ802/4501, and MJ15003/MJ15004.

There are also a few threads on this site regarding modifications that can improve the sound, just search for Digi-125 or just Google it. I haven't tried the mods but the author Tomcat was quite impressed with his efforts. From memory the original schematic is in the thread.

The full article is on Paul Cambies' web site

Index of /~cambie

I hope this helps!!!;)
Ah yes, the DIGI125. I remember it well. For such a small PCB, they sounded very good. After a sustained pounding with loud rock (Stones and many others), one of them caught fire and, yes, those were flames coming from the board.

That was in the olden days before I discovered that there is no comparison between active and passive speakers.
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