Explendid amplifier designed by Michael Bittner, our MikeB

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#3,582
feedback capacitor for Toshiba 2SC5200/2SA1943

Because this is my first post on this forum so
A very big greetings to all.

Because my native language is polish so please take that in consideration and don't make fun of my spelling mistakes.

and the question:

i can't find mica caps of the value 3,3pF in my local store the only ones are ceramic, but there is a Silver Mica cap 5pF easy to get is this value to far from the original application for toshibas?

I know that the question about feedback cap was thrown like million times, but the thread is so long that reading it all is just impossible.
 
#3,585
PMA said:
You have had a transient voltage potential difference between grounds of both instruments. Always protect this 10R resistor by anti-parallel diodes of higher current rating, like 1N5408.
Click to expand...


Thanks very much for your assistance and reply.....

I wonder to know ............ by anti-parallel by 1n5408.
Shall I parallel 10 R with 1n5408?
if so... the 1n5408's K pin is Ground position?
 
#3,586
Like this:
 

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#3,588
Nordic said:
symasm46-1.gif


I think this images shows the traces better...
Just noticed a small trace missing... allready fixed on my files.
Click to expand...

I understand the intention behind the separated ground tracks, but is there not a risk of creating inductance with all those long tracks? In particular, C12 and C13 lose their benefit of being close to the output devices because of this.

Maybe better to flood-fill in a big C shape. Or better still, use a double-sided board with the topside as a ground plane.
 
#3,590
Which transformer?

Hello guys!
I ordered the equipment today 🙂
but i dont know what sort of transformer i have to buy.
36V ok but how many ampare and Ac or Dc (Dc right?)
and which means the "+/- 36v" 35v-37v? or -36v on the one an + 36v on the other wire??

and can enybody post a link where to by the transformer in germany??

this is a very cool project and i hope that everything will went nice
sorry for my horrible english


[...] (dont know how to end a post in english 😉
 
#3,592
Re: Which transformer?

Shong said:
Hello guys!
I ordered the equipment today 🙂
but i dont know what sort of transformer i have to buy.
36V ok but how many ampare and Ac or Dc (Dc right?)
and which means the "+/- 36v" 35v-37v? or -36v on the one an + 36v on the other wire??

and can enybody post a link where to by the transformer in germany??

this is a very cool project and i hope that everything will went nice
sorry for my horrible english


[...] (dont know how to end a post in english 😉
Click to expand...

http://de.farnell.com/9530770/elektrotechnik/product.us0?sku=multicomp-mcta250-25&_requestid=129214

Use one of these if you're driving 8 ohm speakers. For less than 8 ohms maybe use one of these for each channel, or search for a 25, 25V transformer rated at 500VA.

you will also need one or two bridge rectifiers, rated at least 200V 15A and two or more 10000uF capacitors, rated at least 50V.

You might also need to limit the inrush current. Be careful! there's a lot of power in those wires 🙂
 
#3,594
Shong said:
thank you for the quick answer.
why 2*25V ?? on the symasym homepage is written that the supply has to be 36V
and why 2*
sorry my electrical knollage is very basic
Click to expand...

The amplifier needs a +36 and a -36V DC supply. There are two windings on the transformer; one provides the + and one the -.

Alternating voltage is quoted as an RMS value; after rectification the DC voltage is 1.41 times the RMS.

I think you need to read up on some electrical theory and practice before attempting to build equipment that uses mains power; if you are not careful you could destroy a lot of expensive components or suffer injury.

Have a look here:

http://sound.westhost.com/

good luck,

Chris
 
#3,595
thanks to you ,too, bremen nacht.
the Trafo is for 115V inputvoltage, so its unusable in germany 🙁
and i dont realy know how to put these things togeter you listet.
can you please paint something vor me with the symasym as a blackbox??
this would help me a lot! paint the trafo too, maybe i understand then why it has to be 2 times 25v
 
#3,597
sorry but this is a little bit to confuzing.
i dont think that i will find the information i need on this site, because of m bad english and because most of it is newland for me.

i will buy the things bremen nacht told me to buy and will come back here if i have problems finding out how to build the powwer suply.
 
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