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Old 23rd July 2012, 10:39 AM   #1
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Default After search...need schematic to stereo preamp with only 4 bjt transistors

Hi all , how are you ?
I want to build a simple stereo preamp with gain of X5-X6

Something like this preamp stage in Marantz 2226 (this stage is before the tone control )

i did a search here but I founded only complicated preamps
I want preap with only 4 BJT transistors , 2 to each side .

do you have a recommedation for me ? or you think I can build this marantz 2226 stage . and it will be just fine ?
thanks have a nice day .
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Old 23rd July 2012, 11:05 AM   #2
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Circuit around RE05, RE07 & RE08 does not look right to me!

Anyway, just out of interest: why are you limiting your design to the use of 'just' two BJTs per channel? However I agree that less is more (sometimes)...

Andy
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Old 23rd July 2012, 11:12 AM   #3
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thanks for the replies , i don't know why think something wrong with RE 05 07 08
but the schema shows that there is connection to ground here ,
but there isn't .
it is goes straits to the other channel
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Old 23rd July 2012, 11:18 AM   #4
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But without short circuit across RE08, should work OK, and give a gain of about x3.7 if using for example ZTX651 / ZTX751 for the transistors.

Andy
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Old 23rd July 2012, 11:23 AM   #5
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Looks like a half of diamond buffer. Do the proper diamond buffer and throw the caps away.
Two additional BJTs are better than two additional coupling caps. Much better.

edit: ahh, you need gain. I always though of preamps as unity-gain devices....
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Last edited by s3tup; 23rd July 2012 at 11:31 AM.
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Old 23rd July 2012, 11:34 AM   #6
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so 8 BJT transistor will ok ( 4 to each side )
but the problem is that I have only positive 35V + , i can't give negetive volt .
actually i can but i want to avoid it and only use positive V

can you recommend me schema for that ? thanks
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Old 23rd July 2012, 11:44 AM   #7
Mooly is offline Mooly  United Kingdom
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This is taken from the Radford HD250 preamp. These simple two transistor gain stages can offer outstanding performance and are easily altered to suit.
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Old 23rd July 2012, 11:46 AM   #8
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beat me to it!
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Old 23rd July 2012, 11:54 AM   #9
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thanks , look simple as I want ,
but how I adjust it to the 35 V ?
can you do that for me ?
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Old 23rd July 2012, 11:57 AM   #10
Mooly is offline Mooly  United Kingdom
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Quote:
Originally Posted by WhiteRhino View Post
thanks , look simple as I want ,
but how I adjust it to the 35 V ?
can you do that for me ?
I'll see what I can come up with

Be later today...
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