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 Forum index » DIY Hardware and Software » YuSynth
2sc1583 steiner VCF
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isak



Joined: Dec 13, 2009
Posts: 697
Location: Israel
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PostPosted: Tue Sep 18, 2012 2:41 am    Post subject: 2sc1583 steiner VCF Reply with quote  Mark this post and the followings unread

Hi Yves Smile

i need your pro advice please.
i want to build the 2sc1583 steiner vcf but i dont know how to match transistors, I've found this on ebay..
http://www.ebay.com/itm/4-X-MATCHED-PHILIPS-BC547-BC547C-NPN-TRANSISTOR-/251091775191?pt=US_Amplifier_Parts_Components&hash=item3a763c6ed7
is it ok to use?

the second question..
by the boom the reso pot should be 22k-25k.
i have only 50k pot, i found by mistake that if i take 50k pot and put a 50k resistor between leg 1 and leg 3 the pot become 25k.
can i use this 50k pot with 50k resistor to have 25k pot for the reso?

thanks in advance,
Isak E.

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yusynth



Joined: Nov 24, 2005
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Location: France

PostPosted: Mon Sep 24, 2012 4:17 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi

If you have a DVM with the diode testing function you can just use this function to measure the Vbe voltage drop of your transistors and select those that don't differ by more than 2mV. Otherwise you can build this simple tester I described here :
http://electro-music.com/forum/viewtopic.php?highlight=transistor+matching&t=34177

For your pot problem, a simpler solution is to use the 50K pot without adding a parallel resistor that would change the response curve of the pot. Instead you may simply change the value of R13 to 56K and R14 to 10K.

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isak



Joined: Dec 13, 2009
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PostPosted: Mon Sep 24, 2012 11:27 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi Yves.

for the diode test this is what i need to do?
Quote:
take an NPN transistor, connect the base to the collector, switch your DVM to diode test and connect the positive lead to collector and negative to emitter

if yes...i did it and it gave the number 637, is that the Vbe?
(its moves now from 638 to 639)

thank you for the link it helped me!
does the pic attached method is more accurate?
can the power be 12V instead 15V?
need to be AC or DC?

sorry for lots of questions, still learning.


testeur_vbe_490.gif
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isak



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PostPosted: Mon Sep 24, 2012 12:03 pm    Post subject: Reply with quote  Mark this post and the followings unread

i found another way...

can you advice me please, can i use +/-12V instead of +/-15V? please see attached pics .
if yes, do i need to modify any resistors value?


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yusynth



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PostPosted: Mon Sep 24, 2012 12:05 pm    Post subject: Reply with quote  Mark this post and the followings unread

Yes this is the voltage drop of the diode junction between base and emitter and as such corresponds to Vbe. 637 means 637mV. If your transistors are within 637 to 639 then this is OK they are matched.

Concerning the schemo you can use 9V, 12V or 15V it does not matter provided that you run the comparison with same voltage source no need to change th resistor value and obviously we are dealing with DC here Wink

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isak



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PostPosted: Mon Sep 24, 2012 12:17 pm    Post subject: Reply with quote  Mark this post and the followings unread

you are a life saver! thank you very much!
you dont know how frustrating it is to not know electronics and want to build the world Confused
but hey... i'm learning Smile

last question...
does the HFE needs to be matched as well?
infect...in what situation i need a Vbe matched and in what situation i need HFE matched?
are there modules that need both Vbe and HFE matching?

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yusynth



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PostPosted: Mon Sep 24, 2012 12:21 pm    Post subject: Reply with quote  Mark this post and the followings unread

HFe is only involved when gain amplification is at stack, Vbe matching is involved for low current application such as current mirrors and differential input stages.
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isak



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PostPosted: Mon Sep 24, 2012 12:22 pm    Post subject: Reply with quote  Mark this post and the followings unread

thank you.
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