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Old 21st October 2012, 01:15 PM   #321
juma is offline juma  Serbia
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Quote:
Originally Posted by gcolnaghi View Post
... i wanted to try my own way only for the fun...
Mission accomplished - the fun you got indeed...
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Old 21st October 2012, 01:51 PM   #322
tinitus is offline tinitus  Europe
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You have been a Member for 4 years.
and btw funny that the schematic was also posted 4 years ago

you 'forgot' the neat regulators in the original curcuit ?
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Old 21st October 2012, 08:44 PM   #323
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PCB is already supplied with regulated +/- 12V. No need to double it onboard.
I joined diyaudio 4 years ago when decided to replace my commercial speakers and go for diy. Selected/built PMS by Troels Gravesen (see below). Only 6 months ago i started to play with electronics. Built an F5 and now looking for an adequate preamp for it. This is way i am considering myself a novice.
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Old 21st October 2012, 08:52 PM   #324
tinitus is offline tinitus  Europe
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nice, and very impressive for a first speaker
and excellent experienced choices as well
my good man, you have passed the novice level a long time ago
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Old 21st December 2012, 06:43 AM   #325
jarkaa is offline jarkaa  Finland
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Hello,

I have a current buffer that has ~500k input impedance and I would like to try the preamp described in post 53.

My problem is the sourcing of j74 fets so i thought that I could try this topology with bjt:s at the input.

Is this possible with direct replacemet?

My plan is also to increase the rail voltage a bit in oreder to get more voltage swing.
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Old 21st December 2012, 06:58 PM   #326
juma is offline juma  Serbia
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BJTs as direct replacement - no way !

But if BJT is your weapon of choice, this can fit the bill (Zin is about 300k, gain about 3.5 V/V, Zout less than 300 Ohms):
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Old 21st December 2012, 07:52 PM   #327
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Default DITTO

I have the same problem with the 2sj74..'they is all gone'!!! I do however have some of the "V" variety which I gather is not a good idea. I also have the 2sk170 in "V".

I need a preamp for my "last" F5 currently sitting near the ungar iron. Should I JBOZ it??or go BJT as shown.Or are the "V" devices workable ??What to do..OH what to do........
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Old 21st December 2012, 08:17 PM   #328
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or just contact spencer and get some sj74BL.
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Old 21st December 2012, 09:10 PM   #329
tinitus is offline tinitus  Europe
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.....or go BJT as shown.
looks great, with just moderate gain...and cheap
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Old 22nd December 2012, 01:22 AM   #330
6L6 is offline 6L6  United States
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or just contact spencer and get some sj74BL.
Who is Spencer, and how can I contact him?
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