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Old 18th June 2012, 02:47 PM   #541
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thanks all, i have a 0,22uf VCap Cutft on the Amp input with a Choke ( 5mohm ac impedance at 1khz) some caps are good but i prefer to keep it small for sound and save money

great olav that you have finally built your SITamp
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Old 18th June 2012, 05:40 PM   #542
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Default Yeah Juanitox - at last...

Hi!

My SIT has been running (somewhat hot) for 1 month approximately now. Got a little stuffed inside - so I`m planning to move some big caps and tighten things up. That way I can try some other solutions - the 100000 uf bypasscaps or other things people have suggested.

But for now I will only take the output cap on the B1 out and try the sound then. Today I got a new speakercable(QED) - and the lower frequencies got magnified greatly and to the bone.
But soon off to sea - and in july off 2 weeks to Spain for a vacation - so my hobby will be put a little aside till autumn.

Best to you and the rest of us Pass-followers!

Olav
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Old 20th June 2012, 10:25 AM   #543
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Quote:
Originally Posted by juanitox View Post
thanks all, i have a 0,22uf VCap Cutft on the Amp input with a Choke ( 5mohm ac impedance at 1khz) some caps are good but i prefer to keep it small for sound and save money

great olav that you have finally built your SITamp
I can't see why you need the choke on the input unless you have RF present from somewhere else ?
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Old 20th June 2012, 10:52 AM   #544
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Question Hi all!

Report from my set-up: Today I have removed the output cap(10uf) on my B1. So the chain is more and more stripped= 2 transistors on the B1 - 1 input 1 uf.
On th 2SK82SIT there are 1 transistor and 1 input cap(10uf) and 1 output cap (10000 uf w/ 10 uf bypass poly).

Less is more - and the low freq is so..... much better.

And the sound is a big step forward - like Ryan Adams is in the room with his Ashes and Fire. And there are no noise from anything in my chain. You can hear a week humming from the transformers close by(0,5m).
Now I only need a better potmeter on the B1 - suggestion anyone???

Best

Olav
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Old 21st June 2012, 05:19 PM   #545
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Something is wrong if you can hear the transformers humming. The B1 is amazingly silent even with a standard WallMart power supply.
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Old 21st June 2012, 06:00 PM   #546
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Quote:
Originally Posted by KatieandDad View Post
I can't see why you need the choke on the input unless you have RF present from somewhere else ?
a grid choke as gate leak resistor , have a low DC resistance ( about 1,5kohm) what is good for the sit bias and a high AC impedance to reduce the input Cap of my input from 10uf to 0,22uf ..
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Old 21st June 2012, 06:16 PM   #547
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Quote:
Now I only need a better potmeter on the B1 - suggestion anyone???
if you don't afraid about accuracy , a Goldpoint or Dact are good , TKD plastique POT are good too but less transparent , PEC carbon is good to add some meat on the bone but can be scratchy if there is any DC and not very accurate on low level. i like to make use shunt type with one caddock or nude vishay series ( 27K) and any of these pots as shunt resistor ( 20K)

cheers olav..
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Old 21st June 2012, 07:37 PM   #548
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Default Not my B1 - humming... some from SIT

Quote:
Originally Posted by KatieandDad View Post
Something is wrong if you can hear the transformers humming. The B1 is amazingly silent even with a standard WallMart power supply.
KatieandDad - sorry for misinformation.

My B1 is very silent(a quiet powersupply from an old notebook) but there a some weak humming from the two big 400watts transformer in each of the mono 2SK82SIT (LĀmp) - and that is as expected. But you have to keep your ear closeby to hear it!

Best

Olav
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Old 22nd June 2012, 12:40 PM   #549
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If the transformers are humming it is definitely not due to being overloaded, the B1 takes about 10-20mA from its supply.

You could try potting them in potting compound, might be cheaper just to buy a better quality transformer.
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Old 18th October 2012, 09:22 AM   #550
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Default Output Caps C101 and C201

Hi

Can anyone in the know please tell me the reason for such a big cap (10uF) on the output? I would prefer to use the same as input, 1uF again? It will not have an effect on the audible frequency range unless I am missing something.

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