GC passive pre-amp dissapointment

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#141
postpunk said:
Someone asked if there was buzz in any other ppl's buffers at any volume setting, and yes, I have a buzz when my volume is at the lowest setting. I had this problem with the 50k pot too.
Click to expand...

Try a resistor in series with the input (after the pot.) Something in the range of 470R to 1K should work to eliminate the noise. Quality counts here, b/t/w. I have had good luck with both Kiwame and PRP resistors in this spot.

-d
 
#143
Hi there,
I wouldn't sware to the fact that I increased the restance value. I am running mine with +/-18V rails. The transistors are a mix from PC power supplies (matched between buffers).
Its all so long ago now I don't remember the details and I don't want to poke around the case.

Shoog
 
#146
Upupa, Carlos ; Let me explain this buzz.. When I turned the pot fully counter clockwise the buzz came all at once, almost like a bang, and when I then touched the grounded chassis it made difference to the tonality of the buzz. But if I turned the pot up by only 1mm, it got as silent as umm... silence. I don´t understand why, but with the 470r resistor it is ok.
 
#147
To postpunk : 470 R connected in series with brush ? Do you have a scope ? Buzzing can have two reasons : ground loop or oscilation of active circuit. Look at first by scope at output of amp, if isn't there ( by buzzing ) hf oscilations. Do you have some internal pics of this preamp ?
 
#148
Here is my build of Nuuks psu.

Been very busy at work finishing a pop video and a series of bog roll adverts so not nearly enough time of late to get on with the serious matter of building my buffer.
 

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#149
And this is the current state of the Buffer board. It currently has the second stage of rectification for one channel and i am about to do the same for the other channel.

Hopefully all be together by the weekend but lots of deadlines at work might mean it gets put back.

fil
 

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#152
Upupa Epops said:
To postpunk : 470 R connected in series with brush ? Do you have a scope ? Buzzing can have two reasons : ground loop or oscilation of active circuit. Look at first by scope at output of amp, if isn't there ( by buzzing ) hf oscilations. Do you have some internal pics of this preamp ?
Click to expand...

What I was told is that when the pot is set to full-minimum position, it shorts out R2 and this affects the bias voltage for Q2 which causes the noise.
 
#156
Hi all,

This thread had been dead for a while i know however i have just finished my Nuuk design psu and buffer. Havent had chance yet due to work to actually listen to it, 70hrs per weeks at the moment unfortunately.

I have also got a new 10k log alps pot to stick in so there is a way to go.

One thing i was wondering was wether the resistors ihave built it with are 1/8 watt 1% metal film. Are these too low power?
Also one channel is gving about 15.15 -/+ and the oterh 14.85 +/- will this level of difference be audible and how would i get around it. Will i need to change the resistor on the regs or should i use apot?

Any advice greatfully recieved.

Fil
 
#157
One thing i was wondering was wether the resistors ihave built it with are 1/8 watt 1% metal film. Are these too low power?
Click to expand...

They're fine Fil. 😉

Also one channel is gving about 15.15 -/+ and the oterh 14.85 +/- will this level of difference be audible and how would i get around it. Will i need to change the resistor on the regs or should i use apot?
Click to expand...

No problem at all! 🙂

Now steady on - 70 hours a week is a bit excessive isn't it? When will you ever have time for listening? I hope at least you are being paid enough to pay for the resistors! 😀
 
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