GC passive pre-amp dissapointment - Page 3 - diyAudio
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Old 3rd June 2005, 04:24 PM   #21
Nuuk is offline Nuuk  United Kingdom
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Quote:
Are the 100nf caps mentioned without a farnell order code X2 or Y2 class caps? Thats all i can find. Sorry it this is a stupid question.
No not stupid!

I use polypropylenes but the ones I use are no longer available. Farnell code 387-8480 will do fine!

As a rule, you will only use Class X2 or Y2 with mains voltages.
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Old 3rd June 2005, 04:28 PM   #22
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I can vouch that Nuuk's buffer is really really good.

Compared to my Melos pre (that was a stereophile recommended component) with super high end tubes in it (amperex 7308) there is more detail and dynamics with Nuuk's buffered passive. The Melos may be slightly more refined sounding, but that is likely due to the fact that I prefer tube sound. For SS, however, the buffer is great.


Quote:
Originally posted by Nuuk
The transistor buffer must have the output cap - there is over 600mV going into it! Some people have found they need a cap on the input but try it without first.
I needed to put both a 1uF cap and a 1K resistor in series after the pot and before the buffer (I did the cap first and it was not quite enough. adding the resistor fixed the problem, but I did not try it again with just the resistor which may work as well).

For my PS, I used a velleman (essentially a lm317) that has been snubberized and modded with larger voltage caps (63v) running at 30v. I then used a tle2426 to split the rails (2 actually, one for each side as I was not sure that one could provide enough current for both channels) and put 1 1000uF cap and a couple of assorted smaller film caps on each rail (so, that's 4x1000uF plus some other stuff) and this seems to work great. The transformer is about 30VA.

-d
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Old 3rd June 2005, 05:13 PM   #23
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I have just built Nuuks discrete buffer along with the discrete regulators, and I have to say that my gc just doesn't sound like my gc anymore.
I thought that perhaps this buffer-talk was a bit over exagerated, but that is apearantly not the case.

The drums hit harder, but with "air" around them, I can clearly hear hiss on some older recordings which I did not notice before. It's like having a new system.
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Old 3rd June 2005, 05:18 PM   #24
Nuuk is offline Nuuk  United Kingdom
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Quote:
I needed to put both a 1uF cap and a 1K resistor in series after the pot and before the buffer (I did the cap first and it was not quite enough. adding the resistor fixed the problem, but I did not try it again with just the resistor which may work as well).
I'll update the GCpreamp page with that in case anybody else needs it!
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Old 3rd June 2005, 05:22 PM   #25
Nuuk is offline Nuuk  United Kingdom
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I have just built Nuuks discrete buffer............
Another happy customer!
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Old 3rd June 2005, 05:35 PM   #26
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Quote:
Originally posted by Nuuk


I'll update the GCpreamp page with that in case anybody else needs it!
This was with a 50K pot, if that is important.

-d
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Old 3rd June 2005, 05:48 PM   #27
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Quote:
This was with a 50K pot, if that is important.
Yes, it seems to be pots higher than 10K that may cause a problem. Don't ask me why though - I just follow the instructions and pray for success!
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Old 3rd June 2005, 06:35 PM   #28
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Lightbulb A good pre is a good pre

Quote:
Originally posted by postpunk
The drums hit harder, but with "air" around them, I can clearly hear hiss on some older recordings which I did not notice before. It's like having a new system.
Yes, yes, yes!

Now listen to Ben Harper (which are mostly analog recordings) and delight yourself with the hiss.
If the hiss isn't there, very noticeable in the low passages, there's a blanket somewhere - or everywhere - in the system.

Oh glory, oh joy... can you now listen to your favourite music without tapping your foot?
Sing along, enjoy.
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Old 3rd June 2005, 11:02 PM   #29
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Nuuk,

Your a star , if only i could get such quick responses out of Dell ever time one of our servers go down!!

The more people talk about Nuuk's buffer the more i want to do it, by the way is there a great deal of difference between the two types of secondary regulation. I guess the decreet method is more sophisticated however looks like it will take up a lot more space and the enclosure i have in mind is pretty small.

Also which buffer did people build out of the 2 described, just interested. I like the idea of the simple one. So few components seems to appeal after build the GC.


Cheers,

Fil
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Old 4th June 2005, 08:19 AM   #30
Nuuk is offline Nuuk  United Kingdom
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Quote:
by the way is there a great deal of difference between the two types of secondary regulation. I guess the decreet method is more sophisticated however looks like it will take up a lot more space and the enclosure i have in mind is pretty small.
IMHO, the discrete regs are marginally better but it is very close. As regards space, there isn't a lot in it and if you look at the DD GC pre-amp
Click the image to open in full size.
you can see it all fits in quite a small space!

Quote:
Also which buffer did people build out of the 2 described, just interested. I like the idea of the simple one. So few components seems to appeal after build the GC.
If you mean the three transistor (BJT) buffer and the Jfet, then I can't tell you how many of each have been built. I have built both and the BJT is certainly easier/cheaper to build, and more compact. Sound-wise, they are both excellent!
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