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Old 4th December 2003, 01:11 AM   #1
grataku is offline grataku  United States
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Default K&K Audio Balanced Linestage

What do you guys think about this preamp?

http://hometown.aol.com/kevinc927/my...linestage.html

I don't get the connection of the output trafo.
I am still looking to do something different for my new preamp and I just stumbled on this today while browsing for some trafos...

It looks like a more complicated than this half assed idea I had awhile ago:
http://diyaudio.com/forums/showthrea...923#post254923

or maybe it's a way to do it that actually works!
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Old 4th December 2003, 03:46 AM   #2
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Default It depends

on what your goals are with it. Are you planning on using it to tinker with and try different experiments, or use it for just general backround music?
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Old 4th December 2003, 04:18 AM   #3
grataku is offline grataku  United States
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Uh?


You could start by giving me your opinion about the K&K circuit, if you have one.
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Old 4th December 2003, 12:56 PM   #4
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Default Re: K&K Audio Balanced Linestage

Quote:
Originally posted by grataku
What do you guys think about this preamp?

http://hometown.aol.com/kevinc927/my...linestage.html
I've not heard it (though Bas has built one) but it looks like it could be a great little pre. Kevin knows his stuff and is an experienced designer, and it uses a lot of qualirt components.

Quote:
I don't get the connection of the output trafo.
It's parallel feed, or parafeed. The tube is loaded by a constant current source instead of a resistor or choke (though either could be used with lower performance) and it feeds cap-coupled into the OPT. Because the OPT doesn't need to carry any DC, it can have no gap and a higher rpimary inductance for the same core size and winding pattern.

Quote:
or maybe it's a way to do it that actually works!
Yes
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Old 4th December 2003, 04:15 PM   #5
grataku is offline grataku  United States
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Thanks Brett,
could you elaborate on the why choke loading and a current sink would be inferior to this design?
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Old 4th December 2003, 07:09 PM   #6
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Default Well

I would definitely change the FET regulator in favor of a vacuum tube one.

I did research and testing of FET regulators and they substantially alter the sonics. In fact even one 1N914 signal diode will alter the sonics in a farily moderate impedance circuit. A 1N914 is very low in junction capacitance, has a rise time of 5ns, nanoseconds.

I think it best to use SS only when it is minimal in the sonic equation.
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Old 4th December 2003, 07:38 PM   #7
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Quote:
Originally posted by grataku
Thanks Brett,
could you elaborate on the why choke loading and a current sink would be inferior to this design?
The CCS is the best IMO/IME. Chokes have an impedance that varies with frequency; if you wind them with enough inductance, tha parasitic capacitance can affect the top end, but there are some designs that do very well and it's not that much of an issue. Resistors give a sloped loadline and more distortion. The CCS also gives about 60dB aditional isolation from the power supply, at least a single (ie not cascoded) DN2450 does.

Based on my experience with these particular devices, as well as Gary Pimm's various CCS's, they're great. And this from someone who didn't even like using sand at all for a long time.
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Old 4th December 2003, 08:33 PM   #8
grataku is offline grataku  United States
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Brett,
I like the design alot. However, I would have liked to see little better CCS, more "Pimm-esque". The PS seems very good too.
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Old 5th December 2003, 06:49 AM   #9
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Quote:
Originally posted by grataku
Brett,
I like the design alot. However, I would have liked to see little better CCS, more "Pimm-esque". The PS seems very good too.
Then cascode them or sub in BBMCCS's. The performance of the single DN is not as good as Gary's BBMCCS or cascoded DN's, but it's about $15 worth of extra parts you can easily add in later, and it doesn't need the batteries, though Douglas/Bandersnatch/Sector 7G has tried versions with additional battery supplied bias. See Bas' site.

The cascode and BBMCCS versions would also allow you to try driving the OPTs from the mu o/p too.
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Old 5th December 2003, 06:50 AM   #10
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