Line stage with 12AU7 and 6CG7 anyone? - diyAudio
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Old 10th February 2011, 04:55 PM   #1
sbelyo is offline sbelyo  United States
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Default Line stage with 12AU7 and 6CG7 anyone?

Hi All...

A while back I built this Headphone OTL amp by Kurt Strain. I could never really get it to produce much base, but the midrange was buttery smooth and I liked the detail on the high end. At this point I have scrapped this amp and I don't use it, but I'd like to build a linstage with the 12AU7 and 6CG7 because I could hear some really nice sound qualities in there. I also have the hammond 269EX as well.

HeadWize - Project: An OTL Tube Headphone Amplifier by Kurt Strain

Can anyone reccomend a nice line stage or even a tube buffer circuit with these tubes that I could mate with an output stage of a DAC?

Thanks
Steve
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Old 10th February 2011, 07:36 PM   #2
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10uF won't get you much bass with a 300 ohm (or lower) headphone. Not a big fan of this design (would prefer a White Cathode Follower with a high transconductance tube like the 6922).

Check out the Akido - it's certainly popular around here and there is a combination that will work with your tubes of choice.
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Old 11th February 2011, 12:55 AM   #3
sbelyo is offline sbelyo  United States
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I increased the 10uf cap to like 30uf or more I can't remember but it didn't do much.

I'll check out the akido
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Old 11th February 2011, 04:42 AM   #4
wa2ise is offline wa2ise  United States
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Well, there's the cathode follower circuit, plate tied to around 180VDC, cathode resistor 10K, and grid biased to ground thru a half megohm resistor. Click the image to open in full size. The 5963 is similar to a 12AU7.
Or similar to what I did to buffer a modified DAC using a TDA1543 (the 6111 is a low mu triode, somewhat similar to the 12AU7)
Click the image to open in full size.
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Old 11th February 2011, 08:16 AM   #5
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Quote:
Originally Posted by sbelyo View Post
I increased the 10uf cap to like 30uf or more I can't remember but it didn't do much.
Makes sense. Into a 32Ohm load and for a corner frequency of 50Hz, you'd have needed about 100uF. About 250uF for 20Hz. The value of C1 mentioned in the Kurt Strain Headwize article seems to be based on a 600Ohm headphone impedance, and even then it's sort of skinny.
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Old 11th February 2011, 12:29 PM   #6
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for my headphone amplifier, I used 470uF output caps. The White Cathode follower was pretty good driving headphones, but I found that a Mosfet buffer does even a better job with lo-z cans.
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Old 11th February 2011, 12:55 PM   #7
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Try the Beta follower instead of the mu-follower in Morgan Jones book. Ray
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