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Old 23rd November 2004, 04:03 PM   #1
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Default Can anyone recommend a good buffer circuit

For my first attempt at tube DIY I want to make a simple low voltage buffer for my cd Player. The DAC has a 2.4V p-p balanced output, although I can easily change this to a unbalanced o/p if required.

I want a good, simple, reliable circuit that will operate at no more than about +/-35V with a low input impendance and no output transformer.

Can anyone recommend something.

Kind regards
Paul
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Old 23rd November 2004, 04:06 PM   #2
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Default Re: Can anyone recommend a good buffer circuit

Quote:
Originally posted by primalsea
...... that will operate at no more than about +/-35V with a low input impendance and no output transformer.
Transistors.
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Old 23rd November 2004, 04:22 PM   #3
Wodgy is offline Wodgy  United States
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With a B+ of 35V, a basic cathode follower using the 12AE6A makes the most sense.
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Old 23rd November 2004, 05:34 PM   #4
Yvesm is offline Yvesm  France
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Quote:
.. at no more than about +/-35V with a low input impendance and no output transformer.
Why not an SRPP with a 6GM8 / ECC86 ?
As per "Tube CAD", allows for about 10mA plate current, gain should be around 17 dB with no cathode bypass and output Z less than 2K.
Moreover, with symetrical supply, the output could easily be set at ground potential, eliminating the need for any output cap.

Yves.
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Old 23rd November 2004, 08:34 PM   #5
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I agree with Geek, use transistors.

http://www.borbelyaudio.com/adobe/ae699bor.pdf

Page 3 shows some simple JFET buffers with performance measurements.
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Old 23rd November 2004, 10:29 PM   #6
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"...... that will operate at no more than about +/-35V with a low input impendance and no output transformer.

Transistors."


Ha Ha, Aren't you people supposed to be trying to convert everybody to the wonders of tubes!

As this will be my first tube project I wanted something simple to build and fault find if it goes wrong. Thats the idea of low voltage and no transformer. If it goes wrong I wont cry over all that cash thats gone up in smoke!

I thought I would sample some of that valve sound in a little way first of all to see what the fuss is about.

For the others thanks for the leads, Say you havent got any circuits to post. I have found some but have no idea if they are reliable.
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Old 23rd November 2004, 10:33 PM   #7
SY is offline SY  United States
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If you're going to the bother of using tubes, go to the bother of using reasonable voltages for them. If you insist on limiting yourself to 30 volts, the tube choices are awfully slim- Nuvistors are logical, but darn hard to source, microphonic, and expensive.

A 100-200V supply isn't all that expensive or difficult.
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Old 23rd November 2004, 10:36 PM   #8
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This is a great sounding little one and hard to overdrive

http://geek.scorpiorising.ca/contrib...12AU7-SRPP.png
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Old 23rd November 2004, 10:51 PM   #9
moamps is offline moamps  Croatia
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buffer with ecc88 (6dj8)
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File Type: jpg buffer2.jpg (43.7 KB, 417 views)
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Old 23rd November 2004, 10:58 PM   #10
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I like tubes if I'm looking for voltage gain, especially for small input voltages, like phono preamps, or if the output needs large voltage swings at modest currents, like electrostatic headphone drivers.

If i'm looking for a buffer, with no voltage gain, some current gain, with line-level signal voltages and supply voltage less than 100V I find that transistors, especially jfet input and bipolar output, work well and have little sonic coloration if biased class A.
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