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Old 1st August 2011, 07:43 AM   #1
ryuji is offline ryuji  United States
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Join Date: Feb 2011
Location: massachusetts
Default preamplifier/driver for 807

me and my friend were discussing using 5 6SN7 halfs per channel to drive my 807's but i have seen a few projects of people using single 6au6's instead. The intentions were to have aikido line stages run into another triode as driver for the 807's.

are both solutions equivalent, or is one solution vastly superior to the other?

15 6SN7's verses five 6au6's and probably two 6SN7's for my subwoofer preamp? certainly a cost difference.
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Old 1st August 2011, 10:22 AM   #2
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Just curious if you have a build thread for this project. Do you use this for HT or multichannel music?
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Old 1st August 2011, 04:31 PM   #3
ryuji is offline ryuji  United States
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i use the output from my xonar d2x; compared to the majority of HT boxes, the d2x has better adc and preamplification

Quote:
Output Signal-to-Noise Ratio (A-Weighted):
118dB for all channels dB dB
Input Signal-to-Noise Ratio (A-Weighted):
118 dB dB
Output THD+N at 1kHz:
0.0004% (-108dB)
Input THD+N at 1kHz:
0.0004% (-108dB)
Frequency Response (-3dB, 24-bit/96kHz input):
<10Hz to 46kHz (for all channels)
Frequency Response (-3dB, 24-bit/192kHz input):
<10Hz to 46kHz (for all channels)
Output/Input Full-Scale Voltage
2 Vrms (5.65 Vp-p)
Sample Rate Conversion Quality:
Almost lossless, high-fidelity floating-point filters, with:
-140dB THD+N (typical value for 44.1K->48KHz, 24bit)
145dB Dynamic Range (typical value for 44.1K->48KHz, 24bit)
dont have a worklog thread but i can show how it looks now:
Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.
can show the schematics too and other information if you like

Last edited by ryuji; 1st August 2011 at 04:52 PM.
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Old 1st August 2011, 04:34 PM   #4
ryuji is offline ryuji  United States
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Oh, forgot to add, This amplifier is used for games/music/movies
mostly listen to metal/rock

i dont own a tv, my PC does everything for me
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Old 2nd August 2011, 05:24 PM   #5
ryuji is offline ryuji  United States
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doing some looking around, apparently the 6au6's are terribly microphonic. kind of considering using 6V6's instead. could use similar design architecture to what im using now, just adjusted for higher idle current. the -20v bias line on the 6v6 looks damn linear as long as your past 200v plate.

aikidos and more 6SN7's for drivers would require about half a ampere of b+ power in addition to collectively per channel consuming two times as much heater current as the 6v6, im thinking i'd need no more then 180 mA b+ current with this solution.

anyone have circuit/experience with using a 6v6 as a driver i can look at?
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Old 2nd August 2011, 07:49 PM   #6
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maybe try using a pentode like ef86/el84?
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Old 2nd August 2011, 08:10 PM   #7
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Quote:
Originally Posted by ryuji View Post
me and my friend were discussing using 5 6SN7 halfs per channel to drive my 807's but i have seen a few projects of people using single 6au6's instead. The intentions were to have aikido line stages run into another triode as driver for the 807's.
This is absurd. The 807 isn't that tough of a load. I used one section of a 6SN7 as a cathode follower to drive PP 807s (attached). Even if you intended to operate 'em in Class AB2, a source follower could get the job done easily. Even in Class AB2, it isn't a hard load.
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Old 2nd August 2011, 08:36 PM   #8
ryuji is offline ryuji  United States
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the number of half's was because i was putting together a preamp and then a driver, but i guess your saying that a single half can possibly handle 1~2v rms line input just fine? when i tried running my current 12at7's just by themselves it wasnt quite enough amplification

im kind of interested in pentode driver, the 6au6 looks great on paper but i have had multiple friends/people tell me that they can/tend to be so microphonic that you can blow on them at hear it

guess i should have said that my design considerations include preamp.

Last edited by ryuji; 2nd August 2011 at 08:41 PM.
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Old 3rd August 2011, 07:26 AM   #9
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Quote:
Originally Posted by ryuji View Post

im kind of interested in pentode driver, the 6au6 looks great on paper but i have had multiple friends/people tell me that they can/tend to be so microphonic that you can blow on them at hear it

guess i should have said that my design considerations include preamp.
I've used several brands of 6AU6 but have never experienced microphonic behavior with any of them. I'm currently using Sylvanias from 1976 with no issues.

Steve
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Old 3rd August 2011, 06:35 PM   #10
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Quote:
Originally Posted by ryuji View Post
im kind of interested in pentode driver, the 6au6 looks great on paper but i have had multiple friends/people tell me that they can/tend to be so microphonic that you can blow on them at hear it

guess i should have said that my design considerations include preamp.
This can be true of any VT. Some vintage 6SN7s are just about that bad. I've seen 6BQ7s (dual triode) that ring like bells. You can find samples that are nastily microphonic, and samples that are not.
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