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 NEW  Matt presents bias and operation data for the 6V6 tube in SE operation - 6V6 Single-Ended (SE) Ultra Linear (UL) Bias Optimization.

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PostPosted: 03 Dec 2011, 00:43 
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Joined: 17 Aug 2011, 06:05
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mark / matt / tom- good news.
everything works - 100% spot on.
the PSU circuit gives me (no exploding caps) but unloaded voltage of 300+ V for the 12Axx and 12.16 on the heater side - regulated and clean as thanks to the 7812.

on the PCB side with a 12AT7 - i've only heard music via my test bench and a 5w full range - but no issues - no hum, no hiss, no noise, just plain old tunes, nice highs (even for the fullrange) and mid bass seems fine. fine reproduction. am very VERY happy.

tom - tunes were driven by the LM1875/TDA2050 tom special - wunderbar.

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PostPosted: 03 Dec 2011, 08:59 
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Grega wrote:
mark / matt / tom- good news.
everything works - 100% spot on.
the PSU circuit gives me (no exploding caps) but unloaded voltage of 300+ V for the 12Axx and 12.16 on the heater side - regulated and clean as thanks to the 7812.

on the PCB side with a 12AT7 - i've only heard music via my test bench and a 5w full range - but no issues - no hum, no hiss, no noise, just plain old tunes, nice highs (even for the fullrange) and mid bass seems fine. fine reproduction. am very VERY happy.

tom - tunes were driven by the LM1875/TDA2050 tom special - wunderbar.

Grega what is HT loaded. And check bias V.

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PostPosted: 03 Dec 2011, 18:14 
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Morning Mark

145v loaded on 1 and 6
1.9v bias on 3 and 8 - i think thats Bias right? voltages seem right. thats with a 12AT7 in there at the moment

Its bloody loud - gain is extreme

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PostPosted: 03 Dec 2011, 18:56 
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oh, linear pots for volume control FTL.......off to jaycar again........mark i need to get frequent flyer points for that joint of late :)
there is a slight bit of hum up at the top end of the scale too.

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PostPosted: 03 Dec 2011, 19:06 
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What at full volume?

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PostPosted: 03 Dec 2011, 20:10 
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yes, full volume dude

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PostPosted: 03 Dec 2011, 20:46 
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i did this over lunch too ;

Image

matt - better?
mark, sorry, what better to do over lunch (than eat) :D

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PostPosted: 03 Dec 2011, 21:24 
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Nice design. I like this board even better.

One question... why screw terminals on the audio but soldier pads for the B+ and filament power?

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PostPosted: 04 Dec 2011, 00:54 
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matt. noted. v3 coming up :D :D :D :D :D
the only thing i don't like about this is the proximity of the B+ to the RIN (right input) - but that will also be part of v3 :D

i rolled a 12AU7 in place of the 12AT7. the 12AU7 is a JJ - the 12AT7 was an EH.
i like the sound of the 12AU7 significantly more (although I am listening to ATB at the moment - sorry - but I don't mind some 'doof doof') the low end thru my little custom bookshelfs (vifa 6.5 and fostex ft17h). main thing of note with the 12AU7 is the top of the tube is glowing - am guessing this is the heater - the 12AT7 was not. is this normal?

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PostPosted: 04 Dec 2011, 01:31 
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right
B+/- is now in a terminal. RIN is moved more inward away from the B+/- also
the heater i would like to leave as pads - so the wires can be twisted accordingly - happy to hear otherwise - i read somewhere that the reason for twisting wires was only for AC to stop hum - is the same relevant for DC?
must say i like the board better now. mark - any input dude? i'll etch a couple more and send them on to you guys too - as we'll be moving from beta to alpha now :D hehehehehehe

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