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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: 04 Dec 2011, 03:32 
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Grega wrote:
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?

Funny with Paris the original photo is with a a 12AT7 which show top and bottom of the heaters. Th other images are of a 12AU7. Almost no heater visibility for the 12AU7. Damn.

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PostPosted: 04 Dec 2011, 03:42 
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Grega wrote:
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

It is probably only necessary to twist AC wiring. But often even when I use DC on the heaters I twist it. The brd. looks good and really what makes it a 12AU7 or any 12A?? is the tube and passive component value you use. So this is a good universal brd. for any single stage tube pre. Good work Grega.

No what would make the brd. even better is the inclusion of the PS. So one longish brd. with PS at one end and tube at the other. We could call this the "Uni-board, universal super simple single stage tube preamp" or UUSSSTP ??!!?? or "U24STP". Hard to believe I'm not on drugs.

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PostPosted: 04 Dec 2011, 04:05 
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No what would make the brd. even better is the inclusion of the PS. So one longish brd. with PS at one end and tube at the other. We could call this the "Uni-board, universal super simple single stage tube preamp" or UUSSSTP ??!!?? or "U24STP". Hard to believe I'm not on drugs.


mark - not hard to do - BTW i 'boarded' your PSU setup - so its 99% done already. my problem is my eagle license only allows me to do a 100x100 board. see what i can do. solongas it all fits on a copper board from jaycar, no worries - very doable :D

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PostPosted: 04 Dec 2011, 18:11 
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here is the PSU side Mark ;

Image

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PostPosted: 04 Dec 2011, 20:07 
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Quote:
mark - not hard to do - BTW i 'boarded' your PSU setup - so its 99% done already. my problem is my eagle license only allows me to do a 100x100 board. see what i can do. solongas it all fits on a copper board from jaycar, no worries - very doable
Maybe i can help here.
I could throw the layout into Sprint (no size limit) and join the boards together to i.e. 160x100 (euro card size). Would take a "minute" but it's doable!
The only important thing to know is the grid / comp. size.. Eagle free doesn't support gerbers and i will have to redraw the tracks from the images.

It's just an offer...

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PostPosted: 04 Dec 2011, 20:39 
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tom, my eagle is licensed actually --> but only lets me do a 100x100 board...........supposed to be able to export as gerbers from it.
the grid is 1.27mm, the components would take a while to sort - easier to do when i am at home.

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PostPosted: 05 Dec 2011, 03:07 
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Guys this is really looking good.. I add snubbing to the diode bridge and each filter cap in the HT and before the reg. and after. But these can be soldered under the brd. direct to the caps and bridge.

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PostPosted: 05 Dec 2011, 04:23 
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can vouch for it working very VERY well this board..............using it at present.
i will add them in mark. 100nf OK?

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PostPosted: 05 Dec 2011, 05:47 
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Grega wrote:
can vouch for it working very VERY well this board..............using it at present.
i will add them in mark. 100nf OK?


The ones you will have to add in is the four around the rec. bridge for the HT. These should be Jaycar brown 0.01uf/630 poly caps. The rest I feel it is actually best to put them underneath directly on the cap legs. Those that go across the caps are 0.1uf/630V Jaycar brown polies. The one cap on the end of the end of the 12V and HT run are 0.1uf. The one 0.01uf after the 12V bridge (across the pos. and neg rails) is another you can add (if it isn't there) this time 0.01uf.

The 220uf cap is a Jaycar low ESR type.

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PostPosted: 05 Dec 2011, 20:12 
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Ouch - Sorry, just overlooked "my eagle license"...

How does the Belton noval sockets fit to the Eagle lib. sockets? Aren't they too small? What about using PCB mount sockets??
BTW - Which PCB dimensions would you prefer?

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Some of my projects: TDA2050 Chip Amp, the LM3886 Gainclone Thread and the Szekeres Headamp Thread.


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