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Super simple single stage tube preamp
http://diyaudioprojects.com/Forum/viewtopic.php?f=9&t=3266
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Author:  Grega [ 05 Dec 2011, 20:45 ]
Post subject:  Re: Super simple single stage tube preamp

oh figured out i can export to gerbers too. all good mate. the problem is the next step up in eagle license is mega dollars. its a darn good product, but, wondering what the next logical step is.

the sockets i am using are AOK.
i've not put up a picture of the finished thing - i tinned the legs of the socket and then soldered direct to the board and they lined up pretty much spot on. i checked the 8 pin sockets i have for my 6L6GCs and they appear to be the same lastnight - will be doing a board as per my 6L6 mono block setup in the next few days. although i have to redeo the heatsinking for the TDAs tom as i had them thermal shutting lastnight.

Author:  tombethe [ 08 Dec 2011, 07:22 ]
Post subject:  Re: Super simple single stage tube preamp

Hi all,

just an "all in one" example - not ready yet - it's just a test...:
Attachment:
ssup 130x100.GIF

Size is 100 high - 130 long. Fits perfectly on a standard euro size card. The tube socket is a standard 24mm / 22mm ceramic 36° PCB mount socket.
Socket is "upside down", solders on the copper side. Should work OK.
Pot is a Alps RK27. BTW - Bleeder added, Mark's snubbers added, 1N4007 diodes (can be swapped to xxxxxx), Regulator caps added,
Regulator dropper diode added (for ~12,6V), plain copper ground... Lead spacing is 3,5mm, 7,5mm and 10mm.
Filter caps for HT are 100uF / 400V - 7,5mm leads, Heater filter is 4700uF and some uF after the 7812. Maybe 1000 or so..
I think i'll add a protection diode for the 7812 too. The tube socket is yet a little out of centre (0,6mm)... I'll revise it tonight...

Please share your thoughts ;-).

Author:  mwhouston [ 08 Dec 2011, 15:50 ]
Post subject:  Re: Super simple single stage tube preamp

tombethe: Looking very good. Hard to imagine when all copper plate bu that's the way to go.

Author:  Grega [ 08 Dec 2011, 21:38 ]
Post subject:  Re: Super simple single stage tube preamp

tom - marvellous work mate!

Author:  tombethe [ 09 Dec 2011, 18:35 ]
Post subject:  Re: Super simple single stage tube preamp

TYA mates!

Ok - here is the revised and modified version:
Attachment:
ssup copper.gbr.png


Changes:
Shrinked to 125length x 90height, regulator protection added, Terminal orientation changed, socket put in center...
Should be OK now.

What about omitting the Volume pot from the board?? It will drop the size to 90 x 100 and allows to mount the board in any place / direction.
Attachment:
ssup copper_potless.gbr.png
Now it would be good to know some component sizes (mainly the capacitor lead spacing from the jaycar components).

BTW - the files are now available as Sprint, Gerber (have to check for compatiblity) and Printsize positive PDFs.

Author:  Grega [ 09 Dec 2011, 21:05 ]
Post subject:  Re: Super simple single stage tube preamp

marvellous tom - well done.
i used all 1w resistors - their lead spacing is 13mm
in the valve stage
the film .47uf has lead spacing of 27mm
the electrolytic has spacing of 2.5mm

i'll get u the lead spacing in the psu stage soon dude.

Author:  tombethe [ 17 Dec 2011, 02:52 ]
Post subject:  Re: Super simple single stage tube preamp

This is the latest and final version.
I have replaced some caps to allow different sizes and some tracks were changed a little.
Attachment:
Comp layout potless.gbr.png

The files will come soon.

Author:  Suncalc [ 17 Dec 2011, 13:13 ]
Post subject:  Re: Super simple single stage tube preamp

Tom, this looks awesome! This looks like there is no preferred side for components (other than the tube socket) with the possible exception of the 7812. I also like that one could simply replace R1 with an off board inductor and get even better filtering and lower noise. C5 and C6 are obviously optional depending on the desired cathode bypass state. This is really excellent.

I would suggest one very small change. I would add two resistors from terminals 1 and 8 to ground. This would allow the board to be used with an output potentiometer (by leaving the resistors off the board) or a fixed output resistance as a stand alone gain stage (with the resistors on the board). Just a suggestion.

Excellent work!

Author:  mwhouston [ 17 Dec 2011, 18:02 ]
Post subject:  Re: Super simple single stage tube preamp

Tom: yes it looks very good. Great to see the development and changes as they go through.

You need to build a few to test the layout etc. then offer them up as kits complete with Jaycar parts. Or just board, parts list and some brief instructions. Could be a buck in it.

Author:  tombethe [ 19 Dec 2011, 02:34 ]
Post subject:  Re: Super simple single stage tube preamp

Suncalc wrote:
Tom, this looks awesome! This looks like there is no preferred side for components (other than the tube socket) with the possible exception of the 7812. I also like that one could simply replace R1 with an off board inductor and get even better filtering and lower noise. C5 and C6 are obviously optional depending on the desired cathode bypass state. This is really excellent.

I would suggest one very small change. I would add two resistors from terminals 1 and 8 to ground. This would allow the board to be used with an output potentiometer (by leaving the resistors off the board) or a fixed output resistance as a stand alone gain stage (with the resistors on the board). Just a suggestion.

Excellent work!

Matt,
Thanks a lot! The 7812 can be mounted upside down. The pins stay in the same direction.
Yes, R1 can be replaced with the choke leads, that's what i will do. I have some more time at the beginning of the next week.
I hope i'll have a proto ready after christmasmas for some first and final testings. The first prints were very promising, except
some solder pad sizes. Some were to small for soldering the wires directly and i want to change them for at least 20AWG
with enough copper surface on the pads. The Resistor pads will be added ;-).

Mark,
the layout is for (and from) Your and Matt's project and for the Forum members and guests.
I've spent some hours with it to get some serious and well thought stuff. The layout is 100% hand made (No Autorouting or fixed DRC),
just plain component placement, adjusting the sizes, track adjustement and taking care of minimal parallel tracks (capacitive induction) except the heater DC -
and thinking about the versatile usage of the boards...
I believe it could make the simple preamp even more simple and this might help a lot other people out there.
Basically it is more simple to print a positive, etch the board and hook up the wires. The count of errors is minimized
and you don't have to think about point 2 point component wirings. The chance to get problems with noise or HF through
the wiring also is minimized.

I'd rather like to enjoy some posts and pics from happy builders than having trouble with a buisiness..
Maybe later..

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