ST35 converted to ST50 with 6L6GC

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ST35 converted to ST50 with 6L6GC

Postby tubes4hifi » Sun Apr 11, 2004 6:41 pm

hello fellow tube lovers!
I can never leave well enough alone and since I've had "tube fever" for several years now, it seems I have to build me a new tube amp at least every month or two.
So here's my latest, I call it the ST50. It's got the revC ST35 PCB as it's heart, but I put in octal sockets on the chassis and wired them up to the PCB so I could run it with 6L6GC tubes, for about 25 watts per channel.
It's not quite done yet but I couldn't resist posting the photo!
So wait a week or so before you ask me how it sounds.
I'm using the Hammond 1650F OPTs and Hammond 272HX for power.
I'd really like to put a 5AR4 rectifier in the large space behind the small tubes, so I may need slightly more voltage from the power transformer to do that. It would look better, and hey, another thing I want to try!

Oh shucks, I can't remember how to upload a photo, and my computer FTP is messed up this weekend, so I can't post to my website either . . .

Roy www.tubes4hifi.com[/img]
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the pics of the ST50

Postby Shannon Parks » Sun Apr 11, 2004 8:07 pm

This is crazy - way to go, Roy!

Shannon

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ST50 photos

Postby tubes4hifi » Mon Apr 12, 2004 7:16 am

thanks for posting the photos Shannon.
Now with the top view photo you see I need to fill that space with a rectifier tube!
Now don't anyone start thinking about EL34 tubes, they use way too much filament current, want lots of B+, and so would need a HUGE power transformer compared to what is on this small chassis.
Besides I've already got a great EL34 amp!
That's why I thought of the 6L6's they only use a little more current than 6BQ5's (EL84) but much bigger glass envelope, so the tube to me doesn't seem to run so HOT!
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ST-35 board with octal sockets?!?!?

Postby TerrySmith » Mon Apr 12, 2004 7:42 pm

This really intrigues me! Is it possible to make the ST-35 board with octal sockets? Maybe a modified rev-B for the power supply layout.

I realize it won't be a ST-35, but a universal board with an all triode front end.
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Re: ST-35 board with octal sockets?!?!?

Postby Shannon Parks » Mon Apr 12, 2004 8:48 pm

TerrySmith wrote:This really intrigues me! Is it possible to make the ST-35 board with octal sockets? Maybe a modified rev-B for the power supply layout.

I realize it won't be a ST-35, but a universal board with an all triode front end.


I'm thinking a ST35-type board with a differential front end using a CCS would be cool. I could make a mini-9 version and an octal version - say for a 6V6 or other low powered (or triode strapped) octal. Lots of fun possibilites out there!

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Gosh, thats real purdy

Postby dhuebert » Tue Apr 13, 2004 7:10 am

Apart from the octal sockets, are there any other mods necessary?

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2 in 1 ?

Postby EWBrown » Tue Apr 13, 2004 11:13 am

I'm thinking a ST35-type board with a differential front end using a CCS would be cool. I could make a mini-9 version and an octal version - say for a 6V6 or other low powered (or triode strapped) octal. Lots of fun possibilites out there!

Shannon



Just another wild and crazy idea..... How hard would it be to co-axially fit both 8 and 9 pin socket "footprints" on the PCB?

/ed :tongue8:
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Re: 2 in 1 ?

Postby Shannon Parks » Tue Apr 13, 2004 11:35 am

EWBrown wrote:
I'm thinking a ST35-type board with a differential front end using a CCS would be cool. I could make a mini-9 version and an octal version - say for a 6V6 or other low powered (or triode strapped) octal. Lots of fun possibilites out there!

Shannon



Just another wild and crazy idea..... How hard would it be to co-axially fit both 8 and 9 pin socket "footprints" on the PCB?

/ed :tongue8:


Since I'm relaying out both the Ike and ST35 boards this week I'm looking at doing just that to the Eiclone where the 12AX7 is. Pretty dang tight. On the ST35 board it looks impossible. I'd rather just do a new board with octals (and a different driver circuit for fun).

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octal + 9p sockets

Postby tubes4hifi » Wed Apr 14, 2004 5:38 pm

I hope I didn't whip up too much excitement, I also do PCB layouts and they do take some time, although revisions aren't too bad. :redhotevil:
I wouldn't want to put any extra work on Shannon, but I think it is quite possible to do the combo octal and 9p on the DIY ST35 PCB, especially if you use the smaller footprint 9p sockets with 5/8 spacing instead of 13/16.
Then fit the octal 1.0" right around it. There was only one pin with a crossover trace if you orient the sockets correctly. I'd do it myself :? but I don't use a PCB supplier that does the THICK PCBs like Shannon's supplier.
I do want to put in my vote again (!!!) for an EIclone with all octal tubes, like a 6SL7 gain and 6SN7 driver. :D
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the easy way

Postby Guest » Wed Apr 14, 2004 5:55 pm

of course the easy way is just to do what I did, use chassis mount octal sockets above (or easier yet, over to the sides of) the PCB and run short jumper wires. :sign7:

:signbye:
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ST-50

Postby TerrySmith » Mon Jun 28, 2004 10:02 pm

Hey Roy,

Did you ever get the kinks out of the ST-50? :williamshatter:

We're moving to east Tenn, so it'll be a couple of months before I burn anymore solder! :sonarsmile:
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AES has the YJs

Postby EWBrown » Thu Aug 19, 2004 5:43 am

AES www.tubesandmore.com has the "yellowjacket" tube adapters in several "flavors" (6L6, 7951, 6V6 to EL84) at $29.95 each. I haven't tried these, and at nearly $120 to set up an amplifier, It probably won't happen too soon...

So a DIY35 could be set up with octal sockets, and these adapters would allow the use of EL84s in place of the 6L6GCs, etc. I would probably go the "drug store tube tester" approach for a prototype, and have paralleled
octal and 9 pin sockets for all six tubes, so we're talking 12 (or 13 with a 5AR4/GZ34 rectifier) tube sockets, and all this wouldn't fit too neatly on an 8X12 chassis surface. The traditional "tube checker" look, indeed...

If one goes one step further, the 17 X 10 inch stainless steel ST-70 "dynaclone" chassis that Uncle Ned had available, was pre-punched so
that either EL34s, or PPP EL84s could be used, see my "stainless steel behemoth" photos in the gallery, I went with Octals and used the supplied hole plugs to fill the 8 9-pin socket holes, though I may wire in these sockets at a later date.

http://www.diytube.com/jalbum/ed/slides ... d%20b.html

/ed B in NH
Last edited by EWBrown on Fri Dec 17, 2004 8:29 am, edited 1 time in total.
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Sansui 100A output transformers?

Postby Norri Wilson » Tue Aug 24, 2004 11:30 am

Hi everyone,

This is my first post here and have not made it to amateur status yet (newbie), but I am working on it.

I would like to know if the Sansui 1000A output transformers would work with the 6L6 25 watt amplifier using the ST-35 board submitted by
Ed Brown? Also, any comments on the quality of the Sansui transformers?

Thanks for anyone who replies.

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Disregard my above post!

Postby Guest » Wed Aug 25, 2004 9:15 pm

Hi everyone,

I have to admit after ready my post above, that I made several errors.
The main error was to call the 6L6 25 watt amplifier in the above project as being submitted by Ed Brown.
I do want to apologize to Roy Mottram and Ed brown for this error, for Roy Mottram is the contributor of this fine looking amplifier. It also looks as if I misspelled my own name, what a first post.

I do want to thank you Roy for answering my Email questions about my Curcio Daniel preamp today.

I found out the impedance of my Sansui 1000A output transfomers are, primary: 3600-0-3600 ohms.
It is obvious that they will not work with the ST-35 6L6 project above.

Now, if someone could tell me how to erase my first post in error, I could try to start over.

Thanks

Norris Wilson
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