813 SE circuit,will it work?

Richard Ellis · 19th November 2006, 08:37 AM

Ok.... after the umpteenth time (trying to do the picture) lets see if you guys/gals think this beast will work right...its' a melding of different circuits...I don't have the sims to just plug it in & my take is many of you will know the curves of said tubes by heart by now...for me this is very new...I was trained on solid state...alot of this stuff seems like Smith charts....who can tell me what a Smith chart is ??
Here goes..
_______________________________Rick.........

Fuling · 19th November 2006, 11:02 AM

1M is a way too high value for the grid leak, I think the datasheet says 33k or so and even with cathode bias I would keep it below 100k.
I would also choose something "beefier" than 6SN7 in the driver position, but OTOH it´s an UL output stage so it might be quite easy to drive.

EC8010 · 19th November 2006, 01:47 PM

Once upon a time (very briefly) I could use a Smith chart. RF engineers use them for analysing complex (j) circuits at a single frequency.

Richard Ellis · 19th November 2006, 01:59 PM

And the prize goes to the fellow from the UK for correctly identifying the use of a Smith chart...I once could use the dang thing...very complex stuff, but now I'd have to learn it all over again..
On the grid as "Fuling" noted..yeah it seemed rather high, I thought the value might have something to do with the previous stage.
Should the coupling cap between stages be rated for the second stage voltage? EG 900V+????????
As I researched the 813 the consensus is that it is easily driven typically less so than a 300B. The notation was a third of the power to drive, opposed to the 300B.
_________________________________Rick..........

SY · 19th November 2006, 02:01 PM

I assume you're powering the output stage filament with DC? The supply is, of course, in series with the input signal, so would be pretty critical.

Richard Ellis · 19th November 2006, 02:08 PM

Yes the filament is DC, driven by a pair of TO3 transistors....I'll have to keep the voltage differential somewhat close so I don't have massive power dissipation & add even more heat.
The filaments for the 6SN7 will be driven by a LM317K ....any way you look at it I will have heatsinks everywhere dissipating heat.

sparky813 · 19th November 2006, 03:05 PM

Robert Willis has several SE designs, just Google "Robert Willis diy 813" Also the thread: "Transmitter tube amp" on this website has a good discussion of grid resistance requirements. I am not sure I understand it yet. I have a PP ultralinear breadboard and I am enjoying listening to it. Sparky.

19th November 2006, 01:47 PM	#3
EC8010 diyAudio Moderator Join Date: Jan 2003 Location: Near London. UK	Once upon a time (very briefly) I could use a Smith chart. RF engineers use them for analysing complex (j) circuits at a single frequency. __________________ The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...

19th November 2006, 02:01 PM	#5
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	I assume you're powering the output stage filament with DC? The supply is, of course, in series with the input signal, so would be pretty critical. __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

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19th November 2006, 11:02 AM	#2
Fuling diyAudio Member Join Date: Aug 2001 Location: Sweden (Mora)	1M is a way too high value for the grid leak, I think the datasheet says 33k or so and even with cathode bias I would keep it below 100k. I would also choose something "beefier" than 6SN7 in the driver position, but OTOH it´s an UL output stage so it might be quite easy to drive.

19th November 2006, 01:59 PM	#4
Richard Ellis diyAudio Member Join Date: Sep 2006 Location: Mar del Plata, a BIG seasonal getaway city, can see the Ocean from our residence.	And the prize goes to the fellow from the UK for correctly identifying the use of a Smith chart...I once could use the dang thing...very complex stuff, but now I'd have to learn it all over again.. On the grid as "Fuling" noted..yeah it seemed rather high, I thought the value might have something to do with the previous stage. Should the coupling cap between stages be rated for the second stage voltage? EG 900V+???????? As I researched the 813 the consensus is that it is easily driven typically less so than a 300B. The notation was a third of the power to drive, opposed to the 300B. _________________________________Rick..........

19th November 2006, 02:08 PM	#6
Richard Ellis diyAudio Member Join Date: Sep 2006 Location: Mar del Plata, a BIG seasonal getaway city, can see the Ocean from our residence.	Yes the filament is DC, driven by a pair of TO3 transistors....I'll have to keep the voltage differential somewhat close so I don't have massive power dissipation & add even more heat. The filaments for the 6SN7 will be driven by a LM317K ....any way you look at it I will have heatsinks everywhere dissipating heat.

19th November 2006, 03:05 PM	#7
sparky813 diyAudio Member Join Date: Oct 2006	Robert Willis has several SE designs, just Google "Robert Willis diy 813" Also the thread: "Transmitter tube amp" on this website has a good discussion of grid resistance requirements. I am not sure I understand it yet. I have a PP ultralinear breadboard and I am enjoying listening to it. Sparky.

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