Replacing 9 pin tube socket with 8 pin octal socket

TravAndAlex

New member
I'm doing a major Crack rebuild and since I have far more 6SN7 tubes (currently with the Garage1217 adapter), I'd like to just enlarge the 9 pin hole and replace it with an 8 pin octal socket that I have on hand.  Is there a guide or listing of what pin numbers will change from the 9 pin to the 8 pin?  Searches have found others that have done this, but not the specifics.

Also, can you run a 6SN7 without the Speedball upgrade?

Cheers!
 
What I did was print out the datasheets for the 12AU7 and 6SN7 and put them side by side. Then make the necessary pin number changes.

http://tdsl.duncanamps.com/show.php?des=12au7
http://tdsl.duncanamps.com/show.php?des=6sn7

The only other thing you need to consider is where the LED's tie to the Center pin of the 9 pin socket. The 8 pin doesn't have a solder tab like the 9 pin does. I added a small terminal strip near the Octal socket. There was a photo I posted a while back but I think it was on the other (old) forum.

Yes, the 6SN7 will work just fine with or without the Speedball upgrade.
 
Thanks! 

So just to confirm that I'm not too stunned about the whole thing... I'm basically matching pin layout in the diagram?

9-pin  8-pin

1  2
2  1
3  3
4  7
5  8
6  5
7  4
8  6
9  -


 

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I'm probably wrong, but I don't think that is correct.  It looks to me like you do not have a completed circuit for the heater.  I think 9 should go to 8 and 4/5 should go to 7 (or vice versa?).
 
diynewbie said:
I'm probably wrong, but I don't think that is correct.  It looks to me like you do not have a completed circuit for the heater.  I think 9 should go to 8 and 4/5 should go to 7 (or vice versa?).

Good catch. You are correct.
Since the Crack uses AC heating the polarity isn't important.

9-pin  8-pin

1      2
2      1
3      3
4/5    7
9      8
6      5
7      4
8      6
 
Yes. Available from various sources, including that famous auction site.
 

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Thanks very much for your reply.  It will be quite helpful to me.  I have several 6sn tubes that I used in a Darkvoice 336 before the Bottlehead.  I will get an adapter right away.  Thanks again
 
You should also look at this thread:
https://bottlehead.com/smf/index.php?topic=7742.0
Not all adapters are equally good. I got one of these and have had no issues.
 
That forum thread is pretty dated by now, their website has them under Accessories.
Also, starting at $40 they seem to have a healthy percentage of audiophile tax applied!  ;D
 
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