[Bill Epstein]

What's happening electrically and how is it better/different from the conventional way of coming off pin 8 of the rectifier?

Further, is it using the secondary that allows just the one smoothing cap with no choke or resistor?

If one didn't mind the expense, would a conventional B+ voltage from the rectifier with an CLC filter be better, or just different and more expensive?

[amandarae]

My thoughts....

What is the significance of Clarinet B+ from the 5V secondary center tap?
It is basically the same point as pin 8 or pin 2

What's happening electrically and how is it better/different from the conventional way of coming off pin 8 of the rectifier?
 Difference if any should be negligible.  You can connect it to pin 2 also.

If one didn't mind the expense, would a conventional B+ voltage from the rectifier with an CLC filter be better, or just different and more expensive? 

Of course, it is better ripple measurements wise, because of additional filtering.  But probably not necessary in this case as per design.  If needed, to reduce hum, then for sure Jim included that in the circuit already.

[hagtech]

I like the way the rectifier filament is balanced AC-wise with it's output.  That's what the center tap does for you. 

A CLC filter would be a little better, but you have to be careful to properly tune the LC section so as not to create an underdamped load response.  An LCLC would be best.  That's what I did in the TRUMPET and the C3 proto.  The YUKI (1W guitar amp) uses the CLC type, but only because I needed to get the B+ as high as possible.

jh

[Bill Epstein]

Thanks for that. Thinking of trying out the center tap B+ on my Aikido, and since the B+ is already on the high side and I have a nice 5 mH choke on the shelf .......

[hagtech]

5mH won't do anything.  Sorry.  You need 5H.

jh

[Bill Epstein]

Of course you're right, it's 5H, don't know where the 'm' came from!