BA283 pins J&A

[wells2p]

can someone tell me when pins J&A of ba283 would need to have a resistor eg increased current instead of being bridged and what value would be used? see below: thank you

 

[Khron]

What're the odds those numbers along the bottom there, are suggested resistor values?

8.2, 15, 27, 56, 120, 330 are all in the E12 series of values.

https://en.wikipedia.org/wiki/E_series_of_preferred_numbers#E12
Best educated guess would be, if one was expecting to drive lower-than-standard impedances, for whatever reason? Maybe not quite as low as, say, a speaker, but...

A quick google search for "neve ba283 resistor current" indicated this thread as a top result, and in particular this post by PRR (and more, further down):

https://groupdiy.com/threads/questions-re-design-of-neve-ba283.6425/post-75424
And here's some info "straight from the horse's mouth", as it were, right on the first page:

http://sethglassman.com/BA283AV.pdf

 

[wells2p]

Oh snap I can’t believe I missed those values at the bottom of the page especially since I’ve looked at it so many times - many thanks

 

[wells2p]

Great info from PRR in link - thanks again

 

[Loetinator]

What're the odds those numbers along the bottom there, are suggested resistor values?

8.2, 15, 27, 56, 120, 330 are all in the E12 series of values.

https://en.wikipedia.org/wiki/E_series_of_preferred_numbers#E12
Best educated guess would be, if one was expecting to drive lower-than-standard impedances, for whatever reason? Maybe not quite as low as, say, a speaker, but...

A quick google search for "neve ba283 resistor current" indicated this thread as a top result, and in particular this post by PRR (and more, further down):

https://groupdiy.com/threads/questions-re-design-of-neve-ba283.6425/post-75424
And here's some info "straight from the horse's mouth", as it were, right on the first page:

http://sethglassman.com/BA283AV.pdf

Hello
Those pins have to get a suitable resistor to biss the output transistor

When i built my ba283 i had distortion on the output in the upper halfwave of my test sine

That was because i thought that the 4k7 pot would do the job of biasing

if you ground J you will get a lot of current thru all parts of the chain (Transformator, Transistor, especially 47ohms resistor)

Fiddled around and biased with 1k

Of course that was no science but i had no motivation to dive into the specs

My suggestion would be to apply a sine on the input with two times your expected level and check the resistor witch will lead to a correct amplification without drawning too much current

I settled at 50mA and it works fine

Regards

 

[ruffrecords]

Pins J and A are supposed to be connected directly together.


Cheers

Ian