[JN] PP 45 amp

Ben bfranchuk at jetnet.ab.ca
Sun Aug 16 12:03:02 CDT 2009

Christian Rintelen wrote:
> the reason "they don't seem to make" 15k ITs is simple. it's almost 
> impossible to wind a high Z IT with decent bandwith. you didn't specify 
> if your driver stage is SE or differential. if differential, you could 
> use a LL1660S (<http://lundahl.se/pdfs/datash/1660s.pdf>). the sowter 
> 9525 is OK for tubes with up to 5k plate resistance 
> (<http://www.sowter.co.uk/specs/9525.htm>). another option would be to 
> parafeed (active or choke load for the driver tube and cap coupling to 
> the IT. parafeed greatly lowers the demands on the IT because no DC = no 
> airgap = higher inductance.

I don't have driver stage since I don't have a transformer yet.
Not quite 'Catch 22'.

> i once had tribute wind me a custom IT for a 56 to 45 midrange amp. that 
> was easier too, because the IT didn't have to handle the lowest 
> octaves... (iirc the amp overall measured +/- 0dB from 30 to 25k)

I kind of like the idea of using a 56 tube, the old tubes have less 

> ©

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