[JN] PP 45 amp

Christian Rintelen christian at rintelen.ch
Sun Aug 16 11:15:34 CDT 2009

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 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)


best ©

Ben wrote:
> henry platt wrote:
>> Hi Ben,
>>  Just check out Lynn Olson's Amity project. The trannies spec'd for 
>> it are without equal IMHO
>> http://www.nutshellhifi.com/triode1.html
> The gotya is they don't say what the 2nd interstage transformer is.
> The Amity is a good amp, but I don't need all that power. I want a
> amp to play music, not sit in it!. I am looking at a 10 ma budget
> on the driver to the 45's per channel. This looks like I'll need
> about a 15K interstage transformer, and that they don't seem to make.
> Ben.

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