carnhill tx

[skal1]

Hey lads,

do any of you  know what  the max current is at the center tap and out of balance plate current of a  carnhill tx vtb 2290.

cheers

skal

 

[CJ]

i would not go above 30 ma total plate current,

unbalanced current could be 10- 15 ma,

a 2290 will give you a nice compressed sound due to core saturation,

a 2291  (gapped version) will give you less distortion at the low end,

here is a graph showing the difference between gapped and un-gapped at low f>

(DIY version, 10 ma DC unbalanced current)

 

[skal1]

Nice 1 CJ ,oh forgot to ask, how much henries are in the  primary/secondary

Cheers

skal

 

[CJ]

here is Henrys vs Freq graph for the DIY version,

only ran an unbalanced DC plot or the series connection, it is in green,

i used a slightly bigger stack than square, so a few extra lams, kind of like the Sowter fat boy version of the 1166/2567,

to get sec inductance, just divide by Z ratio which is turns ratio squared,

so divide by 4^2 = 16 for series connected pri and sec,

looks like you would have about 64/16= 4 Henries sec inductance for the unbalanced DC graph @ 10 Hz,

to get individual sec inductance, divide by 4, so figure about 1 Henry a piece,

if building a Reddi DI, your 1 K sec pot will work differently with the Carnhill vs the stock Cinemag, as the DCR on the 2290/91  sec in series is about 44 ohms and the Cinemag is about 132, so the pot will clamp the output less as you turn it down on the Carnhill,
there is also a tone effect when turning down the pot, seems to roll off some high end, this effect will also be slightly different with the Carnhill,

 

[skal1]

sweet

cheers
skl