600R T-Atten. -> st.ives 31267 -> 1176 input ??

hello,

I want to use a st. ives 31267 input transformer for my next 1176 project.

the ratio of the original utc O-12 transformer is 500:200 ohms (2,5:1)



what ratio should I choose for the 31267 ??

4:1 (10k-2k4) or (2k4-600)
1:1 (2k4-2k4)

will it work properly with a 600 ohm t-pad attenuator in front ??
or should I better use an O-12 or one of Ed's altran O-12 clones...??


thanks for your help!

matthias

Hej Matthias, 31267 is a great choice. Use it as 2:1. 10K/ 2k4
That gives 6 dB attenuation.
The ratio and impedance has a root correspondance.
2:1 ratio gives 4 times impedance change.
Cheers Bo

thanks!

do you think it's ok to use a 600 ohms t-attenuator pot in front of the 10k transformer input, or do I need something like a 10K t-attenuator ?

mat

600 att > 10k input might give you an extended freq. response (at least on low levels) plus maybe a cleaner sound.
with a 10k source frequency response might be not as good (but still plenty since it is specified for 10k) because primary inductance, leakage inductance, interwinding capacitance etc..have more effect (color??)

before you buy/build an attenuator just connect a 600 and a 10k resistor in series to the input and listen/measure.

if you don´t like it you also have the option to wire the transformer 2k4:600
an try with a 600 or 2k attenutor

steff

thanks for pointing that out!

I think I'll try both and make some measurements and listening test...