J99 Input Transformer question
Posted:
Wed Aug 13, 2008 10:33 pmby davidmen
Hi Tim, since the op amps (the 990 and the sc99) are low impedance inputs, the lundahl 1538xl seems to be some medium to high impedance input tx, compared with the JT -16; Are the 1538xl raising the noise floor a little bit since the 1:5 ratio? Don't get me wrong, the 1538xl it's one of the best input tx, my concern is about the noise floor. Thanks.
Posted:
Fri Aug 15, 2008 7:51 amby tpryan
The 1538XL can be connected 1:5 or 2:5. Normal operation on the J99 is 2:5, not much different than the 2:4 of the JT-16. Jumpering for 1:5 gives another 6dB of gain for very low-z sources, something you can't do with the JT-16. Also, J99 input impedance is a slightly old-fashioned 1200 ohms, which gives somewhat better immunity to real world high impedance noise sources.