룬달 LL1676 1:1 사용법
룬달 인풋트랜스 LL1676(아몰퍼스 코아)를 1:1로 사용하여 아주 좋은 결과를 얻었다는
측정자 : 린올손(오로라 앰프 설계자)
LL1676을 1:1 결선법
1차 : + 측 ( 7+9번), -측 ( 6,10번)
2차 : + 측 2번, -측 5번 ( 1,4번은 연결)
그라운드 : 8번
입력신호 2V RMS에서 3Hz-160kHz
I was at Gary Dahl's place and did some additional testing(12K load per half-secondary), and the 1:1 LL1676 is the best I've seen for input and phase-splitting applications. Performance at HF is dramatically better at 1:1 than 1:2 ratio.
At 1:2, small phase deviations appear around 10kHz, and amplitude mismatch is about 5% at the same frequency - OK but not wonderful. (The smaller LL1544A is quite a bit better in that regard.) The effective HF limit is about 70kHz.
With Kevin's 1:1 connection (posted above), HF performance of the LL1676 is in another league altogether, and superior to the LL1544A. The best I've seen from any transformer. HF first resonance is at 160kHz (!), and phase-match viewed on XY and dual-trace mode is visibly perfect up to and beyond 100kHz. It's uncanny to rotate the oscillator knob from 500Hz to 5kHz, and the next decade higher, with no visible change to the XY display, just a straight line, no tendency to open into a loop at all. Overlapping traces in dual-trace mode shows better than 1% matching through 50kHz and above.
The most severe test is a dual-trace 10kHz square wave, with harmonics out to 90kHz and extreme sensitivity to phase rotation of the harmonics. This is where the 1:1 connected LL1676 pulls ahead of the LL1544A, with both square waves almost entirely overlapping. By comparison, the LL1544A shows noticeably different ripple patterns for each half-secondary, and the dissimilarity with the 1:2 LL1676 is quite obvious.
So hat's off to Per Lundahl and Kevin for this achievement! All that and amorphous too!
Very high overload limits from what I could tell. No THD measurement, just looking for gross distortion on the scope. The 1:1 LL1676 was good for 6V rms at 10Hz (!!!), and 15 or more volts from 20Hz on up (!!!). The HP generator was only good for 15V rms, so I didn't go further. Huge amount of headroom.
I should also add that at more normal voltages of 2V rms, the square-wave at 10Hz had no visible tilting or roll-off, so the small-signal performance must have been good to 3 Hz. Pretty remarkable for a transformer ... 3Hz to 160kHz.
그림은 게리핌의 결선도입니다.