Hi, I am new to the hobby and have been working my way through books and articles and learning to use LTSPice.
I am interested in designing, simulating, and building a parafeed line stage and have been looking at the Lundahl LL1930 transformer for parafeed line stage applications. I was wondering if anyone has built a line stage using this transformer.
The transformer has two primary windings and two secondary windings with a 5.1 : 1 or 11.6 : 1 turns ratio and. Static resistance of each primary is listed as 610 ohms and the static resistance of each secondary is listed as 16 ohms.
I do not see a listing for the primary impedance however, and I am wondering what tubes are recommended for use with this transformer.
More generally, I would also be interested to learn about the thought process you use when designing a new amplifier/preamplifier from a systems perspective. Do you begin with a circuit topology and then pick a transformer and work through the circuit backwards optimizing as you go, or start from the source and work towards the output, or use another strategy altogether. Many thanks, Martin.
I am interested in designing, simulating, and building a parafeed line stage and have been looking at the Lundahl LL1930 transformer for parafeed line stage applications. I was wondering if anyone has built a line stage using this transformer.
The transformer has two primary windings and two secondary windings with a 5.1 : 1 or 11.6 : 1 turns ratio and. Static resistance of each primary is listed as 610 ohms and the static resistance of each secondary is listed as 16 ohms.
I do not see a listing for the primary impedance however, and I am wondering what tubes are recommended for use with this transformer.
More generally, I would also be interested to learn about the thought process you use when designing a new amplifier/preamplifier from a systems perspective. Do you begin with a circuit topology and then pick a transformer and work through the circuit backwards optimizing as you go, or start from the source and work towards the output, or use another strategy altogether. Many thanks, Martin.
Source impedance 4.5k. Primaries connected in series.
Frequency response. Connection and signal level as above. Secondary load 10k.
20 Hz – 30kHz < +/- 0.1 dB
-0.1dB @ 20Hz with 4.5k source. You should be able to work it out from that.
-0.1dB point is about 4 octaves up from the -3dB point. 16X. So the -3dB point is like 1.2Hz or better. A 1 Henry coil would be about 8 Ohms at 1.2Hz. But it must be near 4,500 Ohms. So it must be 500-600 Henries. And a precision spec is not warranted because iron-cores are very variable with level and frequency; we just try for "big".
Frequency response. Connection and signal level as above. Secondary load 10k.
20 Hz – 30kHz < +/- 0.1 dB
-0.1dB @ 20Hz with 4.5k source. You should be able to work it out from that.
-0.1dB point is about 4 octaves up from the -3dB point. 16X. So the -3dB point is like 1.2Hz or better. A 1 Henry coil would be about 8 Ohms at 1.2Hz. But it must be near 4,500 Ohms. So it must be 500-600 Henries. And a precision spec is not warranted because iron-cores are very variable with level and frequency; we just try for "big".
