If it is analog, the 1x4 is optimized best for that. The 1x4 (four 30 AWG wires in the conductor) is a nice improvement over the GEN 1 design for analog signals. The better OFE copper in the 1x1 (one 25 AWG conductor) design isn’t going to sound as good as the 1x4 in TPC as the Vp linearity and coherence improvements really show up in the analog optimized design. And yes, the TPC 1x4 is cheaper than the 1x1 OFE. Try them out and see!
I designed the GEN 1 XLR @ AES/EBU impedance for the BAV XLR design, as the pro’s use digital audio. The RCA was set-up to match the GEN 1 XLR in reactive properties (L and C) so the sound quality is matched using the gen 1 RCA and XLR for analog audio. This also matches the higher impedance.
The impedance when using the RCA or XLR analog isn’t as critical as digital so the GEN II 1x4 and 4x4 can be optimized for audio frequencies and not worry about AES/EBU. Thus the GEN II RCA and XLR are analog only optimized designs.
OK but what about RCA 75-ohm SPDIF? For that we recommend using an optimize digital cable, 1694A. People have used the GEN 1 RCA for SPDIF with a solid copper signal wire (DO NOT use the GEN II for digital) and reported good results. But it isn’t the right impedance for 75-ohm SPDIF because GEN 1 RCA is matched to the AES/EBU 115-ohm +/- 15 OHM standard the XLR needed for the pro market.
Out of the ICONOCLAST project, the trickle down product to the wider market is the BAV XLR AES/EBU design. The pro’s don’t use RCA or speaker cables (XLR input powered speakers).
ANALOG - use the 1x4 GEN II RCA
SPDIF DIGITAL - use the 1694A RCA.