I saw this thread and decided to add to it. I recently obtained two pairs of Tunnelbridge ICs for evaluation. I tried them in three different configurations. The following is a brief summary, which I hope to supplement as time goes on.
I first installed one pair of Tunnelbridge interconnects between my DAC and my digital room correction device (I don't use a preamp). The Tunnelbridge ICs replaced the Tara Labs Zero Golds, my reference interconnect. The differences were immediately evident even though I deliberately avoided any serious listening. The first was an improvement in bass response (really). The second was a change in the perspective of the soundstage. Finally, the character of vocals changed, and initially in a way I wasn't sure I liked. I let the cables break in for 24 hours before my first listening session.
After 24 hours I sat for my first listen. First, the terrific bass response that I heard initially remained. I made a point of playing a variety of music with significant bass content, both electronic and acoustic, staccato percussive and "grindingly grungy". The result was definitely the best replication of bass I've achieved in my system. Second, the change in soundstage was now clear. The perspective had moved from the 15th row to the 10th row, and the performers became a bit larger (by which I mean closer to life-size). Third, the sound of vocals remained a bit perplexing, but had changed in a way that made me able to better identify what seemed out of kilter. The clarity and accuracy of instruments was generally as good as the incredible Tara Zero Golds. However, the voices in the same frequency sounded different from what I've been used to. They were not bad - they just didn't sound quite like real life. It was as though they were inserted by way of a separate track after the instruments were recorded and the engineer had not yet made the necessary adjustments to fully integrate the vocal and instrumental tracks. I decided to let things play for another 24 hours and listen again the next day. I’m glad I did.
When I resumed the next evening, the bass and soundstaging remained the same, but the vocals had changed dramatically, sounding much more natural. The significant improvement over the second 24 hours led me to conclude it was a break-in issue, so I decided to insert the second pair of Tunnelbridge ICs. I biamp with two pairs of Electrocompaniet monoblocks, and Electrocompaniet makes those amps with both imputs and outputs, so you can biamp by daisy-chaining them. Consequently, the second pair of Tunnelbridge ICs were substituted for the Silent Source Music Reference ICs I use between the bass and mid/treble monoblocks. I worried that this configuration would accentuate the disconnected vocals I had heard when I inserted the first pair of Tunnelbridges. To my very pleasant surprise, not only did the vocals become completely integrated with the musical instruments, but upper bass response improved significantly.
I loved the sound and left this configuration in for a week, but couldn't help thinking that I have two of the best interconnects money can buy (the Silent Source Music Reference and the Tara Labs Zero Golds) and I should figure out how to incorporate them. The problem is that I need a 4 meter run from room correction to my amps, and I use Silent Source Silver Signatures for that connection. Though it was not an ideal configuration to test the Tunnelbridge system, I decided to "creatively" incorporate the Tara Zero Golds and Silent Source Music Reference ICs into the system. I reconnected the Silent Source Music Reference to the outputs of my RP-1 digital room correction device to get halfway to my bass amp, then connected the Tunnelbridge ICs to the Silent Source IC's source end to get to my bass amp. The Tara Labs Zero Gold was then inserted between the bass amp and mid/treble amp. The result exceeded my expectations. The bass performance was even better than before, the level of detailed nuance was astonishing, performers became totally lifesize, and all of it was suffused with a very organic, natural-sounding presentation.
I recognize that this last cable configuration probably masks some characteristics of the Tunnelbridge that need to be evaluated separately, so I plan to do some testing in another system so that I can do some additional comparisons with other high-end interconnects. I'll try to post my impressions after I get done.