TVC Promethius versus Bent

I don't have personal experience in comparing the Promitheus TVCs to Bent Audio, nor do I have enough personal experience with resistor-based passives to say anything particularly insightful about differences in sound quality in comparison with transformer-based passives. However, I do have extensive experience with the Promitheus dual-box EI-core TVC and the new double C-core dual-box Signature TVC in my SET audio system.

The Promitheus EI-core TVCs are an excellent value with very good sound quality, but Nicholas Chua has really raised the stakes with his new line of C-core based TVCs. The C-core TVCs have more fullness, weight and body to the music and they give you an uncanny sense of presence. If you want to see what a TVC can really do, I can heartily recommend the new C-core TVCs in the Promitheus line of products. The Signature TVC is a force to be reckoned with that, in my audio system, competes very effectively with high end active preamps.

Pubul57, I am also challenged technically, but here is what I know (or, I should say, what I think I know...any of you EE types should feel free to correct me where I go astray): The type of core (EI vs. C in this case) simply describes the shape of the ferrous core in the transformer through which the music signal is effectively transfered from the primary windings (input) to the secondary windings (output) as the result of magnetic inductance. (The signal flowing around the core on the primary windings induces a magnetic flux in the core, which, in turn, induces an electrical signal on the secondary windings.)

With respect to the transformers that Promitheus is using in their TVCs, the EI-core transformer is rather small with comparatively thick core laminations (.35mm). The C-core transformer is much larger and heavier and uses finer laminations in the construction of the core (.05mm). The result is much better sound quality in the bigger and more expensive transformer. The flagship model TVC is the Signature model, which uses a pair of the C-cores in each transformer (one transformer per channel) and also uses more expensive Elma switches as the source selector and volume control. The sound quality of the flagship Signature TVC is significantly better than the EI-core models, which, in and of themselves are very good (and an excellent value).

ET, if you get a chance to try the Promitheus Signature TVC, I think you will find it worth your while. The new TVC has better top end frequency extension, dynamics, bass weight and overall refinement/finesse than the less expensive EI-core units. I would be very interested in how the new Signature TVC compares with a system such as yours, which sounds like a well-optimized Placette RVC implementation.

Mrtennis, can you clarify which Promitheus TVC it was that you compared to the Bent TVC? Was it one of the budget (i.e., under $1k) TVC models that is built around EI-core Rev. 3 transformers? Or was it one of the newer Reference C-Core or Signature (Double C-core) models?

Mingles, Nick is now including a grounding lug on the rear of each chassis to allow the transformers to be grounded. It sounds like the same wiring scheme that you described for the Sonic Euphoria. Nonetheless, I have never encountered the hum problem that you mentioned with any of the three Promitheus TVCs I have owned. (I have owned the Reference Dual-Box rev. 3 EI-core TVC, the Reference C-core TVC, and the Signature Double C-core TVC.) They have all been dead silent in all three of my audio systems where I have experimented with them. This makes me wonder whether Nick has done something to improve on his wiring configuration beyond the addition of the ground lug.

The new Promitheus TVCs that are built around either a single or double C-core transformer improve significantly on bass frequency extension. These TVCs have a much fuller, weightier sound than that of the TVCs built around the rev. 3 EI-core transformer. In addition, the Signature (double C-core) TVC provides uncanny presence, palpability and image saturation. If you get a chance to audition the new top model (i.e., the Signature TVC), I think you will be very pleased.

I agree that the chassis for the Promitheus TVCs could certainly be more attractive. However, the looks have never bothered me much because of the way the dark color of the TVCs has tended to make them disappear in my equipment racks.