Thank you all for your support. I realize that when it comes to a 'tube buffer', there is really nothing of quality on the market and most are the same basic circuit that anyone can make. I have something different and better in mind, obviously.
I want to keep it simple and < $995. It will be sold direct, not through dealers, so the value will be high!
RE VC, it isn't that it would add significantly to the cost, but it would be a volume pot, not a stepper or autoformer based control, etc., as the budget will simply not allow. Having said that, I have access to good and not expensive volume pots that could be designed in, with a bypass.
RE XLR inputs and outputs, there are two ways to do this and both add some cost. If I use transformers, it will add a non-trivial cost. Good transformers are not cheap! I could also design it to be fully differential and this would mean four tubes instead of two. This is the lesser cost way to go. There is even the possibility of designing it in such a way that tubes LA and LB, RA and RB could allow for some mixing and matching of tubes for different sound. I.e. not requiring a matched quad, but rather two matched pairs. One could be warm and sweet, the other fast. It would be a way to adjust the sound and tone.
'Tone Adjust' is a key feature of this design to me. I DON'T mean that it will have tone controls, nor will it have gain. Lastly, no feedback. Feedback and tone controls (traditional) would all require gain. I also don't like to use either FB or tone controls. Rather, with different tubes and perhaps different circuit implementation that is adjustable on the fly, the customer could adjust the tone of the product to suit their ears. I have already shared one way that this could be done.
I think the tube rectifier is key as it also allows a further 'tone tuning'. To be clear, 'tone tuning' does not equate to added distortion or reduced bandwidth!
I think that adding say two inputs and two pairs of outputs could be implemented in the base model as I can see the benefit of this. Perhaps XLR and RCA outs, where the XLR outs are fully balanced? Also fully balanced inputs and RCA inputs. I need to know how many people want balanced inputs and outputs.
My plan for this product is for it to be as simple to use as a connect and forget, setup, but adjustable to allow people to taylor the sound to their tastes also, if they choose. I also don't want any dip switches or anything that requires taking the cover off. I plan for tubes to be fully exposed and the front panel controls to be simple and 'on-the-fly' as our PH 9.0 and PH 150 phono stages are.
Aesthetically, it will be clean and physically slim. I don't know that it will be full 17"W and I would prefer to keep the enclosure height to close to 3"H. It could be set directly on top of a digital or analog source, provided it doesn't need to reject heat. I don't typically recommend this from a noise standpoint, but in this case, if there are not signal transformers used, it could be done. Tubes will be on top and exposed, so all heat will be rejected up and out of the unit.
I would like to see a simple faceplate with one knob in the center, for power on/off and input select. Perhaps one or two other buttons for other features, but ideally clean, simple and uncluttered. This is not a preamp, not a professional mixing device with knobs and switches to adjust. It is meant to be clean, simple and easy to use, but still allow flexibility for the user who wants to experiment with different 'tone'.
Thanks guys, this product is long overdue and the design has left the station!