But here’s the kicker: This thread was put up as a promotional device. You can tell because the manufacturer is talking about his products, often more than once in many of his posts. This is against the Audiogon rules, but because I and others are posting here as well, the entire thread doesn’t have to be taken down.
A promotional device in what manner? Do you think Roger is using this thread to try and sell more products? Since you called out Roger on this I will say you are walking a fine line here Ralph, especially given what you once told me in a conversation we had about marketing. The thread was started so that Roger can share his knowledge and experience with the community. He has requested that other designers not respond to the questions asked of him, and from my perspective it’s not that you don’t bring value to the discussion (and I get it’s a public forum), but when you bring up the self promotion stuff, I have to agree with George that it is the pot calling the kettle black.
You consistently promote balanced differential designs, not always mentioning products specifically, although correct me if I am wrong, but you have mentioned the MP-1 was one of the first balanced preamps in high end audio on more than one occasion. I have read many threads where you reference how your preamps solve the issue of cable artifacts coloring the sound, that you make them unity gain with a buffered output, and you have mentioned or alluded to your amplifier designs many a time as well. Granted you do so in a gentlemanly manner and as a means to educate. However, isn’t that what Roger is doing as well?
Here is an example from 12/26/2017:
Our MP-3 preamp is based on the first balanced preamp circuit ever sold to high end audio (our MP-1). It has a direct-coupled output (despite being a tube preamp) and has bandwidth to about 400KHz.
Here is an older example:
How the MP-1 works is it has a direct-coupled output. The output impedance is low enough that it can drive 32-ohm headphones easily. It is designed to drive 600 ohms without effort; obviously its output impedance has to be well below that in order to do so.
Because its outputs are direct-coupled, the output impedance is flat from 1Hz to 200KHz or thereabouts. So it really can drive 200 foot interconnects without difficulty.
It my opinion that getting rid of the output coupling caps is the single best thing you can do with a tube preamp to improve transparency and bandwidth.
The MP-1 was/is the first balanced line preamp for high end audio.
Roger is being very generous with his time (as you have over the years) and trying to answer as many questions as possible. Is he self promoting? His experience for sure. Does he mention his products? Yes. Does he push them? Not in my opinion. From my perspective he references them to supplement responses relevant to his experience or in direct response to questions about that product from other members posting on this thread. I see nothing wrong with that, especially since you have done the same on Audiogon.