OK, the final kink is worked out!
I designed the PH 9.0 with the same switching logic as the PH 150, for MM-Mute-MC input. Well, one or two components in the circuit were different and I found that due to some variation in one part, there was a pop when switching from MM-Mute and Mute-MM, on some units, but not all. I have spent the week beating my head against the wall trying to find the reason and solution.
Well, it turns out that this particular component is simply different than the other previously used. It is also quieter and offers better performance, but the one difference does require a revised switching logic. So, the PH 9.0 will have a four position selector switch. Despite the face plate indicating MM - Mute - MC, it will actually be MC -Mute - Mute - MC. This way, when switching from MM or MC to mute, there is no possibility of any pop or tick at all.
Now that this is resolved, I have also gone over other operating parameters and optimized other parts of the circuit that I am now ready to start shipping units next week.
Thank you all for your patience!
I know that many mfrs. would never share an 'issue' much less how it is resolved. I would rather just be open with you all about it. The new part offers better performance and if this requires a four position switch, then so be it!
It is my goal for this to be the BEST < $3K tube phono on the market! I would like to think that it will be the best < $3K phono on the market PERIOD, but the tube/SS debate will always rage on. Suffice to say, it is QUIET, and sounds amazing!