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Were there any beta testers? Did they like the phono preamp?
Hi, Yes. And they love it. Worse they don't want to return the prototypes and pre-production versions and are arranging to buy them. All are now spoken for. I have one and it is my main one in my system. Since I can have anything I want within reason I figure it makes a statement. Now if we can only get the suppliers and fabricators to go back to work things would be nice. As long as the virus hangs around it interferes with that.
Speaking of virus, I received pfizer second dose on MAR 2 2020. We will defeat this virus. Find a name yet for phono? You ended your design with third generation on OCT 25 2020. From OCT 25 2020 to APR 10 2021, you had time to evaluate phono. Any more changes or options to consider?
Hi, No firm name yet. The third pre-production ones only differ from the second with a slight change in transformer orientation and slightly smaller case. Otherwise the same. We may swap some of the ECC803s with 7025s. The jury is out on it. They are supposed to be quieter, but I have one hand built one with 803s and one version 2 with 7025s and I can't really tell much difference. Both test and measure the same within expected tube tolerances (about 1 db for S/N ...response is identical). The best 7025s were from EH and the worst were TAD. ECC803S were JJ standard pin (not gold pin...they were worse!). To me they both sound the same as well.
For your phono, you have your own version of super regulator? https://www.diyaudiostore.com/products/super-regulator
Hi, that one seems to good only for low voltages. The preamp uses voltages in the 200-250 volt range. We do use a pair of LR8K4 regulators on the B+. No regulation is needed on the heater DC supply as the particular rectifiers we use drop just the right amount of voltage so it can feed the tube heaters.