too many tubes on the phono section (10 tubes total ), no way it can handle .20v low mc, even when the manufacture claims that it has a total of 78db gain, both chassis are the flimsiest designs, the power supply parts are from surplus ( not a single caps & resistors that are quality built in the power supply section). the silks screen letters would fade after many use. That in all equal to very noisy preamp!
We run cartridges of that output routinely at shows and of course with customers. The main reason the tube count is high in the phono is that there are three 12AT7s in the front end of each phono section that are in parallel for lower noise and greater ability to drive the cathodes of the 12AT7 with which they are in a differential cascode circuit. This give the input circuit quite a lot of gain with low noise. These days any high end preamp has to work with 0.2mV cartridges. The equalization is passive and executed differentially; the losses of that are made up by the following gain stage. So that’s 5 tubes per channel.
The MP-1 chassis is made of 1/8" aluminum. The side panels are 1/4" machined aluminum. They hold together quite well- we’ve been shipping nationally with either UPS or FedEx ground and internationally for over 35 years; you can have an alright shipping container but when shipping like that, the chassis design has to be robust, especially when going overseas. You can’t have it coming back because a chassis fell apart or got tweaked, and none of them have.
There are no screens on the boards; the text is etched. The boards have a mil-spec ’conformal coating’ to prevent damage from corrosion or moisture.
Most of the resistors used were made custom for us- if not by Caddock, then by Vishay (Draloric). We purchase the filter capacitors in the power supplies from a variety of vendors such as Mouser and DigiKey- to my knowledge none of them are selling surplus parts. The power transformers are all custom built to our spec; we were recently issued a patent for our use of the transformers. Because of their proprietary nature they certainly can’t be sourced surplus!
When you have old stock 12AT7s that will work with 99 out of 100 preamps with the single odd guy being the Atma-sphere...guess what is to blame? I have nothing but the highest respect for Ralph and Atma-sphere but I think that blaming old stock tubes is nonsense and noise at least with the older MP-1s was a real problem.
The problem we’re up against is that we’re using the preamp with really low output cartridges without the help of either an SUT or solid state input circuits- its all-tube. To do that you simply need low noise tubes. I agree that many of the NOS 12AT7s that we can’t use will work fine in other preamps but those preamps can’t take a LOMC cartridge in directly while being all-tube. However my insistence for low noise tubes really only applies to the input tubes- the 3 in the rear of each channel. The remaining two tubes in each channel can be NOS as they are less noise sensitive. Its also true that in the older preamps this was a more serious issue- to make them work the first two input tubes had to be low noise. We changed that up a bit when the Mk3.3 was introduced 5 years ago.
