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Re: Modding the MP-1?

Posted by Ralph (M) on November 1, 2006 at 08:55:46

In Reply to: Re: Modding the MP-1? posted by Lew on October 31, 2006 at 07:21:15:

Hi Lew,

We've added resistors in the cathodes of the output circlotron to enhance current sharing, and with the regulators we have right now, the noise is so low that even the MP-3 is acceptable with less than 0.3mV at any volume- we used the ZYX Universe at RMAF with our MP-3 and that cartidge is 0.25mV. They worked great together!

We tried low noise transistors in the phono like you are proposing about 4-5 years ago. You really have to hand-pick the transistors for low noise!! Otherwise you are better off with the tubes.

The regulator plays a big role. So far we have had exposure to two MP-1s that were modified with the original Super Reg; in both cases these preamps fell well short of our stock expectations- our regulators not only sounded better but were quieter too, even after setting up the SR to run at the newer increased B+ voltages. The SR is a really competent regulator and I am not sure why this has been the case, although we suspect problems that arose from faulty installation.

So my advice is to scrutinize the regulator first before you try your other experiments!

Also, *DO NOT* use *ANY* type of NOS 12AT7s in the MP-1! *NO* NOS 12AT7s are *actually* quiet, despite claims by *ANYONE* to the contrary!! You really will have to use new tubes to get the proper noise performance: EHs, EIs and JJs all have to be hand-picked for low noise and microphonics. We have very good luck with the Chinese 12AT7s because we see so many more of them that are acceptable. I added the emphasis above because it is really true; anyone thinking that they have a source of quiet NOS tubes is sadly mistaken- all the truely quiet NOS tubes were shipped out 3 decades ago. All that remains now are the rejects.

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