Neumann WV2 based Phono amplifier
Part 1
For a long time I have wanted to build myself a phono amplifier to acompany my modified Space Audio WE91B and Altec 604E Alnico.
Initially I thought of the Marantz 7C phono section because of Yazaki-san`s excellent articles over at Jeff`s Place, and it made a lot of sense. The M7C have been highly phrased for it`s build and high sonic quality, and I see many people that i admire in the audio world swear to it. I had even started to collect the components needed.
Then I became aware of the EMT 139st through mr. Vliets site, I have also noticed that vintage EMT record players are very sought after, so I thought that the 139st must be an even better choice than the M7C.
By chance I became aware of the Neumann WV2..... again through mr Vliet`s postings.
If my investigation are right, this phono preamplifier was actual not sold as a standalone unit, but was developed to be used inside Neumann`s vinyl cutting machines for evaluating the final vinyl master, so I figured out that this MUST be the HOLY GRALE of all vintage phono preamplifiers.
The fact that there is not much information on the web about it, and that the original items that i have found for sale goes for as much as $10.000 in Asia, in addition the cathode bias is set with batteries. It has to be good and my curiosity rised even more.
So i googled and collected as much information as I could, and finally decided to go for it.
Mono & Stereo posted an article about mr Vliet`s Neumann WV2 project. This was the first schematics i acquired. After some more searching i got hold of some good resolution and complete drawings on Groupe DIY site. This was very helpful in understand the components that was a part of the active RIAA network.
Since I only wanted to use this as a Phono preamplifier I had to isolate the phono section. And I would also like to use it with my beloved Shure V15-III MR, so I needed to stripp away the MC transformer and associated components as well.
I collected the needed components for the project, NOS Telefunken EF804 and EF 804s tubes, Amtrans AMRT and Allen Bradley resistor, 1.2V batteries, the rest of the components I already had from earlier upgrading projects. With all the components in house I started to build a prototype as a "birds nest". Welcome to the "CROW`S NEST VERSION"
Time for the first listening test:
Deep and articulated bass, good depth and with in the sound stage, spacial, but with some remaining issues. Motorboating was one, hum was the second.
Some late night google search taught me about grid stopper resistor, so a 3k resistor soldered directly on the grid of the first tube solved most of the motorboating issue, i could stil hear it, but it was faint. The next problem in the CROW nest was the hum. This I almost solved with playing around with cable routing, so tyding up the nest a little helped, but did not take it away the hum completely.
But at least, the Neumann WV2 Crows Nest version proved that this was definitely a project worth wild to refine further.
In the next post I will talk about the refinement and deviation of the original schematic.
