gofar99 Messages: 1949 Registered: May 2010 Location: Southern Arizona
Illuminati (5th Degree)
Hi Everyone, To do some low noise testing I needed to build a solid state phono preamp. The results exceeded my expectations sufficiently that I wrote it up for diyers. So here it is....
gofar99 Messages: 1949 Registered: May 2010 Location: Southern Arizona
Illuminati (5th Degree)
Hi Everyone, This is an easy build and very nice sounding. I listened to it again today and it is better than the SS one I use for comparison (a Simaudio Moon LP3). The sound is not as clinical as the Moon. It is warmer and smoother at least in my system. I believe the LP3 has an edge on S/N but then it is the quietest device I have ever run into with a S/N on MM of -106 dbv and -90 on LOMC. This one is the same for LOMC, but not that quiet for MM. As FYI, anything over about -80 dbv is so quiet in an audio system that the background noise in the listening room will be far higher. I design for a minimum of -90 in all my projects as that gives a really comfortable margin.
gofar99 Messages: 1949 Registered: May 2010 Location: Southern Arizona
Illuminati (5th Degree)
Hi Everyone, an update. I attached a revised schematic. One small change for gain (300R vs 330R) but the thing can do NAB tape playback if you have a reel to reel player now as well.
gofar99 Messages: 1949 Registered: May 2010 Location: Southern Arizona
Illuminati (5th Degree)
Hi, As promised....it works great. Low noise, clean sound and sufficient gain. Either the high or low gain can be used and it seems to work best into the 47K load.
These look at interesting schematics. I've been looking for some ideas for my next project and it looks like I've found it. I'll let you know how it turns out.
gofar99 Messages: 1949 Registered: May 2010 Location: Southern Arizona
Illuminati (5th Degree)
Hi, I don't know if this should be here or in source with the reel to reel recorder....anyhow I rewired the tape recorder (yes I know it was really nice and new to me only about two weeks ago). The change was to make it possible to send the output from the tape play back heads to an external preamp...yup the one that was the subject of this thread. I can switch from internal preamps to external now.
This was a major improvement in an already good machine. The S/N is about 6 db better and the sound is every bit as good or perhaps even better than before. I used the high gain setting, NAB equalization and 47K input loading. Works great. A really worthy upgrade to most any recorder.
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