November 2011
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Informal Comparison of Six Phono Preamps

By | November 23rd, 2011|Categories: DIY AUDIOFILE|Tags: , , |

This is a project that sort of evolved from an interest to see how good a particular phonograph preamplifier was. Not the one I designed, but one from a DIY kit. If I would have known how difficult and possibly inconclusive it would become, I might have not done it. As it was, the experience was valuable in several ways. First let it be clear in everyone’s mind that this comparison is largely subjective and based on what I hear or can measure.Read the full article

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Knock-Down Birch Speaker Cabinets

By | November 12th, 2011|Categories: DIY AUDIOFILE|Tags: |

Speaker building is a lot of fun and there are many who would love to try it out but can’t due to some common woodworking hurdles.  You may not have the space, tools or skills necessary to build a good loudspeaker enclosure.  For others sawdust or climate (winter) could be the problem.  Fortunately there are some great solutions that can eliminate much of the woodworking necessary to build a speaker box.  For a number of years Dayton Audio has been producing pre-made speaker enclosures like the Dayton pre-made curved speaker cabinets which make it real simple to put together a great looking finished speaker.  Perhaps the only downside to the great looking ready-made cabinets is that they eliminate too much DIY and they are bulky to ship.Read the full article

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Groovewatt Tube RIAA Phono Preamp

By | November 3rd, 2011|Categories: DIY AUDIOFILE|Tags: , , |

The latest project from Bruce’s workbench is the Groovewatt, a tube based RIAA phono preamplifier.  The Groovewatt is the result of over one year of work and several build iterations.  Bruce set some pretty high performance requirements for the tube preamp and he is very pleased with the results. 

Second Groovewatt Build 
The Groovewatt uses a symmetrical SRPP (12AX7) input stage which feeds a passive RIAA equalization network. The second gain stage is nearly identical to the input stage and is direct coupled to the third stage which is a cathode follower (12AT7).  Bruce used Gold Pin JJ ECC83S for the SRPP stages and half of a ECC81 for each side of the cathode follower.  The power supply is solid state and DC is used for the tube heaters.  Total gain of the RIAA phono preamp is about 45 dB which should be sufficient for use with a high output MC cartridge.Read the full article

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