Welcome to Roscoe Primrose's DIY Intermediate System Page!

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Whole System

A Major Intermediate Step

View of the system as seen from the listening position. The system went though small variations on this basic setup for over two years. The system consisted of a DIY turntable based on an old Rek-o-Kut bearing and platter, Audio Tecnica tonearm, Denon DL-301 low output MC, Denon AU-320 MC step-up transformer, DIY interstage transformer coupled phono stage/passive line stage. Digital front-end wass a Theta Data Basic transport, factory upgraded to Basic II, and a homebrew non-oversampling, digital filterless DAC. Amps were homebrew, alternating between direct coupled 5842-2A3/45 SEs with MagneQuest RS-330 of Tango XE-20S outputs and IT coupled 5842-845 SEs with MagneQuest FS-100 OTs. Speakers were Altec 515Bs in JBL 4560 cabinets (JBL's answer to the Altec 825/828 cabs, the Altecs are a bit bigger, and I think they do better below the horn cutoff, but the JBLs have an exponential (rather than radiused) flare and are better built) with Altec 803Bs with 288Bs (20ohm) on top. Tuner is a Fisher FM-100B. Cableing is XLO, Goertz and homebrew. Listening room is 15'x17' with a cathedral ceiling.

Closeup view of the system rack.

System Rack

Close-up and side views of the right speaker.

Speaker Close-up Speaker Side View

The side view of the right speaker, shows the offset required to provide proper time alignment of the drivers. The wife thinks this arrangement is particularly unattractive, so I'm saving up for a digital crossover (or, better yet, the larger, deeper, JBL 4550 cabinets) so I can do time alignment in the crossover and restore marital bliss ;-).

45 Monoblock Close-up view of the right amp and crossover, amp is 5842 direct coupled to a 2A3 or 45, Single Ended. Rectifier is a 5AR4. Amps are on about revision 60, they started life as 2A3 monoblocks, capacitor coupled. I tried interstage transformer coupleing with some inexpensive ($15US) Allied Electronics ITs, and even with the el-cheapo ITs it was still a huge step up from the Audio Note paper in oil coupling caps I had been using. I also tried using a 26 is a driver, with an IT with a 3:1 stepup ratio to get the required voltage gain, but I could never get the 26 quiet enough to use. Next I tried direct coupling, which was another step up. I still want to try IT coupling again sometime with decent ITs, but I've got other things to spend my money on for now. I swapped back and forth between 2A3s and 45s several times, with each different coupling scheme, also tried each with the old stock 2A3 monoplates I have. In every case I liked the 2A3 monoplates and 45s the best, but I've only got three, and they're too expensive. The doubling of power with the 2A3s is nice, but the 45 is still enough power with my current speakers, I've got about 30, and they're cheap, so that's what I settled on. A PDF version of the schematic is available. Crossover is 780Hz, first order, with Alpha Core foil inductors and oil caps.

An earlier DIY turntable project:

Rek-o-Kut DIY Turntable On the left, the Rek-o-Kut K-33 turntable that provided the platter and bearing for the turntable I'm in the process of building.

On the right, an in progress view from the top of my DIY turntable. Turntable is a string driven turntable based on a Rek-o-Kut K-33 bearing and platter with a Kenwood direct drive turntable being used as a motor. Plinth is a five layer 3/4" MDF with 1/8" cork and DynaMat used as constrained layer damping. One of these days I'll get around to building a matching plinth/base for the Kenwood motor...

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