I know the majority of this info is available through the search function or on the old Oade board, but I figured it would be benefitial to have it all in one place. Feel free to comment/correct/add information as needed. I'm not claiming any of this info as my own, but I was too lazy to quote the different sources.
The M148 is a purist design pre amp built by Doug Oade with the best quality components made. Originally built by Doug for Doug back in the 80's, he started building & selling to the public because so many other folks liked it. A limited number were produced, and they are no longer built (with the few exceptions every now and again). The design has been refined, due to parts improvements, but is basically the same today. High quality Jensen transformers and discrete transistors are hand matched to better than one percent tolerances. All point to point wiring is used to avoid the problems associated with PCB traces and to ensure the most transparent sound available. It features a max input of -10dB, a fixed 20 db gain stage, and all discrete transistor design. While it is solid state, it was built to sound "tubeish". It is colored by design with a warm, fat, grainless, punchy low end while still being transparent and detailed with no background noise. It was designed to help digital sound analog. It has one switch; on and off.
The M148 has XLR connectors, but has an unbalanced output. XLR's were used for their long life and solid connection. Since the cable length from the M148 to the recorder is short, no electronics were added to the signal path to balance the output.
It is constructed in an 8” x 2 ½” x 5” aluminum chassis with gold plated contacts for inputs and outputs and weighs about XX pounds. A handy battery meter lets you know the amount of charge in the batteries at the push of a button. This unit is now available in a 48 volt version, the M148. Like the M118, the M148 comes with a Five year parts and labor warranty, excepting the battery pack, which is warranted for 90 days.
The rechargeable battery pack will save the end user a surprising amount of money over the units lifetime (still unknown, we have 12 year old units still in the field today!). With over 12 hours of record time available (estimated 14 on full charge), it is unsurpassed as a reliable work-horse. The M148 uses 8 each, 6 volt gel cell (SLA) Powersonic PS-605 batteries in series to provide pure DC with no DC > DC converter. This is partly responsible for it being such a clean pre. The charger should output about 54 volts DC. After a full charge a real healthy voltage is 54-56V. If your battery is a little older it should be closer to 53V. Going below 48 is where you start having problems. If you are below 48 you might not want to start another set. The batteries have a 300 cycle lifetime, but should be replaced every 3 years max. The M148 should not be operated while plugged into the charger.
Lead acid batteries hate being left discharged, so remember to store it fully charged and with the power switch in the off position ( to the left). Recharge about 2 hours for every 1 hour used. The charger is not a "smart" chargers and will overcharge the batteries if left connected for too long, so overnight charge = GOOD, multiday charge = bad. The amber light on the front shows a full charge when the button above it is lit. The red one goes out when the unit is too low on juice to work. The amber light on the rear shows you’re getting power for a charge. The bottom right input is the right channel while the right output is directly above it.
Topic: Oade M148 Info (Read 13462 times)