Please note that this article was originally published about 5 years ago in POSITIVE FEEDBACK, and may not accurately reflect my current opinions, and does not reflect my current system.

More from the strange land of tweak audio.... A few days ago a relative of mine happened to stop by for a short visit and observed a pair of Magnepan MG 1.4's sitting in the living/listening room. He stared at them in amazement for a few moments before asking my fiancee what they were. When she replied that they were planar loudspkrs he didn't believe her and repeated the question when I walked in the room. My demonstration convinced him that they were indeed loudspeakers and further served to pique his interest in audio. I believe that some day he will probably join the ranks of high end audiophiles. The message I'm trying to convey is that the most unlikely situations may provide an opportunity to infect another hapless soul with high end mania and help to ensure the popularity not to mention survival of our hobby..... I'm experimenting again with the Sony CDP-790 CD player I told you about in a previous article. This time I plan to replace the external op-amp with a tube output stage consisting of a common cathode voltage amplifier and a cascaded cathode follower with unity gain and loop fdbk of roughly 32 dB. There's lots of room for mods. I'm also investigating an apparent lack of bass (not extension, just quantity) when compared with the Magnavox CDB-582. The Sony was superior in every other respect, however, from detail to soundstage and timbre. The Magnavox became very congested, confused and strident on material from Harmonia Mundi's Tarentule - Tarentelle HMC #90379, but in fairness the 582 was stock. Differences on Tracy Chapman's albums were less pronounced, but the sound of stringed instruments seemed to lose most of its character and her voice sounded harder and somewhat congealed. I have recently acquired quite a number of the Mercury Living Presence CD's and they are without a doubt some of the best sounding CD's I have ever heard. Detail and instrumental textures are very good to excellent depending on the particular CD. Timbre seems substantially correct. Those mastered from 35 mm magnetic film are quieter and have somewhat greater dynamic range. Sound staging is were they seem to fall a bit short-localization seems good across the stage, but depth is not present to any great degree. You owe it yourself to check these out. They will bring great music to many who, like myself, cannot even afford the original pressings. On another subject I'm going to attempt to describe my listening environment and the system that I use as a reference. First the room - the living room, it abutts on the kitchen area and the combined length of both rooms is just under 30 feet, the rooms are contiguous and divided solely by a beam and a half wall of about 3 feet. The living room alone is 19 feet long and 13 feet wide and is almost a perfect rectangle except for a hall way at the right rear end of the room. The speakers are Magnepan MG 1.4's and are located about 3 feet out from the rear wall and about 3 to 4 feet from the side walls. The power amplifier of choice is a 30 watt per channel all triode design based on Citation II transformers, the amplifier is pure differential, dc coupled except at the output stage grids and is inherently self-balancing in the driver stages. The pre-amplifier is also one of my custom designs and features passive equalization, paralleled triodes and no global feedback in the phono amplifier, the line stage features a self-balancing cathode coupled phase inverter permitting the selection of output polarity which in turn drives a low impedance buffer stage with limited global feedback. Local feedback is employed in all stages in lieu of large amounts of global feedback. The turntable is a Pink Triangle with Audio-Craft AC-2000MKII arm with high mass arm tube and a Monster Alpha II cartridge. ( See Feb. '91 for the nightmarish description of this table....) The CD player is a modified Sony CDP-790 also previously described. The sound is well, interesting, lucid, detailed and very, very clean. Neutrality has been one of my major goals, my one beef with this system is that although the bass is tight, clean and extended, the quantity is a little on the meager side. I will probably add a good subwoofer at a future date. Some of you may be experiencing serious RFI problems due to inconsiderate CB enthusiasts - in this area 500 watt linear amplifiers are common, along with illegally modified imported 11 meter ham gear. If you suspect that your problems stem from the same sort of activities the best recourse is the FCC or a screen room....... Good coaxial interconnect cables are a must under these circumstances and the best sounding of these is probably the StraightWire Maestro. Those on a serious budget will find that the Radio-Shack 8 mm Megacable discussed in a previous article is pretty good also. Moderately large ferrite cores make good filters for line cords and power cables - just take a few turns around the core. Speaker cables are a major source of pick up and if the level of interference is constant regardless of volume control setting and mute status, then this a most likely path. Reducing pick-up through speaker cables is problematical at best and at worst almost impossible - the best advice here is to keep speaker cables very short, and if possible to move the Zobel network ( series RC network ) to the output terminals. Most RFI advise the use of ceramic caps. from the inputs and outputs to ground, but I don't like using ceramic bypass caps. and chokes because they color the sound, reduce bandwidth and may adversely affect the stability margin. ( Ceramic capacitors are not noted for good linearity when large audio voltages are impressed across them - they generate massive quantities of harmonic distortion due to changes in their dialectric constant caused perhaps by piezo-electric stress. Incidentally, tube power amplifiers are generally somewhat more resistant to interference coupled thru the speaker leads due in part to the lack of intrinsic diode junctions in the amplifier devices and also due to the isolation provided by the output transformer.

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©1998 By Kevin R. Kennedy