Feb 14, 2011
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Professional Engineer at a Research and Development entity.(nice & advanced test equipment at hand!)

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    Professional Engineer at a Research and Development entity.(nice & advanced test equipment at hand!)
    All DIY-Do It Yourself, music, photography, aviation, mechanics, electronics, live Audio recording.
    DIY Audio. Live recording. Continue experimenting with ambisonics, other than two channel sound recording and reproduction, Digital signal handling. Present day Audio is just an illusion, we are still far away from convincing a listener he is actually hearing a live musician performing in its living room!
    Headphone Inventory:
    Sennheiser 414, 424X, some old Koss electrostatic ones, Sennheiser HD-280 PRO, too many Sony's to remember, Shure In-ear E-1's, SE-420 (gone). Shure 535's (happy the first 20 minutes, before they hurt my ears because they are bulky for my pinna and their output tube is too short to place the plugs at the proper insertion depth), since october 2011 the Shure SRH-940 (happy with them). The very Old Sennheiser HD-414 have a passive equalization network proposed by Nelson Pass (I guess) which corrects their otherwise unbalanced sound nicely, but the highs are still veiled compared to modern designs. The supposedly better (then top-of-the-line) 424X are NOT better in ANY way... I only keep them on hand to prove my point that a good design is VERY difficult to improve, and that the designers usually produce bad results when trying to improve an already succesfull design. (my rule-of-thumb: many times the "Top-of-the-Line" model or the most expensive one, is NOT as good sounding as the second or third model down the line of a certain manufacturer).
    Headphone Amp Inventory:
    A couple of DIY headphone amps, one solid state with discrete devices and one with tubes, still getting those to sound completely "right"... (but already "good" sounding and much less expensive than commercial offerings). Since December 2011, a Lehmannaudio Black Linear Cube. (Very happy with it).
    Source Inventory:
    Oldie but GOODIE, much modified Thorens TD-160-Super turntable with modified Grace 747 Arm and Old Grace F9E and F9E-Ruby phono cartridge, a Shure V-15 Type IV and an Ortofon Moving coil unit. Many Direct-to-disc and "Audiophile" Vinyl records (good old analog...)

    Modified HarmanKardon CD recorder used to copy CD's and also to record live concerts; original live recordings made with an small 24 Bit-96 KHz PCM recorder, some recordings made with digital converters coupled to VCR's, Some others made on good Old ANALOG tapes (recorded on a highly modified TEAC 10" magnetic tape reel-to-reel tape deck, and a beautifully preserved REVOX too). Some very good performances captured with an old Marantz PMD-430 Cassette Recorder with DBX or Dolby NR.
    Live recordings mostly made with a pair of DIY PZM-type microphones, and after several years I have finally found their proper use.
    Cable Inventory:
    Not a believer of using outreageously expensive "snake-oil" cables. Good old properly grounded, standard quality cabling has shown to me that cables are not deserving their cult following, at least no one has been able to demonstrate to me that special cables are worth their high price when tested side to side with my good quality "standard" cables. (Most recordings have been made trough many feet of standard cabling in Studios... Properly grounded and shielded cabling DO usually work fine. If cable is causing a change in sound, something is wrong.
    Power-Related Components:
    Same as above, a well filtered dedicated line with RF filtering and good spike protection is usually enought. MILES of common electrical mains cable are between the power company and the user, a couple of feet of exotic power cable is not going to "solve" any perceived "problem", or something is not right.
    (Hint: Check Grounding, polarity, clean and preserved contacts, freedom from Radio Frecuency interference, etc.) Again: if a Power "conditioner" is required or perceived as an improvmente, something is amiss.
    Other Audio Equipment:
    Two systems based on very Old Vintage DYNACO tube equipment, carefully modified. Another system based on much modified David Hafler preamp feeding a DIY Active 3-way Crossover with 24 dB/oct Linkwitz-Riley alignement feeding THREE separate power amplifiers, feeding a multi-driver speaker system. The "midrange" amplifier is a modified David Hafler XL-280 MosFet output amp. I have assembled, tested and measured, and then critically listened to as much as maybe 60 to 70 pairs of speakers during many years (I used to build and sell Speakers to help me pay for my university degree), and found that PASSIVE CROSSOVERS are a very difficult to get-working-properly thing, and UNDERSTAND WHY the complex impedances of the drivers interact with the passive crossover and the single amplifier, the ACTIVE, Electronic Crossover becomes the only logical, reasonable and demonstrated approach. My own-designed and built speaker systems are now TRI-AMPLIFIED, using Fourth-Order 24 dB/Octave Linkwitz-Riley Crossovers made by an Australian Engineer who sells the circuit boards, allowing you to get top results without having to resort to exotic amplifier designs that have to fight the unwinable battle against the very complex impedances and changing impedances of the dynamic driver units. By using a set of Not-so-expensive and Not-so-powerful amplifiers in a triamplified system, a DIY system can rival standard (passive crossover) Very Expensive speaker & Huge-Extremely expensive amplifier at much reduced cost; and in that way, you are in control of phase anomalies, time domain artifacts (arrival time driver alignment, widely variying driver efficiencies and crossover frecuencies.
    The last assurance that the resulting sound IS indeed a good one, is when one invites some musicians and record producers, together with a couple of Sound Engineers to you home, and ALL of them become entirely surprised when they hear some original, first generation recordings and realize how realistic and convincingly my relatively inexpensive "made in home" sound system sounds to their ears.
    Audio-Related Tweaks:
    Turntable: Look for the many articles on the web on Thorens turntable mods.
    Arm: The aluminum shaft was nitrided to raise the elastic modulus (rigidity), and then a very thin ruberized coating took control of some residual resonances. A good vinyl test record and an audio analizer is a must; borrow one.
    Preamp: The usual power supply extra filtering and grounding scheme revision/correction. Better passive volume and balance potentiometers were an improvement, but the original David Hafler designed circuits were extremely well done for their modest price and age. Better quality parts usually give a little extra improvement, but not always.
    Power Amps: Same as above, but heavy toroidal transformers are a good improvement, even at their "high" price (nothing compared to the Exotic factory-built amplifiers!) Large Power Supply capacitors between 2 to 3 times the original value; more than that is not desirable and will stress the rectifier bridge and weld the power switch contacts!.
    BEST TWEAK of all: Go the Active Crossover way and multi-amplify your DIY Speakers!!!
    Music Preferences:
    Acoustic Jazz, Bossa-Nova and Brazilian Jazz (from Antonio Carlos Jobim vintage, Joao Gilberto and many others to mention . "American" Jazz, Big Band Jazz; Some light Classical and String Quartet baroque music.

    Live performances and Live Concert Recordings (some 24-Bit, 192 KHz lately). Some other taped directly to good-old ANALOG tape recorders (Modified TEAC and REVOX Reel-to-Reel 10" at 7-1/2 Inches per second and 15 IPS, half-track and full-track).
    Old Film based Photography (Canon FD), Digital SLR Photography (Nikon), Auto mechanics and modifications (Turbo and Super Charging, because at our very high altitude engines only produce 74% of their sea-level power!) General Aviation (when money allows!).
    Professional Engineer by profession, scientist by vocation. DIY on many fields, not only Audio.
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