Cable "burning": Real or VooDoo ???

Afrk: Sorry I have no answer for you regarding DouTech. Music Direct has Mobie in stock, but insists on list price. I was able to order the Mobie from AudioNut @15% discount, but it's backordered. No big savings, but M.D. acted so snobbish on the phone that I couldn't stomach the attitude & went to AudioNut instead. G&D transforms will sell directly to the consumer, FYI.

Audiofrk, I have a Duo-Tech and a Mobie. While the Duo-Tech is more versatile in terms of what you can hook up to it and "burn in", I prefer the Mobie.

As to Steve's question, what else would a "good" engineer do when something doesn't "feel right" even though it is functionally perfect ? They "tweak" and "re-engineer" !!!

By this, i mean altering components by make, model or specifications, re-arrange component & wire layout, try various voltage and bias levels, etc... Call it "circuit evolution", "upgrading", "modifying", etc... but it takes place EVERY day. They do this until they feel comfortable with the results and then send out the unit for production.

Those that DON'T take the time to refine and perfect their products are simply the "whores" of the industry and out to make a quick buck. This is why we have "off the shelf" companies like Pioneer, Kenwood, Technics, etc... and "refiners" like many of the "esoteric" or "specialty" brands. This is not to say that crooks and shysters don't abound in either circle, some more than others.

For reference purposes, let's go back to a piece of "audio history". We'll use the Perreaux PMF series of amps. The PMF-2150 was the first production stereo amp to use Mosfets for output devices. By doing further refinement using the same basic output circuitry but "finessing" the overall design, Peter Perreaux was able to DRASTICALLY alter EVERY aspect of the amp. He played games with the power supply, voltage & bias levels and lay-out of the parts. His "re-design" of the same basic circuit ( same type and number of output devices per channel as the original 2150 ) was called the PMF-3150.

As such, the 3150 performs NOTHING like the 2150. ANYONE that has listened to these two amps within the same system will testify to this fact. ANYONE that looks inside the amps will easily be able to see their similarities due to the majority of parts that were retained. At the same time, they would also notice the differences due to those same parts being configured quite differently within the chassis. Besides ALL of that and what is most important to YOU, the units also MEASURE very differently. Same chassis, majority of the same components, very similar designs in terms of schematics but quite different performance overall.

This brings us to another point. Since most "basic" audio designs have already been done, all that is left for most companies to do is to "tweak" or put THEIR "signature" onto an existing topology, circuit or design. As you are well aware, there are only a "few" folks that are truly "stretching" the audio design "cookbook". With that in mind, most of these "new models" are simply refinements and improvements to "tried & true" models. As such, some of these "new models" do sound MUCH better than the originals even though they might MEASURE poorer or make use of parts that share the same exact "parts values". As such, we've come a LONG way even though much of it "appears" to be the same. Sean
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Sean - If I were a designer with a design that was as technically perfect as the state of the art would allow and yet some audiophiles complained that it "wasn't right" or wasn't musical or wasn't lifelike here's what I would think about trying.

First, I would consider injecting noise into the output. Now, no one likes noise during the quite passages so I would make it a smart noise injector that varied its output with with volumn and perhaps energy in the high frequencies. The noise spectrum would probably not have lower frequencies - one would have to experiment. The circuit would recognize testing conditions and not operate. I suspect that noise gives music an airy lifelike quality that many like.

Next, I would lower the damping factor. As the damping factor lowers the amplifier begins to get involved in the music. Lower damping factor may or may not have a pleasant effect, so, a damping factor control knob could be an attractive feature. From a marketing standpoint I would give it a name something like "Voicing".

I would also experiment with increased harmonic distortion. I don't know if it is possible to increase lower harmonic distortion without increasing itermodulation distortion. IM creates unnatural frequencies and is always unpleasant. Harmonic distortion on the other hand is what music is all about. All musical instruments owe their sonic character to harmonic distortion of the fundamental. Just the right kind of harmonic distortion could, I suppose, make an amplifier seem more musical.

Stevenmj: I believe that most of what you mention has already been used in past and present designs (both tube and SS). You may want to go through the Tweaker's Asylum at AA and see what you can find on these concepts. I suspect that the "air" that you mention is really a type of re-verb that is most noticeable in quite a few tube designs which incorporate low to zero feedback and which may also stem from the types of tubes used in the designs (many small signal tubes types are somewhat microphonic, even those that test well, and may add to this sense of air/reverb). There are also quite a few tube designs in which you can "dial in" the feedback, though I am not aware of any SS designs with this feature off hand. Once again I am not a technical person, just your average theorist.

Stevenj, I cannot tell if your post is in jest, or you are sincere. If you are suggesting that lowering and raising the damping factor with a switch is a joke, I can assure you that it is not.

Controlling an amplifiers damping factor is not novel. The Wolcott Presence amplifiers have had this feature for two years. The user has easy access to a toggle switch for both high and low position, and a rotary knob that adjusts within each range. Adjustment of these controls provides performance changes that are not only easy to hear, but at the discretion of the listener.

The man who invented this product is an engineer who values specifications, but is also aware that the reproduction of music is an art as well. If it is of any interest to you, the switch changes the positive control feedback voltage internally, without affecting the load to the output transformer.