Does anyone care to ask an amplifier designer a technical question? My door is open.
@tinear Richard... I am enjoying the heck out of this forum and am learning quite a lot. I am interested in your thoughts and insight into Bob Carver’s latest tube amps I heard the amps were very light weight, had tiny transformers in those big cans. He has to be cutting corners somewhere at those prices. Check the weight of the 275. Wheres the measurement? Roger |
My understanding of the technical reason is it reduces the negative affects of the crossover by (almost) directly connecting the amplifier to the drivers.Bi-Wiring has no effect on the crossover. In an electronic circuit, when current flows through a resistance, voltage is developed. In a Mono-Wire system the tweeter connection is modulated by the woofer current. By providing a direct path to the low impedance amplifier output, the tweeter is not modulated by the woofer circuit current. On some program material, it is quite evident, not so much on others. YMMV. The best crossover is no crossover. When are we going to stop piddling around with tiny effects when we can bi amp and do something that really makes a difference.As mentioned earlier, the devil is in the details. Some speaker crossovers are more complex in their action than a symmetric electronic one. My dbx223 sits in the cupboard because the dual 4th order did not sound as well as the 4th/2nd passive on the mains or the electronic 3rd / passive 1st for the sub. Digital may have promise, but at this stage, new hardware elicits no interest. |
For a technical look at Bi-Wiring, please see http://ielogical.com/Audio/CableSnakeOil.php/#BiWire Please note that these are Spice models and not actual system measurements. He was doing fine till he got here on #1.. To go back to our marble and donut example, a higher frequency would be represented by inserting a marble faster in the tube, with a correspondingly fast-moving donut. So with a multi-frequency signal such as music, the higher frequencies entering the cable reach the other end earlier than the lower frequencies. Do they higher frequencies get there sooner, i think not. The second part is skin effect which has pretty well been delt with as a no go in reasonablely small conductors. Dielectric on a 8 ohm cable is ludirus. Hes just measuring inductance for that time thing. Whenever people start talking about time, they suck in the audiophiles and make big errors in logic. Sorry I cant read anymore without ruining my day. |
In an electronic circuit, when current flows through a resistance, voltage is developed. Most would say when a voltage is applied aross a resistance a current flows. An ampifier supplies a voltage and the current is determined by the load. Tere is no current till there is a load. However in designing a preamp (the most difficult thing to get right) is that we drop voltages across resistors to get our operating points. Has anyone thought why preamps have so many more resistors than anything else? But I am still thinking about voltages not so much currents till I get to the output stage of a power amp. As mentioned earlier, the devil is in the details. Some speaker crossovers are more complex in their action than a symmetric electronic one. My dbx223 sits in the cupboard because the dual 4th order did not sound as well as the 4th/2nd passive on the mains or the electronic 3rd / passive 1st for the sub. Digital may have promise, but at this stage, new hardware elicits no interest. The RM-3 crossover I use is all discrete push pull followers in the high end, op amps in the low. DIgital crossovers are not recommended. Too may A/D and D/A coversions to be done well at a price. Then there is the code that runs them. Analong crossovers are available, why get a digital one? Good drivers need no correction because they are good, look at the response curves. No one is going to convince me that a bunch of coils (some with iron) capacitors, lossy resistors is better than a direct connection to the drivers. Audiophiles will spend copiouis dollars on cables that have minimal effects and ignore the real powerful effects because they are daunted by the thought of bi amping. Get some help, read some books, do something important. Is there a bi-amping group somewhere on this forum? I'd rather go there and help them. Seems all I get here is disagreement. HAPPY NEW YEAR, Make a resolution to do something important to your system. At a minimum make a bi amp speaker, even a little one. Crossover kits are available for less than the price of a bi wire. |
Regarding differences in cable propagation velocity as a function of frequency, the following paper (which I and another member had referenced in posts here a few years ago) appears to me to be credible as well as informative: http://www.audiosystemsgroup.com/TransLines-LowFreq.pdf See Figure 2 of that paper, although it addresses a coaxial cable rather than speaker cables. It can be seen that propagation velocity does decrease considerably at low audio frequencies compared to high audio frequencies. However, even at 20 Hz the propagation velocity, while much slower than at higher frequencies, is still about 5,000,000 meters per second, easily fast enough to be utterly inconsequential in the context of a home audio system, despite claims in some marketing literature to the contrary. As Ralph aptly said in another context here not long ago, where there is an effect there is snake oil for it. I would add that is particularly likely to be true when the claimed effect is not or cannot be looked at in a quantitative manner. ... the velocity of propagation of the signal (versus the velocity of the actual electrons) is determined by the dielectric or insulation material that the electromagnetic wave is predominantly traveling through. I believe that this statement is correct, and is unrelated to skin effect. Cable propagation velocities are usually somewhere between around 50% and 95% or so of the speed of light in a vacuum, and are dependent on the dielectric constant of the insulating material surrounding the conductors. Numerous references can be found on the web in support of that. The reason is that signal energy is conveyed in the form of an electromagnetic wave (rather than by the associated but vastly slower "drift velocity" of electrons), and for the most part that wave propagates outside of the conductors, within the dielectric (aside from a small fraction of that energy that is absorbed by the resistance of the cable itself). Again, though, whether an audio signal propagates from one end of an audio cable to another at 1 nanosecond per foot (close to the speed of light in a vacuum) or at 2 nanoseconds per foot, or somewhere in between, is utterly inconsequential. And if a 1 ns/foot cable sounds different than a 2 ns/foot cable, the reason is something else. Regards, -- Al |
