Edgar
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Posts posted by Edgar
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1 minute ago, Tom05 said:
1% THD at 322 watts 8 ohms . 01 THD at 1 watt 8 ohms
<.002% THD at 200 Watts 8 Ohms.
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OK, I just skimmed the entire thread, and did not see the following mentioned anywhere:
Look at Figure 8 here. This is a typical distortion characteristic for a class AB amplifier. This happens to be a brute, an Adcom GFA-565, but lower-power class AB amplifiers distort in much the same way -- their distortion curves will just be "slid", in entirety, toward the left side of the graph.
The important point is that the distortion at very low power (left end of the graph) is almost 20 dB higher than it is just before clipping (right end of the graph, just before the point where the curves suddenly shoot upward vertically). So if you're connecting your 99 dB sensitive speakers to this amplifier, and it's spending all of its time below 1 Watt, you're experiencing about 20 dB more harmonic distortion than if you used a low-power amplifier with just enough headroom to handle transients.
Too much of a good thing is a bad thing. Unfortunately, that even applies to too much power.
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Don & Kathy's House of Music, Saint Louis, MO, around 1977. Klipschorns. Fleetwood Mac, "The Chain".
The kick drum in the opening gut-punched me like I'd never experienced before. Later, during the bass riff toward the end, I could almost see the bass notes rippling through the room.
Very impressive to an 18-year-old (at the time).
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1 hour ago, pnort said:
How do you adjust the volume with three amplifiers to get the right balance from the three separate drivers?
The volume control can be implemented as a multichannel analog attenuator, after the crossover, or in the mathematics of DSP crossover itself.
In theory, analog volume controls are superior to digital volume controls. Analog controls reduce the noise level along with the signal level. Digital volume controls reduce the signal level but the noise floor remains the same (and then, only if the signal is properly dithered after attenuation).
In practice, as long as the noise floor of the DAC is below the noise floor of the listening room (or of the other electronics), it is a non-issue. And with modern DACs, this is fairly easy to achieve. In addition, digital volume controls are superior in terms of channel tracking and attenuation accuracy.
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58 minutes ago, diamonddelts said:
I wonder if you can use a pair of big amps with the Heritage Jubilee? I was thinking 350 W per channel for the HF/MF and 500 watts per channel for the low end.
In addition to being severe overkill, it can actually backfire on you. It is not uncommon for a Class-AB amplifier to have considerably more distortion at very low power than it does just before clipping. A fairly typical example of that is shown in Figure 3 here. With super-efficient speakers like the Jubilee, you're likely to spend nearly all of your time below 1 Watt, where distortion is at its highest.
Other amplifier types may behave somewhat differently. Class-D can be better or worse, depending upon implementation. And you're probably not considering a 500 Watt Class-A amp.
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12 hours ago, Travis In Austin said:
The main theme in these scams is that the person you are dealing with insists on a form of payment where there is no recourse because it’s a cash equivalent - Western Union (or equivalent), Pay Pal friends and family (IIRC), any type of a cash app. There is no recourse for the person sending the money (like a credit card) and no tracking, like with a check.
OK I get that, but what if I showed up at his door, in person? The location in the St. Louis ad was only about 50 miles from me. What would have happened if I had called his bluff and wanted to hear the items before buying?
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8 hours ago, babadono said:
Op had an electrician check out his house, I certainly HOPE he would have checked for hot and neutral reversal.
Still worth a double-check, though. For just a few dollars, that gadget is a nice thing to keep around anyway.
8 hours ago, babadono said:My understanding so far is that this is a single integrated amplifier system. Where would any kind of isolator go?
Ah, well, that eliminates one possibility. Still useful as general knowledge.
Another thing to check: I once encountered a situation where everything on one particular circuit acted strangely. The wiring checked-out OK. When I looked at the breaker, I found that it had tripped, but only partway -- literally the lever was partway between "ON" and "OFF". There was just enough continuity to satisfy the receptacle-testing gadget, but under load things got weird. I reset the breaker and all was well again.
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2 hours ago, mark1101 said:
Dumb question: Have you tried a "cheater" plug (temporarily) just to see if lifting ground does anything? Obviously, this is not safe and hopefully you are plugged into a GFI anyhow.
Another dumb question: Have you tried shorting the inputs when you power up and have nothing connected on those inputs?
Neither question is dumb; both are standard procedures in a case like this. Also check to see if the "hot" and "neutral" connections in the wall plug are reversed. One of these will do the job for you.
I have a (solid state) amplifier that only hums when the ground is lifted. I have another (solid state) amplifier that always hums unless I use one of these.
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25 minutes ago, hanksjim1 said:
Intentional...
Ah, well, then I really am naive. 🙁
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13 hours ago, 83 LSIs said:
Went to another forum and didn't last long before those in charge handed him his coat.
I'm probably naive, but I could never tell whether Captain Beefheart's failure to deliver was intentional, or was because he overestimated his own capabilities.
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I've never understood how such a scam works. What, you call the guy and he says, "Haha, fooled you! They really don't exist. Don't you feel stupid?" What's the point?
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I thought it might look too good to be true, but you never know.
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13 hours ago, Travis In Austin said:
That came out great, is it a composite or a single shot. I took a bunch, but didn't turn out like that hundred (In Wyoming)
What did you use?
It's a single shot. During totality I kept shooting as fast as my camera would allow. It was set to auto-bracket (+1, 0,-1) F-stop, and this was the best of that particular trio.
Canon T3i with an old (non-autofocus) Tokina 100-300mm zoom set to 300mm and focused at infinity. I didn't record the aperture setting, but it was probably around F8.
EDIT: If I remember correctly, I based my exposure upon info here.
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From the 2017 eclipse, taken in DeSoto, MO. You may use it without compensation if you like, but credit the photographer (me).
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4 hours ago, The Dude said:
I am looking to take my audio out from my phone via USB-C to either SPDIF/TOSLINK or Coax that will be connected to my Helix DSP in my car system. I want to keep it at as digital as possible, so would something like this work?
Douk Audio U2 XMOS XU208 Digital Interface, USB to TOSLINK Coaxial/Optical Audio Adapter, for DAC/Preamp/Amplifier, Support PCM & DSD64 (Upgrade Version) https://a.co/d/fXxRxQn
I've been using an earlier version of this (USB2 instead of USB-C) for several years. It has been 100% reliable. I'm not sure that there are XMOS drivers available for Android or iPhone, though -- I recall having to search a bit for Windows drivers.
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Well, Jefferson City, MO and Springfield, MO are only a couple-hundred miles apart. But Gainesville is in Florida.
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Hmmm ... also shows up in Springfield, MO craigslist. Another scam?
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10 minutes ago, PrestonTom said:
To further confuse the issue.
Shelving filter parameters can be all over the place depending on the manufacturer. For most the "frequency" of the shelf is the 3 db down point (behringer and yamaha etc). However for some it is the midway point of the transition (I forget if that is "mid" freq on a linear space or log space).
In my designs, it was the "natural" frequency in the prototype Laplace-Domain transfer function. That frequency may not show any obvious relationship to the 3dB frequency or the "mid" frequency, depending upon the values of the other parameters -- for example, what is the "3dB" frequency in a shelf that only boosts 2dB? But my definition is at least self-consistent.
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It looks like Xilica used the parameter definitions for shelving filters from the RB-J Cookbook. Robert Bristow-Johnson defined the "shelf slope" parameter as "... (for shelving EQ only). When S=1, the shelf slope is as steep as it can be and remain monotonically increasing or decreasing gain with frequency."
Years ago I designed a DSP package for EV that included shelving filters. I do not know if they continued to use my definitions of the parameters in subsequent products, but if they did then you can assume that the EV "shelf slope" parameter is equal to 1 in all cases. The difference between the "6 dB" shelf and the "12 dB" shelf is that the 6 dB version is based upon a 1st-order transfer function, and the 12 dB version is based upon a 2nd-order transfer function.
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14 minutes ago, the real Duke Spinner said:
Missing mine
Do not have to be hi-fi to be pleasing
True. I just find amusing the reverence for the 1970s gear that has developed on some of the audio forums. (Not necessarily this one -- I haven't really paid attention, other than to chuckle a bit when I see it.)
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On 8/23/2023 at 3:13 PM, the real Duke Spinner said:
I have such great luck with 1970s Pioneer, Sansui, Nikko
Funny thing is: back in the 1970s we considered that stuff "mid-fi". How times change.
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9 hours ago, Deang said:
We call them “phones”, but they are really pocket super computers.
In 1993 I developed a digital signal processing algorithm that required so much computation that I thought I'd never see it run in "real time" during my lifetime.
By about 2015 it was running in "real time" on a telephone.
What a great time to be an engineer.
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Driving your speakers with more power than they "need"
in 2-Channel Home Audio
Posted
That is why the ears should always be the final arbiters.