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| Just how bad is it? Audio mixer with headphone amp. |
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| BrianHG:
--- Quote from: paulca on February 25, 2018, 05:54:16 pm ---heard them clip or distort very often. Too soft. --- End quote --- They wont be soft anymore with all your gain everywhere + a 30v supply range. Also, sometimes, there is clipping in your source as well. |
| paulca:
BTW... the general pattern in the book is to present the basic "default" textbook solution and the discuss it's problems. Then present known designs by some amazingly intelligent people, sometimes the author which try to "have their cake and eat it" with little draw backs. From my main background in software engineering, I see this happen a lot. And... I agree... sledgehammer to crack a nut often actually makes things worse! Back on topic, the second iteration of design in the book on headphone amps is this, which addresses a few problems with the first (a) posted above. I haven't read all my way between the sections, but it ends explaining that you might as well just use parallel 5532s. I think he owns shares in TI. |
| paulca:
--- Quote from: BrianHG on February 25, 2018, 05:59:19 pm --- --- Quote from: paulca on February 25, 2018, 05:54:16 pm ---heard them clip or distort very often. Too soft. --- End quote --- They wont be soft anymore with all your gain everywhere + a 30v supply range. Also, sometimes, there is clipping in your source as well. --- End quote --- I have +17db MAX on the input and only if the gain knob is maxed out. At "half way", it will have 0db gain. (remember active gain). I mentioned i have not decided on the master volume and might not use an active gain "block", but if I do and it's at "nominal" it will be 0db gain. So a full path through the mixer might have absolutely zero gain until the power amp. Zero gain and zero attenuation mind. Flat gain structure, so the only noise added is the op amp inherent noise which is tiny. Of course I can have at least the +17db on the input preamp and ... unless I change it another +17db on the output volume. Actually, 17+17db is probably not = 34db, but there might be a risk of actually killing headphones with an accidental volume setting which could be an issue. I want driven hard, not release smoke. |
| Audioguru:
Of course opamps and most power amps have a current limiter for protection against idiots who short the output to ground. But the current limiter usually does absolutely nothing when the current is not too high for it. Why do cars have brakes? They are not used all the time (but idiots drive with both feet on the pedals). |
| paulca:
--- Quote from: Audioguru on February 25, 2018, 06:12:43 pm ---Of course opamps and most power amps have a current limiter for protection against idiots who short the output to ground. But the current limiter usually does absolutely nothing when the current is not too high for it. Why do cars have brakes? They are not used all the time (but idiots drive with both feet on the pedals). --- End quote --- Fair enough. I'm probably mixing two different things. Somewhere in the early 90s after "Sony Walkman" devices started to put out some serious headphone volume a group of nannies with pitch forks forced some sort of regulation on such devices and Sony and most major brands adapted these... To limit damaging teenagers ears. It is hard today to find a device without such a limit. My experiences with the NE5532 have pretty much told me that by using similar chips for headphone amps their inherent current limit almost matches or comes in under those soft regulations on output. Which is why almost all headphone out devices today are effectively limited to "Nanny state" mode. I don't want to cook the headphones or my ears, but I do want to know where the ceiling is. I want to be able to overdrive them, I want to know where the limit is and the headphones clip. I don't want it imposed upon me. Which loops back to one of the first design criteria I selected. When you have a limited output and a quiet signal, you are incapable of addressing that issue. You need pre-amp gain to lift it to a normal level to do that. |
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