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| Just how bad is it? Audio mixer with headphone amp. |
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| BrianHG:
--- Quote from: paulca on February 27, 2018, 09:22:24 pm ---Scoped them from the audio out and they both show as sine waves. Slight wobbly, but I was holding the probe to the jack plug. :) Come to think... you can't really do a 20Khz square wave with a 48Khz digital source, not very well anyway, it's going to filter down to a sine anyway isn't it? --- End quote --- If my samples are wobbly, your sound card must be set to 44.1Khz, not 48Khz. Give these 2 a try, they have a native 44100hz sample rate: |
| BrianHG:
--- Quote from: paulca on February 27, 2018, 09:30:59 pm ---That PCM2707 sounds a thousand times better than my Intel HDA on my motherboard. Maybe not in it's sound reproduction, but in the fact that the PC onboard sound is completely saturated in video card noise. Was sending me nuts until I happened to hook up that DAC which is a £3 board from Alice on ebay. No more noise. My my audio project, which this thread's amp is the heart of I hope to use a PCM2902 or similar. I'm open to suggestions. --- End quote --- I must have gotten lucky with my Asus motherboard and HP laptop. Full flat to 96Khz completely noise free even wired direct to a 500 watt amp, using the desktop volume settings. Note I use the plugs in the back of my motherboard and never wire those front panel unshielded audio jacks. Also read reviews on the audio performance of the PC motherboard I chose. |
| paulca:
Try a pair of headphones on max gain, don't play any audio. Now move the mouse around. If you can't hear the buzzt-t-t-t-tbuzzzt-t-t-t you are lucky. Now bear in mind the video card in my PC, which regrettably sits smack bang on top of the chipset more or less and right beside the back plane connectors, not 2 cm from the audio jacks, has dual 10A 12V rails, dedicated to it alone. NVideo GTX 980. (It's so big it doesn't quite fit in the case and pushes one of the HD bays out the front. |
| Bassman59:
--- Quote from: paulca on February 25, 2018, 06:00:44 pm ---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. --- End quote --- Here's the thing -- that book (which I have) was written a long time ago. Not that the principles have changed since it was published, but the devices available for our use have improved greatly. Back then, the jellybean op-amps couldn't drive headphones, hence the designs using discrete transistor buffers or specialist buffer amplifiers. Nothing wrong with using them. But you can save yourself some aggravation and simplify your design by using something like the OPA551 op-amp. Low distortion and enough drive to clean the wax outta your ears. |
| Bassman59:
--- Quote from: paulca on February 25, 2018, 05:42:29 pm ---I think we agree, however do not be fooled into thinking that "everything is digital today". In the past few years I have probably seen about 20 mixing desks in person, I have yet to see a digital one (that wasn't a PC or Mac based thing). Small 8 to 16 channel mixing desks you would use as an audio semi-pro running a few gigs and recording a few demo tapes would be like buying a higher grade oscilloscope. Priced, today, around £1000. A fully digital mixer would cost about ten times that. --- End quote --- I'm a mostly-retired soundguy, but several times a year I still get on the bus to mix front-of-house on tour for old friends who are a well-regarded college/indie rock band. We play venues like the 9:30 Club in Washington, DC (the best club in the country), the Sinclair in Cambridge, MA, Rough Trade and Williamsburg Hall Of Music in Brooklyn, NY, World Cafe Live and Union Transfer in Philadephia, PA. Plus we do the occasional festival and outdoor gig (Central Park Summerstage). Over all of the shows in the last, oh, ten years, I can think of exactly one venue that still has an analog console: the Met in Pawtucket, RI, and that piece of crap needs to get gone. Everywhere else has digital. 9:30 has DiGiCo (which I love), Rough Trade and WCL have Midas Pro 2, Sinclair has Avid SC-48, and the festivals bring out Avid Profile or SC-48 because everyone who'll mix a band on those shows can walk up to it and get right to work. The big theater here in my city has a Yamaha M7CL. The 400-cap club across the street from it has a Soundcraft Si Performer 3, and the other 400-cap club up the street has a Midas M32. The Behringer X-32 has taken over the small-club market. A friend mixes at a hall in NJ on a Mackie DL32R, which sounds really good but I hate iPad mixing (I've tried, and I can't do it, I need tactile feel.). Analog consoles for live sound have gone the way of the dinosaur. The last time I mixed on a Midas H3000 was nearly ten years ago. I did see one last summer at Pitchfork in Chicago; PJ Harvey headlined my stage and her FOH guy had one. But he was the exception, and her monitor guy used a Yamaha PM-5D. The reasons are obvious: racks of outboard gear (effects, dynamics, EQs) are unnecessary, it's all at your fingers, and it saves truck pack space. FOH area can be smaller, reducing seat-kill for theaters. Recall of settings makes switchover between acts as simple as a button press. Wireless control means you can stand at a vocal position and ring out a monitor wedge and make adjustments right there, instead of yelling over to the person at the desk. Anyway, back to the design. |
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