Ask MetaFilter questions tagged with preamp

Through the luminiferous aether

strangecargo — Mon, 26 Jan 2009 15:05:55 -0800

RFInterferenceFilter: This is a continuation of this question. Summarizing: I'm experiencing a loud buzzing noise in my stereo, accompanied by interference from local FM radio stations. I've done more investigation and have eliminated my power as a (direct) cause of the noise. The original post has a more detailed description/history of my problem. After some investigation with an oscilloscope, I ended up with this image of my AC power superimposed over the noisy preamp output (close-ups here and here). My working theory at the time was that the hiccups at the top and bottom of the sine wave in the AC output were causing the corresponding jumps in preamp output (which would conveniently explain 120Hz buzzing). In order to test this theory, I got my hands on an AC power regenerator and tried powering my preamp with that. The noise didn't go away (and didn't really change). In the course of scratching my head at this development, I also discovered that the noise doesn't go away when I physically unplug the preamp and allow it to run for a few seconds from only the power left in the power supply reservoir capacitors. Of course, the noise goes away when the energy in the capacitors is used up.

So now I'm left with this: 60/120Hz buzzing and FM radio interference when everything is physically isolated from my AC power (ie: preamp has been totally unplugged, driving the inputs of a laptop running from batteries). This leads me to believe that the cause of the noise is RFI/EMI, and that the hiccups in my power are not the cause of my issues, but are instead also caused by whatever is causing the noise in my preamp, which would explain why they are temporally coincident. I'm still inclined to believe that this is somehow power-related, as the hiccups and my AC power are in perfect synchronization, but nothing as simple as the line-noise-sails-through-power-supply that I had initially hoped for.

I'm an engineer, but not an electrical one; I've managed to debug this problem to this point, but I'm pretty much out of my element here. I don't understand enough of the principles at work to figure out this issue past this point or what I can do to try and fix it. Suggestions, please!

Recommend a budget phono preamp

The Michael The — Wed, 31 Dec 2008 09:14:53 -0800

Which budget phono preamp (less than $50) should I buy? I've got a Technics SL1650 that I'll be connecting to a Yamaha RX-V540, neither of which has an integrated phono preamp. I'd like to pay as little as possible for that separate preamp, certainly under $50. I understand that I'll be sacrificing sound quality vs. a higher-low-end $100-$200 model, but frankly I just want to play my records. So, let's have your recommendations for something that's less than $50 but doesn't sound like complete crap.

Looking for a Nice, Relatively Inexpensive Turntable+PreAmp

robdon — Sun, 05 Oct 2008 12:12:21 -0800

VinylFilter: Looking for a quality Turntable and PreAmp to fill the needs of a poor audiophile ($500-650 Budget) I've been easing into the world of audiophilia for quite a while now; I've spent my time combing through countless issues of Stereophile, practically live on the Head-Fi forums, and have replaced all of my digital music library with tasty, tasty FLAC. However, after living next to someone with a turntable, and hearing the warm, buttery sound emanating from his turntable rig, I want one. I plan on listening mostly through a pair of DT770 Pro Headphones [80 Ω] (and to a lesser extent a pair of Grados) but will likely purchase a proper Power Amplifier and set of monitors at some point in the future. Just looking for something that will last me awhile and make the vinyl I've had my eye on sound fantastic through my cans.

I've heard fantastic things about the Rega P3, but I feel it might be a touch pricey when you factor in a preamp...

500-650$ Total Budget

Should I eat -- er, solder -- this? On the aging and toughness of ceramic disc capacitors.

Your Time Machine Sucks — Fri, 22 Aug 2008 04:30:01 -0800

Should I eat – er, solder – this? I'm building a preamp and I just discovered that I'm low on 0.1μF 50v ceramic disc capacitors. My question is about whether it's worth trying to salvage more from another (already disassembled) piece of equipment. I noticed that I have lots of green ceramic disc caps with happy little 104s on them (don't know the voltage, but it seems improbable that it's less than 50v) on the carcass of a portable CD player which I've already largely disassembled in order to liberate its DC motors. I don't think I have the means to accurately test the caps. They are old.

So, the question: how hardy are these things? When they have been put on the board, they will have been through two solderings and a desoldering, plus however many years of portable CD-playing service. Worth a try, or go to the damn store and get some new capacitors ffs? Thank you.

Using Ipod Line-Out

jimmyjimjim — Fri, 11 Apr 2008 09:07:17 -0800

I'm an old stodgy audiophile finding myself forced to resort to iPod, but I want to make the most of it. First of all, I'm looking for a solution that will allow me to use line-out audio on my ipod (5th generation), and simultaneously charge via AC. Does such a thing exist? Also, what's the standard audiophile solution for on-the-go listening? Headphones into mini-preamp into dock, I'd suppose?

or, get what you pay for

acro — Thu, 10 Apr 2008 21:21:27 -0800

Going mobile and recording audio in the field: what microphone preamp and phantom power solutions are going to work well on a tight budget?* (*less than $150) More specifically: Sound Devices MP-1 - Single Channel Portable Microphone Preamplifier is way over my budget (but ideal), and none of the cheaper ART tube amps are offered with battery power options. Mobility is key: interviews, concerts and lectures are my primary intended uses. Quality wise, I'm looking to use audio recorded with standard definition digital video footage. Not important really, but my digital recorder right now is an Iaudio 7 (with an un-powered line-in, recording into wma).
Thanks.

Crass consumerism strikes again

FelliniBlank — Fri, 27 Jul 2007 19:34:25 -0800

Tell me how much I need to spend on audio preamp(s) and amplifier(s) to make my home stereo system sound jaw-droppingly great. Ze muzeek, she eez my life, so two years ago I upgraded some of my very low-end stereo components to these moderately better ones:

Goldring GR2 turntable

NAD C542 CD player, and

Orb Audio speaker system (two "MOD2" double-satellite assemblies + a subwoofer)

WAY better sound, baby, but that's when the money ran out, so I couldn't replace the basic Onkyo receiver with a nice preamp(s) + amp(s) to make the most of the other components.

Now I have some pennies saved and have started looking at equipment and reviews. This is where you come in. I might could swing $1500 tops for the whole enchilada if absolutely necessary, but I'd like to spend as little as it takes to get good quality gear -- new or used -- that actually makes an audible improvement to my non-audiophile, non-engineer ears. And even if I do drop the whole $1500, I'm not exactly sure how to divide it between the different components so that I'm investing the right proportion in each one.

The question:
To get preamp and amp equipment that is of comparable quality to the rest of my system and that will help it live up to its full potential, how much should I be looking to spend on each of the following:

1) phono preamp
2) line preamp
3) or instead of 1+2, a single preamp with phono stage
and
4) monoblock or two-channel amp(s) with max 110 wpc output (25-75 watts is probably plenty for my small, decently efficient speakers in a 13x20ish foot room)

Or if you think the existing Onkyo receiver is up to the job and I should put my wallet away, g'head and say so.

Other info:
-- This is just for music; I have zero interest in home theater audio. My musical tastes run the gamut.

-- SS or tube is fine, but I doubt that decently isolated hybrids are within my budget. As a vinyl-loving middle-aged Luddite who digs warm, rich sound, I'm drawn to the concept of vacuum tubes, and the basic Antique Sound Labs preamp and monoblock amps are appealing and affordable. But I don't know if I'd like the reality of tube gear. It would have to go in this type of open rack and would have at most a few inches of clearance above it, and I'm not sure that's sufficient for ventilating tube components. Also, I'd get cranky if I had to let the thing warm up for an hour before it stopped sounding like shit.

Please take it easy on the acousticalese; IANAPhysicist.