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kctess5 17th February 2013 08:00 AM

Quiet amplifier
 
One of my absolute hugest pet peeves is hearing buzz coming from my speakers. When there is a definite frequency audible that is the worst, but wide range white noise is also pretty bad. I have heard some VERY high quality gear and I've never understood how audible noise is acceptable from amps/dacs that cost ~$4000+, why would anyone spend that much on a noisy component?!

I'm looking for a lower power amp that is particularly quiet. It will be used with speakers that are 95dB efficient so 10 to 15 watts is enough for me. The noise should be inaudible from no more than about a foot away from the speakers, though less than that is welcome. I have googled this a fair amount and all I can find is people talking about specific op amps and components.

Class A is preferable, though AB is ok, and I *might* consider class D. Tube amp suggestions are also welcome, as long as they are well reputed. I would like to stay under $250 though will take suggestions that are a little higher, I am on a pretty low budget (almost a college student). I don't want to do a kit because all the kits I have made have been very noisy, presumably because of my mediocre wire routing.

Thanks!

chris661 17th February 2013 09:13 AM

If college may happen shortly, I'd avoid valves (AKA tubes at your side of the pond ;) ). You don't want to have to worry about damaging/replacing them, as there are other things you should be spending money on.

I've got an amp6-basic from 41Hz, powered by a 12v 5A laptop PSU. Had it for years, and it just keeps working.
IMHO, it'd fit the bill nicely: it'll provide enough power in a compact form-factor, and sound decent doing so.

I'm using it to drive >500Hz into a pair of Fostex FE126s. Noise is just about audible with my ear next to the cone, but given the stupidly messy wiring of my current stereo, its hardly surprising there's noise.

I know you said you don't want a kit, but this'd probably be <$100 all done.

Chris

xrk971 17th February 2013 10:59 AM

I second that class D amps are the way to go if you want low noise, which is counter-intuitive because traditionally you want to keep digital switching away from analog components to reduce noise. Note that tubes are inherently higher temperature devices and will intrinsically have more noise (thermal), all else equal. The bigger problem is 60 Hz line freq hum leaking in due to ground loops from bad design or bad construction techniques.

vacuphile 17th February 2013 11:03 AM

I second what Chris and xrk971 said about classD. Certainly with a budget of 250 USD, that's the way to go. 41Hz has some very affordable kits.

IG81 17th February 2013 03:50 PM

If a used amplifier is acceptable, you can get a Yamaha M-45 for your budget. It's way more powerful than what you say you need at ~120W, but that's not a bad thing in my book. :) You can run it in class A up to ~10W IIRC and its self-noise is extremely low. I use mine to drive 113dB/W/m compression drivers on a bi-amped two-way and have no problem. If components upstream have noise of their own, you can turn down the input level on the Yamaha and keep SNR higher upstream.

IG

cyclecamper 17th February 2013 03:57 PM

A lot of push-pull tube stuff was designed thinking they can get away with terrible power filtering for the power output stage because in theory the push/pull cancels hum from the power supply. In reality, the splitter is never perfect, the push and pull sides are never perfectgly balanced, the bias supply gets polluted, etc. etc.

ssportclay 17th February 2013 07:58 PM

Since your speakers are so efficient, all you need is a little class D amplifier. One of the little Topping Tripath chip units would be the obvious choice. The newer Texas Instruments digital amplifier chips seem to be getting a lot of attention lately. Look at the Muse Audio M50, Guanzo DP-101, or FEI XIANG FX502A. These all use the TI TPA3123 chip if you want to try something different than a Tripath. You could also try a TPA3116D2 or TPA3118D2 evaluation module but you will need a 24 volt/4 amp power supply and you will not have a case if you care. Texas Instruments released those last 2 chips last summer so they are very new designs.

Bob Brines 17th February 2013 08:40 PM

I have the big Topping which is based on the TA2020. I love it, but all of the Tripath chips are getting long in the tooth. I need to get one of the new TI amps. I'll look at the suggestions above. Needs to be 20w/ch or greater.

Bob

kctess5 17th February 2013 09:04 PM

I've had mostly class D amps. They just seem a little lifeless and I was hoping to get something class A. I'll have to check out that Yamaha M45.

I am currently using a bit of a hotrod 41hz amp-6 basic. A friend of mine made it, it's got some high quality caps installed and stuff. It's pretty good but I can still hear a bit of a buzz, and the wiring looks like it should be lower noise.

xrk971 17th February 2013 09:29 PM

I just got my TPA3116D2 chip and all the caps and resistors to go with them, should be starting the build soon. It's a little hairy because the amp is a 0.6 mm pitch SMD and parts are like dust bits. iIRC 50 watts/channel and 0.1 %THD at 30 watts w 24v supply.


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