Buying a stereo audio amp (trying to cut through the rubbish) - Page 1
Forum section: electronics / general

author: jeremy
author_rank: Super Contributor
timestamp: September 10, 2012, 05:55:47 am
content: Hi all,I want to buy a stereo audio amp. I don't need HDMI switchers, Bluetooth, a bunch of blue LEDS and 12 different inputs, I just want to listen to the music I like loud and have it sound good. Does anyone know where I could start with this? I don't want to spend all that much ($300 tops) and I am definitely open to buying a good kit. Most of the consumer stores I've looked at just sell the crazy feature packed ones with 7.1 speakers. I'm sure someone here must have gone through this before.I'd rather not build my own yet I am interested in building my own speakers. When I get those working I'll go back and make oneThanks.

author: PeterG
author_rank: Frequent Contributor
timestamp: September 10, 2012, 06:06:37 am
content: I would have a look at you local op-shop. I have found many gems in second hand stores.Regards

author: Raff
author_rank: Regular Contributor
timestamp: September 10, 2012, 08:37:21 am
content: If I were looking to buy a quality stereo amp, I'd be looking at brands such as Yamaha, NAD, Luxman, Marantz and the like. I have seen classic 1980's Yamaha amps for sale on e-bay for example at good prices. I'd recommend 100 watts a side or better, that way even if you dont use all that power you still have lots of headroom keeping distortion lower at normal listening levels. These dyas all the new amps around seem to be of the home theatre type with 7.1 channels and HDMI etc.Regards,Raff

author: nanofrog
author_rank: Super Contributor
timestamp: September 10, 2012, 10:58:28 pm
content: Another vote for used. And you might want to add Rotel and Adcom to the list of potential brands to look for IMHO.

author: FenderBender
author_rank: Super Contributor
timestamp: September 10, 2012, 11:37:56 pm
content: Yeah a good amp from the late 70s and 80s is likely still working to this day, and if it needs some TLC, you can surely fix them up. Should be nothing more than discrete components I would expect. Some big TO-3s on a heatsink and the like.Though I have one of those little bookshelf systems that were prominent a few years ago. (Center amp section and two bookshelf speakers). I garbage picked an Aiwa system. Very nice indeed. Internerals were very good. A good indicator I like to look at is the electrolytic capacitors since they have distinguishable names on them. If they are a brand I've never heard of, I have to assume that they cheaped out on not only the elctrolytics but everything else. Likewise, if the electrolytics are a good brand Japanese capacitor or similar, then it's usually safe to assume that they didn't cut too many corners. This Aiwa system had nothing but Nichicon and Rubycons, and the good ones too, 105*C etc.So there are some more recent amps out there too. Don't limit yourself to dinosaur amps. If you can take a look inside of one before you buy it, that would be nice.

author: FenderBender
author_rank: Super Contributor
timestamp: September 10, 2012, 11:39:44 pm
content: Wow just looked up Aiwa...Sony bought them. God @*#*&@(. F U Sony. They're gobbling up all the good brands.

author: Psi
author_rank: Super Contributor
timestamp: September 10, 2012, 11:48:41 pm
content: The speakers and cabinet have far more effect on how good it sounds than the amp.A pretty average amp and matched speakers+cabinet will outperform the other way around by a significant margin.Building awesome speakers yourself is a huge undertaking and a bit crazy.Building a good power amp is pretty easy.Unless you meant building the speakercabinetyourself and buying the speakers, then it's more reasonable, there are lots of online guides for speaker cabinet construction and tuning. But still, without an proper sound lab to see what cabinet changes do to the response it will be very hard to make anything approaching good quality bought speakers.If you want a setup that sounds awesome build a gainclone amp from some LM3886's and buy some Klipsch speakers.

author: FenderBender
author_rank: Super Contributor
timestamp: September 10, 2012, 11:52:29 pm
content: Yeah I'd agree. Speaker construction, frequency response, sensitivity...or what ever else makes a speaker good ...and equally as important is the enclosure it is in and if it has some sort of filter network. You could probably get one of those el cheapo 90% efficient class-d/g/t (whatever) amps and make some really nice sounds with good speakers, even if the amp isn't theoretically all that great.Psi is right.

author: JuiceKing
author_rank: Regular Contributor
timestamp: September 11, 2012, 12:04:55 am
content: For high-quality speaker designs that you can certainly build yourself, check out PI Speakers. I built PI-4 speakers (well, I assembled them after hiring a carpenter to make the boxes for me) and they kick butt. The designs are simple and use high-quality parts from Eminence and JBL.http://www.pispeakers.com/contents.htmlAs a rule, the PI speakers are very efficient, so a 50-100W amp will be PLENTY for domestic use.

author: FenderBender
author_rank: Super Contributor
timestamp: September 11, 2012, 12:09:08 am
content: These are the speakers I built:http://techtalk.parts-express.com/entry.php?73-%93Sophomores%94-writeupAlso built this sub:http://techtalk.parts-express.com/showthread.php?212847-quot-Biumph-quot-aka-quot-Triumph-V2-quot

author: Raff
author_rank: Regular Contributor
timestamp: September 11, 2012, 12:19:59 am
content: I agree about speakers etc. I built many a speaker setup during the 70s and 80s. I favoured Philips, E-Tone and Tandy (believe it or not) drivers back then. Those Aussie made E-tone 12 ich drivers were awesome. its a fun project and you can get pretty good sound if you have a couple of decent reference books to follow. I used 19mm chipboard with internal inch by inch bracing. I even modified old RTR loadspeakers with a mix of VIFA, SEAS and Philps drivers, sounded so good a mate bought them from me. If you are anywhere near the Gold Coast, I can recommend Gold Coast Hi Fi, they often have quality used amps speakers and the like, and you can listen to the sysem properly there too. I still have some of my amp projects lying around, like my PLaymaster Mosfet amp and ETI "Brute" amps. Above all have fun with your project.Regards,Raff

author: Psi
author_rank: Super Contributor
timestamp: September 11, 2012, 12:21:26 am
content: When he says he's "building speakers" he might mean- Welding up the frame, winding the voice coil, installing magnets and making some speakers (Crazy)- Doing the complex math for sound propagation and designing his own speaker cabinet given the specs/response of some purchased speakers (Difficult)- Following someone else's plans for a speaker cabinet design and installing some purchased speakers. (Easy)

author: Raff
author_rank: Regular Contributor
timestamp: September 11, 2012, 04:16:55 am
content: Wow, I didn't even consider that, I just assume when people say they are going to build speakers it means the boxes, not the drivers themselves.Still I have seen some fine examples of home built drivers on the 'net.One bloke built a horn loaded system so large he had thew house built to suit and the backs of the bass horns went out the wall and into the back yard!I wonder what it sounds like? Awesome I'd imagine. From memory it has separate amps for each driver as well.

author: jeremy
author_rank: Super Contributor
timestamp: September 11, 2012, 07:00:24 am
content: Thanks for all the input guys, looks like once again ebay is where it's at. I'm trying to do the second of psi's options; buy drivers and design the box. I work with a lot of smart people who know how to do this stuff and have access to all sorts of soundproof rooms and calibrated microphones. And the maths isn't that hard if you just throw it all into matlabBut by the sounds of it going for a speaker kit/rescue speakers first might be a better option so I can listen to my music in the meantime.

author: Psi
author_rank: Super Contributor
timestamp: September 11, 2012, 08:01:18 am
content: Quote from: jeremy on September 11, 2012, 07:00:24 amThat definitely makes things a lot easier.

author: jeremy
author_rank: Super Contributor
timestamp: September 29, 2012, 04:42:26 am
content: Just a quick update: I bought a broken NAD 3155 stereo amp off ebay for $50 (fuse popped when plugged in). One of the bridge rectifier diodes had gone short and another little glass diode on the left amp had shattered to open circuit. Total fix cost: $0 (I had replacement parts lying around anyway!). And it even sounds great with the old speakers I found. It was quite interesting actually, I've never seen a diode with cracked glass before; any idea what could cause this?Anyway, thanks again for all your help guys.

author: Pentium100
author_rank: Frequent Contributor
timestamp: September 29, 2012, 05:25:02 am
content: Quote from: jeremy on September 29, 2012, 04:42:26 amMy guess would be too much current.Anyway, yea, used amps are great. I have a Denon PMA-1080R (120W/channel at 8 ohms, enough for my 90W speakers) and it sounds great (though it blew up once after I bought it - seems that there were some repairs done on it and a couple of transistors were replaced with ones that are not in the substitution book)

author: T4P
author_rank: Super Contributor
timestamp: September 29, 2012, 07:50:32 am
content: Too much current, i have seen diodes (in cheap chinese crap) with their case totally missingOr maybe it's just a "diode" and i also have seen idiots blow diodes up by connecting in reverse, that freaking stinks! (Although i like to blow stuff up but the epoxy stinks)

author: Rerouter
author_rank: Super Contributor
timestamp: September 29, 2012, 08:50:11 am
content: equally thinking too much current, but i have on 2 cases seen it happen from water ingress into the casing where a start up surge caused it to boil enough that it blew the casing off, in one of those cases the diode still was functioingly fine but replaced anyway, the other one, the water had actually corroded it to such an extent that without the casing the leads disintergrated,