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DIY amp full kit recommendations: <$120, max 60 watts per channel

post #1 of 22
6/11/12 at 9:54pm
Thread Starter 
I have a pair of vintage speakers. I thought I had an amp built in to my subwoofer. I was wrong, my subwoofer amp is pretty sub par. So i'm left with no amplifier and no reciever in the entire house to power these Pioneer HPM-60 speakers with.

The speakers want 30 watts each (recommended) or 60 watts RMS max recommended each. Obviously I can put any bigger amp on it and just not turn the amp up as loud. I'm not sure, but I feel like anything lower than 20 watts per channel will be cutting it too close.

Anyways, do you guys have any recommendations for full kits that I can try? I was hoping that something similar to the CMOY existed but something that was geared towards speakers. Maybe a class D or some other opamp based 30-60 watt amp (per channel) design?

I did find the chipamp.com website. Is that a recommended website to buy from? Have you guys tried anything in particular?

Alternatively, theres a couple of amps like the Lepai t-amp 2020 or something and theres a couple dayton t-amps like the DT-100a. Those are valid choices too. I figured that if I'm going to have to spend money on this, i might as well have some fun with it and make it a project of some sort while my funds recharge for other stuff I have to save up for. (computer monitor, computer cooling, keyboard/mouse)
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post #2 of 22
6/13/12 at 12:39pm

I have the lepai TA2020A+ and it is a massive bang for the buck. The reason why the amplifier is only $25 is because they cheaped out on many of the parts, Spend $20 on the amplifier, a much better power supply ($15), and find a guide online including the parts that you can buy to upgrade the quality of the components inside. The outcome will be an amplifier that is able to outperform a lot of amplifiers in it's price range when it comes to sound quality (NOT driving power which your not looking for).

 

Find a guide online that includes the list of upgrades. There's also plenty of youtube video's about the amplifier and the modifications you can do to it.

It'll be a fun experience upgrading the amplifier and it will run you under $100. When i got the Lepai I was actually in the same situation as you. Money was tight yet I still wanted to upgrade my "battle station"

Even after getting a 27" 2560x1440 IPS monitor, a mechanical keyboard, and a desktop that costed me way over a grand, I'm still not planning on upgrading my amplifier, it's that good.

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post #3 of 22
6/13/12 at 2:40pm

That lepai is only putting out 20 watts, and while the chances of full on cranking the volume knob to 10 is often rare, if it happens you risk square waving the signal into the speakers, which can wreck them real quick.  Honestly the best bet for a cheap amp is to go to a local music instrument store (guitar center and such, or even better, a mom and pop used instrument store) and you can probably pick up something used putting out like 100 watts for pretty cheap.  And if you are really itching to get your hands dirty you can spray all the connectors, pots and switches with some DeoxIT spray, or if it's rather old you could recap the thing.

 

I'm currently using an old Altec-Lansing 300 watt a side power amp to drive some small kenwood speakers, it's about 20 years old and I picked it up for under $100.

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post #4 of 22
6/13/12 at 10:01pm

Hello again shrim.

 

I'd like to reiterate on what samsquanch is saying. It will be tough for you to find a good power amp kit at this low price range. I know of none myself, but might be some exist out there. If you get a T-amp, I'd recommend you get the Dayton T-amp and not the Lepai, I own the Lepai TA2020, and while it's an ok device, its power output is severely limited. I haven't measured it myself, but I'd feel comfortable in saying that 20W is the value it puts into 4 or 6 ohm loads, not an 8 ohm. I was able to push it to clipping with both my bookshelves (Overnight Sensation MT, 85db/W) and my vintage Kenwood floorstanders. The Dayton Tamp, on the other hand, is a much more robust amp compared to the Lepai. I have my doubts it pushes a legit 50W out, but it'll be enough to power those speakers you mentioned.

 

That being said, I think a better solution for you would be to get a integrated amp or zone amp. I'd recommend an NAD integrated or Parasound Z-amp. A good integrated should be able to fit into a desktop environment easily, whereas an older vintage receiver would be much bulkier and heavier sitting on your desk. You can probably find something of that ilk for around $100 if you look around and are patient.

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post #5 of 22
6/14/12 at 7:02am
Thread Starter 
Yes, the TA2020 by Lepai, if I plug it into an 8 ohm load, will only be outputting 13 watts max. I know this is barely anything, but if I was going to spend around 100 bucks, I feel like it is a better idea to save up for a proper receiver that can deliver a proper amount of power per channel into 8 ohms.

My logic was that i'd rather spend around 25-30 bucks on a cheap crappy "for the time being" amp that will get the job done for 6 months or so, OR I can spend about 100 bucks on a proper DIY kit that will get the job done for a year or so. OR I can save up and spend 200-300 on a proper receiver that will get the job done for 2-3+ years. However, my budget right now is as follows:

Current savings is ~120 dollars. my first priority is a monitor for my computer, as I still have my dad's work monitor comandeered ($320). Second priority is a proper CPU cooler ($100). Third priority is still up in the air for the time being. I wanted to spend the next 80-100 dollars on a fan controller, acoustic damping material and a few fans for the computer because as my computer stands right now, I have absolutely 0 fan speed control. Because of this, no matter how good any of my speaker/headphone setups may sound, my computer has a blinding blue light and sounds like an air strip. These upgrades are all out of necessity more than simple want. I'm using solely the fans that came with my case, as the person who gave me the computer components to work with neglected to give me any sort of working computer fans.

I still havent even received my first paycheck from my part time job (college student) but it should be coming in 1 week from today.

So with that being said, here was my plan/options:

1) I figured i'd go to best buy and get an amplifier that did 20-25 wpc into 4 ohms or specifically 10-15 wpc into 8 ohms. I'd test that out with the speakers, see if I can get things volume matched, and see what is possible with that little power into these relatively sensitive speakers. If this worked with the best buy product, I'd get the Lepai product, return the best buy product, and work with that at low volumes until my funds built up. My room is only 10.5 feet x 10.5 feet x 12 feet high. It is VERY small. The speakers are scarcely 2 meters away from my head. I feel like I wont be needing too much power to get them to a comfortable, or even loud, listening level. In the past 2 years there has only been 2-3 times when I have been in a situation to blare music throughout the house, and I DO have a sound system of some sort on every floor, so i'm sure there is some way I can use phones or laptops to stream music to each of those systems respectively without having to blare music from floor 3 onto floor 1.

2) Build this here: http://diyaudioprojects.com/Chip/DIY-TDA2050-Hi-Fi-Chip-Amplifier/ However. I have absolutely no clue what this project is talking about. It is pretty far above my head as a DIY'er and assumes a fair bit of prior knowledge and access to parts/materials/tools that I'm pretty sure I dont have. If I had a proper mouser/digikey parts list it would be much much easier but at this point I dont even know how to properly choose parts. Also, I'm pretty sure that while this entire project's parts alone dont cost more than 30-60 bucks, that toroidal transformer looks MIGHTY PRICEY. (and fairly sexy to boot).

3) Suck it up and just stare loningly at these speakers until I can afford a receiver. I dont see the point in buying a 100 dollar pre-built amplifier because that is the point at which I start getting into used/refurb receiver ranges. At this point I might as well just save up for a proper receiver or something.

Option 1 is what i'm leaning towards because it is the quickest and cheapest method, but as i'm becoming less and less immature, i'm learning that quick and cheap is often not the right/best option. I am also learning that patience, while sucking very hard, yields the best results.

What do you guys say?

Also, hello, ojneg!

EDIT: Also, the option of taking apart and modding the Lepai 2020 into some sort of massive beast sounds pretty sexy. Dayton also sells a pretty cheap Class D 100 watt per channel into 4 ohm kit. My only issue with that is that there was no option for volume control, and i have no idea how gain works with that. I'd need some way to control that. I have 2 RK27 alps blue 50k pots just sitting around. That is also a valid option.
Edited by shrimants - 6/14/12 at 7:04am
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post #6 of 22
6/14/12 at 8:55am

That Gainclone amp does look like a sweet project. It wouldn't be too tough to build, but you have to think about the cost. Each amp board looks to be relatively cheap, but when you bring in a power supply, step-down, enclosure, heatsinks, and all the other jacks and accessories you'll easily go over $120. In terms of cost effectiveness, I don't think spending that much on a 25W chipamp is the best idea in terms of longevity. If I was to DIY my own power amp (which I do plan on doing in the future) I'd look at one of the discrete Class-A MOSFET designs on that same site.

 

Obviously those go way beyond your price range too, but I know that feel bro. I'm a college student too, and it's hard to finance an audio hobby on minimum wage and saved birthday money. Couple that with a PC building hobby and you'll find yourself out of luck. I haven't upgraded my PC in almost 3 years since I started getting into audio.

 

Again, I'll recommend that you wait it out and keep your eye on Craigslist and eBay. There's a chance someone will want to get rid of their dad's big, bulky stereo for a new iPod, and you might be able to find something on the cheap.

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post #7 of 22
6/14/12 at 9:09am

with DIY at the bottom end you don't "save money" - where there is mass market consumer product it is common for the finished product to cost less than a fraction of buying the raw parts in small quantity

 

garage sale/flea market/recycling center consumer audio amps would likely be your cheapest solution - or source of parts

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post #8 of 22
6/14/12 at 9:37am
Quote:
Originally Posted by shrimants View Post

 I wanted to spend the next 80-100 dollars on a fan controller, acoustic damping material and a few fans for the computer because as my computer stands right now, I have absolutely 0 fan speed control. Because of this, no matter how good any of my speaker/headphone setups may sound, my computer has a blinding blue light and sounds like an air strip. These upgrades are all out of necessity more than simple want. I'm using solely the fans that came with my case, as the person who gave me the computer components to work with neglected to give me any sort of working computer fans.

 

Here's an easy way to save some money:  Make your own fan controller, all it'll require is enough DPDT toggles for the fans you have.  I used to do this back when I was into building gaming rigs in the early 2000's, many 12vdc fans won't run at 5vdc so if you were to use a switch to toggle between feeding the fan 12vdc and 5vdc there's a chance that when you flip from 12 to 5 the fan will stop spinning, BUT you can get them to run on 7vdc pretty well.  What you end up doing is using the positive from the 12 volt side (typically the yellow wire) as the positive to the fan, and the positive 5 volt wire (typically red) as your negative/gnd/0vdc, this winds up giving you 7 volts.  So when you're really hammering on your system you switch to 12 volts, but when you need things to be quieter you flip to 7 volts.  Switches are cheap, you can probably get premade cables at Radioshack that already have the Molex connector on them.  All said and done with you might spend $20.

 

Also, just another nudge towards used power amps, they're designed to be pretty quiet and reliable, so if you can score a used Crown/QSC/Lab Gruppen/Altec Lansing/Peavey amp it'll last you a long time and will treat you reeeeaaaallllll nice.

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post #9 of 22
6/15/12 at 9:39am
Thread Starter 
I forgot to mention, if I go for a DIY design, my dad pays for half of the cost. That is why it ends up saving me money. He figures that it is an educational experience and that it is obviously easier for me to save up money and simply buy a pre-made device, but I dont learn anything that way. So if I go the DIY route, a 200 dollar design would only cost me 100 dollars. However, if it is only going to give me the performance of the 89 dollar dayton DTA-100a then I am definitely better off waiting. One thing I have to do anyways is figure out how to create a simple active preamp with gain 1. Basically it is just a way to lower line level volume to more manageable levels instead of having to use software volume control methods.

So far, i'm hoping my GF's dad, the one who gave me the speakers for my b-day, will let me borrow his receiver until such time that I get funding built up. I think for my computer cooling issue, i'll still go H100 and use its built in cooler, but i'll get a silent 120mm case fan, a 140mm PSU fan (no connector/whatever necessary) and another 120mm 4-pin fan that i can connect to CPU header. That way my CPU header can control AND report fan speeds for the front case fan, set to silent mode. The H100 can cool the CPU while the front case fan will only control overall temps/air flow. The rear fan wont have any speed reporting but it will be 3-pin so it will at least have speed control and be quieter. I think i can forgo the fan controller in this way. That should lower the cost from 200 ish to like 130.

Alternatively, i can get just the H80 and a single 120mm 4-pin and leave chassis fan disconnected/ignored. I feel like that is not enough air flow though. And H100 is way more efficient at cooling than H80 considering the relatively minor price increase.
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post #10 of 22
6/15/12 at 10:07am

When I get home from work today I can post some pictures as well as a schematic of the preamp I built, real simple, real cheap, and sounds suprisingly good.

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post #11 of 22
6/15/12 at 8:14pm
Thread Starter 
That would be most excellent. So far from what i've seen, there are a couple of options that would work swimmingly. I have Audioengine A5's (built in amp), Active subwoofer (built in amp), and passive bookshelfs (for which i'll have an amp). With these three things, if I set them all close to 50% volume and then volume match them to a proper level, I can use some sort of 3-channel preamp to control them. So the question now is, how do I control 3 devices at once? Software control is out. that just lowers bit depth going to my DAC and introduces all kinds of problems for me. Its time for that to come to an end. A preamp or a receiver can do this. I think a receiver is a combination of a preamp and an amp in most cases, so I either have to buy a receiver or a preamp.

Possible store bought choices are:

Harman Kardon 3390 - $250, has a biult in amp and a pre-out and a sub out.

Pioneer 522K - $250, has a built in amp and a pre-out and a sub out. Also, its a 5.1 receiver and it would probably let me use the pre-out as a rear channel, meaning I might be able to get some sort of stereoX2 or 5.1 channel thing later on in the game. Plus expandability. If nothing else, I think this is my best option if I HAVE to spend this kind of money.

Emotiva USP-1 Stereo Preamp - $400 or used for cheaper. This has a high pass output, low pass sub out, and full range output. The full range can go to passives, the high/low can go to the active speaker/sub. Only problem is, it costs so darn much and I would never even use 90% of the inputs on it. I'm strictly a computer audio guy, I never plan on buying and owning CD's except to make FLAC rips, and I certainly wont ever get blu ray or a vinyl player or a Tape player or anything like that. I feel like this product would be wasted on me.

Is there something cheaper and more suited to what I need?

Ideally, an active preamp with 3 stereo outputs.

BTW, I've temporarily acquired a receiver from my gf's dad, who gave me the speakers. He will let me borrow it this sunday until such time that I can buy the dayton amp. That should give me plenty of audition time too.
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post #12 of 22
6/15/12 at 10:16pm

if you have 24 bit DAC, properly setup sw that is no longer true - even Windows now can spec a 24 bit output device, independent of source bit depth - then the digital volume works smoothly, the "extra bits" from the multiplies are dithered by the unavoidable analog electronics's noise floor

 

lots of "audiophile truisms" have been wiped out by technological advance

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post #13 of 22
6/15/12 at 11:42pm

indeed, proper high bit depth digital volume now leaves ANY analogue control at ANY price, in the dust IMO. there is not much opinion in there, 40-64bit controls are now available, show me an analogue control with that precision in noise, channel matching etc and i'll show you a unicorn


Edited by qusp - 6/16/12 at 12:02am
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post #14 of 22
6/16/12 at 8:17am
Thread Starter 
But heres the thing. windows does support 24/96 (or is it 192 now?). My music is still in 16/44.1 or 16/48 for 99% of my collection. Does upsampling in windows A) screw with the sound quality or B) do anything to the actual bit depth of the audio? I dont know how this volume process works with windows, but i feel like if you have a 16 bit audio file and you have windows upsampling, it would just play the audio file back in 16 bits, 44.1 khz. And that if you lower the volume, you'd still lower the 16 bit depth of the original file. Either that or you could represent the 16 bits of data every 44.1 times per second (even though windows is sending this data to the DAC 48 or 96 or 192 times per second) and thus when you lower the volume, lowering the bit depth wouldnt technically bring you below the 16 bit "barrier".

The way it does it is the second way, right? Or is there a third possibility that i didnt think of?

Also, a problem with what you guys are saying: my current DAC only supports application level volume control. not OS level. So it doesnt have its own built in digital volume control. This is just my hypothesis, but I think that what windows does with its volume is to say "play [THIS] audio stream at [this] gain." However, the gamma 2, with the way the chip was implemented, ignores the gain that windows tells it to apply, including "mute".

So anyways, I know my problem could be solved by getting a different DAC that does listen to windows' volume control. I could probably just use a splitter and volume matching to control the volume, but spending 200 on a proper DAC vs 250 (possibly less) on a receiver, vs even less on a passive preamp of some sort might be a way better course of action.

Latest idea I had, if i go the active preamp route, I might build 3 copies of the CMOY amp, skip the power supply circuit and design my own PSU that can power the 3 constantly. Heck, I might even do 4 or 5 copies so that I have an area to plug up to 2 pairs of headphones, and design some sort of muting circuit into there. Its a proven design, I just have to make sure that if it has a gain of 1 or 2, that the opamps I choose to use will remain stable.
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post #15 of 22
6/16/12 at 9:01am

my understanding is that the audio stream in later Windoz converts everything to 32 bit floats, volume multiplies will be done in the 32 bit float representation - then the stream will be truncated/dithered to the bit depth of the selected audio ouput hardware - ie can be a 24 bit DAC - even with 16 bit source

 

no need for any hardware specific methods - all done in SW before the bits are streamed to output buffer


Edited by jcx - 6/16/12 at 9:05am
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