Off-Grid Party Sound Systems

Step 3 Efficient amplifiers

For amplifiers there is really only one choice: a Tripath-based amp, sometimes called a T-amp, Class-T amp, or Digital amp.  These ultra-efficient wonders are inexpensive but obscure.

(a note on terms:  "Class-T" is a marketing term.  All T-amps are technically "Class-D" amps, sometimes refrerred to as "Digital" amps. There exist non-Tripath class-D amps, but all the ones I have seen are either very small or only for use with subwoofers (they are not "full spectrum").

T-amps are available in a couple of different sizes, based on different amp chips:

• TA2024 based amps: 10 watts per channel, runs on 8V to 16V DC
• TA2020 based amps: 20 watts per channel, runs on 8V to 16V DC
• TK2050 based amps: 100 watts per channel, runs on 8V to 36V DC (needs 24V for full power rating)
• TA2022 based amps: 100 watts per channel, requires custom power supply

Those are the most common models i currently see available for purchase.  Most of the ones I can find are only sold direct from Chinese vendors through Ebay.  This means they are cheap, but it will take 2 weeks to get it.  Please post if you know of other sources for these amps.

I bought and tested several of the common amps I found on ebay.  Note that there are many vendors on ebay all selling the same amps (or copies of the same amps).  The names of the amps get a bit confusing, its easier to go by the photos.

How to find these on ebay.com:  search for the amp chip:  TA2020, etc.  You will find tons of these amps.

Stand alone amps (amps with a plastic or metal case):

• SMALL: Dayton DTA-1 from parts-express.com, $45.  TA2024 based.    This amp includes a built-in battery holder.  It runs at full power for 3-5 hours on 8 rechargeable AA's.  If you want a small system, this amp is really convenient and recommended.
• MEDIUM: "SMSL" or "Topping" type TA2020 amp - $20 - I bought one from ebay seller indeed-hi-fi-lab. This amp is very good quality with durable construction, and sounds great. It also has a small and attractive case. indeed-hi-fi-lab seems to have 2 variations called the "Tripath TA2020 Mini Cute Class T Amp Amplifier Ipod MP3" and the "NEW Class T Amp TA2020 Amplifier Tripath Chip TA 2020". Rest assured mine is the "mini cute" type, but the other one looks equally well made in their photos.
• LARGE: Dayton DTA-100a from parts-express.com, $95.  TK2050 based.  This is a 24V amp and includes a wall wart.
• BAD:  "Lepai" TA2020 amp from ebay seller "box-them", $20. The internal construction of this amp is low quality. It also broke after a few days use so - NOT RECOMMENDED - particularly as there are better options for about the same price.

Bare board amps (no case included):

• BIG:  "TK2050" and "TK2050-improved" amps - $40 - from ebay seller sureelectronics. The "improved" version is now available from parts-express.com also.   These are "bare board" amps without a case. I built several sound systems using these amps.  Note that you MUST use a powered mixer (see later step about this) to to get full power out of these, but even so these are the best deal going for a high power setup.
• MEDIUM:  "MKII TA2020" and "MKIII TA2020" amps - $25 to $35 - from ebay seller arjenhelder_electronic.  These amps are top quality and sound great.  These are "bare board" amps with no case.  They also come with bare wires for power and audio input, so you'll have to do some soldering to hook them up.  These also need some vibration-proofing if you plan to use them on a bike.

Comments

[slaterbsb]

Hello!

This is amazing!

I'm currently pricing a system, and had a couple questions:

If I have a pair of B212XL or B215XL should I have a single DTA-100a or will I need one for each speaker?

[kwahlgren]

Are these t-amps bridgeable to Mono? I'm looking to use a Pioneer B20FU20-51FW driver and id rather have both channels powering it.

[dan]

no. the only way to use both channels is to use one channel for the woofer and one for the tweeter, that is one benefit of my monoXover device discussed later in the project.

[esmash]

So does this mean it is possible to send all 200w to one woofer? If so, how could this be done? Thanks

[Qsam]

so if u have an active speaker u still need an amp and a mixer?

[Zem]

Is there a volume control for the MKII TA2020? I'm thinking of buying that. Would it just be volume from the input device?

[dan]

no, most of the bare board amps you control volume from your mp3 player.

[Zem]

Okay, thanks!

[sbriggs]

Note that you MUST use a powered mixer to to get full power out of these, but even so these are the best deal going for a high power setup.

Could you explain this statement to me please? Is this as a power source or for the audio?

[dan]

i added a new step "mixers" to explain it better. let me know if it still does not make sense.

[sbriggs]

That's brilliant! I've found the whole instructable very informative. Thank you! If you don't mind me asking a couple of questions (I'm pretty new to all this!).
- You say that having an efficient amp like the T-class you use is x2 better. Does this just mean it drains the battery less quickly? Because in terms of ensuring the amp is suitable for the speakers, we still use the power per channel rating given to the amp to compare with the RMS power of the speakers, yes?
- By choosing efficient speakers and perhaps deciding to use pre-amp crossovers, we can achieve "more output for the same amount of power". My question is, is it a problem to run a speaker/woofer at way below its RMS power? I understand that it wouldn't be being used to its full potential, but I just wanted to check it wasn't actually damaging in any way. Say I used the mini ipod TA2020 amp (so 20W/channel) with say an efficient (98dB SPL @ 1W/1m) 250W RMS speaker. Is this an issue?
- Finally, I have a pre-amp for my record player to connect to the cheap Hi-Fi system I own. Would this do the same job in boosting the MP3 player's signal as the powered mixer you use before running it into the TK2050 amp?
Sorry for the barrage of probably-quite-mundane questions but your instructable has got me hooked and I really want to learn and build more!

[dan]

- running a speaker below rated power: this is no different than turning down your volume knob below 100%. so of course it is no problem. speaker power rating is always the maximum the speaker can handle. to put it another way: never use an amp with a higher power rating than the speaker. your amp should always have lower power rating than the speaker to avoid speaker blowouts. an amp with 50% the power rating of the speaker is very reasonable. if the amp only has 10% of the power of the speaker then you just won't get as loud as the speaker is capable of - but that might be fine for your application. most amps are protected from overheating and blowout electronically, while speakers often are not.

- a pre-amp serves the same function here as the powered mixer. so yes, that will work.

- 't-class is 2x better': yes, i mean it has equal sound output to normal "A/B" amps with 1/2 the power use. so, that means you can use a smaller, lighter battery.

[N.I.Patterson]

Hmm. The received wisdom in general (at least in live sound applications and amongst long in the tooth audiophiles...........I do both I must confess!!) is that there is no issue to running a speaker with an amp well above its power rating ( I ran my own expensive reference 200w speakers with a BGW 750a no problem, it's hugely powerful.). To be precise a speaker likes to 'see' clean UNDISTORTED power up to its maximum rating. An over specified (in terms of power with regards to the speaker) amplifier will drive a speaker cleanly without any distortion. Running an underpowered amplifier into a speaker though for fairly long periods (say over 15mins at a guess at least) at high levels will produce lots of evil distortion. This distortion over time will cause the voice coil of the speaker to heat....more likely past the point of no return and cause it in turn to burnout. An underpowered amplifier is capable of exceeding its specifications by quite some way in general. A 20wpc rms amplifier may produce (at a guess) 80wpc channel of something that cannot really be said to resemble music. We all know its signature sound, harsh, objectionable, edgy etc. We choose to ignore these warning signs when we are drunk, ignorant, distracted (driving) and on and on. The speaker will let you know that you have exceeded its and the amplifiers limits by refusing to party anymore. So that speaker that was capable of handling 40wpc rms has just been ko'd by a little 20wpc amplifier. Running a speaker with a big amplifier (as big as you like really) is a good idea BUT YOU HAVE TO BE REPONSIBLE THE SAME AS RUNNING IT WITH A LOW POWERED AMPLIFIER. No matter what wattage of amplifier speaker combination you use you can blow nearly any speaker......I think. If it sounds distorted and you play it like that for long enough something may well give. Things break. Speakers are things with finite capabilities. Also if you are playing rap/reggae/drum and bass/r&b and what not AND boosting the bass and treble still further you are inviting trouble. Music like this will sap any reserves even from a well specified amplifier. Power ratings tthough are not going to save your speakers from misuse. Your ears, experience and knowledge of application of the speakers specifications/parameters may. I venture this info by the way from having, in a past life, had to deal with distressed customers who no matter what you enlightened them to previously went off on a tangent and returned with 'toasted' speakers. Oh well after repairing said speaker they were definitely a little more 'open' to any further information you could give them! Oh yes amps are protected, at least professional amps are, from burnout but speakers have to fend for themselves as they are the 'messangers'. Messangers (Julian Assange maybe?!!!!) tend to get shot at the best of times!!

[dan]

yes, if you hear distortion you should turn things down until it stops. i still recommend an under-powered amp because it will not be able to blow the speaker in seconds, perhaps only after a long time playing with highly noticeable distortion. an over-powered amp on the other hand can blow the speaker in seconds simply by turning up the volume knob. in a home-theater setup that might not be a big risk, but in an outdoor/mobile environment there is a lot of chaos and its way too easy to have someone bump your volume.

[N.I.Patterson]

Good point Dan, your brand of real world experience supercedes theoretical advantages I concede. I did sound for my brother recently at a very big christmas golf club party (he runs a successful Motown/popular music act) and he impressed upon me to address the routing of the cables for the system with a little bit more care "never underestimate drunk people" he said!! Yes in the chaos of live performance of any kind a variable may arise that will leave you with more than a touch of egg adorning your countenance!! I guess also in a home situation if you have an inquisitive toddler sharing your home space you may rue the day you placed an amplifier capable of armageddon lovingly into the heart of your system.

[sbriggs]

Thank you so much for your help!
I've just remembered I've got my grandad's old PA system in the attic. They're colossal, probably massively inefficient, 16ohm 70W beasts. I'm gonna see if I can work them/one into some sort of system. Perhaps in a bi-amp system with one TK2050 amp trying it's best to get them going and then a smaller TA2020 running the higher frequencies through some bookshelf speakers.
It started here! Thanks for your brilliant instructable and helpful advice!

[lurchkjw]

Thanks, Dan! This is a great tutorial. I built one using an old home entertainment center speaker. Not sure how efficient it is, but it sounds great!

I bought the "NEW Class T Amp TA2020 Amplifier Tripath Chip TA 2020". It requires an adapter plug from the battery (unless you want to try side-stepping it and soldering the leads directly to the board). I bought an Enercell adaptaplug "N" for $6.99 and an Adaptaplug Replacement Socket for $3.69. My power source is the 10 AA battery holder from Mouser, so I just soldered the leads from that to the replacement socket leads. If you solder the red positive lead from the batteries to the lead with writing on the Enercell socket, You just have to line up the "+" on the adapter plug with the "tip" side of the socket.

[Varsity_Prom]

lurchkjw,

(Disclaimer: I am a beginner when it comes to electrical components, etc)
I purchased the Tripath TA2020 Mini Cute Class T Amp to power my setup. I also had to purchase an adaptaplug and socket. I aligned the + and the tip sides, but then must have screwed up the ground when connecting to the battery's wires (closed cell lead: 12V 18ah).

Obviously it immediately started smoking and I unplugged the amp. I took it apart and attempt to solder the melted portion of the circuit board, but I think I'm hosed. It did turn on after I corrected the wiring, but would not push any sound.

So, I do not mind ordering another amp, but want to make sure that the battery didn't contribute to the failure. Does it matter if the battery is 18ah and the max input is 9-13V and 5amps (which I realize is different from amp hour). I still want to make sure the 18ah won't somehow melt the next one (wired correctly)

Any thoughts? I have gone throught 3 car stereos in the past 4 years and was REALLY hoping to finally have it right. Damn!

[dan]

18ah does not matter. it means it will run longer. i highly recommend a multi-meter so you can check your voltage before plugging! they are not expensive.

[zeroemission]

it's sad about the lepais. they're dirt cheap and look really cool, especially the ones with the blue illuminated volume knobs. the look so much better than sonic impacts.

there are a few other 10wpc amps like the topping around the same $100 mark.

microFidelity has a nice looking little aluminum cased 50wpc unit out now for around $60 (model 100) at those power levels though, the amp isn't the limiting factor, it's all of the batteries needed to get a 24v+ power supply.

i like the sure 100w unit best though. it's only $40 or so and looks great naked and is the most boom for the buck you can get.