Class D Amp Recommendations?

[elwood]

I'm trying to keep my SS amp design super efficient (I want it to run on batteries and be super light) so I've been checking out Class D amp ICs. I know they've gotten a bad reputation in the past for being high distortion, but it appears that new ones are getting pretty good. Obviously you want to keep it out of clipping and the PCB layout and output filtering is a bit more of a challenge, but the power supply and heat savings are very impressive.

So, I've been checking out the TPA3106D1 from TI. Looks like a great part, and works with a single supply. Can do >30W into 8 ohms with <1% THD from a single +24V supply at >90% efficiency.

How much power do most people feel they need for a solid state power amp? Mine will be driving a 1x12" open back combo with a speaker rated at >100dB SPL 1W/1m.

Does anyone have other recommendations of parts or have experimented with Class D at all?

[syndromet]

I have tried a few tests with Class D, but have never gotten any good results.

You should however check out Class T chips, like the ones found over at www.41hz.com

I built one of their AMP-5 kits, and tested it with guitar. sounds absoloutly wonderfull with a good preamp. They seem to be even better than class D when it comes to heat and power consumption. I also saw that you were building a Butique amp, and I think Class T have a way better reputation than class D. I also think it would be kind of hard getting a good reputation if you use the same chips as most cheap SS amps use, and I belive that is quite often Class D.

[elwood]

Those Tripath ICs certainly have very good specs. Note that according to Wikipedia: "Rather than being a separate "class" of amplifier, Class T is a registered trademark for Tripath's amplifier technologies. It is an implementation of Class D amplifiers..." So essentially it's just a better implementation than other companies are currently doing. Looks quite fine, but another part of that article suggested that Tripath filed for bankruptcy protection last year... seems like a bit of a risk to use one of their parts in a new product.

What were the problems that you had with Class D?

[jfetter]

I'm giving it a go with the TPA3106D1 and dsPIC33 for a combo unit. The dsp will let me do in software what I've been trying to accomplish in analog. The target is a smooth overdive with mild reverb. The dspic33fj128mc804 has a 16bit dac and 12 bit A2D. I'm planning on trying oversampling to get 14bit. We'll see.

Running on 24vdc I guess about 35w.

Strange no one is using this part.

[joecool85]

I'm giving it a go with the TPA3106D1 and dsPIC33 for a combo unit. The dsp will let me do in software what I've been trying to accomplish in analog. The target is a smooth overdive with mild reverb. The dspic33fj128mc804 has a 16bit dac and 12 bit A2D. I'm planning on trying oversampling to get 14bit. We'll see.

Running on 24vdc I guess about 35w.

Strange no one is using this part.

Let us know how it goes, I'm curious to say the least.

[ponchojuan]

A number of guys on the DIYaudio site have been playing around with this amp board to get familiar with class d amplifiers.  They can be tricky to do from scratch.  Take a look.  Seems pretty good bang for the buck.

http://www.sureelectronics.net/goods.php?id=918

poncho

[gbono]

Anyone?

http://www.irf.com/product-info/audio/classddesign.html

[Zappacat]

I'm giving it a go with the TPA3106D1 and dsPIC33 for a combo unit. The dsp will let me do in software what I've been trying to accomplish in analog. The target is a smooth overdive with mild reverb. The dspic33fj128mc804 has a 16bit dac and 12 bit A2D. I'm planning on trying oversampling to get 14bit. We'll see.

Running on 24vdc I guess about 35w.

Strange no one is using this part.

What ever happened with this ?  Did you get this to work well?

[Minion]

One thing about useing a Class D amp that I don"t like is that many have a certain threshold for the input signal , if you excede that threshold you fry the amp , some of them it is as low as 1v , and seeing as my Guitar by it"s self puts out up to 4v it allways seemed unsuitable .....


Cheers

[joecool85]

One thing about useing a Class D amp that I don"t like is that many have a certain threshold for the input signal , if you excede that threshold you fry the amp , some of them it is as low as 1v , and seeing as my Guitar by it"s self puts out up to 4v it allways seemed unsuitable .....


Cheers

Interesting.  I hadn't heard about this, however, I don't know much about class d amps on the whole anyway.

[Minion]

One thing about useing a Class D amp that I don"t like is that many have a certain threshold for the input signal , if you excede that threshold you fry the amp , some of them it is as low as 1v , and seeing as my Guitar by it"s self puts out up to 4v it allways seemed unsuitable .....


Cheers

Interesting.  I hadn't heard about this, however, I don't know much about class d amps on the whole anyway.

Yea , I was looking at getting one of those 4 x 100w tripath Class d modules from sure electronics for a quad ouput bass amp I wanted to build but after a reading the documentation for the modules it had a warning about excedeing a 1v input voltage and that it could results in failure ... I suppose you could build some sort of voltage divider network to bring down the input voltage to a reasonable level for the class d amp ....

[J M Fahey]

Hi Minion.
That bit about a signal over one volt killing an amplifier (even if Class D) sounds strange to me.
It *did* happen on some germanium power amps in the early 60's .
Can you please post some link to that page?
I guess they might have said something not very clearly which *could*  be understood so, but probably they were meaning something else.
And even if that were so, a couple clipping diodes just before the amp's input would prevent it.
Thanks.
Juan Manuel Fahey

[Minion]

Actually I can"t remember if it was exactly 1v but it was some low voltage ....


this is the module I was talking about

http://cgi.ebay.ca/2-100W-4-TK2050-Class-D-Audio-Amplifier-Board-improved_W0QQitemZ250524283772QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item3a5469337c


if you go down and look at "Warning #3" it says not to use a Preamp because to high a input voltage will fry the chip .....

[joecool85]

Actually I can"t remember if it was exactly 1v but it was some low voltage ....


this is the module I was talking about

http://cgi.ebay.ca/2-100W-4-TK2050-Class-D-Audio-Amplifier-Board-improved_W0QQitemZ250524283772QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item3a5469337c


if you go down and look at "Warning #3" it says not to use a Preamp because to high a input voltage will fry the chip .....

Sounds like they just have it set up so you don't need a preamp due to high voltage multiplication.  But you could easily attenuate the signal after the preamp if you wanted to shape your tone etc.  Also, something to consider is that a guitar doesn't put out much signal compared to say, an mp3 player.  So it might well be that you DO need a preamp for guitar, but you don't for other audio sources.

[J M Fahey]

Hi. I just checked the link in EBay.
All I can say is that I'd rename the sellers "UN"Sure Electronics and I'd avoid buying advanced products from them.
They sound (write) very Chinese, which by itself is not bad, but they build a wall of excuses to avoid honoring their guarantee and the money back clause.
They claim that the amplifier will be damaged by:
1) "Low-quality pots" 
2) "Unstable (¿non stabilized?) power supply"
3) "Use of a preamplifier" 
4) They seem to imply that they have no short-circuit protection.
5) "Heat problems", which sounds somewhat strange considering the high efficiency and the fan supplied.
Since you have to pay the return costs and probably can't get the 15U$S worlwide flat rate they do (and they might pay even much less than that), you might choose just not to ask for a refund.
Caveat Emptor : "Let the buyer beware".