DIY Amps

[MrBoat]

Just going to put this here as a recent topic of interest. I have ordered one of the smallish chip amps from Parts Express, along with a power supply just to mess with.

This is the board.
http://www.parts-express.com/sure-electronics-aa-ab32189-2x100w-tda7498-class-d-amplifier-board--320-303

This is the recommended power supply.
http://www.parts-express.com/mean-well-mw-nes-200-24-24-vdc-88a-200w-regulated-switching-power-supply--320-3140

These class D amp boards are well ahead of my time so I am curious, especially after having used the Behringer 3000dsp amp, which is also a class D amp.

Again, as with many things Audioholics influenced, there ends up this inevitable 'sucking' sound around my wallet at times at the mere mention of audio desires. Still, this is all funds I used to blow on consumables such as cigarettes just a few short years ago so, that's my justification. No money spent on hardware is anywhere near a category of foolishness as that 35 year expenditure.

All it takes is some audio gearhead to post some links and we're off!

Will see where this goes, and so as not to clog up the thread upstairs as this evolves from one day to the next. . . .or not.

 

[TheWarrior]

I'm still content with subwoofer building, and hopefully later this year, speaker building. Amps are pretty cheap and reliable these days, although I totally relate on craving a true DIY system!

 

[KEW]

Regarding class D amps, I think they are showing up in enough places these days that they must have worked out all of the kinks.
For example, I recently saw Presonus R65/R80 pro audio monitors which have a class D amps for the AMT tweeter (as well as the mid-bass driver).

Air Motion Transformers from Mundorf

Mundorf offers today's largest selection of Air Motion Transformer (AMT) tweeters worldwide. The different lines were developed for certain applications and requirements. All Mundorf HiFi AMT tweeters have two superior key properties: excellent transient response and outstanding low distortion ratio. The differences lie mainly in their frequency ranges, sound pressure levels and dispersion angles.

from the Madisound site:
https://www.madisoundspeakerstore.com/amt/

My point is these tweeters offer a lot of detail, and to produce a monitor for the recording studio using an amp which had any audible flaws would be just dumb. These guys do nothing but listen critically all of the time.

That said, there may still be some Class D products out there with the flaws of yesteryear.

 

[lovinthehd]

I've always admired this diy amp build.

 

[slipperybidness]

@lovinthehd
@KEW

Hypex N-Core seems to be the king of the Class D hill!

Guess what, ATI is about to release a line of Class D amps, using linear PS, and using the Hypex N-Cores!!! That info is in the new S&V Mag, but it hasn't posted to their website yet.

Then, of course, I really think the Crown Drivecore Class D amps are bulletproof.

 

[MrBoat]

I'm still content with subwoofer building, and hopefully later this year, speaker building. Amps are pretty cheap and reliable these days, although I totally relate on craving a true DIY system!

So far, I've built two sets of speakers and a sub. Many more I would like to build. The problem being, these projects start eating up cu. ft. of living space rather quickly. Unfortunately for me, I peaked early with the Tempests. Those speakers would be really hard to top from here on out. Great for initial end goal, bad for a hobby that depends greatly on the DIY aspect.

These amps are tiny and can get really involved for their size. This does come with a caveat. The amount of time spent with regard to actual audible differences if you happen to be of a practical/logical mindset to start with.

Still, I spent two hours reading about these poor bastards mod'ng one of these amps. The great part being, it tends to expose some of the brilliant minds that are into this sort of thing. Tortured as they may be.

 

[MrBoat]

Regarding class D amps, I think they are showing up in enough places these days that they must have worked out all of the kinks.
For example, I recently saw Presonus R65/R80 pro audio monitors which have a class D amps for the AMT tweeter (as well as the mid-bass driver).

from the Madisound site:
https://www.madisoundspeakerstore.com/amt/

My point is these tweeters offer a lot of detail, and to produce a monitor for the recording studio using an amp which had any audible flaws would be just dumb. These guys do nothing but listen critically all of the time.

That said, there may still be some Class D products out there with the flaws of yesteryear.

Some of the little chip amps that come with pc desktop speakers, what they manage to get out of those is a sign of just where this has gone over the years. Car audio, yet another.

 

[MrBoat]

I've always admired this diy amp build.

I will check that thread out tonight.

This is a rather impressive play-by play of a really nice build.
http://www.diyaudio.com/forums/chip-amps/265827-lm3886-fullrange.html

 

[MrBoat]

This site here caused me some research around the net. As much as the idea of hardwiring my own chip amp intrigues me, I like the idea of PCB kits too. And as tiny as these things can be, there is nothing that says you can't do both. Of course there are others.

http://chipamp.com/

 

[MrBoat]

@lovinthehd
@KEW

Hypex N-Core seems to be the king of the Class D hill!

Guess what, ATI is about to release a line of Class D amps, using linear PS, and using the Hypex N-Cores!!! That info is in the new S&V Mag, but it hasn't posted to their website yet.

Then, of course, I really think the Crown Drivecore Class D amps are bulletproof.

You're another one of these damned Audioholics that can cause people to do/spend more than they intended while stumbling into this site. Audioholic "Ninja" indeed. Lovinthehd, and the other member, ski2xblack too.

Building the Tempests and the subwoofer were monumental milestones. And now I have a sensitive pair of speakers that happens to be one of the favorable ingredients for these chip amp builds. I still can't get over the amount of sound that comes out of these speakers with just a couple watts. Totally upended my understanding of audio and power requirements.

 

[slipperybidness]

I will check that thread out tonight.

This is a rather impressive play-by play of a really nice build.
http://www.diyaudio.com/forums/chip-amps/265827-lm3886-fullrange.html

Thanks, I'll have to read that thread when I get some time.

I've bought stuff from this guy, but I've never bought any of his kits, just some chips and PCBs.

http://chipamp.com/

I believe he did a lot of his work with the guy from Audiosector. But, Audiosector tends to be very minimalist design, honestly I just don't agree with some of his design decisions.
http://www.audiosector.com/

Using pre-fabbed PCBs is nice. I do want to do my own custom PCB etching eventually.

And, note that a PCB can be a good starting point, you can still do some "circuit bending" by modding the PCB or adding your own board, etc.

 

[MrBoat]

Thanks, I'll have to read that thread when I get some time.

I've bought stuff from this guy, but I've never bought any of his kits, just some chips and PCBs.

http://chipamp.com/

I believe he did a lot of his work with the guy from Audiosector. But, Audiosector tends to be very minimalist design, honestly I just don't agree with some of his design decisions.
http://www.audiosector.com/

Theirs kind of starts where the original Gaincard kind of leaves off though, right? Obviously, this has evolved greatly from there it seems.

I only have about two-three nights light reading into this. I haven't really gotten past the whole power supply part yet. This weekend I will have less distractions here in which to try to make some heads/tails of this without crowding into my sleep time so much.

Still, the idea of building from a rather inexpensive kit to get feet wet can be a good way to get over the hump with the understanding of these kinds of things or familiarity with what certain parts do without trying to retain it mentally at first. Seems as if the years and all the other information I have stored has diminished my attention span a little.

 

[TLS Guy]

I would get a 36 volt power supply and not 24. 24 volts will just about give you 100 watts. A 6 ohm speaker would require exactly 24 volts, peak to peak. However the continuous power will actually be the root mean square of 100 watts. With 24 volts that unit will only deliver 70 watts at peak into 8 ohms.

You can work out how much power you will get from a given voltage and speaker impedance. The amp can not output a higher voltage than the power supply. Power is the square of the voltage divided by the speaker impedance. Now that is for DC. However sound is AC so for a sine wave the continuous power will be the root mean square of what you calculate using the above formula.
So for a sine wave driving a 6 ohm load with a peak to peak voltage of 24 volts, the continuous RMS power is 100/1.4 which is 71 watts.

You will get much better performance if you use a 36 volt power supply. A 36 volt power supply would give you 100 watts RMS into an 8 ohm load. That would be well within the maximum current rating of the amp.

You had better make sure that the speaker impedance is actually six ohms or above. A four ohm speaker will exceed the current rating of the amp by 50%.

If you don't know the curve, I would buy a DAT 2 woofer tester from parts express. Now you are getting more involved that unit is a basic part of your tool kit.

 

[MrBoat]

I would get a 36 volt power supply and not 24. 24 volts will just about give you 100 watts. A 6 ohm speaker would require exactly 24 volts, peak to peak. However the continuous power will actually be the root mean square of 100 watts. With 24 volts that unit will only deliver 70 watts at peak into 8 ohms.

You can work out how much power you will get from a given voltage and speaker impedance. The amp can not output a higher voltage than the power supply. Power is the square of the voltage divided by the speaker impedance. Now that is for DC. However sound is AC so for a sine wave the continuous power will be the root mean square of what you calculate using the above formula.

You will get much better performance if you use a 36 volt power supply.

I actually read that and did do the math exercise and somehow I was coming out with around 25-30 watts RMS on a good day. But I really didn't want to spend more on a power supply for this amp. I honestly thought it was/is a toy. I was expecting to be surprised if it actually worked. It was an impulse thing.

This was all right on the cusp of looking into other chip amps and DIY power supplies as part of it. Thinking, I would hate to spend too much on one if I was just going to end up building my own after the fact.

I appreciate your input, TLSguy. I can always upgrade the power supply if I decide to do something with that little amp or if it turns out to be worth doing.

 

[TLS Guy]

I actually read that and did do the math exercise and somehow I was coming out with around 25-30 watts RMS on a good day. But I really didn't want to spend more on a power supply for this amp. I honestly thought it was/is a toy. I was expecting to be surprised if it actually worked. It was an impulse thing.

This was all right on the cusp of looking into other chip amps and DIY power supplies as part of it. Thinking, I would hate to spend too much on one if I was just going to end up building my own after the fact.

I appreciate your input, TLSguy. I can always upgrade the power supply if I decide to do something with that little amp or if it turns out to be worth doing.

I have revised and extended my remarks as they say in Congress. Look at my last post one more time.

 

[ski2xblack]

Hmmm, seems that I have a Tempest impedance graph somewhere but can't find it...double check with Erich if you don't want to get a woofer tester and measure it yourself...I don't think they fall more than a tiny bit below 8, but otherwise above that across the board, so I think you'll be fine.

 

[MrBoat]

I have revised and extended my remarks as they say in Congress. Look at my last post one more time.

I read some reviews that complained of noise, distortion or both using the 36V supply. Since it's kind of apparent that my speaker building days are not over (don't need any more large ones), it will not surprise me if I build some smaller, super efficient speakers to pair with this amp adventure. I actually have two pair of speakers that are above the 90's in sensitivity, and an older set of Sansui (SP-X8000, if my memory serves me right without digging them out of the closet) that need surrounds that were closer too 100, IIRC.

 

[MrBoat]

Hmmm, seems that I have a Tempest impedance graph somewhere but can't find it...double check with Erich if you don't want to get a woofer tester and measure it yourself...I don't think they fall more than a tiny bit below 8, but otherwise above that across the board, so I think you'll be fine.

They are advertised as 8 ohm speakers on the site.

 

[TLS Guy]

They are advertised as 8 ohm speakers on the site.

What a manufacturer says the impedance of his speakers are means nothing. The vast majority of speakers these days are 4 ohm, even though advertised as 8 ohm

 

[MrBoat]

What a manufacturer says the impedance of his speakers are means nothing. The vast majority of speakers these days are 4 ohm, even though advertised as 8 ohm

I can believe that with manufactured units, but the Tempests are DIY and a bit more hands-on with the developers of the kit. I will research it at any rate, per your suggestion.