Sure-Electronics.com class d amps

[v-bro]

P13502-ND Panasonic choke 10uH price for 100+ is 0,73EUR.

 

[Tekko]

These amps work at a mere 250-400KHz so you need more like 30µH.

Another good idea would be winding both coils for one channel on the same core, this halves the amount of turns needed for each leg of the bridge and it also saves some room, having one core instead of two per channel.

 

[v-bro]

These amps work at a mere 250-400KHz so you need more like 30µH.

Of course! I didn't know the switching frequency of this amp, I merely copied what I have found before for a Tripath amp....

Another good idea would be winding both coils for one channel on the same core, this halves the amount of turns needed for each leg of the bridge and it also saves some room, having one core instead of two per channel.

Just like the chokes on AMP9-B (and several more 41hz amps...)

 

[v-bro]

41hz amps are using Amplifier/Audio chokes, made by Sagami, Japan.
The most important parameter is that the inductance is independent
of current (up to the rated current) and that resistance is low.

 

[col]

would something like this do it?

http://jaycar.com.au/productView.as...&pageNumber=&priceMin=&priceMax=&SUBCATID=883

only problem, to buy 8 of them is almost the same cost as the amp!

Hope my 2 amp9-basic arrive soon.

 

[col]

Inductor noise?

Something interesting to report.

I took a couple of inductors out of a dead computer PSU and unwound-rewound one of them with two lots of 10 turns, so 2 wires each wound around the core 10 times. Soldered it back onto the PCB and put a signal through it. There is NO noise. Trouble is that it will only play part of the frequency range probably around 1khz up. I guess I got the amount of turns wrong or the core is too big or something. The interesting thing is that from 1khz up before is where most of the white noise was. It is completely gone. Could this be the right direction?

Picture:

http://pix.minirig.org.au/main.php?g2_itemId=288

 

[Möter]

That's an awesome finding col, Tekko! I'm quite annoyed of the noise since now the beeping is gone (you better don't ask what caused it. Stupid me. ), because it's very noticable in quite parts of music.

If I'd get one of the toroids suggested by you, Tekko, which amount of turns would it require for each leg and is your suggestion still valid if I use one core for both legs?

 

[v-bro]

OK, but do you still have good high frequencies?

The core you're using is from a common mode choke, that material has far too much permeability and will give a far too high value in uH. A core like that is likely to saturate too quick and get VERY hot after a while....

It is a good find on the other hand, if there are still high frequencies than you can try other coils, I'm pretty sure Jan (from 41hz) won't mind to send toroidal cores and enamelled wire to wind coils yourself that ARE suitable. Just mail him....

 

[djk]

Try hooking your coil up with the correct phase if you want some bass (reverse one set of ins and outs).

 

[Tekko]

The core you took out of a power supply is a dc filter core (yellow with white rim) is not suitable for class d, losses are far too high, you will notice the core getting hot after a while.

The core i suggested is a super high quality iron powder core with super small losses.

For calculating the turns theres this handy dandy claculator proggy: Mini ring core calculator, it can only calculate a single winding inductor, but take the turns you get and divide by two.

Then you wind it in the same way as a common mode choke, like this: http://www.tubecad.com/2007/02/05/common-mode_choke.png

 

[col]

Just tried reversing 2 of the connections, think I lifted a track though as that channel doesn't work now. moved it to another one. I think I'm getting more frequency now but heavily attenuated. I have the volume of my input up as high as it will go and there is hardly any volume coming out of the speaker. when i disconnect the rca I can hear very slight hiss

Iv'e noticed that its getting closer and closer to the junk bin

 

[big russ]

I've got one of these amps too and keen to reduce the hiss a bit.
Are these inductors suitable?
http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=6171322

 

[kstrain]

Unless I've missed something, nobody has shown how to reduce the hiss (in a working amplifier).

Are we sure it is not just the intrinsic noise at the input multiplied by the (quite high) gain? The noise is quite white.

Ken

 

[Bearman]

I believe you are possibly right Ken. I have replaced the inductors on one channel, and it doesnt change a thing. If we can just figure out which one is the gain resistor.

 

[col]

I've got one of these amps too and keen to reduce the hiss a bit.
Are these inductors suitable?
http://uk.rs-online.com/web/search/...oduct&R=6171322

Big Russ, those inductors only have one winding. It would be difficult to get two of them in the space where the old inductors are. Also, I don't think it will cure it of white noise. My last experiment with the Inductors wasn't very successful.

My 41hz amp9s have arrived now. I'm going to focus on them. If anyone wants my SureElectronics 4*100w for testing email me and I will drop it in the post to them. It's been hacked a bit and is down one channel as I lifted a track doing the inductor experiments. Still has another 3 to play with though. Would be good for testing, better than wrecking a new one.

 

[Tekko]

I could see what i can do with it.

 

[e_fortier]

Eventually more power from Sure Electronics

Hi,

Just to give you the heads up.

I sent a question to Sure Electronics about having a 50W stereo amp and this is what they answered.

------------------------------------------

Dear Sir,
Thanks a lot for your letter.
We are sorry that we do not have a plan to build the amplifier in about 50 watts.
We have a plan to make a more powerful one.
It would be about 500 watts.
Don't hesitate to contact us if you have any questions.
Best wishes.
Sure Electronics

-------------------------------------------

Hi,

I recently purchased a few amplifiers based on Tripath TA2024 (AA-AB012) and they sounds very good, thank you.

The other amplifier you have are rated 2x100W or 4x100W. (Size about 150mm x 150mm)

I have noticed that you also have one amplifier using the MPS7720 rated 8watts/4 or 8 ohm

My question : Are you planning in building other amplifer with medium power, maybe around 50W ? I'm asking you because MPS also has an IC which is MP7782 which gives you 50W at 4 or 8 ohm. I'm not affiliated in any way to MPS, I would just like to know if this is something you are planning in the future.

Thank you in advance for answering my question.

Best regards,
Eric Fortier

 

[TheMG]

Are we sure it is not just the intrinsic noise at the input multiplied by the (quite high) gain? The noise is quite white.

That would be my guess too. Unfortunately the gain of the amplifier as far as I can tell is internally set to an absurdly high value. Too bad, it would be a very respectable low-cost amplifier if it wasn't for the noise, and it could be as simple as lowering the gain.

I haven't measured what the gain actually is though. Maybe I'll do that. But it's definitely very high.

 

[col]

Tekko, did you want it? Iv'e taken the heat sink of it and put it on my amp9-basic (which is totally quite) apart from that it is good to go. Shouldn't cost too much if i just drop it in an airmail envelope. Email me your address. Although from what TheMG and others are saying now it seems to be the gain set too high internally on the chip. Might not be much you could do with it.

 

[Tekko]

I have other heatsinks.

I´d prefer not to publish my adress here, but i cannot send email to you since you have stated not to show your email.