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HIFI power amp discussions
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Author:  Yungman [ 21 Sep 2018, 03:01 ]
Post subject:  Re: HIFI power amp discussions

ILoveHiFi wrote:
2.5A results in about 58-60C in a 20C ambient
The SMPS is hot and the transistors are near thermal limit if you take into account of heat trasnfser limits

The amp swings +-2v to rails


Thermal management is a big issue for power amp. You don't have enough power of the SMPS. You peak current for each channel is 22V/8=2.75A. For stereo you can have the same signal on both channel at the same time, you peak current is 2 X 2.75 = 5.5A. Your SMPS might shutdown. That's the reason I started out with 10A supply. Then I still have a lot of cap as reservoir. That's why it turned out it's cheaper to use torroidal power transformer and do it the conventional way.

Particularly I am doing dual monoblock, that is each side of the amp is independent to the other side, Each channel has it's own transformer, it's own filter caps, totally separated from each other.

For class A swing to 22Vpeak, for 8ohm load, you need bias current of 1.375A minimum. for +/-24V, the dissipation is 48 X 1.375 = 66W/ch. Your chassis barely big enough. It will get very hot already. Your chassis is about the same size as my small one, I run about 60W heat, it's hot.

For +/-24V, you get 30W of class A power output into 8 ohm. That's the reason I do high bias class AB instead. I run 1A bias, that gives me 16W of class A power, and 58W of total power. My amp is low power for 8ohm, but I design the amps to be able to drive low impedance easily to 2ohm or lower. My speaker is 4ohm, so it is a 116W amp.

My big chassis is a 50W class A chassis, I can get 100W into 8 ohm or 200W into 4ohm.

Author:  ILoveHiFi [ 21 Sep 2018, 15:37 ]
Post subject:  Re: HIFI power amp discussions

I'm using two seperate 24v 4 amp supplies for left and right = 4pcs
It is duall monoblock.

+-22v peak to peak is satisfitying enough for most oscassionas but I do want to get booming louder. High sensitivity 101db 15inch speakers do get screaming loud and good, the room and furniture does shake and I like

Not allot of output caps but 2200uF on each supply. Some SMPS noise but neglitbly small after feedback which cancels the noise out.
Better op amp front end will deffintly increase high frequency gain and cancel out noise even more.

Author:  Yungman [ 21 Sep 2018, 16:04 ]
Post subject:  Re: HIFI power amp discussions

ILoveHiFi wrote:
I'm using two seperate 24v 4 amp supplies for left and right = 4pcs
It is duall monoblock.

+-22v peak to peak is satisfitying enough for most oscassionas but I do want to get booming louder. High sensitivity 101db 15inch speakers do get screaming loud and good, the room and furniture does shake and I like

Not allot of output caps but 2200uF on each supply. Some SMPS noise but neglitbly small after feedback which cancels the noise out.
Better op amp front end will deffintly increase high frequency gain and cancel out noise even more.


I am not knocking SMPS at all like I described before. I just said it's better to use beefier ones. I yet to read up SMPS to design one, I have too many new ideas on the amp, don't have time to get to that for a while. I can find traditional transformer rectifier and filter caps that can fit the chassis and cheap, so it's no hurry on this part. I am 3 designs behind, one I actually have pcb and no time to even try yet.

My next major design is error correction on OPS, then I have a 70W tube amp that I already designed and many parts ordered, still sitting there. I am retired, but this is like a part time job already. Have an idea and design is easy, It's a lot of work building the amp. I am very nitpicking on how to build the amp. I am building amps that the construction better than most very expensive amps. I use big wires, all on terminal blocks, no soldering wires between boards and between different part of the amp. Everything screwed on, I can take the whole amp apart without using a soldering iron. It takes a long time to build one.

Author:  ILoveHiFi [ 21 Sep 2018, 16:08 ]
Post subject:  Re: HIFI power amp discussions

Well beefier ones will cost me a fortune, the current ones does fine and I don't see any plorbem.
My current ones are very commonly avalible in china and dirt cheap.

I think maybe the big boys are using full/half bridge smps converter so the ripple is much less than my common avalible ones which are fly back. So you recomend me those.

Time constaint is deffintly a large factor in any audio research project, therefore I do things as quick as I can before I get old. I keep research builds and actually quality builds(taking time) totally seperate.

I have so many research schematics that I can think of and I can contiune another 3+ moths every day doing hifi only for whole day and not run out of ideas. I am lacking time.

Author:  Yungman [ 21 Sep 2018, 16:16 ]
Post subject:  Re: HIFI power amp discussions

ILoveHiFi wrote:
Well beefier ones will cost me a fortune, the current ones does fine and I don't see any plorbem.
My current ones are very commonly avalible in china and dirt cheap.

I think maybe the big boys are using full/half bridge smps converter so the ripple is much less than my common avalible ones which are fly back. So you recomend me those.


I have no idea, I never really look too deep. The two in the picture were from China. They are cheap and I use it long enough to trust them. If I remember correctly, it's about $24 each. 24V 10A. Very common and cheap like dirt. I don't have problem with noise. If you do 24V, you have tons to choose from on ebay, their size can fit the chassis also. I want 32V, only one I can find is Meanwell. I have very good luck with SMPS from China on ebay.

As I said, the Meanwell 27V 10A is too big, I tried so hard to try to fit into my chassis, I just couldn't. They tend to be too long. That's why I need to design and layout the pcb the right dimension to fit. So go to the back burner.

If you have a chance, go on ebay and get a bigger one, you'll thank me for that. also, you can crank it up to about 27V to get higher power.

https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2380057.m570.l2632.R2.TR12.TRC2.A0.H0.X24V+p.TRS0&_nkw=24v+power+supply&_sacat=20697

Author:  ILoveHiFi [ 21 Sep 2018, 16:21 ]
Post subject:  Re: HIFI power amp discussions

I do have one of the big boys at 24v and 480w which powers my peltiers for computer water cooling, inside shows if rember correctly either 2 or 4 power mosfets meaning its full bridge converter or half bridge, so ripple is same as buck boost much lower than fly back.

The 24v 4 amp ones cost about 10-12usd per pice on aliexpress that is with shipping combined. but from taobao china only 20-24rmb each.
 
480w is only 68-90rmb each on taobao

Author:  Yungman [ 21 Sep 2018, 18:03 ]
Post subject:  Re: HIFI power amp discussions

Where do you live? What is rmb?

Can you give me the Taobao site. I want to look at them also.

Author:  ILoveHiFi [ 21 Sep 2018, 23:36 ]
Post subject:  Re: HIFI power amp discussions

Taobao site is for Chinese only can't buy overseas, RMB is chinese currentcy.

Author:  Yungman [ 22 Sep 2018, 00:25 ]
Post subject:  Re: HIFI power amp discussions

ILoveHiFi wrote:
Taobao site is for Chinese only can't buy overseas, RMB is chinese currentcy.


Where are you living, I thought you are in Canada East Coast. You're in China?

Author:  ILoveHiFi [ 22 Sep 2018, 00:26 ]
Post subject:  Re: HIFI power amp discussions

I'm in New Zealand

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