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BPA300 Round 2
BPA300 Round 2
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Old 16th September 2011, 12:45 AM   #1151
Munga is offline Munga  Australia
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tryonziess thanks so much!
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Old 17th September 2011, 05:59 AM   #1152
kuldeepsingh is offline kuldeepsingh  India
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excellent work buddy.. get a nice enclosure for the beauties.
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Old 17th September 2011, 10:27 AM   #1153
tryonziess is offline tryonziess  United States
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It is a really nice feeling when you spend so much time hunting down just the right set of parts and getting everything soldered into those small SMD spaces hook up the juice and it works. I never get tired of a job without smoke.
It is rare that I come across someone at work or anywhere around here who has a true productive hobby. Aside from shooting poor defenseless animals and watching the reruns of the Beverly Hillbillies most of the crowd around here has no hobbies at all. Just spend all of your money on Friday night and listen to music in the car.
I only wish I could have started this many decades ago when my learning abilities were somewhat more acute.

I shall see if I can find those pcb's and I will wait for the chassis and cabinet design to be posted. Truly nice job.

Tad
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Old 18th September 2011, 08:24 PM   #1154
regiregi22 is offline regiregi22  Europe
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Quote:
Originally Posted by tryonziess View Post
There are also some good builds utilizing the LME frontend chips which gives you the choice of monolithic frontend and discrete output section. These also have fabulous specs. You can use the same power supply and experiment.
Could you provide us with some examples? I remember to have seen something but, what would you recommend?
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Old 18th September 2011, 08:57 PM   #1155
tryonziess is offline tryonziess  United States
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I can only recommend what you might be comfortable with budget and skills wise. Panson (google pansonaudio) has some nice inexpensive boards which he designed that will get you going in the right direction utilizing the LME498xx series from National. The major advantage, in my opinion, to the LME series over the monolithic 3886 is footprint space for heat transfer. Using 4 mosfet or bjt output transistors to construct your project from the LME frontend will give you a much cooler running amp -- this being my experience.
The LM3886 has to cool the entire frontend and output section on it's small die. The LMExx series also offers Class A operation in one of it's offerings.

I just got back upstairs after sorting through my plethora of stuff. Rehashing this thread has gotten me in the mood to finish some of these projects. The weather has also made a nice contribution. I need to start winding up some plus/minus balancing transformers to split up my single end signal.

If my memory serves me correctly I sent out several hundred of these BPA pcb's for a gentlemen in England who ran into some trouble. Peranders took over from there and many folks got to finish there builds. Time sure goes by fast.

One more reminder. Alexw88 who did such a splendid job with this layout chose to power his amps with approximately 25 finished D.C. volts. The published material states that higher voltage is usable, however, this is a bridge/parallel design. Mucho more heat to deal with.

If enough interest is out there we could have a few hundred boards made up and distribute them around the globe as before. I do not know if there is a current supply of these boards available at the present. They are not expensive to have made and the parts are few and inexpensive. A very nice project to get into chipamps with. The Jeff Rowland model 10 cost 6500 dollars. I checked this out last night. The BPA300 is a close exact copy electronically speaking. The chassis is another thing altogether.

Tad
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Old 18th September 2011, 09:53 PM   #1156
regiregi22 is offline regiregi22  Europe
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Well, i will show you some progress I've made around my BPA-300 construction. It's being made for a friend, as a no-mind-cost proyect, so everything is quite overspecified. It's encased as two monoblocks inside the same enclosure.

Attached are some pictures of the materials,

2x 500VA 2x25vac ordered from toroidy.pl
4x 100.000uF 40v RIFA PEH200
16x 2.200uF 50v Panasonic FC
Hefty refurbished big heatsinks (from military equipment)
Other received stuff...
Attached Images
File Type: jpg a.jpg (325.5 KB, 258 views)
File Type: jpg cond.jpg (164.2 KB, 251 views)
File Type: jpg disipador.jpg (112.9 KB, 247 views)
File Type: jpg eee.jpg (80.7 KB, 242 views)
File Type: jpg c.jpg (276.1 KB, 240 views)
File Type: jpg e.jpg (292.0 KB, 55 views)
File Type: jpg d.jpg (343.8 KB, 48 views)
File Type: jpg b.jpg (319.3 KB, 47 views)
File Type: jpg comp.jpg (272.2 KB, 63 views)
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Old 19th September 2011, 01:39 PM   #1157
bcmbob is offline bcmbob  United States
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Hey tryonziess,

You got me thinking about the heat sinks so I went a little nuts yesterday. I think this will give both enough mass and air flow for all eight chips. The plate (10.25" x 3") and the thickest part of the modular pieces are .25" thick. I thought about mounting with fins up (as they should be) but it added too much height.

Click the image to open in full size.

Click the image to open in full size.

Will try to surface grind mating surfaces but I have some good thermal transfer tape as a backup.

Click the image to open in full size.

The HS will be mounted on posts but there is enough room to place a thin fan above or below if needed. I think top and bottom case vents will probably work.

Click the image to open in full size.

Click the image to open in full size.

With the BPA-150 tests completed, I've removed the in and out sockets to be rebuilt to match those on the dbx crossover. The board is 17" x 11" and eventually will be a metal mounting surface.
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Old 19th September 2011, 01:43 PM   #1158
udailey is offline udailey  United States
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BPA300 Round 2
Bob, sideways is correct it allows better airflow than straight up .
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Old 19th September 2011, 02:39 PM   #1159
bcmbob is offline bcmbob  United States
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Thanks Uriah, that's what I thought but I've read a bunch of posts promoting fins up as best. I'll stick with this. If it doesn't work I guess I could install a 3" chimney on top
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Old 19th September 2011, 09:45 PM   #1160
tryonziess is offline tryonziess  United States
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Where did you get those nice Rifa capacitors. I have always considered them to be at the top of the pile. They pack a serious charge. Mind me asking how much you had to pay.

I found that placing a nice thick piece of copper or aluminum on the top of the Lm3886 as they did in the Jeff Rowland helps smooth out the heat transfer. Also, one long strip of Kapton tape will cover all three chips fold up and insulate the top if you use the header pieceA of metal.

What is the board with the four rectifiers for. It has a large transistor at the back against the heatsink? Did you also, mount the film caps on the legs of the LM3886 chips for stability as recommended in the literature. Important.

What you going to use for the volume control? Let us not skimp here you are doing a good job.

Ain't this stuff fun. And it does not pollute at all. It is also legal.

Tad
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