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BPA300 Round 2

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#241
Rhysh,
What heat load are we going to have to dissipate in the regulated frontend. It will have to be at LEAST as large as the main 3886 sink. I like this idea. It will put a nice clean power source into the BPA 300. This should yield a superb amp.

Any chance of using mosfets for the reg frontend. I have about 400 of them laying around waiting for some purpose. They are also much cheaper than bjt -- in my neighborhood anyway.

Thanks for the hard work on this.
Tad
 
#242
tryonziess said:
Rhysh,
What heat load are we going to have to dissipate in the regulated frontend. It will have to be at LEAST as large as the main 3886 sink. I like this idea. It will put a nice clean power source into the BPA 300. This should yield a superb amp.

Any chance of using mosfets for the reg frontend. I have about 400 of them laying around waiting for some purpose. They are also much cheaper than bjt -- in my neighborhood anyway.

Thanks for the hard work on this.
Tad
Click to expand...


It depends on how hard you are running the amp, the heatsink will need to be large but not overkill, i will need to do some further calculations.

I will have a look at using fets, but the 3055's simulate really well, they are cheap aswell.

The new idea is to have the cap bank on a seperate PCB, so the regulator can be directly mounted onto a heatsink. I am now thinking 3 x 3055 per channel which allows for huge output current.
 
#243
Rhysh,
We might be getting into something really nice here. There has not been any really great stuff floating around since the AX thread.
This twist on a proven LM3886 design might turn a few heads when all is implemented.
It is common knowledge that the LM3886 can faithfully reproduce recorded music. I might have to move a few things over on the shelf and give this guy front row for awhile I have always liked the way my current BPA sounds it is just a little bit harsh at times. Maybe some super clean power will make an improvement.

Keep us tuned in to what you develop.
Tad
 
#245
rhysh said:
I am now thinking 3 x 3055 per channel which allows for huge output current.
Click to expand...
yes, that will help satisfy the current demand of a reactive 8ohm load. i.e. 200W into 8r0 and 8ohms.
The smoothing caps and decoupling normally satisfy the transient current demand, but the regulator is stuck between the load and the smoothing caps

I don't think three will do for 300W into 5.4ohms.
 
#248
I am interested, I have a pair on Conrad MF35-151.5 heatsinks (would those be enough to utilize for everything?) and a case from PAR Metal that I spec'ed out! I was just strating to figure out what do do for a PS, (as you have seen be tryig to figure out what makes a good cap for a PS in the other threads)
 
#251
mikesnowdon said:
It looks like the TP powerreg is up to the job 'as-is' just needs sufficient heat sinking on the reg's I believe. Just a case of incorporating that onto a PCB with smoothing and rectifier bridge, no?
Click to expand...


I have been reading over the thread, and it looks like it needs lots of tweaking to get it right, there is a lot of debait about which transistors to use, and also the use of capacitors. I will load the powerreg into the simulator and see what happens.
 
#252
Right, I'm starting to think about buying the other parts that I need for PSU etc. Can I just check that a transformer with dual 25V secondaries is sufficient?

That would put about 35V after rectification. Is that enough for both a simple unregulated supply as well as a regulated one, should I choose to upgrade later on?

Thanks.
 
#253
rhysh said:



I have been reading over the thread, and it looks like it needs lots of tweaking to get it right, there is a lot of debait about which transistors to use, and also the use of capacitors. I will load the powerreg into the simulator and see what happens.
Click to expand...


Cool.

Maybe contact Teddy Pardo and get his opinion on it too? I think he has a preferred BOM for the basic version, might need a couple of changes for the BPA though.
 
#254
Sjallog,
The 25 volt trannys will work but you will have to get rid of a lot of heat in only 6 devices with that much voltage. Though this is just my opinion I would try for 22 volt trannies.
The current BPA I have runs VERY hot at 34 volt rails with 25 volt transformers. I drive a line array with 20 speakers per tower at 4 ohm load. It gets real loud at three forths volume.
If you read the full writeup on Shine7.com about Alex's amps he makes mention of how hot his cases get. If you look at the actual area to be cooled on the rear of the chip you can see why there is a problem. You only have 6 devices and 300 watts to cool. There is just not enough surface area. It works but for how long.

I will make another set of amps from Rhysh's second group buy and I think 20 or 22 volts will be my choice for transformers.

Rhysh, With the regulator heat and output heat I am beginning to think backup fan cooling. For those hard rock moments.

Just my two cents. Tad
 
#257
Just giving it a read over..

It looks like there are two options im willing to go with, there is the standard TIP3055 method, or the powerreg.

I am reviewing both options, but trying to be time efficient at the same time as i want to get this amp built!
 
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