Burning Amplifier BA-2

[audiok]

That's similar to Salas' shunt regulator.

[AndrewT]

Originally Posted by audiok

Shunt regulator for BA2

which part of the BA2 is supplied by this regulator?

[Melon Head]

I am quite sure he is feeding the first two stages with the shunt reg

[Chad]

I've put a B.O.M together for a stereo version of the BA-2. I've attached the file. If anyone sees an error please let me know so I can fix it. I've got finish filling it in with prices, who get my parts from etc. I.E. Blues for 2SJ74's.

This is my first build in several years, so I'm little rusty. I'm not sure if the resistors that don't have the wattage next to them on the schematic should be 1/4 or 1/2 watt.


All the caps on boards and post transformer should probably be 40vdc or better.

Chad

P.S. Nelson thank you for donating your time and designs to help us DIYers. Now I'm gonna have build a converter after I finish this amp.

[The Space Egg Corp]

[QUOTE=Zen Mod;2255643]you can always use Serbian nickel perfect alloy

Great move Zen Mod. I never thought about making my own washers out of spare change before. Any idea of the c/w of those chunky Serb numbers?
English 2p's could be good, although I was told once that destroying currency could land you a stint in the Tower of London from the Queen. Never mind I won't tell her if you don,t. I am definitely going to use 2p's on the trannys in my new amp build. Cool tip Zen Mod.

Cheers Holmes :2 c:

[The Space Egg Corp]

Originally Posted by audiok

I have 8pcs of 33,000uF/40Vdc capacitor. And I’m going to build BA2 amp with this. Please tell me what max AC voltage should I use ? Thanks.

How you doing audiok? I like your avatar. This is how I always do my PSU's

The simple and reliable way to get DC volts from AC for this type of PSU is:
ACvolts X 1.41 = DCvolts
18volts X 1.41 = 25.38volts
20volts X 1.41 = 28.20volts
25volts X 1.41 = 35.25volts
I shall be using transformers with 18volt secondarys giving 25.38volts.
Nelson reckons 7watts of heat/PSUvolt.
So the amp output stage will dissipate 177.66watts of heat/channel.
The amp will have 12 MOSFET's/channel.
The transformer will also produce significant heat, some thing often overlooked. Check my post on transformer cooling in BA-1 forum.

All the best to you Simon

[audiok]

Originally Posted by The Space Egg Corp

How you doing audiok? I like your avatar. This is how I always do my PSU's

The simple and reliable way to get DC volts from AC for this type of PSU is:
ACvolts X 1.41 = DCvolts
18volts X 1.41 = 25.38volts
20volts X 1.41 = 28.20volts
25volts X 1.41 = 35.25volts
I shall be using transformers with 18volt secondarys giving 25.38volts.
Nelson reckons 7watts of heat/PSUvolt.
So the amp output stage will dissipate 177.66watts of heat/channel.
The amp will have 12 MOSFET's/channel.
The transformer will also produce significant heat, some thing often overlooked. Check my post on transformer cooling in BA-1 forum.

All the best to you Simon

Dear Simon,

Thanks your advise.
Now I using transformer 600VA with 20VAC secondary. It produces around 23.6VDC. Bias current at 3A per channel.

[generg]

I am a little bit in trouble....


in BA-1 we have only one cap that influences the sound between front end and output stage C203 10uF going to the upper IRF240 bank. (lower bank only CCS)

But in BA-2 we have two caps that influence the sound C203 and C101, like in F4!?

So it is useless to invest in C203 much money when C1o1 is of low quality? Should both be of the same quality? Could I also take 2 x 220uF like in F4?

Any answer before I invest to much money in C203 welcome!!

THX

[juma]

Originally Posted by The Space Egg Corp

... The simple and reliable way to get DC volts from AC for this type of PSU is: ....

Sorry, but it doesn't work that simple in real life - there are loses: voltage drop on diodes in rectifier, ESR of the filter capacitor, transformer's voltage sag under heavier load - not to mention electrical network instabilities...
That's why you'll never see 25.38 V DC coming from 18V AC - as soon as you load it it will be about 23V DC at most.


Audiok, you filter caps might have a bit higher ESR or your transformer sags a bit more, but generally, the values you mention are acceptable with 3A load.

[JimM]

Is a zobel necessary for the BA2 output stage to keep it stable? I would think not since it is not in the feed back loop. Also has any one built a BA2 yet? If so what were the results?