DIY F2 clone

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Here is some work in progress.
Toroid is a 250VA 18+18V. Military grade of course. ;)
I would have preferred a bigger one but could not get my hands on it.

Fins are recycled from an old Kustom amp, 16.5 x 12.3 cm.
Wine is a cheap Cabernet, better pictures to follow.

/Hugo
 

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SCD

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Off Topic a bit

My fonkens and bifonkens sound best with my little EL84 amp. They pretty much suck with my Cambridge Audio SE500. They are not bad with my MiniA (but it has a hum).
I think a well exicuted current source amp will be the ticket. Nelson's article on fullrange drivers and amps is great, cause he spends time talking about the Fostex drivers.
Good luck

Nice P to P by the way.
 
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Obviously, I must have done something wrong.
This is the square wave at +/-1Khz, speakers attached, low output power.
I would be thankful if someone could tell me how to set P1. On a certain point, bias is set at +/- 2.7A. I can still increase P1 but bias stays put.

/Hugo
 

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Thanks Steen. Done. :)

I used very common components, no 1% resistors except R3 which is 47 ohm instead of 47.5.
At the source of Q1 I attached a 7W 0.68ohm and the resistors R23..R26 are replaced by 3 X 0.22ohm.
I can't imagine that this would affect the square wave that much. Or is my imagination off track? :)

/Hugo
 

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steenoe

steenoe

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Looking at your picture, those Mosfet's are too close to the top of the heatsinks. I dont mean to be rude or something, but my best guess is, that they will run too hot in that position! My rule of thump is, one third up from the bottom!! BTW turn them upside down.

Steen:)
 
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Rude? I wouldn't even think you could be rude.:)

I could turn the whole construction upside down -I mean the heat sinks- without changing anything. Then, the center of the mosfets would be at 1/4 of the bottom and the pins would point upwards. But why would you turn the mosfets upside down?

/Hugo
 
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hugz

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Hugo, your progression looks nice. how long did it take? What are the rating on those heatsinks, and how hot do they get?

A general question for everyone.. is 300VA transformer good enough?

Also, how important is mosfet matching? If i want a decently matched pair of mosfets, how many should I buy?
 
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I don't know the Rth of the heats sinks I used but found a nice calculator online.
http://www.frigprim.com/
Think in terms of +/-30W per mosfets to dissipate.

As I did everything PtP, it's a constant improvising how to place each part. I like this approach for simple designs because it's much more fun than plugging parts into PCB holes. Sure it takes more time. I guess it took about a whole day spread over a week to assemble.

I used a 250VA transformer and it gets warm but not excessive. 300VA is enough to be real safe.
As for the mosfets, I don't believe any matching should be done. I selected the gain device for highest transconductance.

/Hugo
 
Fuling

Fuling

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So, increasing C4 to 15000uF is enough to get a nice slow startup process even if the rail voltage comes up instantly?
That´s interesting news for a project I have in mind, I want to get as high rail voltage as possible (CLC-filtering) out of my surplus transformer so I don´t want to waste 4-5V across a cap multiplier.
 
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