F5 power amplifier

Dougie085 said:



Did you wind your own transformers?
No, ;) I found some high quality 20V / ~200Va surplus toroids so I bought a small pile of them for 10 bucks each.

flg said:

Did you measure with a 4 Point measurement? Typically a handheld will be about 1 ohm with the leads shrted together
;)
I used my "dead-short" reading as "0". Subtracting that number from my final reading. It was the best I could do :)

I'm heating up the iron now...

7/10

Oh and Magura, Incredible!, for what application?
 
apassgear said:
This is iteration V2 of the previous layout (post 235) now we have the FET’s spread out that may suit other builders.

If some one is interested in building any of the two versions just PM me and I will prepare pdf files suitable for etching.

Though pin marks are correct please take in consideration that the case outline of Q1 or Q2 could be reversed on one of those since I didn’t look up the spec sheet.

Read also post 263 for other details.

apassgear, gimme a copy pls as PM sent !
thanks a million
 
Dougie085 said:
minimum size transformer for a monoblock

This isn't an SE, but a PP Class A amp of a mere 25W/8 continuous.

With a constant power draw of <65W you can easily get by on a decent 160VA without any hum.
A common 160/180VA toroid is roughly 1/3" less high than a 225/250VA but has an identical outer diameter, there's hardly case dimension saved with the little one.
A 250VA has 1% better regulation, no benefit there as a rail level of 24Vdc requires 35V caps anyway.
Price tag difference for the 250VA is less than $10 extra, for a few bucks more you get less rail sag and a lower donut temperature.
My Papa sez 6 Amps continuous : 6A x 18Vac x 2 is less than 250VA.
Much higher than the 250 is somewhat irrational as a single-pair output stage only handles 300Watts dissipation Max.
Me rule of pinky finger is not to pick a PS with more continuous spunk than what will kill the output stage.
 
So the F5 does 25W/8ohms? Does it change much at 4ohms? My friend that originally showed me it had said it was like 50watts but maybe that was 4 ohms or maybe he just figured it wrong? Could you use 2 amp boards and run them balanced to get more power? Or would it be better to just add more output devices? Or maybe your just talking in general :D I'm not really sure how to figure out watt output or what not.
 
Just a note:

I will not send etching files to people that are not posting on this thread so just chip in and let us know you.

BTW, the etching files do have some mods including space for screw holes for board fixing and they are 1:1 scale when properly printed, the file shown on post 344 is not to scale.
 
Good point Tony

This is a cooperative discussion regarding the project. I do not think it is reasonable to jump ahead and bypass the mag. article. I am waiting for my copy of AxP to show up so I can offer some useful discussion, observation, or questions.

I am in 100% agreement with NP that it is important to support AxP magazine.

Once the mag. has been out for a while discussion will proceed at full speed.

Be patient there will be lots of interesting discussion