F4 power amplifier

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juma

juma

Member
Joined 2005
gbeard,
there's an easy remedy:
- drill some holes and put your input/output connectors somewhere around big PSU caps
- rotate the amp so that your top plate will become the front plate and the front plate will become the top plate. The toroid will be at the bottom and the heatsinks will become correctly oriented. Big caps may need some additional fixing/bolting.
 
BigE

BigE

Member
Joined 2008
neoinc said:
I am building a crippled F4 with BA3 for front end but not sure if i am doing it correct.

To remove the F4 input buffer, R1,R2,R3,R4,Q1,Q2,D1 and D2 are not soldered. The BA3 output will goes between C1 and C2 on F4. Is this correct?

For the output MOSFETs, I have both Fairchild and Vishay devices. Is there a preferred one for this amp?
Click to expand...

Itsmee said:
You do need D1 & D2, you don't need D3 & D4, you also don't need R24, R25, C3 & C4.

Yes
Click to expand...

P2 stays, with wiper connected only to P2 output?

To make fully balanced, can we then simply disconnect C1 from C2 and connect XLR -'ve to C1 and XLR +'ve to C2?
 
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G

gbeard

Member
Joined 2007
juma: gbeard,
there's an easy remedy:
- drill some holes and put your input/output connectors somewhere around big PSU caps
- rotate the amp so that your top plate will become the front plate and the front plate will become the top plate. The toroid will be at the bottom and the heatsinks will become correctly oriented. Big caps may need some additional fixing/bolting.
Click to expand...

juma, thanks for that suggestion. I may consider this as an option, but now I am thinking I may just unbolt them and turn them over. It will require a little more drilling, but that could be the easiest way out (other than living with it the way it is...)

Antoinel: Maybe it is all right the way you have it; provided the suggested heatsink temperature is not exceeded. As you have it, heatsink temperature is probably uniform through out versus some gradient with the alternate fins perpendicular to the chassis; because cool air enters at the bottom, rushes upward across the fins and emerges as a hot wind at the top. Fortunately, as you listen to your diyF4 you will be doing the experiment.
Click to expand...

I am running at 250 mV right now. I can hold my hand on the sinks for 5 seconds or so. The only measurement device I had on hand was an old candy thermometer. It works pretty good and showed a steady 50 deg C in the middle of the sink. I ran it at 275 mV for while, but it seemed to be too hot.
 
Zen Mod

Zen Mod

Official Court Jester
Joined 2003
zenmod.in.rs/
Paid Member
BigE said:
......
To make fully balanced, can we then simply disconnect C1 from C2 and connect XLR -'ve to C1 and XLR +'ve to C2?
Click to expand...

BigE said:
Answering own question.... no, that will give it a balanced input, but not a balanced output.

Seems like one should be able to disconnect the 240's from the 9240's to amplify each polarity independently....
Click to expand...

nope

it will give ya poof!

I had exactly same idea once (in public ! ) , but then it was really late night (early morning) and I was thinking in real morning that I probably had some bad mushrooms that night

:rofl:
 
BigE

BigE

Member
Joined 2008
having trouble with F4 crippled of ZM post 3904.... 2N is 1N, that I know. TL431AS, ED or plain gives same problems.... Vout spikes with a 1V AC input into the KV range.... potentiometers are set at mid range = 1.

Any help in getting this going would be appreciated....
 

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BigE

BigE

Member
Joined 2008
Fourier analysis shows around 2.5% with 10V input at 400 Hz...... Simulation goes unstable at 1K.....?

Does anyone have any ideas? I know, probably me, but..... The voltage around the TL431 was set by swaping P1 and P2 for resistors -- it's DC operating points are darn close to +4 and -4 Volts....+4 going to the resistors connected to the 240's and -4 going to the resistors connected to the 9240s....does that seem reasonable?

Thanks for any help here!
 
L

lhquam

Member
Joined 2010
Who is the moderator for this thread?

I have a large post to make for my completed Curly-F4 packaged in a Store Deluxe 4U chassis. It consists of a John Curl/LSK-Pre based folded-cascode voltage gain stage board which piggybacks on the DIYAudio Store Cviller F4 board.

My post will include schematic, photos, distortion plots, other measurements, and listening experience. Does this belong here or in a new thread?
 
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