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A guide to building the Pass F4 amplifier.
A guide to building the Pass F4 amplifier.
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Old 26th April 2014, 04:11 PM   #211
Zen Mod is offline Zen Mod  Serbia
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A guide to building the Pass F4 amplifier.
one thing is already having SET amp ( loading it with 2-3 times higher load then speaker) and boosting it with F4 ............. and another thing is using/making completely new preamp , for same purpose
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Old 26th April 2014, 04:28 PM   #212
willamp is offline willamp  United States
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Originally Posted by Zen Mod View Post
one thing is already having SET amp ( loading it with 2-3 times higher load then speaker) and boosting it with F4 ............. and another thing is using/making completely new preamp , for same purpose
Yes, I don't already have an SET so would be possibly building just for this purpose. That's what makes me want to figure out if I can maximize the SET/F4 combo.
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Old 26th April 2014, 04:41 PM   #213
bjorgens is offline bjorgens  United States
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I'm in the former camp as Zen Mod describes it... Already have a lovely preamp and a pair 300b amps. I'm building the F4 for fun but still intend to keep my amps as is. Neat ideas though

B

Last edited by bjorgens; 26th April 2014 at 04:47 PM.
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Old 27th April 2014, 01:16 AM   #214
6L6 is offline 6L6  United States
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A guide to building the Pass F4 amplifier.
Quote:
Originally Posted by willamp View Post
I'm likely way over simplifying this but is my thinking even close?
You are totally in the ballpark.

Long story made short - the 300B secondary is going to be loaded with the 47K resistor in the input of the F4, and that's a bit high for the transformer, hence the reason for a smaller, higher wattage resistor on the 300B output.

Look back a couple pages, Debra experimented with the loading on her SET amp and found something that worked very well.
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Old 2nd May 2014, 06:10 AM   #215
valvesound is offline valvesound  South Africa
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Has anyone found it worthwhile placing some polyprops with good DF on the supply at the amp boards as the wires running from the power supply board is fairly long?
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Old 2nd May 2014, 06:43 AM   #216
valvesound is offline valvesound  South Africa
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Has anyone found it worthwhile placing some polyprops with good DF on the supply at the amp boards as the wires running from the power supply board is fairly long?
here is a pic added to show the 'long' wires I have running from PS to amp boards
Click the image to open in full size.
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Old 2nd May 2014, 12:10 PM   #217
udailey is offline udailey  United States
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here is a pic added to show the 'long' wires I have running from PS to amp boards
Click the image to open in full size.
Tiny toroid. I dont think it can handle this amp. Whats the VA rating?
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Old 2nd May 2014, 02:38 PM   #218
valvesound is offline valvesound  South Africa
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not quite the answer I was looking for. It is a 300VA, its quite thick (higher) than it looks.
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Old 2nd May 2014, 02:47 PM   #219
6L6 is offline 6L6  United States
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A guide to building the Pass F4 amplifier.
Fantastically clean build! Congratulations!

300VA is fine -- the factory FirstWatt amps use 300VA.

If you are going to add caps at the end of the wires, make them big, not little, as you are making another RC filter, and the amp will look to the closest caps for power if a big transient demands it. Adding some polys at the PSU board can't hurt, if you want to play with it.
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Old 2nd May 2014, 02:53 PM   #220
valvesound is offline valvesound  South Africa
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Originally Posted by 6L6 View Post
Fantastically clean build! Congratulations!

300VA is fine -- the factory FirstWatt amps use 300VA.

If you are going to add caps at the end of the wires, make them big, not little, as you are making another RC filter, and the amp will look to the closest caps for power if a big transient demands it. Adding some polys at the PSU board can't hurt, if you want to play with it.
Thank you for the informative answer 6L6. What do you suggest as 'big' I added 4x 4u7 polys one on each rail, is that ok?
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