F4 power amplifier - Page 353

Zen Mod · 22nd November 2012, 11:13 AM

yes

willamp · 07:17 PM

Hi All,

Getting close to finishing my dual mono F4 clone. It's only been powered up for about an hour and I was listening to it for 15 min or so. Sounds great with the tube pre-amp that is also mostly done. I'm going to let the F4 run a few hours on the bench and re-adjust the bias and offset in preparation for a full listening session tonight. HP339 is saying THD: ~0.0078% at 1 watt into 8 ohm. Real number is likely lower than that as I think the notch filter on the HP needs some work.

The case is the diyaudio deluxe 4u.

Anyway, thanks to Papa and everyone else for all the info you've posted to this site. Without it I'd still be listening to store bought stuff.

Zen Mod · 24th November 2012, 07:38 PM

every stereo F4 deserves proper XLR on back plate

willamp · 24th November 2012, 07:50 PM

Quote:

Originally Posted by Zen Mod

every stereo F4 deserves proper XLR on back plate

Don't worry. 30 minutes with a saw and I can switch the RCA to XLR if/when I need to.

willamp · 24th November 2012, 07:55 PM

Here's a question for ya

Look at the second waveform in my picture, 1st post (1st waveform is 1khz input). This is the HP distortion monitor output. This the signal sent to the meter after the notch filter. See how much fundamental frequency is in the signal? Shouldn't that have been removed? and isn't it throwing my measurements off?

thx

Zen Mod · 24th November 2012, 10:09 PM

well - you must explain your measurement method , so we can decide what's lousy - your building , or measurement skills

willamp · 25th November 2012, 10:09 AM

Well, lets disregard my analyzer question, probably not the right forum for that.

As for the F4: first listening session last night was most enjoyable. It sounds great in my system. Just what I was looking for.

studiostevus · 14th December 2012, 01:53 AM

Quick one: are two 2*26v 120va transformers good to power the f4?

I still have them lying around but am not sure regarding too high voltage and too low power...

Zen Mod · 14th December 2012, 06:15 AM

120VA is limiting factor - you'll need to decrease bias

also - Jfet's are approaching tricky voltages - you'll need to take care of their Idss .....

so - either degeneration or cascooding

studiostevus · 14th December 2012, 07:37 AM

In short no

22nd November 2012, 11:13 AM	#3521
Zen Mod diyAudio Member Join Date: Jan 2003 Location: ancient Batsch , behind Iron Curtain	yes __________________ my Papa is smarter than your Nelson ! tnx to clean thread ; Cook Book ; PSM LS Cook Book ; Baby Diyaudio FORUM ; Mighty ZM's Bloggg;I'm dumb

24th November 2012, 07:38 PM	#3523
Zen Mod diyAudio Member Join Date: Jan 2003 Location: ancient Batsch , behind Iron Curtain	every stereo F4 deserves proper XLR on back plate __________________ my Papa is smarter than your Nelson ! tnx to clean thread ; Cook Book ; PSM LS Cook Book ; Baby Diyaudio FORUM ; Mighty ZM's Bloggg;I'm dumb

24th November 2012, 10:09 PM	#3526
Zen Mod diyAudio Member Join Date: Jan 2003 Location: ancient Batsch , behind Iron Curtain	well - you must explain your measurement method , so we can decide what's lousy - your building , or measurement skills __________________ my Papa is smarter than your Nelson ! tnx to clean thread ; Cook Book ; PSM LS Cook Book ; Baby Diyaudio FORUM ; Mighty ZM's Bloggg;I'm dumb

14th December 2012, 01:53 AM	#3528
studiostevus diyAudio Member Join Date: Oct 2009 Location: Brunei	Quick one: are two 2*26v 120va transformers good to power the f4? I still have them lying around but am not sure regarding too high voltage and too low power... __________________ -------- TDA1541a-S2 / 6072a / MediaplayerDac -- Michell Gyrodec -- Aikido Preamp -- Pass F5 -- Audio Physic Tempo 2SE -- Yamamura Cabling

14th December 2012, 06:15 AM	#3529
Zen Mod diyAudio Member Join Date: Jan 2003 Location: ancient Batsch , behind Iron Curtain	120VA is limiting factor - you'll need to decrease bias also - Jfet's are approaching tricky voltages - you'll need to take care of their Idss ..... so - either degeneration or cascooding __________________ my Papa is smarter than your Nelson ! tnx to clean thread ; Cook Book ; PSM LS Cook Book ; Baby Diyaudio FORUM ; Mighty ZM's Bloggg;I'm dumb


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24th November 2012, 07:55 PM	#3525
willamp diyAudio Member Join Date: Dec 2011 Location: Austin, Texas	Here's a question for ya Look at the second waveform in my picture, 1st post (1st waveform is 1khz input). This is the HP distortion monitor output. This the signal sent to the meter after the notch filter. See how much fundamental frequency is in the signal? Shouldn't that have been removed? and isn't it throwing my measurements off? thx

25th November 2012, 10:09 AM	#3527
willamp diyAudio Member Join Date: Dec 2011 Location: Austin, Texas	Well, lets disregard my analyzer question, probably not the right forum for that. As for the F4: first listening session last night was most enjoyable. It sounds great in my system. Just what I was looking for.

14th December 2012, 07:37 AM	#3530
studiostevus diyAudio Member Join Date: Oct 2009 Location: Brunei	In short no __________________ -------- TDA1541a-S2 / 6072a / MediaplayerDac -- Michell Gyrodec -- Aikido Preamp -- Pass F5 -- Audio Physic Tempo 2SE -- Yamamura Cabling

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