DIY F2 clone

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Joined 2004
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Matching the wallpaper is so stealthy! I had to look 3 times before I saw the speakers :D

That is one smart cat, it knows the warmest place to take a nap.

Does anyone still call you Choky? ;)


open separate thread and give me more porn :p

one day, when I grow up , I'll have big horns too ....... in a meantime I'm content with lesser ones

and they're content with decent 5W :)

Tannoy Brute Force OB ….. now Absolute WAF Tannoy OB | Zen Mod Blog

IMG_1893.jpg
 
Ok, I don't need much power...
To compensate the higher THD maybe I could increase the source resistance from 0.66 ohms to 1 ohm, adding more source local feedback.
One more question, please:
Can I replace 1Mohm input resistance with a 100K volume potentiometer?
Potentiometer control leg to capacitor, right?
What the effect in input impedance (manual says original is 50K)?
 
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Joined 2009
Paid Member
full range

Hello,
I am looking for someone who tried SEAS Exotic F8-8 and/or cube Audio Magus with F2 or F2J? Booth Speakers need compensation, may be the SEAS less. My enclosure is TQWT with a baffle 100 x 26 cm, but I am flexible with the broadness of the baffle.
The Cube Audio is quite brittle in mids and highs; rising to the highs with quite strong resonance between 8 and maybe about 12 kHz, I already tried some cobinations of C+R, but the speaker looses all its magic.
The measurements of the Seas in oppen baffle looks good, compensation may be a lot easier. Compensation with voltage amplifiers (I tried 8W Monster Hiraga with quite pleasing results) is well known, but I have no clue, how to transfer this to the F2 current amplifier needs.

I am using F2J clone.

Thanks in advance

Helmut
 
The one and only
Joined 2001
Paid Member
I have.

Depends on enclosure, OB vs sealed box, but in both cases you get a
boost in bass at resonance and the upper mid is bright.

Networks to address this are a plain parallel resistor for the bottom,
something in the region of 10 to 22 ohms and an RC network (resistor in
series with cap, this in parallel to speaker) values from about 6.8 to 22
ohms and 6.8 to 22 uF.

You can pick more details about some of this from the Current Source
Amplifier article at FIRST WATT

Mostly you want to get some sample values of power resistors, film
capacitors, and play around to see what works best. Clip leads are
fine for initial testing.

:cheers:
 
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Joined 2009
Paid Member
Thanks Mr. Pass, I read this article several times and tried to extract any correlation between speaker and choosen compensation. Difficult. Obviously a higher value for the resistor will result in less influence of the compensation, a higher value for cpacitor will lead to a lower frequenz influenced by the compensation, but there is also a relationship between R and C.
Simulation LX-mini shows also promissing results.
A long life of diy, I have a large bunch of capacitors and power resistors, so game is going on.

br

Helmut
 
Hi there,
F2 seems undeservedly forgotten, and I would say, underrated amplifier. Maybe that's because, it being the transconductance amp, it was less suitable for most "normal" speakers.
But, for fullrangers, it still does a fair bit of magic. So, if you can't "reach" a SIT amp, an F2 will do just fine :)

Regards,
Vix
 
Looking for a little help with my F2J

I completed my F2J clone about 6 weeks ago, and I just have not been able to get it to sound right. It sounds muffled. I have adjusted for even clipping, and changed the input capacitors and tried a B1 buffer and a 20k passive preamp without success. My input and output capacitors are remote mounted due to space limitations on the board, could this be a problem? It may be worth noting that with the B1 the muffled sound was much worse, (the B1 sounded great on my other amps). My speakers are FE206En Wooden Designs Vulcans. I was thinking of changing out the Nichicon KG's that I have for C3, but I don't know what other brand/type of capacitor to change to or if it would even help. Any ideas?

(If this looks familiar, I have posted the pictures in the Pass Amps picture thread)

Thanks!
 

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Official Court Jester
Joined 2003
Paid Member
proper sound card and adequate measuring proggie will give decent results

several threads around with details

I had so many difficulties setting my sound card EMU1212 that I'm utterly confused , even if I got bloody things working everything I need

in short - better not taking any procedural advice of me , never :)