Is the F4 the most-suitable FW amp for me? - Page 2 - diyAudio
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Old 16th February 2011, 05:54 PM   #11
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Quote:
Originally Posted by jeffreybehr View Post
.......
I guess I'll control my infatuation with the F4

.....
naah

not funny enough

it's funnier to build them and listen , than just to buy them and listen
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Old 16th February 2011, 05:59 PM   #12
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Originally Posted by Melon Head View Post
The F4 will sound different depending on what it is driven by, and since a cd player does not have enough voltage to drive the F4 to decent power levels most people will be a putting some sought of high gain preamp or power amp in front of it which will heavily influence the sound coming out of the speakers.
I've always been confused by this... how do you drive an F4 with a power amp? Its in the manual, but never understood how it would work. First of all, how do you connect a power amp to the F4 input?
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Old 16th February 2011, 06:03 PM   #13
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You will have to add rca connectors at the output of the amp to hook up to the F4.
Or use your imagination to come up with many other ideas to connect a power amp to the F4
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Old 16th February 2011, 06:11 PM   #14
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just put 8R dummy load at output of your amp , solder some cable to same , solder RCA to end of cable and plug it in F4

then F4 is current buffer for your flea power amp ( as Papa calls it )

pictures at 6moon F4 presentation

you can use lighter dummy load ( more ohms ) if your tiny power amp is happy with it
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Old 16th February 2011, 06:38 PM   #15
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More often than not you will want to use a dummy load
of a higher impedance, say 16 ohms, and be prepared
to adjust it for different sound.

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Old 16th February 2011, 06:43 PM   #16
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Cool... thanks all! I have some F4 PCBs... someday....
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Old 16th February 2011, 10:27 PM   #17
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Nelson, any comments on the suitability of F4s for my application?

Also, are Cs1 and 2 signal-coupling caps? If so, what is the resistance they're driving? My app requires the amps to have the MR-high-pass filter in them.
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Old 17th February 2011, 07:08 PM   #18
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Originally Posted by jeffreybehr View Post
Nelson, any comments on the suitability of F4s for my application?

Also, are Cs1 and 2 signal-coupling caps? If so, what is the resistance they're driving? My app requires the amps to have the MR-high-pass filter in them.
Nelson?
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Old 20th February 2011, 04:36 PM   #19
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Originally Posted by jeffreybehr View Post
Nelson?
Mr. Pass? Comments on my original and subsequent questions?
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Old 20th February 2011, 05:19 PM   #20
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I'm not able to answer your question but I would like to suggest the possible influence on the sound that may be expected. The F4, using no feedback is subject to some coloration. I beleive ordinarily you would expect mostly 3rd harmonic coloration from this type of circuit. And, although small, it will add a particular sound. Due to the use of IRFP9240s, some 2nd harmonic will predominate, possibly giving it a warmer "tubey" sound. You can read about this phenomina in the BA-2 article in the performance section as the F4 is a very similar output stage. The F5 however does use feedback. And, although it also uses IRFP9240s the gain/feedback topology of the circuit is likely ruducing the 2nd harmonic and distortion overall giving a slightly different sound.
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