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Old 25th January 2013, 05:48 PM   #12861
6L6 is offline 6L6  United States
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F5 power amplifier
Probably not, they are first-tier manufactures who were actually making the things.
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Old 25th January 2013, 05:53 PM   #12862
labjr is offline labjr  United States
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If a company like Linear Systems acquires the right or license to make the parts, what exactly do they get? Like what are they licensing? A recipe? Specs?
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Old 25th January 2013, 08:22 PM   #12863
Pemo is offline Pemo  Mexico
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Quote:
Originally Posted by 6L6 View Post
Are you asking about making a separate chassis for the power supply? Yes, it is a good idea.

Look for the 4-terminal "Speakon" connector from Neutrik to make the cable. Very nice!
Yes, that's exactly what I was thinking !! But....why?
And make a compact F5 also

RGDS

PEMO
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Old 26th January 2013, 11:43 PM   #12864
fakamada is offline fakamada  Poland
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Default F5 - modifying damping factor by lowering feedback

Hi all. Changing harmonics by regulating P3 is already widely known method of changing F5s sound. But what about changing amount of feedback? Papa gave us some hint in F5 Turbo article. There we have half the original feedback and overall distortion was still extremely low. Nelson described effects of this as "mellower" more "relaxing" sound.

What if we'd like to make feedback even lower? How low can we go?
If we look at SIT amps - on paper they go in similar direction:

much higher distortion and low damping factor. Also J2 and F3 are more in this direction when compared to original F5. I suppose that adjusting P3 for 2nd order harmonics AND lowering feedback could get us closer to J2 or F3 sound (or even SIT)

Have anyone tried it? What's the highest reasonable value of feedback resistors? (as for bandwidth - I'm ok with flat 20khz - don't need more)

Regards,
Kuba

Last edited by fakamada; 27th January 2013 at 12:03 AM.
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Old 27th January 2013, 12:55 AM   #12865
6L6 is offline 6L6  United States
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Quote:
Originally Posted by fakamada View Post
But what about changing amount of feedback? Papa gave us some hint in F5 Turbo article. There we have half the original feedback and overall distortion was still extremely low.

Have anyone tried it? What's the highest reasonable value of feedback resistors? (as for bandwidth - I'm ok with flat 20khz - don't need more)
Yes, I have tried it. It works well.

Decreasing the feedback (more ohms in position R5, 6, 7, 8) also has the advantage of increasing the gain of the amplifier, and that is usually the reason people have changed it. I have used 150R in those positions, it sounds great. I know that others have used 220R with good results.
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Old 27th January 2013, 01:35 AM   #12866
fakamada is offline fakamada  Poland
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220ohm is the value from F5 Turbo.
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Old 27th January 2013, 02:27 AM   #12867
fakamada is offline fakamada  Poland
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I'm wondering how low can we go with feedback here.
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Old 27th January 2013, 04:16 AM   #12868
AudioSan is online now AudioSan  Norway
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it is well known from the turbo. but how about the other way? well. i Guess there is not much need og 15db gain or below but it can be done, just as easy. soundwise, it will not make much difference. how about 50ohm resistors? that will give us about 10db gain? right?
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Old 27th January 2013, 05:28 PM   #12869
Floric is offline Floric  Europe
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Lowering the gain by increasing the feedback even further will lead into insability (high frequency oscillations). I don't know the lowest possible feedback for this amp but at least according to simulations a total gain of 10dB is already on the worse side.

If you want to go that way, you would have to change the schematics to stay savely within the stable region. I did this in my headamp by increasing the R from the sources of the JFets to ground à la BA3 Frontend.

Best regards

Flo
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Old 27th January 2013, 07:32 PM   #12870
Nelson Pass is offline Nelson Pass  United States
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F5 power amplifier
The F5 already runs lots of feedback, but you can go for more if you are
willing to put some of those little compensation capacitors in the circuit.

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