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Old 4th July 2013, 10:37 PM   #13231
bcmbob is offline bcmbob  United States
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I hate to admit it, but my trimmers are mounted backwards. I had forgotten that and had to resort to using the meter to rediscover my error. Everything biased correctly a few days ago, doing everything in reverse.
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Old 4th July 2013, 10:40 PM   #13232
WalterW is offline WalterW  Netherlands
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Steve and Matt are wrong, the Bourns click both clockwise and counterclockwise. And they must be zero Ohm initially, and certainly not 5K.
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Old 4th July 2013, 10:42 PM   #13233
6L6 is offline 6L6  United States
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Quote:
Originally Posted by Andersonix View Post
The 'Steve and Matt Document' contradicts initially setting the pots to zero:
Which makes no sense. Max resistance will draw maximum current, and thereby maximum bias.

The 'Jim Document' has a detailed bias procedure - An illustrated guide to building an F5

They said that they measured it, but perhaps they were reading something different by measuring in-circuit. ?
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Old 4th July 2013, 10:48 PM   #13234
alazira is offline alazira  United States
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Quote:
Originally Posted by Andersonix View Post
The 'Steve and Matt Document' contradicts initially setting the pots to zero:
The F5 manual advised setting the pots to zero for initial adjustment.
Quote:
Initial Adjustment
Before applying power to the amplifier, you will want to set the values of P1 and P2 to their minimum. Verify this with an ohmmeter. When it comes times to “fire” up the amp first time, if you have a Variac, use it, fusing the AC line to the amplifier with a 1A fast blow fuse. Turn the Variac up slowly, and if you haven’t popped the fuse, then go ahead and confirm the rail voltages to the channels. Each channel does not need to be attached to a load in order to adjust it. If the only load you have is the loudspeaker, I would advise against using it during adjustment. For each channel you will be adjusting P1 and P2 alternately in order to achieve 0 volts DC at the output and .59 volts across R11 and R12. Each time you adjust P1 you will probably have to go back and adjust P2 again, and so I recommend adjusting the pots in half-measures, alternately setting the pots half-way to their voltage goals and measuring the DC values. Unless there is something very wrong, when the output is at 0 V DC, the values across R11 and R12 will be equal.
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Old 4th July 2013, 10:55 PM   #13235
6L6 is offline 6L6  United States
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Aha! From the dead sea scroll itself... The "Nelson Document"!
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Old 19th July 2013, 09:21 AM   #13236
tonimxp is offline tonimxp  Italy
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Default F5 R1 version tricks and advises

Hello at all! Please a need to ask you what do you think about Aleph
30 vs F5? I have already built my Aleph 30 and I am very satisfied with its
warm sound (similar to a tube), but its ability to control the bass is not its
strong point.
So 'reading around on different forums and needing to use much spare parts of
my old Aleph (dual mono psu, cabinet etc. etc.) I thought that F5 could be ok,
but maybe also aleph X mini monster.
Still reading the forums I learned that P3 pot could minimize distortion .....
but if used skillfully, it could give at the amplifier the right rate of second
harmonic distortion which I think is the peculiarity of the Aleph series.
I still would like to know what does sonically replace R5 R6 R7 R8 100 ohm
with 150 or more.
And finally making a series 50 ohm (fix resistor) +100 ohm (trimmer) + 50 ohms
(resistor fix), can it prevent any damage caused by P3?

Thanks in advance

greeting

Antonio

Last edited by tonimxp; 19th July 2013 at 09:24 AM.
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Old 19th July 2013, 06:07 PM   #13237
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Quote:
Originally Posted by tonimxp View Post
And finally making a series 50 ohm (fix resistor) +100 ohm (trimmer) + 50 ohms (resistor fix), can it prevent any damage caused by P3?
I am not aware of any damage you can cause by P3. I suppose a very
sensitive driver might be damaged by the small DC offset while you are
making adjustments.....

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Old 19th July 2013, 08:46 PM   #13238
tonimxp is offline tonimxp  Italy
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Quote:
Originally Posted by Nelson Pass View Post
I am not aware of any damage you can cause by P3. I suppose a very
sensitive driver might be damaged by the small DC offset while you are
making adjustments.....

Hi! Mister Pass ,many pleasure to receive your reply!

The problems were not about the speakers but the stability of the amplifier circuit.

I had to go find him in the depths of the various forums,it was difficult, but not impossible!

#552 post of F5 Turbo Builders Thread

But then translating the various posts I realized that P3 should not have been the problem of Anilva member

But also AndrewT said to Anilva:

Originally Posted by AndrewT View Post
I said a long time ago that the adjustment VR needs fixed resistors either side to limit the extent of adjustment. Seems folk either don't read or have a memory as bad as mine.

So...please can you dissolve my doubts about:


P3 pot could minimize distortion and/or its interaction can generate a predominance of second harmonic distortion as Aleph series?

What does sonically differences replacing R5 R6 R7 R8 100 ohm
to 150 or more?
And finally making a series 50 ohm (fix resistor) +100 ohm (trimmer) + 50 ohms (resistor fix), for P3 is it however a good idea or just a mental masturbation?

Thanks in advance

Last edited by tonimxp; 19th July 2013 at 08:54 PM.
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Old 19th July 2013, 10:42 PM   #13239
alazira is offline alazira  United States
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Quote:
Originally Posted by tonimxp View Post

Originally Posted by AndrewT View Post
I said a long time ago that the adjustment VR needs fixed resistors either side to limit the extent of adjustment. Seems folk either don't read or have a memory as bad as mine.

So...please can you dissolve my doubts about:


P3 pot could minimize distortion and/or its interaction can generate a predominance of second harmonic distortion as Aleph series?

What does sonically differences replacing R5 R6 R7 R8 100 ohm
to 150 or more?
And finally making a series 50 ohm (fix resistor) +100 ohm (trimmer) + 50 ohms (resistor fix), for P3 is it however a good idea or just a mental masturbation?

Thanks in advance
Increasing R5-R8 will reduce feedback, increase gain and "warm" up the sound.
F5 power amplifier

Regarding P3 vs resistor-trimmer-resistor combination,
in the later it will prevent an accidental shorting to ground if you zero out the trimpot.

Last edited by alazira; 19th July 2013 at 10:44 PM.
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Old 20th July 2013, 08:51 AM   #13240
tonimxp is offline tonimxp  Italy
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This is the Papa's Way

Alternatively, you can increase the value of the Source resistors to 1 ohms,
and increase the value of the feedback resistors from 2 X 100 ohms and 10
ohms to 1 X 100 ohms and 22 ohms.

The lower amount of feedback will warm the sound up, and you can keep
increasing proportional values in the feedback loop if you wish.

Same Q:
1)Other tips about eliminating the current limiter?
2)So how to properly adjust P3?
3)What resistors would be preferred in this project?
4 With 1 ohm Source resistor the accross voltage schould be 1.3V or more compatibly with heatsink dissipation?
5) If i reduce to 100 ohm and increase to 22 ohm the feedback network the respective powers will be 5w(or more) for 100 value and 2w for 22 value?
6) About input partitor which values 1k-100k or 4.75k-47.5k?

Many thanks

Antonio

Last edited by tonimxp; 20th July 2013 at 08:53 AM.
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