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Old 28th June 2009, 12:10 AM   #1
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Default Can you comment these amp

Hello
I would like to know what is your opinion if these amp can be stable .
I'm almost ready populated the PC board but I do not want to burn my Visaton speakers .
Any comment are welcome .
I'd like amplifiers use only a few parts , but not less how much is necessary to be stable .
Thanks
Greets
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Old 28th June 2009, 12:24 AM   #2
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Hello

How I stated I'm crazy about amps uses only a few parts .After I built the ProFet amp an I read Peter D F5 experience .That makes me more to build amps just with a few pars .
The question if these will work properly ?
I made the PC board larger because if the amp save I want to replace the Wima caps with Russian PIO capacitors .

Greets
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Old 28th June 2009, 12:44 AM   #3
Nrik is offline Nrik  Denmark
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Just test and adjust it before you connect it to your speakers.

1)Connect to power supply throug two 4.7 ohm/5W and two 3,15 ampere fast-blow fuses.
2) Turn pot to max resistance before first power up.
3) Adjust pot carefully to desired Idle current ( measure over 4.7 ohm resistor).
4) remove 47 ohm resistors, KEEP THE FUSES in the circuit, or maybe replace them with 5 ampere fast blow.

By the way: Even if you match all the 4 small JFets, you will probably still get DC-offset. Add a DC-servo or a capacitor in the output.
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Old 28th June 2009, 01:24 AM   #4
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It will be a temperature-dependent offset. Also, idle current will highly depend on temperature.
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Old 28th June 2009, 01:57 AM   #5
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Thanks for the advise , if I have to use a DC servo or a output cap I think that would degrade the sound .
Any way I will test it at least one channel how you advised with a cheap speaker , and if blow up because DC offset that mean these amp not to me .
I will set up low bias and with a large heat sink .
I have at least 10 pair these Toshiba mosfets because Lineup wrote those are lateral mosfets .
After I purchase them another guys inform me these not laterals .
So I try to use them . Of course I do not want my Visaton speakers get blown .
Greets
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Old 28th June 2009, 02:04 AM   #6
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Lineup advised this lateral mosfets in case of stable gate to drain voltages, but in this amp they will highly depend on JFETs.
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Old 28th June 2009, 02:25 AM   #7
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Hello
I understand that .
You right ,
About the power mosfets I just explain why I purchase them .
I wanted to use them as a replacement of Hitachi 2SK1058/2SJ162 .
But these mosfets are not laterals .So now I try to use them in some simple circuit .
If it works that OK if not that is OK to .
I just don't want to burn my speaker .
If you know the PrFet amp , that run in Class A and very stable .
I did built that , is a great amp of course with high quality components were used .
It sound clear , and incredible nice with a great detailed mid range and has a great bass also .
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