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Old 4th April 2016, 05:36 PM   #1
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Join Date: Apr 2016
Arrow Modified 2sk1058 mosfet amplifier

First i want to say hello to everyone! Im new here.
Im electrical engineering student and i have some interests in amplifiers.
I want to build "ZCA amplifier" it's class A. Problem is, i can't get 2sk1058!
Im beginner in this world, but i learn quick..

Yesterday i pulled of two pairs of irfz44n from old pcb, and i found a lot of irf630 in box from old projects.
I started with basic schematics from.. link^^

I have done some simulations with these and i will post it in atachments.
But i have several questions for this design.
Do i need 24v supply? Can i get just 12v without 40w resistor?
Can i put this two mosfets in parallel to get more performance, curent and beter heat disipation??
Is pc power supply enough to power this amplifier?
I'm planing to build stereo version! I have several transformers laying around, case! Hopefully i will put together some decent amplifier.
Thank you for any kind of resposne!
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Old 5th April 2016, 05:34 AM   #2
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Why don't you contact the designer, Mark Houston, via his website reference or PM here?
Lateral Mosfets like 2SK1058 can be replaced by EXICON ECX10N20 (Lateral MOSFET | Profusion Audio Design
or identical ALFET products from Magnatech (SEMELAB) Magnatec. ALFET Lateral MOSFETs
(Farnell are also agents: Transistors - MOSFET's (< 600V) | Farnell element14)
Type ALF08N16V is the match.
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Last edited by Ian Finch; 5th April 2016 at 05:46 AM.
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Old 5th April 2016, 10:29 AM   #3
AndrewT is offline AndrewT  Scotland
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Location: Gone on holiday again. back soon.
You have shown a single ended amplifier (SE).
The maximum output is approximately 1/3rd of the supply rail voltage.
i.e. with a 24Vdc supply your maximum output is ~8Vac
When you add on a load the maximum output voltage drops, maybe ~6Vac trying to drive an 8ohms load
The maximum power from 24Vdc will be very approximately 5W (6Vac / 8ohms)
At anything above half maximum voltage the 2nd harmonic will become gross.
So for clean power expect 2W to 3W as a reasonable maximum.

For a 5W amplifier you don't need dual output devices.

Assuming you have 12.1V across the three drain resistors, you have a bias current of 12.1/{5.6+5.6+5.6} = 0.72A
The total dissipation in the three resistors is 0.72A*12.1V = 8.7W (use 5W or 7W or 10W resistors)
The mosFET dissipation is also 8.7W (use a 2C/W sink per device). That should keep your sink below 55C during summer (Ta=30C).
0.72A through an 8ohms load needs 5.76Vpk. That is 2W. The bias of 0.72A cannot drive an 8ohms load. It needs a 16ohms load just for non reactive operation.
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Last edited by AndrewT; 5th April 2016 at 10:38 AM.
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Old 5th April 2016, 12:38 PM   #4
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I will be happy if i get 5 wats, it's enough for my personal use.
And i have stocked some ceramic resistors (5w, 7w, 10w, 15w), that part is solved.
Is it beter to use transformer ( 19vDc (2.5amps)) or smps (pc supply), somehow i will crank it's 12v rails..
Thank you for answering.
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Old 17th July 2016, 08:02 PM   #5
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Location: Rheinhessen
Hallo techno.

Hope this can inspire you a bit in direction you will go.
I catchet that Franse PDF because i am like also the 5-25W power range.
AndrewT could take a little observe view to this, i think L'Audiophile Magazin Amp?https://drive.google.com/file/d/0BwT...Qk0/view?pli=1
Main Page:6.9.7- Les Schemas Single End- scroll near down to: Le SingleMos
2x6,5W- it is with SK1058.
Hope it works.
https://sites.google.com/site/franci...ur/6-9-schemas

The ZCA i have build for testing- all done like Marks project and lowered the
1M Resistor to 470k - sounds better. After paralleling the 470k with 220k it is now 150k and comes a bit magic in sound, but not real satisfying- missed a bit in top end highs. Staging is surprisingly good.
Why don't build the very nice ACA?- Boards are here in Store available.
So you have Reference to comparing.

Cheers Bangla.
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Old 12th September 2016, 09:04 PM   #6
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Hello, techn0!

What is the result of your experiment? Which max power have you managed to achieve?

Regards,
Andrew.
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Old 12th October 2016, 12:46 PM   #7
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Location: Victoria, Australia
Quote:
Originally Posted by AndrewT View Post
You have shown a single ended amplifier (SE).
The maximum output is approximately 1/3rd of the supply rail voltage.
i.e. with a 24Vdc supply your maximum output is ~8Vac
When you add on a load the maximum output voltage drops, maybe ~6Vac trying to drive an 8ohms load
The maximum power from 24Vdc will be very approximately 5W (6Vac / 8ohms)
At anything above half maximum voltage the 2nd harmonic will become gross.
So for clean power expect 2W to 3W as a reasonable maximum.

For a 5W amplifier you don't need dual output devices.

Assuming you have 12.1V across the three drain resistors, you have a bias current of 12.1/{5.6+5.6+5.6} = 0.72A
The total dissipation in the three resistors is 0.72A*12.1V = 8.7W (use 5W or 7W or 10W resistors)
The mosFET dissipation is also 8.7W (use a 2C/W sink per device). That should keep your sink below 55C during summer (Ta=30C).
0.72A through an 8ohms load needs 5.76Vpk. That is 2W. The bias of 0.72A cannot drive an 8ohms load. It needs a 16ohms load just for non reactive operation.
Mate, thanks for the info and calcs . My MCA is a betterr beast and really just as simple.
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