Author Topic: SKA 150 watt mosfet amp from Greg Ball  (Read 450 times)

Offline JANNAS

SKA 150 watt mosfet amp from Greg Ball
« on: May 18, 2018, 11:55:42 AM »
Hallo all,
It is winter in the Free State  and I have to find myself something to do indoors. So building an amp seems the right thing to do ! ;D Have any of you perhaps tried the SKA ( simple killer amp)with the 2 pair mosfets on the output,I read only good things on Diy Audio about its performance.Apparently a very neutral sounding amp :)

Offline PsyCLown

Re: SKA 150 watt mosfet amp from Greg Ball
« Reply #1 on: May 19, 2018, 09:55:05 AM »
Hallo all,
It is winter in the Free State  and I have to find myself something to do indoors. So building an amp seems the right thing to do ! ;D Have any of you perhaps tried the SKA ( simple killer amp)with the 2 pair mosfets on the output,I read only good things on Diy Audio about its performance.Apparently a very neutral sounding amp :)

Never even heard of it, you have a link to the thread on DIY Audio?
Amps: 4x 150W into 8ohm (LJM L15D)
DSP: MiniDSP NanoAVR HDA & UMIK
Speakers:DIY Full Range Phillips AD12202 & Speakerplan's X15 on loan
Sub: DIY 12" ported & Peerless 10" Sealed on loan
Headphones: Beyerdynamic DT770 LE

Offline JANNAS

Re: SKA 150 watt mosfet amp from Greg Ball
« Reply #2 on: May 19, 2018, 10:10:13 AM »
Jip sir, here is the link for the construction thread, beginning with the boards this morning, first have to fix the bloody microwave to heat up last night's braaivleis ! ;D
http://www.diyaudio.com/forums/solid-state/271524-greg-ball-gb150d-simple-killer-amp-channel-mosfet-power-amp.html

Offline JANNAS

Re: SKA 150 watt mosfet amp from Greg Ball
« Reply #3 on: May 19, 2018, 10:16:32 AM »
sorry, have problems loading the schematic, will try again

Offline JANNAS

Re: SKA 150 watt mosfet amp from Greg Ball
« Reply #4 on: May 19, 2018, 11:41:01 AM »
Cannot do it after an upgrdade, but here is the direct link to schematic.
http://www.diyaudio.com/forums/solid-state/238593-ska-gb150d-public-domain-4.html

Offline Dubya Jay Dee

Re: SKA 150 watt mosfet amp from Greg Ball
« Reply #5 on: May 19, 2018, 02:55:00 PM »



Offline JANNAS

Re: SKA 150 watt mosfet amp from Greg Ball
« Reply #6 on: May 19, 2018, 05:03:21 PM »
Thank you sir !! :)

Offline The Godfather

Re: SKA 150 watt mosfet amp from Greg Ball
« Reply #7 on: May 19, 2018, 07:06:59 PM »
I recall greg ball supposedly designing for mark levinson, or so he claimed.

Hie made a statement to the effect that a large portion of the sound character was down to PCB design and layout. I think he was eventually banned

Offline Shonver

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Re: SKA 150 watt mosfet amp from Greg Ball
« Reply #8 on: May 19, 2018, 11:33:36 PM »
It is an unconventional circuit. To me it seems the drive to the output MOSFETs may be problematic. Specifically: the impedance is asymmetrical. Also, the fuses aren't of much use, other than to introduce distortion.
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Offline JANNAS

Re: SKA 150 watt mosfet amp from Greg Ball
« Reply #9 on: May 20, 2018, 06:26:11 AM »
Thanks for the replies all, I have found an improved version of the circuit. Source resistors for each output fet and a mod on the input stage. The circuit apparently has a very good PSSR and has got good reviews. Well, I have all components, so I might just build a channel and see whats cooking. It can be biased in class A to give 50 Watt in class A. I'll see what the day brings ! :D

Offline PsyCLown

Re: SKA 150 watt mosfet amp from Greg Ball
« Reply #10 on: May 20, 2018, 05:29:27 PM »
Thanks for the replies all, I have found an improved version of the circuit. Source resistors for each output fet and a mod on the input stage. The circuit apparently has a very good PSSR and has got good reviews. Well, I have all components, so I might just build a channel and see whats cooking. It can be biased in class A to give 50 Watt in class A. I'll see what the day brings ! :D

Where did you source the boards from or what is your plan with regards to the boards?
Amps: 4x 150W into 8ohm (LJM L15D)
DSP: MiniDSP NanoAVR HDA & UMIK
Speakers:DIY Full Range Phillips AD12202 & Speakerplan's X15 on loan
Sub: DIY 12" ported & Peerless 10" Sealed on loan
Headphones: Beyerdynamic DT770 LE

Offline JANNAS

Re: SKA 150 watt mosfet amp from Greg Ball
« Reply #11 on: May 20, 2018, 06:02:45 PM »
I have the PDF files to make the boards, as easy as two tics and a bokfok ;D, I have everything to build it. It seems the the 2nd harmonic which sounds nice and soft on the ear is what makes it different, I think all second harmonics is leading, 2,4 6 and so this will be a sweet sounding amp, maybe not so accurate. A lot of good accolades on DIY audio. I have build a quasi from Hugh Dean which is superb sounding amp, transistor with a mosfet on op stage working now in Cape Town which has a lot of 2nd harmonics as well. My son in law is very happy with it. He was used to TAG MClaren equipment.  It is just that I am loitering now and have found this thread to the Simple killer Amp to keep out of trouble. :)

Offline The Godfather

Re: SKA 150 watt mosfet amp from Greg Ball
« Reply #12 on: May 20, 2018, 07:02:12 PM »
Certainly looking forward to your updates on progress like the others Jannas.


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Offline JANNAS

Re: SKA 150 watt mosfet amp from Greg Ball
« Reply #13 on: May 20, 2018, 07:09:17 PM »
This post image storie does not allow me to post PDF files, plse help to make this work :???:

Offline JANNAS

Re: SKA 150 watt mosfet amp from Greg Ball
« Reply #14 on: May 20, 2018, 07:19:48 PM »
This is a silk top layout of the amp. I have to sort out this other pdf stuff, I am a installation electrician, but during daytime I work on digital exchanges and particular rectifiers that keeps these things running, so these software stuff buggers me sometimes !! :OMG: