Hi
I do not see the similarities between the 2 circuits. Input stage is different since GB150D is bootstrapped, no VAS stage but follower stage on GB150D and output stage is inverting on GB150D. Also output mosfet are different. Really there is no real similarity worth mentioning
Fab
Thank you for the clarification. Do you have a preference for either board?Hi
I do not see the similarities between the 2 circuits. Input stage is different since GB150D is bootstrapped, no VAS stage but follower stage on GB150D and output stage is inverting on GB150D. Also output mosfet are different. Really there is no real similarity worth mentioning
Fab
Jim's Audio does recommend the same pairs of 2SK1530/2SJ201 MOSFETs for the output of both board. Being a Hitachi MOSFET user for over 20 years, I like their sound better than any vertical MOSFET. (Personal choice, no other reason.)
I remember very well the controversy about using IRFP for audio output when they first came out until Nelson Pass (I believe, not sure) proposed a work around. Now that IRFP is cheap and plentiful, few people mention lateral MOSFET anymore.
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Well I like laterals for experimenting with amplifier design - having to worry about thermal stability is one more tedious detail I'd rather avoid until later when trying out amp topologies. And the robustness of no secondary breakdown is definitely a plus.
The fact they were designed specifically for linear operation is important, power MOSFETs in general are being more and more optimized to fast switching efficiency, and now that GaNFETs are here the Si MOSFETs are chasing the high-frequency low-inductance path, not something that's compatible with TO220/TO247/TO3P/TO264 packages.
Laterals do have issues of course, high voltage-headroom requirements limit efficiency and don't play well in optimized class-G or class-H designs.
And Exicon are producing quality replacements for the Hitachi style laterals in several package types so currently they are a flexible option.
The fact they were designed specifically for linear operation is important, power MOSFETs in general are being more and more optimized to fast switching efficiency, and now that GaNFETs are here the Si MOSFETs are chasing the high-frequency low-inductance path, not something that's compatible with TO220/TO247/TO3P/TO264 packages.
Laterals do have issues of course, high voltage-headroom requirements limit efficiency and don't play well in optimized class-G or class-H designs.
And Exicon are producing quality replacements for the Hitachi style laterals in several package types so currently they are a flexible option.
If you want the real deal, Jlester, a member here sells nice ska150 boards on ebay, has a thread in vendor's.
It's a damn smart amplifier what Gregg did in this design.No resemblance to anything else really...
Did you make your own PCB? Who is your PCB fabricator or seller? Where did you get the "closely matched" transistors?Yes it's quite amazing, I'm waiting for 4 pcb, I have all parts ready, closely matched, and original Samsung mosfet, almost as good as Christmas
I cannot tell any preference because I cannot compare the 2....
GB150D design is more unique in term of topology but that does not mean it sounds better because of the novelty... but it sounds good for me.
Jimsaudio also sells a GB150D pcb w/wo output matched mosfet... I have used jimsaudio pcb for my build with 2SK1530/2SJ201 MOSFETs
Fab
GB150D design is more unique in term of topology but that does not mean it sounds better because of the novelty... but it sounds good for me.
Jimsaudio also sells a GB150D pcb w/wo output matched mosfet... I have used jimsaudio pcb for my build with 2SK1530/2SJ201 MOSFETs
Fab
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I am looking to build a stereo power amp with MOSFET output stage. I am looking at Jack Walton's 120W amp design he published on AudioXpress years ago. I like his LM4702 driven design which spare me of matching small signal transistors. It can work if I can get the PCB and driver IC from Jack. My plan B will be the GB150D using Jim's Audio PCB.
I have been using 3 Sherwood S-6040CP for many years and just recap them last year. I like the dual mono design and the construction, and love its sound. One of the Sherwood went silent recently which prompted me to start thinking backup and replacement. The Jack Walton and Greg Ball design are both excellent, newer and should sound better than the Sherwood.
The last time I built a power amplifier from scratch was more than 40 years ago. I modified James Bongiorno's Ampzilla PCB for +/-50V and single output pairs. I was in graduate school then and had access to an electronics lab and transistor curve tracer. Small signal BJT transistors were cheap and easy to find. I bought a whole bunch of them from Digi-Key to find the best matched pair. I can't fab PCB anymore.
Another challenge is to find a good looking chassis and heatsink without breaking the bank. There are some very good ones on e-bay. But the cost plus shipping will be more than I would pay for an Adcom GFA-545.
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Have you looked at the PeeCeeBee v4H? It's a recent design, the author is active on these forums, there's an excellent PCB available on group buy, dozens of builds have happened in various countries, and the objective specs are really in the top league, specially distortion in the upper reaches of the frequency spectrum. If you're not specifically looking at the SKA150, maybe you could look at this one?
You can use it with either the PSU designed by the same author (with integrated output protection and DC detect) or use the ready-to-run speaker protect boards currently available from XRK on these forums; his boards use solid state switching with no measurable impact on noise or distortion.
A link to the thread or the user ID of the author will be helpful. Otherwise, I don't know how to start search. Thanks.
Hi.
As I wrote above, jlester a member here on diyaudio sells those pcb on ebay.
As for the mosfet I have around 60 of each irfp9240/irfp240 stripped from power amps from the 90s, I reuse, they are vgs matched at 200ma, and pretty close.
2pcs Blank PCB: SKA GB150D by Greg Ball Class-AB Amplifier PCB | eBay
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This is my attempt of SKAGB150D pcb design (single-sided) using Sprint Lay-out, inspired from AlexMM design.
It is great that you've done a single sided board, do you plan to use toner transfer?
If anyone does it and has a full sized .pdf ready to print and transfer I might try
this design.