SKA GB150D now public domain...

[still4given]

Perfect!

 

[Bigun]

I think I'd rather do my own pcb in the end as I want to make a version with only single pair of output devices. Since this will be a deviation from Greg's design I'll take it to a new thread or to Greg's forum.

 

[kcray]

ska-forum links

Everything I've done should be on a thread that is accessible.

I can post some here, just not a lot of time lately.

Mike,

I think if you don't mind, please post the links of corresponding threads on ska-audio forum, here. It would make us easier to navigate in ska-audio forum.

Many Thanks,

-- Peter

 

[Stuey]

Mike's thread: SKA sponsored Audio Forum - Rebuild

 

[kcray]

Stuey Thank You, that was fast

 

[davidsrsb]

I think I'd rather do my own pcb in the end as I want to make a version with only single pair of output devices. Since this will be a deviation from Greg's design I'll take it to a new thread or to Greg's forum.

Start a new thread here.
I would look at the IRFP140/9140 on about 35V rails. No need to use 200V parts and the lower Rds helps. Then the obsolete signal transistors can use something much easier too

 

[PauloPT]

I think I'd rather do my own pcb in the end as I want to make a version with only single pair of output devices.

Why a single output pair? Why not use the schematics as it is and make a board for two pairs of mosfets?

 

[Bigun]

Because a) two pairs requires matching which I admit is only a small additional cost and hassle, but b) because today, there are new MOSFETs that weren't available to Greg originally which can handle the power with only one pair, c) some people say that a single pair sound better at low level details than multiple pairs

 

[Bigun]

Mike's thread: SKA sponsored Audio Forum - Rebuild

Why use a CCS as an emitter load for the driver pair - this limits the current swing in one direction ?

 

[PauloPT]

Because a) two pairs requires matching which I admit is only a small additional cost and hassle, but b) because today, there are new MOSFETs that weren't available to Greg originally which can handle the power with only one pair, c) some people say that a single pair sound better at low level details than multiple pairs

Ok, you convinced me.

Will there be boards available?

 

[Bigun]

Let's see how things progress - if I design a board for myself that others want to use I will not keep it to myself.

 

[PauloPT]

Let's see how things progress - if I design a board for myself that others want to use I will not keep it to myself.

Great! Thanks, Bigun!

 

[Greg Erskine]

I like to see how things work in Spice. I've loaded up the schematic, but it's not set up properly - a starting point for somebody if interested ?

Hi Bigun,

Thanks for posting the LTspice files. I've had hours of fun.

regards

 

[Bigun]

Yes, it can be fun ...And I complain my son spends too much time playing video games

 

[OnAudio]

Nice job Greg,

1. Simple
2. Smart
3. Passes the secret formula minimal checker for possible sweetness

Once the SF Amplifier goes live lets see what these babies can do

kind regards,

Harrison.

 

[Samuel Jayaraj]

The Zener mod was replaced by the RCR mod.

In a couple of threads I came across photos showing the zener mods. It will be nice if someone can post details of the mods for constructors to make their own comparisons.

Is the RCR mod mentioned in the quote above, incorporated in the latest released schematic?

Does R27 need to be changed from 2R7 to 10R?

Thanks,

 

[lanchile]

Because a) two pairs requires matching which I admit is only a small additional cost and hassle, but b) because today, there are new MOSFETs that weren't available to Greg originally which can handle the power with only one pair, c) some people say that a single pair sound better at low level details than multiple pairs

Fewer parts...fewer chances to go wrong!

 

[Bigun]

In a couple of threads I came across photos showing the zener mods. It will be nice if someone can post details of the mods for constructors to make their own comparisons.

Is the RCR mod mentioned in the quote above, incorporated in the latest released schematic?

Does R27 need to be changed from 2R7 to 10R?

Thanks,

Look over on the TGM7 - GB150 build thread - the RCR mod is a split of the current source tail resistor and a capacitor from the junction of the two resistors to the rail.

The zener mod is very similar, uses a zener to regulate the voltage at the same resistors.

My guess - Greg doesn't plan to release all the tweaks and mods. I believe he has confidence that the clever chaps on this forum will figure out their own tweaks and mods.

 

[davidsrsb]

The zener version improves supply rejection dramatically. The original GB design has excellent AC rejection, but allows the bias to collapse if the supply rails sag under load or low mains

 

[AndrewT]

Some have re-affirmed that ska gb150d is now public domain.
That is what Greg has released.

Buy a genuine SKA product to find the tweaks and mods that can be incorporated into the latest non public versions.