SKA GB150D now public domain...

[Samuel Jayaraj]

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

So which poison to pick?

 

[davidsrsb]

I don't know about any "official" zener version, but the RC filtered CCS design posted here has issues if the rails vary very much at dc

 

[Samuel Jayaraj]

I have seen these plus another photo which I will upload after changing the format.

 

[AndrewT]

Is that an extract from Greg's IP that is supplied to customers?

 

[PJN]

Hi Andrew,

It looks like it was taken from Greg's website from pages reserved for customers who bought the amp. When I built mine several years ago I recall following similar instructions that were posted on the owners page.

PJN

 

[Mike Gergen]

The current RCR configuration is 100k, .1u, 330k.

I used a 10u instead. It is an improvement.

 

[Samuel Jayaraj]

Here is another photo where the resistor values appear different.

I have made no particular effort to deliberately infringe upon IP, if any; a simple 'Image' search on Google brought up this information.

 

[Mike Gergen]

That was the original zener mod.

 

[Samuel Jayaraj]

Thanks for the info Mike.

However, the schematic in post #31 from Greg Erksine does not show the updated RCR values and PauloPT confirms in post #30 that the RCR mod replaced the Zener mod. So should one assume that the updated RCR mod enables easier stabilization of the amp, measures better (PSRR) and sounds better as well? ....just logical ramblings, because I am interested in designing a single sided PCB and building. Thanks.

 

[davidsrsb]

RCR does nothing to stabilise the CCS if the mains input varies or if the power supply sags over several seconds under load.
There is no point going crazy over this though, as the mosfet current still varies with supply even if you hold Vgs rock solid

 

[Mike Gergen]

If the supply is sagging that much over that long of a time frame you've got other things to worry about than the CCS.

 

[davidsrsb]

Really, class AB amp supplies have poor regulation as the load current range is so large.
Add in mains swinging from 250V down to 230V when all the air cons go on and you need a stiff CCS

 

[Bigun]

when all the air cons go on

you mean you actually turn them off sometimes

 

[davidsrsb]

Many countries are relaxing their rules on voltage and frequency stability of the mains supply these days to cope with too much unpredictable "green power"

In Malaysia power demand in hosing areas peaks in the evening, when people go home and turn their air cons on, drawing heavy load until the rooms have cooled down.
The distribution system was not built for the load and this makes the supply at the wall socket unstable

 

[Deleted member 148505]

My first iteration for the PCB design for this amp.
I am still aligning the labels hence no component name/values.

PCB size is exactly 3.35 x 3.85 inches

Less than 10x10cm so that pcb manufacturing will be cheap

 

[Stuey]

Hi Jester, what sort of heatsinks is that intended for?

 

[Deleted member 148505]

It will be mounted like P101.

What's the pinout for IRFP9240/IRFP240? Is it G D S?
I can't find it on the datasheet.

 

[Deleted member 148505]

Second iteration using GDS pinout.

I've also made it to be TO-220 compatible. In case there is.

 

[rough512]

Jlester : nice layout !

(fantom@elab)

 

[AndrewT]

What's the pinout for IRFP9240/IRFP240? Is it G D S?.........

Yes, all vertical mosFETs are GDS
All Lateral mosFETs are GSD.