Amp distortion

[ApD]

Hi, AndrewT,

Hi,
A pot in parallel would be better. To be replaced by a fixed resistor on the back of the PCB if there is no room in the layout.

Yes, that would work too. Once the value has been determined, remove both and place just one resistor as R3.

R10a and C4 have a 0.01uS time constant.
I would increase RC by a factor of 50 to 150.
What effect will this have other than the simple filter?

Sorry, I don't see RC in the circuit. Maybe you mean RG - the ground lift resistor? It is typically 10-22 ohms.

In my circuits, the time constant of the input RC filter is usually higher, pole frequency around 100-200kHz. Keep the resistor low so as not to introduce thermal noise at the input.

 

[AndrewT]

Hi,
I omitted time constant from RC, sorry.
R10a and C4 have an RC time constant of 0.01uS that is not 100kHz to 200kHz

 

[ApD]

Hi,
I omitted time constant from RC, sorry.
R10a and C4 have an RC time constant of 0.01uS that is not 100kHz to 200kHz

No, it's not 100-200 kHz, obviously. These values are the "minimum recommended" for stability. Inclreasing both by a factor of 10 or so would do, but there's also nothing wrong in having a wideband, fast-slewing amp, is there? Adjusting the values is a matter of personal preference and sometimes has a noticeable effect on sonic performance - dependant on the cap type.

 

[zeus_threat]

Thanks for the posts

Hi well thanks everyone i have had more mods than i could ever think of. Regarding current mirrors i wanted to add them but my aim was to keep this amp as small and as cheap as possible. Actually i have to re-route the ground for the protoype. The actual prototype has been quick built on veroboard for a quick test running with +-15V PSU for the time being. I'll go for a pcb after everything is stable. Actually there is only 1 track on which all grounds are connected. Attached picture shows how components have been placed on the veroboard. Sorry you will have to rotate the picture. The gray line shows copper tracks and the x denotes track cuts. Any better layout advice fully welcome.
P.S 68R are now 22R.