[Lonely Star] An adaption of the Mesa Boogie Lonestar amp. Seeking comments!

[flo]

Perhaps using an oscilloscope or an "audio probe" will help determining which gain stage is actually oscillating. It's there that gain and/or bandwidth must be reduced in order to remove the oscillation.

[Ripthorn]

I know it has been brought up before, but that gain control is an interesting topology.  maybe try a traditional gain control on the breadboard to see if there are any differences.  Other than that, I can't think exactly why oscillation would occur on min gain unless there is enough gain after the gain control to induce it.   

[Auke Haarsma]

I still have 'a' version on the breadboard. Will fiddle some with the gain, source resistors and caps.

Also, I will prepare the 9V version for release. It is time that more people enjoy this circuit!

Mucho gracias for all the input, feedback and ideas guys!

[anti-idiot]

I still have 'a' version on the breadboard. Will fiddle some with the gain, source resistors and caps.

Also, I will prepare the 9V version for release. It is time that more people enjoy this circuit!

Mucho gracias for all the input, feedback and ideas guys!

Dude, c'mon, this waitin' is killing me! /jk

[Auke Haarsma]

@Anti-Idiot
If nothing weird happens I'll post the project tonite. I just want to make sure that what I post can actually be build and is useful . Parts layout and wiring is already done. Just need to beautify the schematic a bit and do a write up. Ah, also I need to prepare the parts-layout for a 3-knob version and describe the possible mods (that I see).


@Oscilliation
Well, I've used my scope to pinpoint the oscilliation. But, to no avail. I can't really see where it is comming from. It looks like it is already there on the input, but I see no reason why that would be the case. In the 9V-mode I don't see it at the input however...

I've tried different J201's in all Q's. Swapped them to 2n5457's (lower gain) to see if that would help. But no go.

And now for the weirdest thing: It seems somehow (indeed, as Brian mentioned above!) to be related to the Gain pot. The Drive-pot (from the lead channel) doesn't matter at all.

I wrote before that there was oscilliation at min gain. Well, that's not the case.... I somehow managed to swap the Volume pot and the Gain pot when I put back this board into the enclosure. Corrected that now, here are my findings:

Gain pot:

• from 7 o'clock to 9 o'clock: nothing, no oscilliation
• from 9 o'clock to 10 o'clock: faint oscilliation
• from 10 o'clock to 12 o'clock: increasing oscilliation
• from 12 o'clock to 2 o'clock: decreasing oscilliation
• from 2 o'clock to 5  o'clock: Max gain, but NO oscilliation.

So, it is NOT gain related. Or, there is no direct relatation to the amount of gain. If that would be the case you would expect max oscilliation at max gain. Well, at max gain: no oscciliation.

I don't really understand what is going on around the gain pot. Some1 with an idea?

[Ripthorn]

Typically oscillation will  increase in frequency as the gain is increased, so it might be that the frequency of oscillation is just going above the audible spectrum (or high enough to get masked by the guitar).  Of course, I can't speak as to exactly what might be causing it.  If you post the project, then I will try to get it breadboarded over the next couple nights and see what I get.

[mikkemato]

sounclips would be nice!

[Andre]

Have a look here