NYD one bottle, more saturation?

YLab said:

aronaut said:

...reading back through the threads I don't think it was possible to have an output attenuator without a transformer. 

Click to expand...

I'm not sure but I think that a L-pad on the output would do the thing!? Maybe someone could suggest some resistor values?

Click to expand...

..what is so wrong with just replacing R10 with a pot...yes, you might get a strange responce curve, but you get used to it...

j

Just tried swapping the values of R10 all the way down to the 30-100ohm range.  it definitely reduces the output enough to get some interesting saturation without clipping the console.  but it's acting like a HPF along with some reduced top end, actually sounds pretty cool but not really useful enough to implement.  I think I'm not gonna worry about this idea now and leave as is. 

definitely the cool thing is to have the zobel switchable, really useful for top end on ribbons.

thanks everyone

You'll want a (250k) pot with your output coming from the wiper for r10. A 100 ohm resistor is a really bad impedance mismatch, which would explain your loss of bandwidth.

aronaut said:

I searched for the 'no-feedback one bottle' pdf, but no luck: http://www.groupdiy.com/index.php?topic=16727&highlight=, what's up with the www.twin-x.com/groupdiy can never find what I'm looking for there.  anyone still have the pdf?

Click to expand...

Here is the pdf, it was in a thread here by NewYorkDave, called "a quicky" on the Drawing Board, have done a search here but can't find it.

Salvatore said:

aronaut said:

I searched for the 'no-feedback one bottle' pdf, but no luck: http://www.groupdiy.com/index.php?topic=16727&highlight=, what's up with the www.twin-x.com/groupdiy can never find what I'm looking for there.  anyone still have the pdf?

Click to expand...

Here is the pdf, it was in a thread here by NewYorkDave, called "a quicky" on the Drawing Board, have done a search here but can't find it.

Click to expand...

Cool. Thanks for sharing this.

thanks for the pdf 

it's the same difference using a 250k pot for R10, when the NFB loop is at maximum gain (audible saturation) I have to turn the 250k pot down to about 100 ohms to make my console input happy, still resulting in impedance mismatch.  I think the only way to go is output transformer + attenuator.

Sorry, no, you need to wire the pot like a volume control, top lug to C4, bottom lug to ground, wiper as the output.  The the last stage will still see it as a 250k to ground no matter where the wiper is set.  A 100ohm resistor there is a very different situation.

If you don't have a pot handy, try different value resistors in series (on the ground side) with r10, and take your output from the junction of r10 and the new resistor.  This will simulate the voltage divider action of the pot, and keep the last stage happy.  So it will go c4->r10->new resistor->ground and the output comes from between the two resistors in the r10 spot.

Ah.. thanks Baltimore I'm working on it now.

I see no mention of the feedback paths through unbypassed cathode resistors .
You can pop in switchoutable capacitors across both cathode resistors since you've left theory and have gone empirical.

Robert