What do you DO with ROG effects?!?

[Praying_V]

Well then!!  Here's another question:  Let's say I have several different amps.  Is each one's power amp "expecting" a different level of preamp signal?  I mean, could a preamp (solid state or tube) be freely swapped into different power amps, or would its output need to be tweaked depending on the power amp's design?

............................ken

[MartyMart]

Here's an MP3 of my little TDA2050 amp, can have whatever "pre" in front of it.
http://www.aronnelson.com/gallery/main.php/v/Martys-layouts-and-photos/tda_demo.mp3.html

Here's the thread, seemed to have the MP3 missing from it, that's why I posted it separately ??

http://www.diystompboxes.com/smfforum/index.php?topic=57018.0
Some interesting stuff in the thread .

No "OT" but a fine sounding "SS" amp all the same.
I did eventually put it in a large "Alu" box and used the box as the heat-sink ( isolator pad on the chip of course )

Marty.

[DougH]

My intent in suggesting use of output transformers was to permit use of traditional presence controls that actually use the input-to-output differences in transformer signal to clean up the signal.

Mark, a presence control is basically a low pass filter with variable fc that is in a negative feedback loop. The "input" is usually taken from the low voltage secondary side of the output transformer due to convenience, I suspect, as there is no high voltage DC component there. I don't think the xformer serves any purpose other than to provide DC isolation and scale the high signal voltage down to a more manageable level. You could do that with a divider and a cap but with the output xformer you already get that for free.

With 9v pedal circuits, this isn't an issue. Check the Axis Fuzz schematic for a good example of an NFB presence circuit used as a gain control in a fuzz pedal. Also- op amp based distortion pedals implement similar principles in their NFB-loop gain controls.