DOD FX-50 Clipping Diodes

[soupbone]

Again, depends on how you're gonna use it.  The bass rolloff frequency is given by F = 1/[2 * pi * R * C].  With the gain control set to 100k resistance, the gain is around 10.5*, and the bass rolloff begins around 32hz.  With the gain pot down to 10k, the gain is now 69* and the rolloff begins around 230hz.  Drop pot resistance to 5k and gain is now 104X with rolloff starting around 350hz.  At max gain, the rolloff begins around 720hz.

The lesson here is that if you use it with the gain below max, then there will be little or no audible bass loss.  If your preference is to use it near max gain, then the bass loss WILL be noticeable.  My suggestion to increase the value of the .047uf cap was for those whose preference is to run the unit fairly near max gain most of the time.  Keep in mind that the use of germanium clipping diodes will keep the output level fairly modest.  Use of silicon 1N4148 will allow for a noticeably hotter output level, such that decent boost-n-grind can be achieved at less than max gain (in comparison to the Distortion+).  On the other hand, use of those same silicon diodes will also result in less clipping, increasing the tendency to dime the drive/gain control.

Again, no set orthodoxy here.  If your uinclination is to use it for just a touch of hair, then the values shown will do just fine for bass.  If your inclination is to crank the gain up and back off on the volume, then the way to recover that lost bass is by increasing the .047uf cap value.

Regardless of how you address your bass end, unwanted fizzies and harshness are cured by the suggested feedback cap addition, and by increasing the value of the cap paralleling the clipping diodes from .001uf to something roughly 2.5-4 times the existing value.

Great info as always!Thanks Mark!