DOD YJM308 Input Cap question:

[themeanreds]

Hey y'all

I just got a DOD YJM308 ($30/shipped from Music123.com). I would like to mod this to something close to grey 250 specs. My question: Which capicitor is the input cap?

I am not yet well enough versed in modding to glean this from a schematic; any help would be great.

I would also love to learn to fish instead of just begging for some; any advice as to how I can learn to decipher schematics? Articles, books, etc.?

Thanks!

[burnt fingers]

The yjm is pretty darn close to greybox specs.  I think the opamp is the only difference.  Check out Analogman's site.  he mods al variants of the old 250.

Scott

[cd]

I would also love to learn to fish instead of just begging for some; any advice as to how I can learn to decipher schematics? Articles, books, etc.?

Thanks!

Get these two books by Craig Anderton: "Electronic Projects for Musicians" and "DIY Projects for Guitarists".

[themeanreds]

Gotcha; thanks!

Checking out this schematic, methinks that the .001uf cap to the far left is the input schematic, and corellates to C3 on the board:   

http://www.diystompboxes.com/pedals/schems/yjm308.GIF

Anyone know if this is correct?

[wampcat1]

Gotcha; thanks!

Checking out this schematic, methinks that the .001uf cap to the far left is the input schematic, and corellates to C3 on the board:   

http://www.diystompboxes.com/pedals/schems/yjm308.GIF

Anyone know if this is correct?

Yep, that's it.

bw

[petemoore]

  Do something with that.
  I socket all them input caps, except the ones that are ok...
  That ones Teeeeeeeeniiiieeee...and sounds like a mosquito...
  Being able to easily swap or add capacitence to that one is something I think you'll want to try.

[Mark Hammer]

The .047uf cap in series with the Gain control is also a major culprit if your goal is to improve bass response.  Stock, this produces no bass rolloff at minimum gain, but produces a VERY noticeable bass rolloff (starting around 720hz) at maximum gain, and lesser amounts of bass-cutting at medium gain.  As near as I can tell, this was intended to give a two-for-the-price-of-one change in sound, such that as gain went up not only was treble emphasized (because of distortion), but bass was cut.  This cap actually produces more bass loss than the input cap.

Changing it to .22uf or a similar value should give you all the bass you want, even at the highest gain settings.  because bass content is closer to clipping anyways, this will also result in a little more distortion/clipping than the stock version.