Help with a schematic to get more gain

[shawnc]

I proto'd a Marshall 18watt pedal, schematic: http://www.runoffgroove.com/eighteen.html

Now I used 117 model Jfets for it and the only other change was using 300k pots for the pre volume and gain controls. When I crank this pedal, I really don't get too much distortion out of it.

Wondering what I could do to get more gain out of this pedal(mine sounds nothing like the sound files form the page, almost like I am only getting half the gain)

I have the JFETS biased as 4.5 volts, 7.0 volts and 4.5 volts repectivly.

If I used 500k pots instead of the 300k would that make a difference(I could only get the 300k pots locally)

Any ideas on this would be most helpfull.

Thanks

Shawn C

[MartyMart]

You really need to hear this with J201 fets,for much more gain also you first "Vol" or rather "gain" pot
should be a 500k or 470k is close enough.
With your lower value pots and Jfets it just wont be "driven" enough for the right amount of distortion.
If you can find 1M log pots, simply solder a 1M resistor across the two "outer lugs" ( 3 & 1 ) to make this
a 500k pot
( 2 x resistors in parallel of equal size half's the value )

MM.

[Izzy]

Hi I had one question, Where A I suppose to put this circut in DS-1 to get more gain.

I think It should be just before opamp input right?
Anyone?




And can I ignore that volume pot?

[John Lyons]

With volume and gain pots (voltage dividers) the more resistance you have from ground the more gain/volume you will have.
500k has 200K more resistance from ground so there is a lot more gain to be had. Try the 1Meg thing marty sugested above.
Although this will change the taper of the pot to more linear so you won't have as much clean range on the pot in the lower settings.

John

[Izzy]

No I was talking about adding this above shown ciruit in DS-1 for BOOST mode.

[Izzy]

anyone?

[petemoore]

  This stage was made for boostin'
  That's just what it do!
  One of these days this boost...
  is gonna blast all over you !!!
  You been threadin' where you shouldnt'a been threadin'
  You been askin' will this work for you.
  You got you a brand new DS-1 yeah.
  But where it goes, you don't know just yet...
  This stage was made for boostin'
  That's just what it do!
  One of these days this boost is gonna blast a source for you.
  You been thinkin' of stickin' a boost in sooner
  Later might be the place you finally choose
  I bet boost could go into there somewhere yeah.
  If it were me, I'd tack it on the end...
  This stage was made for boostin'
  That's just what it do...
  One one big stage of boost might be too much boost for you....
 

[Izzy]

haha Nice song. I guess if it has some music It would be awesome!

I know its for boosting but I wanted to boost before opamp or may be diode to get more distortion? 

Haha

[MartyMart]

haha Nice song. I guess if it has some music It would be awesome!

I know its for boosting but I wanted to boost before opamp or may be diode to get more distortion? 

Haha

Read the "hundreds" of DS-1 threads, loads of tips for volume/tone/dist increase there !! 
It's just a few resistors caps and some LED's ......

MM.

[mac]

Now I used 117 model Jfets for it and the only other change was using 300k pots for the pre volume and gain controls. When I crank this pedal, I really don't get too much distortion out of it.

2SK117? I'm not sure but, are this fets higher gain than j201?. I built this with BF245A and the right pots and gain was ok as well as the sound.

mac