Smallest sustain circuit possible

[joelap]

Hey,

Finished modding a BD-2.  It just needs more sustain.  Brian Wampler told me that a bd-2 cant get more sustain by modding it, it'll need an external comp or sustain pedal to do so.  But, I'd rather have it built into my BD-2.  Curious if anyone has a link for the most basic sustain circuit possile?  I'd fit it in the battery comparment or something if I need to.  Just need something that'll hold the note for a little bit longer.

Thanks.

Joe

[Phorhas]

If by "sustain" you also mean the illusion of a long decay - then any of the popular opto-comps should do the trick (CA comp, flatline, LA-light etc...). Parts count is near to nothing and the sound is quite good

[joelap]

If by "sustain" you also mean the illusion of a long decay - then any of the popular opto-comps should do the trick (CA comp, flatline, LA-light etc...). Parts count is near to nothing and the sound is quite good

Perfect.  Mind linking me to some of those?  I searched for the Craig Anderton comp a while back and didnt get much other than 1 fortunecity hosted website.

[petemoore]

  Amazing...type in Flatline Compressor at google, and the top choice is
  http://www.geofex.com/PCB_layouts/Layouts/flatline.pdf#search=%22flatline%20compressor%22
  I used to box or testjig circuits to decide which one belongs with which other one, the BD-2 'is' a compressor [if we're talking about a TS topology], in that the diodes limit when voltage exceeds a certain amount, to hit that amount sooner...you could try just a regular gain stage, a booster in front of it.
  I've only built an OS, and a Ross-ish Comp, For 'sustain'...running the Ross or some other 'powerful' [the OS is 'mild' attenuation, transparent and nice] compressor can attenuate/recover hard enough to 'swell'...through a Distortion device this can sound like turning the guitar back up after every attack...[may squash attacks too...]

[joelap]

Hmm... adding a gain stage would be much easier to do.  I could add the gain stage right before the input to the actual circuit (not the switching section), and that wouldnt require much more than an IC, and two resistors for a basic non-invertor.  Would that do the trick?  Could I set up a basic non-inverting amp using a JRC4558 or something, or even any other general purpose op-amp?  How much of a gain factor should I give it?

Thanks,

Joe

[Phorhas]

You can use a differant booster infront of the BD-2 but if you  insist on tapping into the circuit then I gues you could do this:

An FET gainstage could do nicely and it's smaller and quieter than an OA. take C18 (i think - the schem is blurry - it's the one right after R22)

solder two hook up-wires and run them to a breadbord - now you can try what ever comes into mind and you could pre-tune you bosster befor installing it. use apot to trim the bias voltage to about 1/2 of the supply voltage and mesure the resistace from V+ to the FET's drain lug (with no voltage running at the time).
Now, all that's left is to put your tiny booster into a tiny prefboard and solder it in the hook-up wires' place. you could design it like that so a switch will toggle between unity gain and "boost" by disconnecting the bypass capacitor on the FET's source (note that this action may cuase a "pop" as the cap will discharge it self. to avoid that run a 1M resistor from the SOURCE to the bypass cap and the switch will short the resistor, enabling the boost function)

this is all theoretical as I haven't preformed this mod myself.
have fun tuning it to your liking and don't forget an output cap to compensate for the loss C18 

[petemoore]

  You'll have to pick a place in the schematic to splice it in after the input switching and the clipping section to tell what that'd sound like and have 1 bypass' switch bypass all.
  Just 'throwing something in' may well be the optimal choice, however one cant really know whats really good without trying at least a few approaches to See what sounds better to you there'.
  This is why I like testjig and a few different circuit's to sample/match to find a more 'optimal' preboost for distorter...thing is unless you tap inside, you're prebuffer, to have it switched out with the circuit it'd have to be post buffer...I can't say for sure if that'll make a large or small difference [~testing boosts pre-buffer when you'll probably want it placed post-buffer for switching]...if the impedance of the boosts input is high, output is low Z, probably not a huge amount...
  Then there are the wire-runs, which could be troublesome, IIRC the BD-2 isn't super high gain, of course a preboost will signifigantly increase the overall gain, noise will probably be 'somewhat' greater.