What to change for LPB-1 to work with 15v?

[bluesdevil]

I need to use the LPB-1 to boost the signal of the chorus mode in my NeoVibe. I know where and how to wire it in and got it boosting the signal, but the transistor sound is badly misbiased .... fuzzy and cutting out.  I'm thinking it's due to using the 15v power source. Would I have to change all the resistors in the LPB-1 circuit or just tweak the resistor going to the tranny collector? Everything's soldered in place..... just thought I would ask  before I start tearing it all apart.
           Thank you!!

[petemoore]

Don't exceed Exactly 23.5 or so volts [-/+ 10% rating generally, but I think my meter's off a tinch sometimes too] at V/inand use caps rated for 25 volts or more. Applying more than rated is NOt recomennded unless you want to smell what they Doo, wear goggles.
 Data sheets tell max voltage of your components, sometimes they don't always see V+ to V_ though.
 LPB just make sure the caps are rated for whatever voltage they'll be seeing.

[RickL]

I had some luck using an LPB-1 with other than 9 volts (lower in my case) by adjusting the two resistors going to the base of the transistor (one from supply to base, other from ground to base). I temporarily replaced the two resistors with a pot, value equal to the two resistors added together, wiper to base of transistor, one leg to supply the other to ground. Adjust the pot for best sound, remove the pot and measure the two resistances and replace with the nearest standard value resistors. Or just build it using a trim pot in place of the resistors.

I also seem to recall Jack Orman having an article on rebiasing transistors for lower voltages. Should also work for higher voltages I would think.

Edit: I just checked. It's the Low Voltage Boosters article in the Lab Notebook. He also changes the emitter and collecter resististors but I don't know how he determined what values to use.

[bluesdevil]

Many thanks for the replies, gentlemen.  My caps are rated at 100v, so I'm fine there. Also tried raising the collector resistor with no change, which I thought would surely nail it.
   Will definitely try adjusting the 2 resistors (with a pot or sockets) as suggested...... thanks for sharing your experience. Will post back later if successful.

[bluesdevil]

Got it working!!!! Used a 1M linear pot and got 884 and 128 for each resistor and ended up using a 15k instead of 10k on the collector. Sounded distorted when I picked or strummed other than lightly, so I experimented with raising the emitter resistor and settled on 2.7k instead of 390 ohms .  I mounted a 100kA trimpot on the circuit board for volume.... easily brought the level to unity and above.
     Now my NeoVibe kicks ass!!! I was gonna do a blinking LED mod but I'm afraid to muck about with it and risk burning out a perfectly working circuit... but I have a habit of not leaving well enough alone.