BC Rich booster Cap Mod

[bassboy]

Mick, for sure the best way. I'm probably going to run two wires outside of the control cavity and solder onto those, and after determining what I like I'll do a single and careful hard wire soldering without the switch

[bassboy]

This booster was designed to over-drive the preamp input of a tube amp. The eq curve of it was probably set so that the distortion it creates isn't quite as scratchy-sounding, which might explain the low to midrange lift when engaged. I think this was designed for primarily for guitar, but they carried it over to their basses, too.

[g1]

I think this was designed for primarily for guitar, but they carried it over to their basses, too.

I have the guitar, and it (the boost) works very well. And nice to have a 'magic switch' with no pedals to be seen.

[bassboy]

James Tyler offers a mid booster for his guitars. too. For my bass I want to use the booster for raising level when I set the pickups to parallel. Maybe this mod will make it lean more towards a general boost. If it still has some midrange character after the mod, just less of it, it will probably be fine.

[J M Fahey]

No schematic available and by description it sounds like a *crude* single transistor booster or something.

Wouldn´t be surprised, at all, by finding a Germanium transistor there, go figure.

The small input cap mod seems to turn it into a cousin (if not a brother) of the infamous Dallas Rangemaster treble booster.

Whose only justification would be that Eric and Ritchie used them.
Well, not much else available way back then, was it?

Personally I would waste no time polishing a turd and instead would replace it by any modern, much better performing PreAmp/EQ/active electronics module.
Many available on the Market or you might clone whatever some other killer Bass has inside.

Clearly not even the Mod could save this one, that sure says something.

jm2c, YMMV, etc.

[Chuck H]

No schematic available and by description it sounds like a *crude* single transistor booster or something.

Wouldn´t be surprised, at all, by finding a Germanium transistor there, go figure.

The small input cap mod seems to turn it into a cousin (if not a brother) of the infamous Dallas Rangemaster treble booster.

Whose only justification would be that Eric and Ritchie used them.
Well, not much else available way back then, was it?

Personally I would waste no time polishing a turd and instead would replace it by any modern, much better performing PreAmp/EQ/active electronics module.
Many available on the Market or you might clone whatever some other killer Bass has inside.

Clearly not even the Mod could save this one, that sure says something.

jm2c, YMMV, etc.

Well, to be fair the proposed mod hasn't been implemented and tested yet. But generally I do agree with you. Altering the input signal to the boost preamp is somewhat clumsy. Better if the preamp were a stand alone performer. There are likely noise floor consequences. But we don't know if we don't try. We'll see what bassboy reports when parts arrive and after some experimentation.

[Mick Bailey]

G&L used a series capacitor to reduce bass with some of their 6-string guitars and that works pretty well. I wouldn't necessarily say that a series cap will result in a poor outcome. The G&L circuit uses a 1M C taper pot in parallel with the capacitor as a bass control and I've used the same circuit in some Jazzmasters with excellent results.

It did cross my mind as to why the preamp is bass-heavy. You'd expect a preamp to give a flat-response boost but without knowing what the intention of the design was and seeing the schematic it's difficult to say. If the circuit is the same as used for guitar then boosting bass isn't generally what you'd want when pushing an amp as it usually results in a flabby, intermodulated unpleasant distortion.

[bassboy]

My first cap arrived today .0047; this is the suggested mod by the Moser to raise treble. I installed it and yes it did raise the high mids and some treble, but now all the low end is gone. Since this is a bass, not so good for me. I'm still waiting for the cap/resistors suggested by Chuck. The .0047 is a bust for bass. I won't change the circuit out for a modern one because of the value of the original instrument. So back to the bloated bassy sound with no high mids or treble until the other parts arrive.

[bassboy]

Mick, the stock circuit cuts highs and boosts low mids and mids; not hearing a low bass boost to my ears. So that's why it doesn't work for general bass playing, for me, unless maybe I intended using it like a guitar would for soloing. It's a booster that's cool for guitar per g1's above post

[bassboy]

Here is the circuit demo that includes the cap mod --there is a ad in front. You can hear the thump added when using the stock boost, and then you can hear the thump much less when they kick on the cap mod. https://www.google.com/search?q=BC+R...8Go0Hds3M,st:0

[Mick Bailey]

Take a look at this adjustable circuit. You could use a regular small 12 or 25 turn trim pot but due to the taper most of the useful adjustment will be at one end. You could wire this up and leave it inside the bass. You'd still need to pick the best cap value. This comes back to Chuck H's parallel resistor suggestion.

[bassboy]

Mick, thanks for this.

[bassboy]

Chuck, after testing all the cap/resisitor's in your list I settled on your suggestion of 1000pf in parallel with a 51K resistor. It has plenty of boost, and when I switch the pickups from series to parallel the 1000pf/51K combo sounds absolutely killer! Trying many resistors was the ticket, and having a trim pot like Mick suggested would have been great, and would make a nice addition to a circuit like this. The bloated sound of the stock circuit is gone. Now the circuit is acting like a straight up booster with a really nice slightly beefy tone. I truly appreciate all the detailed and time-consuming suggestions by all. Best regards. Keith

[bassboy]

These weeks later I realize I have a noise gate on as I test these combinations. With the gate off I'm noticing noise, a low air type noise (best I can describe it) when I engage the cap/resistor in parallel combo. I have no noise when using just a resistor. Any suggestions? I should add that the booster is original 1978. I just purchased another of this same circuit, but modern and made today by the same maker, and it has no noise when I engage the cap/resistor combo.