Java Boost Bias Voltage? What is with the tone knob?

[vanessa]

I just built a Java Boost (Torchy's vero layout). The schematic I have (found doing searches somewhere) shows Keeley's voltages (on the one that the schematic was based off):

C=2.64
B=8.0
E=8.15

In the article on GEO the recommended collector voltage should be -7V. Why would the collector on the Java not be 7V (it's a negative ground circuit)? Why so low a bias at C (2.64V)?

Also my tone knob does not do much. Is it supposed to be pronounced?

[petemoore]

I just built a Java Boost (Torchy's vero layout). The schematic I have (found doing searches somewhere) shows Keeley's voltages (on the one that the schematic was based off):

C=2.64
B=8.0
E=8.15
  With no explanation these V Readings don't make much sense, unless  they're 'backwards'...
  Assuming they are 'backwards, without the supply voltage, pin voltages for reference purposes are of no use.
  In the article on GEO the recommended collector voltage should be -7V. Why would the collector on the Java not be 7V (it's a negative ground circuit)? Why so low a bias at C (2.64V)?
  The GEO article recommends -7v with a -9v supply.
Also my tone knob does not do much. Is it supposed to be pronounced?
  What does it look like on the schematic?

[vanessa]

The schemo was posted a while back but is no longer available on the forum (maybe got lost in with the move to a new web hosting service?).

Anyway it was a scan of a hand drawn schematic of the Java Boost. The author claimed that it was traced from an original. Torchy's layout confirms this. It shows the Java Boost as a neg ground with a pnp transistor.
But the voltages that the author shows taken from there original Java Boost are these:

"Voltages with 9V Supply"

C=2.64
B=8.0
E=8.15

I changed my C7 to .1uf and it now has a full sweep. I don't find the tone control very useful but hey, I'm not in the marketing business.
 

[gaussmarkov]

hey vanessa,

i just googled keeley's java boost for the schem and there's one on his site.  it's in the pdf file for the manual for the java boost, a single transistor circuit with a +9v supply.  is that the schem you are working from?

i also googled "oc44 boost" on geo and only came up with a zonkbst.pdf, which mentions a -7v reading on the collector of the third transistor with a -9v supply.  is that your other source?

the keeley doc has a paragraph in it on page 4 that may make sense of all this:  "please ensure that you set the collector to -7.2v as measured from the positive supply.  note: this is not a typical measurement."

so i guess that means your collector should be coming in around 2v relative to ground.  yes?

[Melanhead]

how does it sound ? ... I was gonna build one as well. I'm assuming Torchy's layout was correct ?

[vanessa]

hey vanessa,

i just googled keeley's java boost for the schem and there's one on his site.  it's in the pdf file for the manual for the java boost, a single transistor circuit with a +9v supply.  is that the schem you are working from?

i also googled "oc44 boost" on geo and only came up with a zonkbst.pdf, which mentions a -7v reading on the collector of the third transistor with a -9v supply.  is that your other source?

the keeley doc has a paragraph in it on page 4 that may make sense of all this:  "please ensure that you set the collector to -7.2v as measured from the positive supply.  note: this is not a typical measurement."

so i guess that means your collector should be coming in around 2v relative to ground.  yes?

That PDF has been proved incorrect. There are several things that are wrong on it; the big one is that the Java Boost is negative ground and in the PDF it shows it's a positive ground. It also shows that he takes the output off the emitter. The Rangemaster takes it from the collector and so does the real Java Boost. The 5k trimpot is really a 10k taken off the emitter. R2 shows a 220k resistor when it really is a 470k. And it's missing the on-off-on parallel cap switch. 6.8nf for stock and 10nf switched in parallel for mid boost, 47nf for fat.

So flip the transistor around so that the output is taken off the collector, make it negative ground (change up battery, diodes, caps), and sub in those part values and you have a Java Boost schematic.



For the voltages on my schematic my guess is the author had their measurements mixed up. I'm sure it should be +7V @ - ground. But maybe Keeley gives it a little more zing to his using +8V @ - ground.

how does it sound ? ... I was gonna build one as well. I'm assuming Torchy's layout was correct ?

Yes Torchy's layout works great. One issue with it. His 'Level' pot is wired backwards (unless you like to turn your pots CW to turn the volume off). He has lug 3 when it should be 1 and vs. vs...

It sounds great. I'm really enjoying it. I'm using an OC44 @ about 108 hfe. I like the mid-boost switch the best. Really creamy rock/blues distortion. Can you say '20th Century Boy'?  But the fat-boost is a little wolfy (even with tele pups). I would recommend trying a lower value in there, say maybe a .033uf and go from there.

The tone knob is almost useless with a .01uf in there. I think the author of the schematic (scanned, hand drawn one) had confused it with a .1uf. The .1uf works great but in this circuit it seems (for me anyway) to not have any place. I would leave it off. Torchy's layout shows it (.1uf) as a sub. My guess is others figured this out a while ago but no one could get a confirmation on the .1uf value.

[BD13UK]

Vanessa I belive all the Torchy layourts are anow residing here http://www.indyguitarist.com/

[vanessa]

Vanessa I belive all the Torchy layourts are anow residing here http://www.indyguitarist.com/

Errrr, ummm, thank you for the offer but I just built one last night...

But yes I think you can get Torchy's 'Layouts' there as well.

[vanessa]

I know this is not accurate but,

I found a photo of the guts of a Java Boost online. I did a close-up of the trimpots and set mine the same. Of course there are variations to take into account (OC44, hfe's) etc... But with mine set to the same trimpot settings to the "T" my collector voltage came out to +7V.

My conclusion is that hand drawn schemo had the collector voltage mixed up and it was probably +8V.

[analogmike]

The Java and old Orange Treble and Bass booster, and the Apollo version, have a TONE control for Treble and Bass tone. This is just a passive tone control on the input of the effect, it works just like turning down the tone control on your guitar. It does not really sound good when used, and you already have a passive tone control on your guitar, so we left that feature off, like the original Dallas Rangemaster. We found the way to get the tastiest tone was through the input capacitors, which is how our tone switch works. All your tone gets through, none is bled to ground like a passive tone control.

[vanessa]

I agree with that the Orange T&B booster is passive and had its TONE control on the input of the circuit. From the schematics I have come across this points to being true.

But the Java Boost's TONE control is on the output of the circuit taken from the collector and being active.

Interesting, I was reading my June 1995 issue of Guitar Player magazine (Stomp Box Fever!) and I noticed a Vox Treble & Bass Booster. I've never heard of this before and wonder if it's the same as the Orange T&B B?
Rumor has it that the Orange T&B B was made by Sola Sound. I have read they made stuff for Vox back then. Does anyone have a photo of an original Orange T&B B? The Vox T&B B was a small box approx. 1" square by 3" long with one control on it. It might have a 1/4" male phone jack on it.

Sorry it says: "Plug-in-your axe module", in the photo it's partly covered by an i.d. number (75) that is used for i.d. reference in the magazine. So I don't know if it has a 1/4" male jack on it.

[spudulike]

Verified schematic.

[gaussmarkov]

Verified schematic.

thanks, spudulike.  that is very helpful.

i'm digging the violet LED.  with so many different LEDs out there, i wonder whether the colour is the most important characteristic to know?    (seriously)

[vanessa]

Verified schematic.

Thank you! I have another but it is very usefull to compare.

[vanessa]

Since this is negative ground, can I just drop an NPN in this or do I have to change something up?

[petemoore]

  Ok...it's Pos gnd, and looks ok...the input switching is a little 'overlapped' the basic schematic...bias and all looks like an RM.
  The right half of that schem looks like my RM Testboard, I use it to bias Ge's differently, then take the R Readings and build a fixed values circuit from the data gathered.
  I don't know if the 100k is intended as internal trimpot, but loading the input signal more/less may be of benefit, plus this resistor value may help adjust in bias voltages for different transistors.
  The verified schematic looks wierd to me, as though the input comes from 9V+ or something
  The 10k @emitter adjusts gain and bias, not a bad idea for a circuit to match itself to transistors of very low consistancy one to the next.
  The tone pot is the one that makes sense for the circuit to be 'popular'...from one amp to the next, trimming the high end of a circuit with lots of it, and the content of it having as much 'character' as a Ge booster may have...additionally, the circuit doesn't produce gobs of gain, so just trimming off some treble will have about the least drag on output level. Sometimes the circuit could/may make high end noise too,  good to be able to adjust the high end for that reason also.
   I just ended up with an RM with a chosen teeny cap to ground LP Filter at input and small cap to ground at output, which makes it friendly to one amp at a time, these caps are fairly easily changed, voicing pots and switches would make the RM circuit more friendly to different amps, I'm strongly considering adding some to mine.

[petemoore]

Since this is negative ground, can I just drop an NPN in this or do I have to change something up? 
  >It looks to me it's a PNP Circuit, so using an NPN would require inverting the connections to all polarized components.

IT looks like there's 9V+ going to the emitter components as in original RM but modified, that'd be PNP Pos Gnd...I'd wait until someone at least shows my reading error or not before.
 

[vanessa]

Bump...

[Doug_H]

Within the dc blocking caps (the transistor part of the circuit) 9v is applied to the "ground" circuit, to accomodate the pnp transistor. Outside the dc blocking caps it is "0v ground". Perhaps that is part of the confusion. It will work fine this way, just make sure you wire the emitter circuit to 9v and the collector circuit to ground.  The coupling caps are what allow this apparent "flip-flopping" of the grounds in the circuit.

As for the tone control, you might try emailing Robert Keeley and ask him about it. Looks like it should work as is but you can always tune the cap value to taste.

Doug

[vanessa]

Within the dc blocking caps (the transistor part of the circuit) 9v is applied to the "ground" circuit, to accomodate the pnp transistor. Outside the dc blocking caps it is "0v ground". Perhaps that is part of the confusion. It will work fine this way, just make sure you wire the emitter circuit to 9v and the collector circuit to ground.  The coupling caps are what allow this apparent "flip-flopping" of the grounds in the circuit.

I don't understand. So if I wanted to use an NPN just flip that 47uf off the emitter around? Would that do the trick?