Settings of Joes Silver Jub? (Page 1 of 2)

Bass at 10 and master at 10?
thanks Ron

I'm pretty sure he uses the gain channel but I am not positive.

Surprisingly, I tried these settings on my JCA and I loved how it sounded.

He uses the Lead channel. Sounds awesome like that.

The man has spoken...
See you in Birmingham, AL next month, Joe.

I'm a bit late to the party, but what you say is partially correct, but not fully. The OD LED on the front is not in the signal chain and has no relation to creation of OD, it is simply taken from the low voltage switching supply that does control the foot/panel channel switching of the amp. So if it goes out, it;s because you've lost DC switching power and in deed the OD channel will not work. The OD LED on the panel has a constant DC supply on it. That DC supply is haphazardly derived from the tube heater AC supply and used to create an unregulated DC supply. This arrangement is the archiles heel of this era of Marshall amp and is very prone to inducing noise that is very difficult to lead dress away. This circuit also has a rather high failure rate. A much better upgrade is to use a seperate 12V transformer and build a regulated 1A DC supply and let the filament supply just do what it does best, powering the tubes heaters. I've done this mod with 100% success to many Jubilees / late JCM800's. THe difference in noise level  is uncanny. It also means you can common ground the -ve to the chassis, something you can't so with the stock setup because the AC heater supply is center tapped.

As you mentioned, the preamp OD in a Jube is most certainly created by a combination LED's and diodes. THere is a network of Two 3mm red LEDS's and 3 1N4007 silicon Diodes arranged to create asymetrical clipping (like in many OD pedals). This network is placed between gain stages 2 and 3 and essentially clips the peaks off the waveform. THere is a small capacitor across the whole network that rounds the edges of the waveform to better emulate tube clipping. THe reason the efffects loop in these amps works so well is because it is placed just after this part of the circuit and is dealing with low level signals as opposed to having to attenuate them first. The rhythm clip circuit is a pair of parallel 1N4007 diodes arranged to symetrically clip the waveform, but at a much lesser degree than the other network. Symetrical clipping leads to more odd order harmonics and gives the OD a more direct cutting tone. Assymetrical has much more even order harmonics which give overdrive much more 'width' and dimension. However too much even and it's lost in the mix, too much odd and it's too directional. Perfect overdrive is the correct balance of both. It's like a recipe.
The reverse voltage properties of a diode (or LED) are the reason they clip the waveform.

Sorry if this is a bit too techy for this forum, but someone may derive value from it.

Alan.
Carol-Ann

well, now if I ever own a Jub, I might have to ask Carol-Ann to mod it! B)

- Nic from Detroit... posting on JB's Forum since 6-2-2006
Ask me about my handwound Great Lakes Guitar Pickups
Since 2010, Bonamassa fans have taken advantage of my JB friend discount = my cost + shipping.

Yeah it's dead easy to have mixed that up. Joes actually very tech savy when it comes to his gear and is the first one right in there logically fault finding if anything is wrong.

Good question on Red and Green/Yellow LEDS. Glad you asked that. The key is the forward volt drop, which can range from 0.4V to over 1V depending on the device. Basically the diode doesn;t start conducting until it reaches this voltage. THe effect it has on an AC signal is that it clips that amount of voltage from the waveform creating a wave form that has a more flat top, getting closer to a square wave. A square wave is a complex wave that only has odd harmonic integers. That would sound like a buzz saw. So if the +ve and -ve sides of the waveform are clipped differently (assymetrically) the even order harmonics are not phase cancelled out giving the tone more width and a much more pleasing realistic tube like tone. THe small ceramic cap cuts the 'corners' off the square wave which removes some of the high frequency buzziness out. Increasing that value attenuates the highs even more and can be effective in taming a particularly buzzy example.
The use of different color LEDS will affect the symmetry of the waveform because of the different forward volt drop values.
Even a sample of the same model LEDS or diodes you will find quite a variance in forward volt drop. Given there are 7 in a jubilee, it's easy to see why there are so many variations in OD tones among those models. Apart from the obvious condition of tubes, it's this network that defines a warm one from a buzz box and unless you experiment with this network, no end of tube swapping or biasing will warm up a cold buzzy jubilee.
I've had Joes silver one that was his fave for a long time (a Canadian model) on my bench and that had a very balanced network and was naturally a warm and wide amp.

While the Guv'nor does use a smililar type of clipping arrangement, it's a little different. Plus it's acting on a pure guitar signal from an op amp. THe signal levels are higher in the jubilee because it's after a tube gain stage. This is also the reason there are  more clipping devices in series, because the signal levels are higher.

I've no idea about the Cat 5. I assume it's probably a jubilee clone but laid out on a PTP board rather than a PCB. Don could answer that. As mentioned above, the selection of the LED's/diodes is the biggest area of tweaking. The originals use 3mm LEDs. Personally I prefer 5mm, one red and one green while retaining the 1N4007 network. This makes the amp a little more 'classic rock' sounding and not quite as much 80's metal.

Quite honestly, I'm not a huge lover of the Jubilee for three reasons. It's a little thin and buzzy at low volumes, very incosistant one model to the next for the reason stated above and just by personal preference I prefer to control harmonic makeup one stage to the next using tubes and end up with a much lower noise floor and better low volume performance.
The other problem in some scenerios  is the designs inability to clean up well from the guitar volume. Joe leans in to one of his other amps when backing off the volume for cleaner passages. That said that little bit of preamp od mixed in the clean tone along with the trem effect is very signature JB and I do like that a lot.
However, I must say the design does have the most ideal serial effects loop of any amp I'm aware of. This loop design can't be transplanted as is to another amp design simply because it's taking advantage of the low signal levels after the clipping stage.
Here's an interesting point,  if you remove the clipping stage from a jubilee (I have done this) it's actually a clean amp with no preamp gain at all. The whole design is focussed around that network and all of it's preamp OD comes from those solid state devices. Still if you have a good one, it is a fantastic sounding and feeling amp. Joe has the ability to pick the good ones and has an ear for it.

You must also bear in mind that preamp on, it's essentially a power amp stage similar to a Plexi Marshall and Joe runs all his amps in to power tube overdrive. Much of the big warm Jubilee tone he has is in fact the power tubes contribution. THe preamp just adds the spice to the highs and lows.

Hope thats helpful in demystifying the infamous Jubilee !!