Nestor wrote:Alfonso, would you please add to here how you build it a Little? For instance, which are the amps and the guitars you used at home? A picture of them all would be great as well as their specification.
I would love to know which are the basic parameters you used to get this thick sound up and running.
When you talked about the amps at home, do you mean you compared the sound that you could get from an amp, and then you tried to approach it to Mojo?
How did you search this particular timber? I think it is interesting to get there, if you have the patience and time to share this with us… Cheers.
Dear Nestor,
I'm very pleased of your interest on the subject.
The way i built Mojo comes basically from the study of what happens to the guitar sound through all the path of in tube amps.....which are not all equal in design, fortunately I didn't have to reproduce the design but the sound. Anyway, from Mojo's layout it is clear that there are 2 basic saturation blocks, one that resembles an amp with very high headroom where the sound is progressively enriched but it's not too easy to distort, and another one which at the opposite can go pretty brutal and that features six basic selectable circuit topologies that go from the most bluesy to the heavily scooped and some variations in between that i found interesting to my own taste....tweaking and listening, unrelated to any real amp but related to all the memory of music stored in my mind.
I wanted to achieve the most in terms of flexibility....I thought that it would have been really nice to have a single device loaded in Scope that could take care of all my needs. That was the reason of starting with a double channel. But I also realized that making those two channels mixable brought an infinite array of possible sounds. Hence the Mix control.
I was facing also the noise issue. Ok...I thought, I need to put a guitar optimized Noise Gate in here! that was done...but...why don't try to do something to reduce the noise before it happens? One of my favorite pedals came to my mind, my truly loved Keeley's Java Boost. It is basically a germanium booster which has the ability to enrich the sound of the guitar very much, with a switch where you can select from the typical Rangemaster treble boost thing to a more medium effect or a full range one, keeping the sound very clean and noiseless. The beauty of this pedal is that if you are plugged in a tube amp that is just at the very beginning of the crunch, thus still very little noise is heard. and you engage it, you get a stunningly rich and creamy saturation, a noticeable increase in level, but the overall noise is quite less than the one you would have if reaching that saturation and level cranking your amp much more.
This gave me the idea to be able use the output of of the first channel, already enriched and at an healthy level but still with a low amount of noise to feed the second channel. This way you can reach some good levels of saturation keeping the second channel's drive control much lower, thus minimizing the noise as much as possible. Practically transforming the first channel in a sort of (almost)clean boost to drive more efficiently the second one.
Obviously whe you really want to go brutal with a normally noisy guitar
the noise gate becomes necessary most of the times, like in real life high gain amps.
There is also an interesting implementation of the bright switch. I tried to make it inversely dynamic, like a typical vintage bright channel which uses a capacitor as treble bleed across the input gain that increases the treble amount at lower levels. A nice effect of this circuit is that when you clean your sound decreasing the volume on the guitar it helps keeping out some muddiness that might normally occur.
The "british" switches that you can see for each channel are not related to that part of the Marshall circuit that is thought to push into saturation the power tubes earlier than in a typical Fender amp, as this type of saturation is available by tweaking the drive knobs and the color knob and we are not operating tubes here after all, but it is related to the way the tone controls are conceived and shaped, which is what brings an immediate difference in the real world amps. I studied the typical curves of many amps (by charts, I don't have that many amps), detected the main differences between American and British models but i shaped the two curves to my taste.
Now my amps....they have not been my models, but they inspired me somehow....
I have three of them.
The one that really dominates the bunch is also the smallest one. It's an handwired point to point Ceriatone 5e3. Practically the clone of a '57 Tweed Deluxe, except for a standby switch that replaces the ancient phase switch. It is a full class A with 2 JJ 12AX7 (it should have a 12AY7 in V1 but I like it more like this, at least more than the EH 12AY7 that i didn't like at all) and 2 6V6 and obviously a tube rectifier, a 5Y3GT. The speaker is a Jensen P12N, alnico, .
This is the core:
It is mounted in a black steel chassis with high quality custom transformers, a tweed resonant pine cabinet. This baby has an incredible tone.
Then I have a very practical Marshall JCM2000 TSL 100 amp, not at the level of a vintage one but much better than a lot stuff i've heard from the same company. It is quite stock, I'm not using it too much so I'm waiting to upgrade the tubes and maybe a better OT. It sings and screams through a boutique Dragoon Cabinet with two Celestion V30
Here it is (not mine):
Then I have a Fender Hot Rod Deluxe. I was almost selling it when I decided to mod it. With Jean Jacques Ferry, a friend of mine who is a magician of the soldering iron and knows the world of the tube electronics better than anyone else i know, we changed completely its sound. First of all the crappy stock speaker has been changed with a V30 (I had tried it from my cabinet and I liked the combination. Then we changed a lot of stuff, some to blackface specs, with added controls in the lower part of the chassis and now it really acquired that authority and sparkle that was totally missing.
I’ve got so excited about it last night... I started with a loop for fun, and went up to 5 in the early morning building something to improvise upon: 
