I just love the Masters Series (“L”) and Power Series (“10″) from Ibanez ! For a few bucks, you can get a MSL on eBay, full of vintage mojo components ! I like very much my TS10 and I find the MSL lacking “honk”. The adjective “metal” in this pedal is purely marketing, only bandwidth is different from a TS10 (more bass, less honk) …
The components are “vintage” and full of mojo … so rather than seek the Holy Grail TS808 several hundred dollars, why not turn this quite inexpensive MSL into a TS808? The MSL shared with my beloved TS10 the same printed circuit, some components in addition, a different capacitance value in the feedback loop of the op-amp clipping (I suspect of being guilty of the disappearance of honk), and resistance values of the output like TS9 (ie the couple 470R / 100R instead of 100k / 10k to TS808)
Here is Ibanez MSL schematic :
and there is a TS808 schematic (thanks to ggg)
Open the door, Hal …
Let’s see the polarization of the first transistor. On a TS808, the input stage is biased at V / 2. Here it is a bit higher (R2 / (R2 + R3)) x V, we will fix it. Good thing the jumper J5 is at a potential of V / 2, that’s exactly what we need !
We will remove R2, R3, and C2 and solder a jumper between the location where was the + of C2 (C2 – R4) with jumper J5. And that’s it :
We will now replace C6 82nF capacitor by the appropriate value for TS808: 47nF. I use a good quality Panasonic V-Series (ECQ-V) polyester metallized layer. Polypropylene would be welcome, but they are far too big …
Step 3 (optional) :
Well well, the presence of electrochimic capacitors (not polarized) 1uF C3 and C10 bother me a lot … I prefer to replace with 1uF Panasonic … let’s do !
Step 4 :
We will remove all the stuff before the op-amp, including (according to the diagram): R6, Q6, D4, C4, R7, R8, C5, R11. R11 will be replaced by a 10k, and we will place a jumper between C3 and the input 5 of the op-amp :
Step 5 :
The MSL (such as TS10, TS808 etc..) is not “true bypass”: it uses a flip-flop transistor based. On the MSL, a transistor audio stage was added, we will remove it. This transistor is Q6, so there are two Q6 transistors identified on the Maxon printed circuit (don’t care, we will suppress both anyway) : we will remove the Q6 and R39 and R40 and connect C15 to the emitter of Q1 via a jumper. We will also replace the two output resistors R21 and R22 by “good values” (100R, 10k)
Final step :
I replace all coupling resistors and capacitors with carbon comp resistors and capacitors Panasonic …
So how does it sound like ?
Very sweet overdrive, a lot of honk (TS808 720Hz typical frequency), full of sustain and harmonics … a great mod !
Very good reading :
R.G. Keen « The technology of the Tube Screamer » – Steve Cerutti – dolhop at canada dot com : see very interesting document here