More Mods
DSL 50/100 – Joey Voltage Mods
FRONT BOARD:
1. 1M resistor from wiper to ground on VR3
Put a 1M resistor from the wiper to ground of Vr3: This has a dual function. It limits the amount of drive signal possible for low frequencies below 169hz (not taking in account for any other low frequency roll off below this point of course. full up, frequencies below this point will be down -6db, and flat. it also slightly alters the peak response of the shelving filter created by R19,C11, and Vr3.
2. R20: removed and jumpered
jumper R20: adjusts the strength of the aforementioned shelving filter.
3. C10: replaced with .0022uF/ 2.2nf / 222k @63v
Replace C10 with a .0022uf: Reduces the amount of low frequencies passed on to the next stage in conjunction with R19, Vr3, and the source impedance of the driving stage. this has the benefit of tightening the sound by somewhat tailoring the bass content within the guitars useable range, and can encourage a higher mix of second order harmonic content (but that’s for another discussion). This will also help with potential blocking.
4. C12: cut out or replaced with 150pF/.15nf /151k @63v,
Keep C12 or remove: Keeping C12 alters the R19,C11,Vr3 shelving filter further by moving the beginning of the upward shelf high at lower gain settings (because the top half of Vr3, and C12 are now in series with R19/C11 ignoring other circuit impedances of course) giving an edgier sound. when about 3/4 of the way up the shelving effect becomes negligible, and eventually the cap is shorted out by Vr3. Removing it obviously will darken the tone of OD1, and OD2 by removing this effect, but also does so because this now puts larger resistance in series with the grid of the next valve, whose input capacitances will create a low pass filter with this resistance, and bleed highs further.
5. ****C8 replace with .0015uf / 1,5nf/ 152k - only if boomy
MAIN BOARD:
****C46: replaced with same value of 22pF @ 1000v Not installed
6. C9: replaced with 1000pf/1nf / 102k 500v Polyprop
C9 1000pf (.001uf)creates a single pole high pass roll off of around 3.2Khz which is around the fundamental of highest note of the guitar. there are also very few useful harmonics for guitar above this, or that can really be reproduced by most guitar speakers. it also can reduce hiss, as well as rolls off the glassy harmonics of the 220K plate load.
7. C12: replaced with 1uF /102k @ 63v Electrolytic
C12 1Uf provides a more useable mid shelving for overdriven guitar while retaining some current induced feedback for low frequencies. also sounds good for the clean mode as well
8. Replace R30 (470k)with 68k to 220k resistor
Replace R30 (470k)with 68k to 220k resistor this will Decrease the Fizziness and the OVERALL GAIN as well and also brighten the Amp. I personally Piggybacked, (using a pair of test leads), a range of resistors across the Legs of R30 from 82k to 1M and decided I liked 1M the Best. This brought the Value of R30 to 320k. I then soldered it in place across the legs of R30. This way it is easily changed if I decide on a different value without pulling the PIA Mainboard!!! This particular Mod is pretty much season to taste. One of the Techs or Myself can figure out what value you need for "Piggybacking", or you can try and figure it out yourself:
R1XR2 Divided By R1+R2= the Total resistance of Both Resistors combined. Use the Value of R30 (470)k for R1 and the resistor You want to try as the value for R2. (Try: 82k, 120k, 220k, 330k, 470k and 1m)
9. *****BIAS RESISTORS REPLACED:
Newer rev of the board 2008 have already been sorted
R67, R69 with 220K, 1/2 watt, metal film @ 1%
R68, with 33K, 1/2 watt, metal film @ 1%
R77: original stayed in amp because it wasn't a value of 10K as stated in our schematic, but 3.9k instead. We weren't sure if it was a good idea to replace this with a 10K value — and why