berumen77
Active member
****If you don't feel comfortable working inside an amplifier then please do not attempt these mods. Always discharge your capacitors and check your amp for any remaining voltage before working inside an amp.****
Here are a few mods to help tame the 'brightness' and 'ice pick' that some Stilettos have.
Most of the 'icepick' high end that some owners complain about is in the Crunch/Tite Gain/Fluid Drive. These modes are tied in together through gain stages, even Crunch in Channel 1 is tied to them. Looking at the schematic is like looking as a modded cascaded Marshall amp...Superlead, JTM, JCM 800. The Marshall DNA is definitely in this Mesa design. What is surprising is that there are a number of Treble Peaking components in the circuit that are meant to retain clarity but can result in a peaky high end that is almost impossible to dial out as it is continually passed from gain stage to gain stage. Here are a couple mods that can alleviate this and maybe even thicken up the tone.
Onto the mods for Channel 2 of Stage II for ACE, Deuce, Trident
1. You can mod the mid slope resistor, this can thicken up the tone and add a bit more gain to what's going to power section. A higher number will give a tighter feel. Early Marshalls had a 56K or a 33K resistor so that's a cool place to start. Change R38 from the stock 39K value to a 56K resistor. This is the "slope" resistor and sets the eq slope range. I then soldered two wires in parallel to that and connected them to the center lugs of a 3way double pole switch. I wired a 330K resistor on one side and an 82K to the other side. So you get roughly 47K/56K/33K values. It affects the perceived thickness of the mids and tightness in feel. There is voltage going to this component so be aware and be careful!
2. You can also remove C6 (180) and C7 (750) caps. These are a 'bright' cap system tied to the Gain pot of Channel 2 and are most active at lower settings of the control <8, at max gain they are shorted out and have little to no effect. Removing these will thicken the tone but you loose a tiny bit of gain and cut. You can also remove both caps and add a 470pf (471) cap that keeps some of the gain on the upper frequencies (500pf) or even (.005) were older Marshall values and helped to retain clarity at lower settings of the gain control. Try any value from 250pf-.005 (4700pf) and see what works best. Bogner XTC uses 470pf and a 4700pf to have two bright cap voices. The 4700pf cap will up the highs as well as mids and definitely give it a considerable gain increase.
On a side note, on Gain of Channel 1 you have two caps as well. a 120pf and a 500pf. Now the 120pf is always connected but the 500pf gets connected in and out via a relay and depending on the mode of Channel 1. This is why the two Crunch modes sound slightly different. Now, I find it weird that there are also two caps on Gain of Channel 2 but they are both connected to the pot, there is no relay that select one in or out. Not sure if the Stage 1 is like this. Why not just use one cap with a total value of both (180pf+750pf+930pf) or even a .001cap?
3. At C3 (500pf) and R5 (475K) you have the first treble peaking circuit. The capacitor is basically passing frequencies above that value through from the first stage and the resistor limits the frequencies below that to even out the tone. You can piggyback another 470K resistor on the R5 which will bring the value down to about 236K. Basically adding a bit of gain to just the frequencies below the capacitor and makes the tone a bit smoother/thicker and helps to balance with the high end with the inherent upper mid spike. You can also use a jumper wire across the R5 and bypass the entire treble peaking circuit. This adds gain to the mids and lower frequencies and it will affect all the gain modes, it may be too much low end so listen and play all modes before and after. You can also remove just the capacitor or play with just the capacitor value and increase it which will feed a bit more mids and give a bit punchier tone and more gain. I left this stock after experimenting with cap/resistor values and jumping was a bit too woofy with the added lows going through to the next stage.
4. At C14 (500pf) and R19 (475K) you have yet another treble peaking circuit. You can do the same mods as in above in step 3. I actually chose to use the jumper wire and bypass it and left the first treble peaking circuit C3/R5 unmodded. This was pretty much enough to kill the peakyness of the gain modes and by keeping the first treble peaking circuit I was able to retain the initial note definition and clarity, the ability to role down the volume on the guitar and clean up. Now it will add some perceived gain and a thicker feel so see if this is something you like. Tite Gain mode becomes thicker and is really cool for classic gained up Marshall tone.
5. A speaker change can also do wonders. I went from a Vintage 30 to a Warehouse ET65 and it really thickened up the tone. The problem was that even after a speaker change there is no way to dial out the icepick until doing some of the mods. The great thing about these mods is that the components are easily accessible and the mods are reversible if done cleanly. In some case you can use alligator clips to test components before soldering down.
Let me know if you have questions or need the schematic for Stage 2 Ace, Deuce, Trident.
Isaac Berumen
Berumen Guitars
Here are a few mods to help tame the 'brightness' and 'ice pick' that some Stilettos have.
Most of the 'icepick' high end that some owners complain about is in the Crunch/Tite Gain/Fluid Drive. These modes are tied in together through gain stages, even Crunch in Channel 1 is tied to them. Looking at the schematic is like looking as a modded cascaded Marshall amp...Superlead, JTM, JCM 800. The Marshall DNA is definitely in this Mesa design. What is surprising is that there are a number of Treble Peaking components in the circuit that are meant to retain clarity but can result in a peaky high end that is almost impossible to dial out as it is continually passed from gain stage to gain stage. Here are a couple mods that can alleviate this and maybe even thicken up the tone.
Onto the mods for Channel 2 of Stage II for ACE, Deuce, Trident
1. You can mod the mid slope resistor, this can thicken up the tone and add a bit more gain to what's going to power section. A higher number will give a tighter feel. Early Marshalls had a 56K or a 33K resistor so that's a cool place to start. Change R38 from the stock 39K value to a 56K resistor. This is the "slope" resistor and sets the eq slope range. I then soldered two wires in parallel to that and connected them to the center lugs of a 3way double pole switch. I wired a 330K resistor on one side and an 82K to the other side. So you get roughly 47K/56K/33K values. It affects the perceived thickness of the mids and tightness in feel. There is voltage going to this component so be aware and be careful!
2. You can also remove C6 (180) and C7 (750) caps. These are a 'bright' cap system tied to the Gain pot of Channel 2 and are most active at lower settings of the control <8, at max gain they are shorted out and have little to no effect. Removing these will thicken the tone but you loose a tiny bit of gain and cut. You can also remove both caps and add a 470pf (471) cap that keeps some of the gain on the upper frequencies (500pf) or even (.005) were older Marshall values and helped to retain clarity at lower settings of the gain control. Try any value from 250pf-.005 (4700pf) and see what works best. Bogner XTC uses 470pf and a 4700pf to have two bright cap voices. The 4700pf cap will up the highs as well as mids and definitely give it a considerable gain increase.
On a side note, on Gain of Channel 1 you have two caps as well. a 120pf and a 500pf. Now the 120pf is always connected but the 500pf gets connected in and out via a relay and depending on the mode of Channel 1. This is why the two Crunch modes sound slightly different. Now, I find it weird that there are also two caps on Gain of Channel 2 but they are both connected to the pot, there is no relay that select one in or out. Not sure if the Stage 1 is like this. Why not just use one cap with a total value of both (180pf+750pf+930pf) or even a .001cap?
3. At C3 (500pf) and R5 (475K) you have the first treble peaking circuit. The capacitor is basically passing frequencies above that value through from the first stage and the resistor limits the frequencies below that to even out the tone. You can piggyback another 470K resistor on the R5 which will bring the value down to about 236K. Basically adding a bit of gain to just the frequencies below the capacitor and makes the tone a bit smoother/thicker and helps to balance with the high end with the inherent upper mid spike. You can also use a jumper wire across the R5 and bypass the entire treble peaking circuit. This adds gain to the mids and lower frequencies and it will affect all the gain modes, it may be too much low end so listen and play all modes before and after. You can also remove just the capacitor or play with just the capacitor value and increase it which will feed a bit more mids and give a bit punchier tone and more gain. I left this stock after experimenting with cap/resistor values and jumping was a bit too woofy with the added lows going through to the next stage.
4. At C14 (500pf) and R19 (475K) you have yet another treble peaking circuit. You can do the same mods as in above in step 3. I actually chose to use the jumper wire and bypass it and left the first treble peaking circuit C3/R5 unmodded. This was pretty much enough to kill the peakyness of the gain modes and by keeping the first treble peaking circuit I was able to retain the initial note definition and clarity, the ability to role down the volume on the guitar and clean up. Now it will add some perceived gain and a thicker feel so see if this is something you like. Tite Gain mode becomes thicker and is really cool for classic gained up Marshall tone.
5. A speaker change can also do wonders. I went from a Vintage 30 to a Warehouse ET65 and it really thickened up the tone. The problem was that even after a speaker change there is no way to dial out the icepick until doing some of the mods. The great thing about these mods is that the components are easily accessible and the mods are reversible if done cleanly. In some case you can use alligator clips to test components before soldering down.
Let me know if you have questions or need the schematic for Stage 2 Ace, Deuce, Trident.
Isaac Berumen
Berumen Guitars