I'm a metal guy and I have a handful of high gain amps at home that I'm quite fond of. After building the Aion VH Drive Channel (Ampeg VH-140C) I was honestly floored by how close it sounded to the original and how much fun it was to play compared to my actual amps. I immediately looked into other preamp pedals and came across the Dr. Boogey. Aion has the Draco, PedalPCB has the Boogie Monster. Both circuits are for the most part identical.
I did a little deep dive into the Mesa Boogie Dual Rectifier before even starting this build. The schematic for the pedal pretty cosely follows the the Red/Modern channel circuit of the Dual Rectifier. I did find some differences that I ended up incorporating into this build. The first is some filtering after Q1 just before the gain pot. There's a 2.2n cap in parallel with a 680k resistor for some tone shaping (C5 and R6). The values do also appear in the original Dual Rectifier schematic but for the vintage and modern modes they are put in parallel with a 82p cap and a 2.2m resistor, the latter being the default values for the raw mode. This would make the actual values for the vintage/modern modes roughly 2.3n and 520k. For this build I put the raw mode values on the PCB and added a switch to add the vintage/modern mode values in parallel. The difference is quite substantial. The raw mode has less gain, is much more flubby in the bass and lacks the searing highs of the vintage/modern mode.
Another difference is in the tone stack. The treble cap of the Dual Rectifier is 500p with a 180p cap in parallel (equals 680p combined) for the modern mode. The 180p cap is omitted for the raw and vintage modes. A lower value treble cap results in perceived less mids because the range affected by the treble pot moves up in frequencies. This creates a more pronounced gap in the mid frequencies because there's less overlap between the frequencies of the treble and mid pots. I went one step further and decreased the treble cap value to 3.3n. Small aside: the Draco (and Boogie Monster) tone stack is scaled by a factor of 10, so 3.3n is equivalent to 330p for the Dual Rectifier. I put the 3.3n on the PCB and added a 3-way switch to add 1.5n (combined ~5n) in parallel for the raw/vintage tone stack, and 3.3n (combined ~6.8n) for the modern tone stack. In hindsight the 3.3n is a little extreme. If anyone wants to add this switch to their build I'd recommend a 3.9n default value and adjust the values on the switch accordingly (1n and 2.7n) or just stick to the original values - 5n and 5n+1.8n in parallel.
That's about all the changes I incorporated into my build. I personally don't find the raw mode switch before the gain pot that useful. Sure, it's nice to have somewhat of a crunch channel available but to me it's just a little too flubby - but then again I do mostly play metal, so someone else may find it more useful. The tone stack switch on the other hand adds a lot in my opinion, definitely recommended.
So what do I think of the tone of this pedal? I expected to love this more than I eventually did. It does have a distinct Recto vibe. The overall voicing and the tone stack feel really familiar. But the actual distortion created by the JFETs is just not my cup of tea. It's cold and harsh and just screams solid state. There's no sweetness, no warmth and thus it really fails to capture the tube sound. Of course you can play around with the bias but so far I haven't found any combination of voltages that I'm seriously content with. I found the higher the voltage per JFET (5-6v with a 9v power supply), the more I like the characteristics of the distortion but I also feel like I'm losing some of that Recto voicing.
By the way, I used the "chromium" 1590BB2 by Tayda for this build and I can't really recommended it. It's kind of dull and milky and at the same time you'll also see every little scratch. Next time I want a reflective metal type of look I'll probably just try and polish a plain aluminum enclosure to a mirror finish.
I also attached the face plate I intended to have printed for this pedal. Would look cool I reckon but I'm not sure I'll keep the pedal at this point soooo... Yeah. Still happy I built this thing though even though it may not be my cup of tea tonally
I did a little deep dive into the Mesa Boogie Dual Rectifier before even starting this build. The schematic for the pedal pretty cosely follows the the Red/Modern channel circuit of the Dual Rectifier. I did find some differences that I ended up incorporating into this build. The first is some filtering after Q1 just before the gain pot. There's a 2.2n cap in parallel with a 680k resistor for some tone shaping (C5 and R6). The values do also appear in the original Dual Rectifier schematic but for the vintage and modern modes they are put in parallel with a 82p cap and a 2.2m resistor, the latter being the default values for the raw mode. This would make the actual values for the vintage/modern modes roughly 2.3n and 520k. For this build I put the raw mode values on the PCB and added a switch to add the vintage/modern mode values in parallel. The difference is quite substantial. The raw mode has less gain, is much more flubby in the bass and lacks the searing highs of the vintage/modern mode.
Another difference is in the tone stack. The treble cap of the Dual Rectifier is 500p with a 180p cap in parallel (equals 680p combined) for the modern mode. The 180p cap is omitted for the raw and vintage modes. A lower value treble cap results in perceived less mids because the range affected by the treble pot moves up in frequencies. This creates a more pronounced gap in the mid frequencies because there's less overlap between the frequencies of the treble and mid pots. I went one step further and decreased the treble cap value to 3.3n. Small aside: the Draco (and Boogie Monster) tone stack is scaled by a factor of 10, so 3.3n is equivalent to 330p for the Dual Rectifier. I put the 3.3n on the PCB and added a 3-way switch to add 1.5n (combined ~5n) in parallel for the raw/vintage tone stack, and 3.3n (combined ~6.8n) for the modern tone stack. In hindsight the 3.3n is a little extreme. If anyone wants to add this switch to their build I'd recommend a 3.9n default value and adjust the values on the switch accordingly (1n and 2.7n) or just stick to the original values - 5n and 5n+1.8n in parallel.
That's about all the changes I incorporated into my build. I personally don't find the raw mode switch before the gain pot that useful. Sure, it's nice to have somewhat of a crunch channel available but to me it's just a little too flubby - but then again I do mostly play metal, so someone else may find it more useful. The tone stack switch on the other hand adds a lot in my opinion, definitely recommended.
So what do I think of the tone of this pedal? I expected to love this more than I eventually did. It does have a distinct Recto vibe. The overall voicing and the tone stack feel really familiar. But the actual distortion created by the JFETs is just not my cup of tea. It's cold and harsh and just screams solid state. There's no sweetness, no warmth and thus it really fails to capture the tube sound. Of course you can play around with the bias but so far I haven't found any combination of voltages that I'm seriously content with. I found the higher the voltage per JFET (5-6v with a 9v power supply), the more I like the characteristics of the distortion but I also feel like I'm losing some of that Recto voicing.
By the way, I used the "chromium" 1590BB2 by Tayda for this build and I can't really recommended it. It's kind of dull and milky and at the same time you'll also see every little scratch. Next time I want a reflective metal type of look I'll probably just try and polish a plain aluminum enclosure to a mirror finish.
I also attached the face plate I intended to have printed for this pedal. Would look cool I reckon but I'm not sure I'll keep the pedal at this point soooo... Yeah. Still happy I built this thing though even though it may not be my cup of tea tonally
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