bowanderror
Well-known member
There were a few threads in the old (archived) Wish List about both the JHS Colour Box and the JHS Crayon, both supposedly based on the Neve 1073 Preamp/EQ. The Colour Box is the more complicated beast, with balanced IO, expansive EQ, & quite expensive transformers. The Crayon is a simplified version without those 3 features, but sharing the same preamp architecture - which is basically a Neve 1272 Line Amp. I did some tracing, and found basically a component-for-component copy of the 1272, with 2 mostly identical gain stages in series, with an interstage gain control.
For reference, here is the flow diagram from the Neve 1272, showing the two BA283 gain stage modules:
There are some differences between the two BA283 modules used in the 1272, but it looks like JHS just used the first stage twice (based on component values we'll look at later). Here is the schematic:
I wasn't able to find many gutshots of the Crayon, but there is one particularly clear one:
Ignoring the switch/jack board, it looks like a TL072 gain stage on the input, which also seems to contain the support circuitry for the Tilt EQ control & Low-Pass switch. The connection from the TL072 stage to the first BA283 gain stage (below in light blue) is hidden, but it looks like it comes in to C23 through a via. From there, it's pretty much the above schematic, outputting through C24 to the Pre-Vol pot. Lug 2 of the Pre-Vol pot outputs directly to C32 on the input of the second BA283 gain stage (below in yellow), which outputs through C33 or C6 to the Master Volume pot.
I couldn't identify the exact transistors JHS is using, but it's likely a common NPN BJT. The SMD code looks like N1, M1, or %1 to me, with the "L" and unidentified symbol likely a date & plant code. The ideal option would be something low-noise like BCM850, but I'd put my money on something common like PMBT3904.
Overall, a complex-looking pedal that's actually pretty straight forward. The parts are cheap & most of the values are common, so it's a good candidate for a PedalPCB trace or anyone looking to breadboard the BA283 gain stages.
For reference, here is the flow diagram from the Neve 1272, showing the two BA283 gain stage modules:
There are some differences between the two BA283 modules used in the 1272, but it looks like JHS just used the first stage twice (based on component values we'll look at later). Here is the schematic:
I wasn't able to find many gutshots of the Crayon, but there is one particularly clear one:
Ignoring the switch/jack board, it looks like a TL072 gain stage on the input, which also seems to contain the support circuitry for the Tilt EQ control & Low-Pass switch. The connection from the TL072 stage to the first BA283 gain stage (below in light blue) is hidden, but it looks like it comes in to C23 through a via. From there, it's pretty much the above schematic, outputting through C24 to the Pre-Vol pot. Lug 2 of the Pre-Vol pot outputs directly to C32 on the input of the second BA283 gain stage (below in yellow), which outputs through C33 or C6 to the Master Volume pot.
I couldn't identify the exact transistors JHS is using, but it's likely a common NPN BJT. The SMD code looks like N1, M1, or %1 to me, with the "L" and unidentified symbol likely a date & plant code. The ideal option would be something low-noise like BCM850, but I'd put my money on something common like PMBT3904.
Overall, a complex-looking pedal that's actually pretty straight forward. The parts are cheap & most of the values are common, so it's a good candidate for a PedalPCB trace or anyone looking to breadboard the BA283 gain stages.
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