Hoffman Amplifiers Tube Amplifier Forum
Other Stuff => Solid State => Topic started by: jordane on April 09, 2024, 12:37:55 pm
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I just picked up an older Roland Cube-60 (analog, Made in Japan, 70s/80s orange tolex) as a portable jazz box. I'm going to go ahead and replace signal path resistors and caps... just trying to optimize the signal path, maybe reduce a bit of idle noise, and replace some older components with fresh.
I attached a schematic where I lined the signal path (I believe) in red. I don't really plan to use the overdrive or bright cap, so I'm ignoring those. Most of the preamp looks pretty familiar to me having worked on tube amps before. After the master volume, I get a little wonky and I'm not sure how the signal proceeds through the power section, though I could probably guess.
My main question is about the EQ section, right after Q2. It looks very Fender-like to me, with a slight change. Let's say I would like to reduce mids overall (I'd like to increase the mid scoop, as I normally run this amp with mids at 1 or 0). Rather than messing about with the mids resistor, C9, or C10 -- couldn't I just change R18 to 6.8k or something? R18 is where the variable mids resistor normally is on Fenders iirc.
I'm also open to suggestions or recommendations. I'm self-taught on this stuff, so always wanting to learn more.
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> couldn't I just change R18 to 6.8k or something? R18 is where the variable mids resistor normally is on Fenders iirc.
Pot VR4 is the mids resistor. R18 prevents turning Bass to zero. Go ahead and short R18. It will make little difference until Bass is turned to "1".
Considering the age and PCB-delicacy of these vintage amps, I'd leave it strictly alone. If you have too much mids, put an EQ in the PreOut/In loop.
You can try the calculator but there's no exact equivalent to the Cube.
https://www.guitarscience.net/tsc/info.htm
$29.90 7-band EQ (https://www.amazon.com/EX-Band-Equalizer-Guitar-Pedal/dp/B0876NBHRB) in a space-saving mini-sized footprint
Behringer MINIFBQ FBQ800 $63.10
Dunlop MXR Ten Band Graphic EQ $150
Wampler EQuator Equalizer Pedal $200