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Valve pre amp


Ticktock
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My Dad, being a retired electrician who knows his way round a circuit board has volunteered to build me a valve pre amp. My suggestion totally. He's using the "McTube" design I found online, which ,even to me, looks like a simple circuit. I am thinking about a sweep mid eq type tone stack. Just how much will this complicate things? I'll be happy with "valvey grit" but can't help myself from thinking about it going "one louder", as it were.

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I built a little valve overdrive/preamp box a while ago which was loosely based on the Real McTube design. I added a simple tone control in between the two stages (of the kind used in some 50s Fender amps) and changed some component values to make it more amp-y sounding than the stock circuit. Any more complex passive tone stack would be more lossy and you might not have enough signal to overdrive the second triode. Sweepable mids would need an active tone stack and increase the parts count greatly, to the point where you'd essentially be designing something from the ground up.
I'm quite happy with mine, it doesn't get into high gain distortion but is excellent for a bit of grit and it works well as a slightly dirty boost too. My one reservation is that it's quite picky about what the output is plugged into - it's fine into any high impedance input like you would use with a passive bass, but it doesn't work well if it's plugged into a lower impedance input. In my usual setup it's not an issue, but I thought I'd mention it.
There are some photos and my modified schematic in this thread: [url="http://basschat.co.uk/topic/182457-valve-preamp-overdrive-pedal/page__view__findpost__p__1744666"]http://basschat.co.u...ost__p__1744666[/url]

Edited by Beer of the Bass
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