New guitar amp build thread to come...

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New guitar amp build thread to come...

Postby jimtroll » November 15th, 2017, 4:32 am

Hi all,

I've decided to expand my tonal pallette and build a new guitar amp head.

Lately my musical interest has gone toward the stoner/doom metal genre. (Think heavier Black Sabbath, Sleep, Weedeater etc)

I'm not a gigging muso, but I sure like to get a great tone for recording.

I recently rediscovered a schematic for the classic Orange OR120 amp from the early 1970s.

It's a great sounding beastie but it's also 100 Wattsm and I don't want to go deaf grinding out sick riffs. Soooo, there's a clone cct someone's come up with that's a mere 20Watts output.

This is the one I'll build.

So, a little overview:
This amp has 2 12ax7 preamp tubes, and 2 6v6 power tubes.
This gives us 3 gain stages and a single triode for the phase inverter.
A pair of 6v6 tubes can get you roughly 20W output.
The power supply has a solid state rectifier and a series of resistor / capacitor filters.

The tone controls are a bass treble Baxandal network. There's also a presence control in a negative feedback loop to the phase inverter from the secondary side of the output transformer..

The most interesting feature of this amp is a rotary switch control which on the original amp is labeled F.A.C. (Frequency Attenuation Control or some such). It's an RC network which selectively rolls off low frequency signal. In a normal setting it rolls off everything below about 300Hz, but at the other extreme it lets everything above 15Hz hit the 3rd gain stage. This makes for a pretty sludgy sound. Ideal for Doom metal.

I'll post schematics etc once I get started. So far I've either got existing components (tubes and transformers), or got stuff on order. I aim to get this thing started after this Christmas.

Keep you posted, James.
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Joined: January 6th, 2017, 5:08 am
Real name: James Stonehouse


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