Brownface Deluxe 6G3 “Lite” Build

syscokid

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The whole point of posting is that this little project turned out to lead into a pretty cool sounding 20-watt amp. The whole idea of building a clone of a 6G3 started after I briefly considered rewiring my Tweedy style Deluxe 5E3 clone to the Brownface specs, but omitting the tremolo because of the 5E3’s smaller chassis and board. But the more I played through my Tweedy, the more I wanted to keep as it is and start with a completely separate build. So, hot on the heels of T-Rex’s 6G3 build and thread that was posted earlier this month, I’m ready to show off mine. My build resulted in three different versions that started about five months ago. And what I mean by “Lite”, is that the 6G3’s stock tremolo circuit is omitted, the stock fixed bias circuit is replaced with the simpler cathode biased circuit, and some of the original circuit’s voicing has been “lightened”… I’ll explain more later, but all is very similar to what T-Rex put together on his 6G3 clone.

Transformers, chassis, and custom faceplates, are manufactured and sold from Modulus Amplification. My first time trying Modulus’s home built trannies. Head shell cab was built and sold from Guitar Cabinets Direct.

First of all, this is what looks like on the outside currently:
Rebuild October 2025 (1).JPG

Rebuild October 2025 (2).JPG


First version circuit board completed in June. The power tube's cathode bias 250 ohm resistor was modded to produce 400 ohms of total resistance and help keep the bias at about 95%. Eventually, I did order a separate 400 ohm power resister to clean up the add-ons', but i never ended up using it. The whole circuit's grounding and the parallel heater wiring instead of twisted heater wiring, was another inspiration from Modulus Amps. Amp already sounds awesome at this point, but I couldn't leave well enough on it's own.
Transition 2 Fix Bias (1)May.JPEG

But after some enlightening wisdom I picked out from The Amp Garage forum, I changed the amp back to its original and intended fixed bias circuit, but with an added pot for adjustability. A floating mini board hosting the adjustable fixed bias circuit. The normal channel's cathode circuit has been almost Pexified. It's already looking "Frankenstiened"! Version number 2:
Transition 2 Fix Bias (9)June.JPEG

Version 3 came about the main idea to lower the 435v of B+ voltage down to the 380's. Fortunately, Granger Amps had a sweet little add-on kit that will do the trick. I opted for their -51v setup. The little MOSFET secures to the chassis with a screw and heat sink compound. The board with stand-offs floats above it:
MOSFET Voltage Dropper August 1.JPEG
 
Continuing on...

What it looked like prior to version 3:
MOSFET Voltage Dropper August 2.JPG

Version 3 is the major rebuild with new eyelet board with adjusted layout for the eyelets, 95% new caps and resistors, new ground circuit layout, and using the twisted heater wiring against the chassis corner method:
Rebuild October 2025 (3).JPG

Rebuild October 2025 (4).JPG

Mismatch of pots! I don't know what happened to the modern CTS 1 meg Audio pots lately, but they kind of suck. In their place, I had my one last remaning PEC 1 meg audio that filled the spot perfectly. The other I meg audio pot to the extreme right is made by Tokyo Cosmo...aka Tocos. Ordered three of them and all within 10% spec and operate as expected. Seems to be built well at $10 a pop at AES:
Rebuild October 2025 (5).JPG

I just like this pic!
Rebuild October 2025 (7).JPG
 
Forgot to post pic of the cabinet. The brown cab of the 6G3 used to house my 5E3 clone. Once I started ordering parts for the 6G3 build, I also ordered a new cab for the 5E3. You would think I would have selected a tweed covering. At the last second I said screw it, I'm ordering something more colorful... Hello teal!
resized at 1mb.JPG

At my first post, I said this: “some of the original circuit’s voicing has been lightened”. A popular mod for this circuit is to alter the inherent dark tone of the Normal channel and make it more, uhm, exciting by creating a more British flavor. The stock circuit for V1 has a shared cathode with a 1.5K cathode resistor and a 25uF bypass cap. The Normal side also has a 3300pF plate resistor bypass cap that strongly neuters the top end. The mod converts V1 by splitting the tube’s shared cathode to allow for more variety between the two channels. The Bright channel still has a 25uF bypass cap with a 3K cathode resistor. The old Normal channel now has a .68uF bypass cap with a 2.7K cathode resistor, no plate resistor bypass cap, and the channel’s original .01uF tone cap at the tone control is now a .02uF. All this makes for a much tighter and brighter tone experience from the original Normal channel, and I prefer it this way.

Another mod I did that affects the amp’s response in a big way, was to reduce the value of the coupling caps between the phase inverter and power tubes from .1uF down to .02uF. For the time being, this is a turning point moment and I’m really digging it. But I might have made this amp too Marshally, ha ha!

I would also like to note that while I’ve been testing and adjusting the amp to my preference, the amp has been strictly plugged into a 1x12 cab with a Celestion Ruby Alnico 35-watt speaker. The Ruby’s frequency response is very low-mid forward, and at low amp volumes or heavy attenuation from an attenuator it might appear to be a dark sounding speaker. IMO, this speaker really opens up with more punch and articulation when pushed hard. I’m looking forward to auditioning this rig at my friend’s next jamfest and truly hear where this amp’s abilities stand.
 
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