This is where we start. With the chassis removed from the headbox, we gotta get some external stuff off of it. Remove the tubes. This fucker has nine of them. All the jack nuts and two little screws for the DI output need to be removed from the back of the amp. Speaker jacks can stay put, no need to remove them. The power tube retainers also must be removed.
Now we flip the amp and focus on the board. It's gotta come out. It's not as bad as it looks. It's very important (to me) to label the dozen or so wires and connectors that must be removed to get the board out. The board is clearly labeled so by simply marking the wires with a little sharpie you can easily put it all back together.
Now you remove about 6 screws and the board comes right out.
With the board out, we can now mark, drill, and fit the choke. This is the choke. Note - gotta use a rubber grommet where the wires pass through the chassis. We don't want those things rubbing. I just kind of eyeballed it's location because I want it close to where the wires have to go and as you can see there is plenty of real estate available.
This is the resistor that the choke will replace. R106. Gotta go bye-bye.
And buh-bye!
Now the wires from the choke will penetrate the delicate holes left behind where the resistor was. I stood the board up inside the chassis and stuck the wires. The choke is non-polarized and does nothing else, so it doesn't matter which wire goes to which hole. Just stick em in and solder. I made an executive decision here to leave the leads as long as possible instead of cutting them just long enough to reach straight to the soldering spot. The choke's location is pretty much exactly adjacent to where the leads have to go, so sure, a short straight shot is probably better - as I learned from my last modding adventure - but in this case the longer wires leave me with two benefits 1) I can twist them so they self-cancel any noise they may make, and 2) since this thing is permanently wired to the board, the longer leads will give me some flexibility if I have to remove the board again. I can now flip the board if necessary with the choke leads still attached.
Now it's just a matter of putting it all back together, and hot damn alakazam. Done!
One thing I majorly fucked up on....I recorded some before-mod sound clips....and didn't save them.
I know.....fucking n00b.
I'm sorry, I really wanted to show the difference, but I goofed that part and it's too late to go back now!
I'll just try to describe it. The tone differences aren't as significant as the "feel" differences. Even if I hadn't fucked up the recordings, sound clips might not do it justice anyway. It definitely feels and responds punchier and more ballsy. The low end is definitely tighter and more percussive without being muddy or mushy. I really like the low end improvement. It's more noticeable on the higher gain channels, but the cleanish stuff gets benefit too. The fizz is also significantly reduced. This amp can squeal like a pig at stupid gain levels if you're too close to it. That part is much better. It could go into oscillation at high gain levels...but not so much anymore. I have to chalk that up to the high frequency filtering being done by the choke. That's a good thing.
So all in all...the choke was free for me, but it's only like 30-40 bucks US dollars. An hour and a half of pretty easy work and roughly 50 bucks in parts including nuts and bolts and grommets, it really improved the performance of this amp.
