The Amp Garage

Step bits are pretty dam expensive! If you have any friends who are auto enthusiasts I would first see if they have one you might use. If I am working on a chassis that is not bare and I am doing such a mod I make a big Tee Pee of clay or playdough around that hole I am enlarging so it catches 100%...

I also use step bits. One things that's nice about them is that they generally leave less of a burr than regular drill bits, but I'd still recommend picking up a deburring tool. This is the one I use, and it works fine:
https://www.lowes.com/pd/Kobalt-NA-in-R ... 1002599656

If I'm understanding you right, it sounds like the CF is primarily there for the OD channel and that you may not be committed to the clean channel having a CF. If that is the case it may make more sense to just experiment with asymmetric mixing resistors (high values on the lower impedance, CF-drive...

I've played other JTM45s in the past, with KT66 and much preferred the tone and response. My question was trying to confirm that would be the main explanation for the differences or if there could be other reasons/changes the make the amp different. I like to play "almost clean" to me, that circuit...

AC coupling the CF would be a lot easier to figure out in terms of switching without issues versus switching inputs on a DC coupled CF. Although there will still be significant DC on your relay depending on how you bias the CF, at least with AC coupling there would be not direct relationship between...

The major does not feel much louder than a superlead necessarily but it has a different feel and tone. It offers more power and punch that affects bass and mids a bit Makes sense in terms of the 3db difference as power doubles. I haven't looked through too many Major gut shots, but at least on the ...

These are pretty simple amps compared to later Marshalls, so even within “garden variety plexi” you will find significant variations between years and similar-appearing models. Those differences, while subtle on a schematic, will result in very different sounding amplifiers. For example, Cream-era C...

Would leaving the heaters the way they are be an issue? Nope! Heaters can stay as they are unless you're getting 60hz hum. It's possible it'd be quieter if you redressed the heaters to make use of twisted pairs on tube I'm suggesting be reassigned to become V1 (assuming you keep the "V0" assignment...

With 520V on the plates (sagging to ~460) Vg2 should be about 100V below the plates at full power to avoid cooking the screens. What primary impedance are you running? Primary impedance is 3.4K for 2x 6550A's. New multimeter arrives today, but the DMM on life support shows 513V on the plates and 50...

Cool build! With this unpleasant sound persisting despite fairly large grid stoppers that large all around, I'm wondering if this is blocking distortion versus an inaudible oscillation. I'm particularly concerned because of the layout of the first three gain stages being crammed so close together. I...

Gave this a shot and it sounded good! The amp I tested this on isn't a 70s Marshall like mentioned in the original post (just wanted to test the idea), but the amp is a Marshall-style build running 2x KT88s at around 520V on the plates. This amp sags that way I would expect a Marshall to (generally ...

I had a good experience with the parts in the Hiwatt kit I bought from them about 2 years ago. All the pots in mine were 24mm Alphas, all the signal resistors were 1W Vishays, and Xicon branded ceramic sugar cube resistors for the B+ rail. Haven’t had any issues with their electrolytics. This is a n...

I think I will give this a shot sometime this week there's some safety or reliability concern. I can't think of anything specific, including from a dissipation perspective as long as the diode's power rating is up to the task. I figure with a 500V screens node, I'd want a Zener that can stand up to ...

So the recent thread about lowering screen voltages got me thinking about 1970s Marshalls with 6550s. With higher mains voltage now than in the 70s, those amps could be running those 6550s pretty hard with the screens 60-80V above the 440V maximum (if going by the up-rated specifications per the 197...

I tend to prefer the bias wiggle trem. I believe Hoffman was using a version of that, if I remember correctly. The only downside to this is you need to keep the poweramp bias cooler for good trem depth, though I tend to prefer fixed bias fenders on the cooler side anyway. Sluckey's trem-o-nator is ...