What Power Transformer are you using? For our kit, we are using the Hammond 290AX which is 325V.

I think we answered this on email but I’ll add it here in case others have questions too. The Voltage rating of the capacitor can be higher with no issue but NOT lower. So the 475V is just fine.

Basically its saying that the voltage through it can’t exceed that number. So in a power supply section, they need to be much higher than in…[Read more]

The available transformers are jumping around a lot and some manufacturers have the center tap and some don’t. With the 290AX, you do it just like the book says. No need to make an artificial tap.

To me, it really comes down to the high primary voltages. I think Id go with the combination that is getting you closest to 330V and let it ride. Some fluctuation is fine. My sense is that you are getting in the weeds with the 5Y3 calculations. This amp is REALLY forgiving. The design can accommodate quite a…[Read more]

Check the filament lines (green) for a connection to ground. For the one that doesn’t work. Need both of those to fire to get amplification.

If you don’t switch out power tubes, then you don’t need the impedance switch. If you are those two speakers in parallel, you will need to use the 4Ω lead. I’ll have to dig up the specs, its been a while since I looked at it and I don’t recall off hand what color that is.

If you will want to try different tubes, you will need to…[Read more]

Also… It looks like there is a 1 MEG resistor at the center-tap place not a 100Ω. If you swapped those you could have…[Read more]

As far as the Addendum goes, he is referring to the Power Transformer. The letter that came with the kit explains a bit about the current Power Transformers that are available. You have to make an artificial center tap, which is shown in one of the attached images. The newer PT’s went away with the center tap on the filament line, so…[Read more]

Often, when I have an…[Read more]

I would disconnect the yellow wires from the tube and measure them open. The only reason I can think of for the difference is that pin 8 has a load where pin 2 does not. Even at 5.5, that is a bit high.

It seems that your voltages are just high overall. I don’t…[Read more]

The green is a tad high, so that points to the same as the red. That is what powers the power lamp and the filament/heaters for the 12ax7s. Just double-checking, did you use the artificial center tap?

The yellow is the most concerning. I would do some digging there.…[Read more]

Also, what Capacitor values did you go with for C1, C2 and C3?

So using the impedance switch wired as the book (2005 edition) and the diagram on the site wiki shows, you will be able to switch between 6L6/EL34 and 6V6. Actually, in the 6L6 position, you can also use o…[Read more]

As far as wattage, I like to stay at 1W for safety. Typically, I use 1W throughout the build as they are quieter, except in places where more…[Read more]

Double-check that all the grounds are connected properly. I usually connect all the tone and volume control grounds onto a bus wire then connect that to the three-pin ground terminal. Also, double-check the coax wire from pin 7 on the 12AX7. That…[Read more]

What printing of the book do you have? That might help someone at the network identify any discrepancies. The book most of us have used is the two tube version with the addendum that you can find on the Wiki page.

For the filament center tap, you will need to make an artificial one. For some reason, the new PTs removed the filament CT. This is done by attaching a 100Ω resistor from each…[Read more]

It looks like the GRAY on the Classic Tone is the…[Read more]

Welcome to the Tube Amp Net! So, yes. The great thing about the 2 Stroke is that you can swap out the power tube to try different flavors. The only thing you have to watch is the impedance. Take a look at the chart attached. It’s also reflected in the book but this is simplified for the 1 tube 2 Stroke.

Welcome to the Tube Amp Net! So, yes. The great thing about the 2 Stroke is that you can swap out the power tube to try different flavors. The only thing you have to watch is the impedance. Take a look at the chart attached. It’s also reflected in the book but this is simplified for the 1 tube 2 Stroke.

Its pretty hard to see what they are doing there or why. It looks like the Weber Maggie version does something similar: Weber Maggie.

It looks like it might be knocking down the power coming out of the rectifier a bit and doing a bit of filtering depending if the value is the same as on the Maggie. I’d need to throw it on the modeler…[Read more]

Welcome to the site! If you do go with this build, you will love it. It is a simple amp but has a pretty complex and unique sound to it. I love that you can build it such that you can swap the power tubes and that makes a cool way to really hear the different tube differences. I settled on a big bottle KT66 personally 😉

As far as the…[Read more]

Feel free to…[Read more]

After that, I would take some voltage readings and let us know what you get. Pins 1 and 6 of the tube should be around 140-160V. Pin 3 on the power tube should be around 350V, Pin 4 around 300V.

I really love some of the builds from Tiny Zotolla: https://amzn.to/2OsZmdc

His AC30 Top Boost designs are pretty great sounding from Volume 2.

Sorry, just seeing this as we has some email issues. Did you figure this out?

Sorry this is embarrasingly late. The brass plate is really a grounding plate. I typically make a ground bus out of wire and solder it across the back of the pots, then solder all the ground points to that. The end then goes to ground at the three terminal strip. You can also do this with a ground wire. The newer kits come with a strip…[Read more]

For the schematic vs the layout, you are absolutely correct. The extra 1M resistors on the schematic are for the pop suppression modification. We include those parts in the kit as a courtesy. Its a nice modification to make, but its not in the book and the layout is straight from the book.

For the OT, I usually do GREEN and YELLOW.…[Read more]