Andy

There isnt a list of hardware yet, but I plan a build in the next couple of weeks with my son so I can document it. Most folks use the Unibit or a stepped bit to drill the hole for the Impedance Switch in the back. You can do the same for the second 1/4″ jack if you want, but I tend to leave just the one and then wire the speakers to each other…[Read more]

Hey Kirk,

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]

Nope! It has the green and yellow wire so it does not need the artificial center tap.

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.

Woo Hoo! Awesome! Thanks for sharing the results.

Whew. There is a lot to look at here.

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]

Sorry this is so late! All of the kit documents are available on the WIKI page. That included the Addendum made by Dave Hunter to document changes to the kit. Here is the link to the Addendum: https://www.tubeampnetwork.com/wp-content/uploads/2015/07/HUNTER_AmpKitAddendum.pdf

I think that sounds ok. The 12.6 comes from 6.3V to the 9pin and 6.3 to the 4-5 pins. So I don’t think there seems like a PT issue.

Those sound about right. The tubes need 12.6VAC to run those filaments. So you will need 6.3V to pin 9 and 6.3V to pins 4-5 on the preamp to make that work and then 7 and 2 on the power tube. Your previous measure of 3.2 off each green would be problematic.

Ive never measured (or I dont remember that I have) the VDC on the rectifier filament lines. What AC are you getting there?

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.

I never use the brass plate for that reason. Its quite a bit of overkill on this amp. We recommend running a ground strap across the back of the pots that you can tie all the grounds to. Then you can tie that wire to the ground. See the attached image for an example.

See, Im the opposite. I’ve built a few guitars but always miss something crucial. But on amps I’m much more accurate 😉

The dotted line represents a connection. The three power caps and the 1.5k resistors all connect (negative side) and then go to ground. Is that connected on your amp?

Hey Jordan,

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]

It’s possible that the tube is not functioning. Id probably look first for some open joint or misplaced ground somewhere before I replaced it though. Make sure only the places that are supposed to be grounded are grounded.

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]

Hey Doug,

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]

Yikes! Tough question and so application specific! The beauty of the Two Stroke is that you can try different ones. I personally like the KT66 in the two stroke. It feels more beefy to me 😉

Well, that can be a number of things. It could be a cold solder joint somewhere. It could also be the extra gain pushing the tube into self oscillation. I also can’t quite tell from the picture where you have the twisted black and white wires that cut across the amp. Those could be creating an impedance or cross-talk issue.

Often, when I have an…[Read more]

That might be right. I would check with the manufacturer on that one. The Hammond is designed for a pretty large input load swing (from 2.5K to 10K). I just don’t know enough about the Classic Tone to really make a safe call here.

As far as the meters go, I dont have any idea about that. I’ve not seen that problem!

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]

So your red secondary is a bit high, it may be due to the higher input voltage.

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]