Impedence Switch Question

[lgehrig4]

I finished my Express (wired not tested) and as I was going over the connections and labelling the back panel I noticed something.

From the photos an actual Express had the impedence labeled 4-8-16. I'm using the same switch from the build checklist and I wired the switch exactly as the diagram shows. If you have the back panel facing you and you were looking down at my switch the wires from left to right would be Gray(16), yellow(8) and red(4). Prior to adding the OT leads I checked the switch with my meter and the shaft direction corresponded with leads it pointed to (I made a line on the shaft) which was 16-8-4.

Anyone elses like this?

[lgehrig4]

Anyone? I can try to rephrase my question if it not clear.

p.s. I didn't mean to add tat emocicon in my post. that little guy should be an "8"

[martin manning]

Seems like an error in the diagram. Wouldn't you just reverse the 4 and 16-ohm leads from the OT?

You can give that little yellow guy the boot by checking the "Disable Smiles" box below the message text box.

[JoeCon]

Martin

Or switch the label? Don't ask how I know! LOL....

[lgehrig4]

I'm not concerned with the label. Just want to make sure that everything is correct technically.

I guess I'm just being paranoid. I test the switch for continuity prior to installing the OT wires and the swich positions corresponded to the wires it pointed to.

[JoeCon]

lgehrig4

It's just to make sure you match the speaker impedance with the right OT tap. I've seen the switch and I've seen dedicated jacks for 4-8-16 ohms.

I wired mine with 16 ohm tap on the right but labeled it on the left. Luckily I checked before hooking the speakers up. DOH!!

It's not being paranoid it's being careful that everything is wired right. I'm going thru the same thing now...

Enjoy!

[lgehrig4]

Thanks. I don't have a background in electronics so I'm relying heavily on copying what I see. If something doesn't match up I'm afraid to apply what I feel is logic. Can be too costly if wrong.

It's all finished and looks great. Have to buy some fuses and I'll start testing this weekend. I've looked over the amp about 5 times to make sure everything is wired correctly, but I'll check it once more before I fire it up.

[dobbhill]

Some folk find these useful for first-time fire-up:
http://ampgarage.com/forum/viewtopic.php?t=20341

Best of luck!

D

[lgehrig4]

Thanks. I actually fired it up tonight using a variac. I was feeling pretty good at first but all the voltages I measured were off, aside from the mains. Not sure how much of that was due to not having any tubes installed. I'll do this again tomorrow after I read up on some related posts.

[lgehrig4]

Voltages are perfect! Read up on some threads last night and retested everything this morning.

Sounds great already! No hum or unbearable hiss. No weird oscillations. Pretty stable. Right now I'm using mostly JJ's until I break it in. I can't believe how good it sound already without breaking in the caps and with these tubes. Once it opens up a bit more I have a pair of Siemens and assortment of nos preamps to experiment with.

Question: When I built a JTM45, I broke in the caps by pulling the power tubes and running my ipod trough it for a total of about 20hrs (4-5hrs at a time). Can I do the same with this amp?

[martin manning]

Good to hear all is well!

Question: When I built a JTM45, I broke in the caps by pulling the power tubes and running my ipod trough it for a total of about 20hrs (4-5hrs at a time). Can I do the same with this amp?

No problem, same rules apply.