Input resistors and OT choice of wires for impedence

[Steven]

Hi All! New to the forum. New to amp building. Not new to becoming proficient in my hobbies. However……even though I am not stupid (I have an advanced degree) but this electrical stuff is as difficult as anything I’ve ever done. My hat’s off to all you that have managed to master this discipline! Anyway, I still have the mindset that electricity should flow like water. That’s why reading schematics kick my butt. I’m busy trying to read everything I can, but in the meantime I’d like some help on the Two Stroke.

I’m sticking with the plans Andy sent me without modification. The layout doesn’t seem to match the schematic at the input. Specifically, the schematic looks like it has 3 of the 1M resistors that the layout doesn’t. Ok, is that the anti-pop modification? Also, the 1 M resistor spanning the outer-most lugs on the input doesn’t make sense to me either. Why is it on the lug that proceeds to the 68K resistor? That doesn’t match up. I just need someone to take me through this first part of the circuit in a very long and drawn out way.

The next question is about the OT wires for the ESE125. I gather that the 6L6 runs at optimal 5000 on the primary side. The yellow wire is good for 4-16 ohm at 2,500-10,000 ohm on the primary. The schematic calls for green or white (if I’m remembering right – I’m at work right now), but most talk about using the white. The white is good for 8-32 ohm on the primary 2,500 to 10,000 and the green is good for 4-8 ohm at 5000 to 10,000. So why not the green to get the 4 ohm? When would I ever need the 32?

Thanks!

Steve

[Andy]

Hey Steven,

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. It depends on the number of speakers you are using and which tubes you want to switch between. Since I use both the 10” and the 8” at 8Ω each, my impedance is 4Ω.

So GREEN gives me the 6V6 at 4Ω and YELLOW gives me the 6L6 and EL34 at 4Ω.

If you had 1 speaker at 8Ω, you would want WHITE for the 6L6 at 8Ω and YELLOW for the 6V6 at 8Ω.

If you wanted to stay with the 6L6 tubes but wanted to switch between two and one speaker, then you would need to switch between 4Ω and 8Ω impedance so you would do WHITE and YELLOW.

When you are reading the chart on the 125ESE, you have to look at the PRIMARY impedance to know which lead to use. There is a paragraph in the book that *kinda explains about the mismatch being ok here. You are looking at the 5000Ω primary if I recall correctly.

[Author]

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