Confused about power tube

[Mark]

I’m getting ready to build the two-stroke (sourced my parts myself from Hoffman) and going over the “Notes and Updates” document and the layouts. The Notes and Updates refers to the power tube being a single 6L6 but the layouts I have show a single 6V6. Am I missing a more recent layout that’s available somewhere?

Thanks

Mark

[Andy]

Hey Mark,

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.

Attachments:

1. 

   3781D6E7-E621-47ED-AF39-9BD484845AD5.png
   

[Andy]

Hey Mark,

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.

Attachments:

1. 

   3781D6E7-E621-47ED-AF39-9BD484845AD5-1.png
   

[Andy]

You’ll just have to hookup the right color wires, this chart doesnt reflect the colors but the book one does.

[Mark]

Thanks Tan! I only have 8ohm speakers on hand, so I was just going to hardwire it with a single output jack for an 8ohm speaker. So, I guess I can only use 6V6 for now. Is there a mod I could do so I can use 6L6 or EL34 with a single tube socket and single output jack?

[Mark]

… with an 8ohm speaker.

[Andy]

The 8Ω speaker with a 6V6 will use the yellow wire from the 125ESE.
The 8Ω speaker with a 6L6/EL34 will use the white wire from the 125ESE.

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 other tubes. I’ve used KT66 (my favorite), KT77, 6550s, etc. It’s great to play around with them.

[Mark]

I’m using the Classic Tone OT. I think I’ll go ahead and wire up an impedance switch after all. I would really like to try all of those tubes. I’ll have to figure out which wires to use.

[Mark]

So, again, here are the specs for the Classic Tone OT:
http://www.classictone.net/40-18031.pdf

Since this OT is limited to either a 5 or 8k primary, and I have it wired up with the 5k primary, I need to figure out which secondary tap/speaker load combination matches the white wire tap on the 125ESE. So, if I use the 4ohm tap on the Classic Tone (yellow wire) with an 8ohm speaker (which is all I have), then a 6L6 tube will think it’s seeing a 16ohm speaker at a 5k primary (how I have the Classic Tone wired), which would be equivalent to using the white wire on the 125ESE with a 16ohm speaker (a correct secondary/speaker match), correct? That’s how I understand how speaker “mismatching” works, but maybe I’m confused…

[Andy]

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.

[Author]

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