Two Stroke parts clarification (Tube nube)

[Don Frantz]

Just got my Two Stroke kit. I’m new at this so I hope you will have some patience.

1) One of my three power supply caps is 30uf (Spec says 40uf) Is this OK?

2) My Power Transformer P-TF22772 has two yellow, two black, two green, two red and one red with yellow wires. How should I wire this?

3) For signal caps I received three .022uf. Spec says one should be .0047uf. Is this OK?

Also, any tips on the grounding would be helpful. I believe not mixing the power supply ground with the signal ground is one of the main principles? Any photos of finished grounding available for Two Stroke?

Thank you very much–really looking forward to this project and learning about amp design and build.

Don

[Don Frantz]

Just noticed that the kit notes say that the 30 uf is fine.

[Robin]

Hi Don, congratulation on the 2Stroke kit. I working on a new 2Stroke using a 30uF cap too. I’ve built a few 2Strokes, all with 40uF caps but DH says 30uF is cool so I’m trying it.

Here is a link for the PT:
http://www.tubesandmore.com/products/P-TF22772. Note that the P-TF22772 does not include a center tap for the 6.3v (heater) circuit so be sure to add an artificial center tap with 100r resistors on each side of the circuit (green taps) going to ground.

You should have received a .0047uf / 600v (or .005/600) for the tone circuit.

You are correct about good grounding. There are a number of photos posted here on the TAN site you can study. Also be sure to read the information under Two Stroke in the TAN Wiki. Also check out:
http://www.valvewizard.co.uk/Grounding.html

Good luck, feel free to ask questions as you go.

[Don Frantz]

Thank you Robin. I’ll check that all out. Your Two Stroke is a beauty. I’m a little unclear about the artificial transformer center tap. Could you post a little diagram of how I should do this. Thanks you so much for your time and input.

[Robin]

Review the info on the link to the ValveWizard site, there is a good explanation of an artificial center tap there, with options. Basically, there needs to be a ground reference for the 6.3v filament (heater) circuit to provide hum cancellation. Some transformers include a center tap for this purpose, the P-TF22772 does not…no big deal though because you can create an “artificial center tap” by adding a 100r (NOT 100k) resistor to each side of the circuit. If you are building your amp like the book (or kit instructions), the pilot lamp holder is a convenient place to add the resistors. You have the two green wires (the 6.3v taps) going from the PT to the pilot light and then on to V2 and V1, simple add a 100r resistor, going to ground on each one of the taps where they connect to the pilot lamp holder and you’re good to go. BTW, adding the ground reference to the heater circuit is VERY important in terms of hum cancellation.

Some transformers come with center taps for other secondary pairs coming form the PT, unless the schematic calls for these to be connected, DO NOT assume they should go to ground. Simply cap them off and leave them unconnected. With your transformer, only the RED B+ (high voltage) taps should have their center tap (Red and Yellow)connected per the schematic.

[Don Frantz]

That helps a lot! Thank you very much.

[Robin]

You are welcome. Be sure to post when you get her finished… photos are nice too. Don’t hesitate if you have more questions.
Robin

[Andy]

The artificial center tap is a common question. Here is a picture, perhaps this can clear it up.

[attachment=86]CenterTapReplacement_2013-03-19.jpg[/attachment]

[Don Frantz]

Perfect! Thanks you.

[Author]

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