Following 2 Power Tube Amp Design

[DeepBlue]

OH MY GOD!!!!!!! I found my mistake! I have not had the grounding strip all connected! I swear I checked this multiple times, but clearly not. So all the voltages seem to check out now, and low and behold a beautiful sounding amp! I have been raving to my friend for the past hour about how it works! Now my neighbors must be sick of its amazing tone! Wow thank you all sooooo much. I feel like I just gave birth to a child I am so happy!

[Andy]

Congrats man! Love that feeling!

Let us know when you start the next one

[DeepBlue]

Yes amazing! I am about to leave work early to go home and crank it up! I am super stoked!

The sad part is yes I already want to make another.

Also just curious has anyone ever played with changing the values of the cathode and plate resistor to higher values on the 2stroke?

Just wondering what this higher gain setting would do for the amp?

RIght now I am loving the clean!

Question for Robin

YOU mentioned you use the NOS 5Y3 vs a newer one, this swap is easily done just changing out the rectifier correct? I mean the amp is rated for higher Volts so no changes are needed in the circuit correct?

I think I am addicted haha

[Robin]

a good NOS rectifier tube will give you something like a 30-50 B+ voltage drop, so you get a browner, bluesy tone. New rectifier tubes sound more like a solid state circuit with tighter bottom end, bumped up mids and a little louder. Both have their place (IMO).

[beelzebum]

the real difference between NOS 5Y3 or any NOS tube for that matter and a new one is that the newer ones usually are not what they are labeled. a russian 5y3 equivalent tube was not the same as a real US made one. most tubes you can get now are from russia or china and follow the russian specs for the closest tube to what they are labeled. also if you want to try a solid state rectifier but dont want to chop up your amp you can find solid state rectifiers on ebay that plug right into an 8-pin socket.

[DeepBlue]

Awesome. I might give that a try with the NOS 5Y3. I like that browner sound, but its awesome right now also! I have to say its amazing how round, and bell like my strat sounds on this amp!

I guess no one really had much to say about the changing values of say the cathode resistor’s or plate resistor’s to higher values? I was thinking it would be cool if you could design say a rotary switch that allowed one to select for a given number of different combinations hardwired into the amp’s preamp circuit. Anyone have any thoughts on that?

[Andy]

You can change the values around on the plate and the cathode, but in general they need to be changed together. I have a certain Plate/Cathode resistor level that I like in the boutique amps we are building. You have to be careful as they are changing the current in the tube. But if you get a 12AX7 data sheet, you can calculate the values necessary for what you want. For more gain, you might try 220K which is a common Plate value on High Gain amplifiers. I went lower on one amp to give a bit more headroom. Wanted it to break up at higher levels.

Make sure you learn about load lines and practice some Ohms law if you want to play around.

[DeepBlue]

Thanks AJ, yes I know I have a few charts and things, and know a bit about ohms law, so I did know there was certain pair together of each value, I guess I was just curious if anyone had done the mod and had any feeling about the sound. Thanks for your opinion. I was thinking of trying a higher value perhaps in a future design. I

[Rifflicks]

I just finished reading this thread…and wanted to know if there is an updated (corrected) schematic, parts list, and layout drawing available for the original 2 power tube design?
8 watts is more than plenty for my needs.

[Rifflicks]

I forgot to mention I have Dave Hunter’s book but I understand there are some mistakes that have been spotted and corrected.
Another reason I want the original design is that I watched a YouTube video and absolutely fell in love with the tone.

[Andy]

On the WIKI page there are links to the addendum to Dave Hunter’s book. The original layout drawing for 2 tubes is in the book. The Wiki has the single tube layout and schematic.

Most of us agree with the changes, 2 tubes just isn’t necessary in this design, are you looking to build one with 2 tubes?

[Rifflicks]

Thank You for the reply…..Yes, I’d like to build the original with two 6v6 power tubes, and the 10 and 8 inch speaker combination first…I watched a YouTube video and loved the tone. I have built an unmodified 5F2a Princeton and loved the experience and instant results. I have read several places online that the drawings in the book had a few errors….I bought a new book about a month ago and I wasn’t sure if the errors were corrected.
I really want to keep the wattage output low too…..I want to play it dimed without ringing eardrums for days….(I’m getting old)

[Andy]

I dont think the changes were ever made to the book. The addendum has everything you will need to change. To build the original 2 tube design, you will use the layout from the book and just check that the part values are the same from the addendum.

If you use the parts list in the WIKI, just add 1 more Power Tube, 1 more 500Ω 5W resistor and 1 more 25uF/50V capacitor to bring the parts list up to the 2 tube model.

Addendum:
https://www.tubeampnetwork.com/images/HUNTER_AmpKitAddendum.pdf

Parts List:
https://www.tubeampnetwork.com/images/TAN_PartsChecklist.pdf

Right now, the 40uF Sprague Atoms capacitors are really expensive. I have been using a 30uF F&T in its place.

[Robin]

I’m using F&T now too with great results. Remember, with the 2 tube version, you only use two tubes when using 6v6s. There is no down side to building the 2 tube version, but no advantage either. Follow the single tube layout (and schematic) and you should avoid the vague details in the original (book) layout that has caused construction issues for some. Having already built a 5F2a, you should have no problems with the Two Stroke. Good luck! (Btw, wait until you hear what 1 good 6L6 sounds like).

[Rifflicks]

Thanks for the help….I saw that there was an option of using 3 different power tubes with the single tube newer version 2 Stroke….are the 3 tube types instantly interchangeable, or do they require re-biasing the amp when you swap them out…I’m old but somewhat open minded, and sometimes easily persuaded…..doesn’t the larger single tube increase the wattage significantly?

[Author]

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