Build Your Own Clone Message Board

Hi everybody,

I just received the Royal Tweed kit and took a closer look at the kit building instructions. I have three questions with regard to the original 5e3-wiring:

(1) First thing is that the bias resistor is 470 Ohm and not 250 Ohm like the original 5e3. Is this a compromise with regard to the other amp type sounds of the 5F1, 5F2a and 5F10? Or was this value chosen because of the use of 12AX7A in V1?

(2) Does the 470 Ohm bias resistor allow to use a solid state rectifier like the TAD adapter (https://www.tubeampdoctor.com/en/shop_T ... tifier_389) without running the amp too hot?

(3) The V2a-cathode does not have a 25uF capacitor like the original 5e3. Is this possible to add this cap (e.g. with a switch) or would this produce some trouble ?

Kind regards and thanks a lot for your support!

A lot of the changes you are seeing are there for switching between single-ended (5w) and push-pull modes.


The amp uses a 470r cathode bias resistor in singled-ended mode, just like a 5F1 champ. In push-pull, another 470r resistor (R22) is placed in parallel to give approx 235r on the push-pull cathode bias, which is plenty close enough to 250r (within 6%).


I suggest you do some reading up on the use of SS rectifier plugs. It will change the B+ voltage and change the bias on the power tubes. You may need to compensate with different values for R21 & R22. It might not be too appropriate for an amp like this that uses two different output transformers.


It actually does have that cap (it's C8). It's just part of the TR's cut knob. From the website: "The Cut knob on the Tweed Royal controls a negative feedback loop just like the negative feedback loop found on the 5F1 Champ, 5F2a Princeton, and 5F10 Harvard (there was no knob for this on the originals. It was internally hardwired via a single resistor). The 5E3 Deluxe did not have a negative feedback loop. Just like the tone knob, the cut knob on the Tweed Royal has a built-in switch. When you turn it full turn counter clockwise, it removes the negative feedback loop from the circuit completely for 5E3 Deluxe specs." What the copy doesn't mention is that the V2a cathode bypass cap is added to the circuit when the cut knob is turned off. This is my favorite feature of this amp.

IMO - it's best not to look at this amp as a clone of any particular vintage amp (it's not). It has all the recipes for the 50's Champ, Princeton, Harvard, and Deluxe, but it really is much more than that. I think it'd best to build it stock and start tweaking the knobs to find all the different sounds in there.

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MasterDelayer/Reverbrador/Ampaholic/TopJacker

Morgan pretty much said it all. Just know that the Tweed Royal can replicate the circuits of the 5F1, 5F2, and 5E3 EXACTLY. The 5F10 had a fixed bias, which the Tweed Royal cannot do, but replicates in every other way.

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*patience is a virtue*

Please do not PM me. email is prefered. keith@buildyourownclone.com

Thanks a lot for the superfast replies. And sorry for my confusion. You proved again that it is better to look at the schematic and not only at the layout.