DIY 18w style build PT question

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DIY 18w style build PT question

Post by JesseJJ » Thu May 24, 2018 6:49 am

Hello Gents,

For my next amp build I'm looking into a 18w design, single channel. I believe the same layout has been going on on here as well.


The thing I'm wondering about most is what voltages im gonna get away with for my B+. Since I definately wanna go solid state recto way. The PT in this layout has 275v secondaries, where I live I can only find a 300v PT that is suitable for the task. So my question being, what changes do I need to make to make this work with this particular layout.

I got a bit confused with wich resistors I will need to change.

Kind regards,


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Re: DIY 18w style build PT question

Post by danman » Thu May 24, 2018 8:58 pm

I'm gonna say you will end up in the high 300's if you go with ss rectifier. It's a little high for el84's but not unheard of. There are options for lowering B+ such as reversed bias zener diodes in the PT"s centertap or a VVR circuit which will allow you to adjust the B+ from nothing all the way up to max. The VVR also makes for a great bedroom amp because you can dial down the voltages and get power tube breakup without disturbing the neighbors. I would stick to scaling only the power amp and leave the preamp alone as I feel it sounds a little better this way. Check out how it's implemented in this kit...

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