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Budget 300B

I am planning to build the Budget 300B amplifier. I live in Italy (230V) and I was wondering if the Hammond 266M6 is good for 65N7 filaments. I am a beginner and I don't understand which B + the CT should be connected to. Sorry for the stupid question.

Ico

9 answers10 replies

19 Comments

mecoc

Apr 17, 2022

Thanks Skunky. I am grateful to you for the work done and the beautiful videos.

Domenico

mecoc

Apr 17, 2022

I've finally finished assembling Stephe's schematic and the sound is much better than the initial Sunaudio schematic, and the power and distortion too. As I said I am a beginner so I ask a stupid question:

I have a slight but annoying hum that I can eliminate with the two Bourns pots. Do the two pots have to be set the same? If so, at what points should I measure the values? If I change with the Bourns, does it also change the bias?

Thank you very much

Skunkie

Apr 17, 2022

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Replying to

The pots do not have to be the same, they are there to adjust away any minor hum. And these pots have no effect on the bias at all, they simply are fine tuning the center point of the cathode on a directly heated tube. Also, no need to measure anything related to these pots, just adjust them by ear for the least amount of hum. BTW lovely build!

roblund7

Jan 28, 2022

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Excellent work Henryk! Absolutely stunning! I’m about to embark on this project. Would you mind sharing your parts list? Any tips would be greatly appreciated.

Ico Cadeddu

Feb 08, 2022

Replying to

One last question, can I use an OT. with 5600K instead of 5000K? Or maybe 4600K is better? Would I just have a difference in watts or could it cause me other problems? I ask this because in Italy I can more easily get a Lundahl 1623 90mA or Lundahl 2769 instead of Edcor.

Thank you

Ico Cadeddu

Feb 08, 2022

Replying to

ok solved. Sorry I hadn't read Val's post. Thank you

Henryk Pycha

Dec 13, 2021

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Hello, anyone interested. Just finished building the 300b amplifier following the helpful SkunkieDesigns tips. I checked, I measured all the voltage and currents - everything is correct. The sound from this 300b amp is phenomenal I couldn't stop listening to the amp until late at night. I include a photo amplifier 300b on top

Good luck to everyone in building the 300b amplifier.

mecoc

Dec 13, 2021

Replying to

Marvelous ! really beautiful.

Henryk Pycha

Dec 13, 2021

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Henryk Pycha

Dec 13, 2021

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mecoc

Dec 08, 2021

thank you very much ️

mecoc

Dec 12, 2021

Replying to

i am trying to make a pcb without the power section which i will point to point. Did I make any mistakes?

Thanks

Skunkie

Dec 12, 2021

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Replying to

@mecoc The ONLY impact, let me repeat this: THE ONLY IMPACT building any project for 230V vs 120V line voltage is at the primary winding of the power transformer. NOTHING after the power transformer changes as the voltage out of the PT secondary is the same. As far as the PCB, I would recommend wiring the whole amp PTP. Someone else with some free time might be interested in double checking your conversion of the schematic to a PCB layout. I honestly don't have time to.