Spacing requirements between 300B tubes

[marcomariutto]

Hello, I am designing the PCB for a PSE 300B amplifier. I cannot find any documentation regarding what's the minimum spacing between the tubes. Has anyone any reference to share?

Thank you in advance,
Marco

 

[Richard Ellis]

In Morgan Jones seminal book, he recommended the spacing to be at least "One and a half envelopes" spacing...so if your 300B glass is say 50mm diameter , then space them minimum 75mm.

----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------Rick...

 

[rayma]

This also depends on how well the air circulates. Will there be a cover? Are the tubes close to the edge?
Is there a shelf closely above? Are there feet to allow air flow into the bottom?

 

[marcomariutto]

@Richard Ellis thank you for the suggestion. Is the 75mm distance center-to-center?

 

[Richard Ellis]

Center to center?, no....75mm of the outer edge of both tubes. In Morgans book, he suggests the chassis size be bigger than you think...cramped components make for difficulties when one starts filling in spaces & you still have to solder in connecting wiring.

-----------------------------------------------------------------------------------------------------------------------------Rick...

 

[rayma]

Most of the physical volume of a tube amp should be air.

 

[waltube]

Is always suggested to put the tube amp in a free space on the rack ( top)
Then 3-5 cm minimum from the edge of each tube is fine
Some of this my amps ran well since 5-8 years

 

[6A3sUMMER]

Heat?

A 300B at 40 Watts maximum plate dissipation, is different than a 300B operated at 18 Watts plate dissipation.
Do not forget the 5V 1.25A filament dissipates an additional 6 Watts.