45 triode : max 275 or 300 vdc ?

mahleriana · 10th March 2011, 10:51 PM

Hello,
Looking at different datasheets for 45 triode, some say 275v max (RCA) some say 300 v max. Is it a matter of older/newer tube ? I have mainly ...RCA tubes
My amp should give an anode voltage (Va-k) of around 280v ...
As I want to have as low an inductance as possible for the PSU rail, I don't want to add any voltage lowering resistors
Thanks in advance !

JLH · 10th March 2011, 11:29 PM

You and your 45 would be much better off at 250V or less. If you need more power then choose a bigger tube. If your power supply has too much voltage, then redesign it.

tubelab.com · 11th March 2011, 12:02 AM

Quote:

You and your 45 would be much better off at 250V or less.

I suppose that is the proper answer. I however like the sound of a 45 with 320 volts on the plate. All of my tubes are ST shaped 45's that I got on Ebay years ago before they got expensive. None have failed.

I also have a pair of globe shaped National Union NX483's which are 45's with a 5 volt filament. This pair were installed into a Sparton radio in 1929. I don't know how much they were used. I popped them into a Tubelab SE which runs 325 volts of B+ when I built the amp about 6 years ago. They still sound nice and see several hours per week of use.

mahleriana · 11th March 2011, 08:26 AM

I should have a B+ around 335v and a Vk about 55v > Va-k = 280v
Anyway I have redesigned a previous amp and don't want to buy a new power transformer for the moment (it is a 300-0-300 running now with a 5Y3 to lower B+, was originally for a 2A3 amplifier)

10th March 2011, 10:51 PM	#1
mahleriana diyAudio Member Join Date: Nov 2007	45 triode : max 275 or 300 vdc ? Hello, Looking at different datasheets for 45 triode, some say 275v max (RCA) some say 300 v max. Is it a matter of older/newer tube ? I have mainly ...RCA tubes My amp should give an anode voltage (Va-k) of around 280v ... As I want to have as low an inductance as possible for the PSU rail, I don't want to add any voltage lowering resistors Thanks in advance !

10th March 2011, 11:29 PM	#2
JLH diyAudio Member Join Date: Apr 2005 Location: Indianapolis, IN	You and your 45 would be much better off at 250V or less. If you need more power then choose a bigger tube. If your power supply has too much voltage, then redesign it. __________________ Ah, how beautifully the orchestra sounds before a rain! In a dry sunny day there is no way for the instruments to sound this way!

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11th March 2011, 08:26 AM	#4
mahleriana diyAudio Member Join Date: Nov 2007	I should have a B+ around 335v and a Vk about 55v > Va-k = 280v Anyway I have redesigned a previous amp and don't want to buy a new power transformer for the moment (it is a 300-0-300 running now with a 5Y3 to lower B+, was originally for a 2A3 amplifier)

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