Hi specs rectifier needed

Tfan69 · 24th February 2011, 07:28 PM

Hello, i'm going to build a KT88 PP amplifier, and i'd love to use a direct heating rectifier tube... the problem is that i'm having trouble finding a tube capable of these specs: in AC 550v 200mA, because i need 600v after filtering... any ideas??

vega65 · 24th February 2011, 08:41 PM

5R4-GYB ?

vega65 · 24th February 2011, 08:43 PM

Quote:

Originally Posted by vega65

5R4-GYB ?

Sorry did not see dht requirement before posting

Vinylsavor · 24th February 2011, 09:00 PM

Hi!

Quote:

Originally Posted by vega65

Sorry did not see dht requirement before posting

The 5R4 you mentioned IS directly heated...

But why insist on DH rectifiers? If you open yourself for indirectly heated rectifiers an abundance of choices opens up: TV Dampers. They can easily handle the voltage and current requirement. However If you have not settled on the power transformer yet, go for choke input supply and a full wave Graetz bridge.

Best regards

Thomas

Tfan69 · 25th February 2011, 07:03 AM

5R4-GYB fits perfectly thanks

hello Thomas, do you mean using diodes instead of tubes for rectifing??

trobbins · 25th February 2011, 07:08 AM

In the olde days, it was common to use two dual diodes of lower voltage rating in a doubler configuration. The dual diodes in each valve were paralleled to cope with the higher current levels, and the advantage was that the diode voltage spec didn't have to be high, and the filter caps were placed in series and clamped to half HT. The disadvantage was you needed 2x 5V heaters.

However it is sometimes difficult to design the capacitor for valve rectifier circuits, especially doubler, as the ripple current ratings are quite low for low uF electrolytics with high voltage ratings. The only simple workaround is to use larger uF caps of lower voltage rating in series. Many possibly don't check the capacitor ratings.

Ciao, Tim

piero7 · 11:13 AM

2 X 5AR4 plates paralleled for example...

Vinylsavor · 25th February 2011, 02:57 PM

Hi!

Quote:

Originally Posted by Tfan69

5R4-GYB fits perfectly thanks

hello Thomas, do you mean using diodes instead of tubes for rectifing??

I mean vacuum tube diodes like the 6AX4, 6AU4, 6Cj3, etc these are single diodes.

Thomas

Vinylsavor · 25th February 2011, 03:01 PM

Hi!

Quote:

Originally Posted by Tfan69

5R4-GYB fits perfectly thanks

A single 5R4 will be marginal in your application. If you want to use it, use at least two and parallel them.

Thomas

whitelabrat · 25th February 2011, 03:15 PM

How about a pair of 4B32's

24th February 2011, 07:28 PM	#1
Tfan69 diyAudio Member Join Date: May 2009	Hi specs rectifier needed Hello, i'm going to build a KT88 PP amplifier, and i'd love to use a direct heating rectifier tube... the problem is that i'm having trouble finding a tube capable of these specs: in AC 550v 200mA, because i need 600v after filtering... any ideas??

25th February 2011, 11:08 AM	#7
piero7 diyAudio Member Join Date: Apr 2009 Location: Matera	2 X 5AR4 plates paralleled for example... Last edited by piero7; 25th February 2011 at 11:13 AM.

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24th February 2011, 08:41 PM	#2
vega65 diyAudio Member Join Date: Nov 2007	5R4-GYB ?

25th February 2011, 07:03 AM	#5
Tfan69 diyAudio Member Join Date: May 2009	5R4-GYB fits perfectly thanks hello Thomas, do you mean using diodes instead of tubes for rectifing??

25th February 2011, 07:08 AM	#6
trobbins diyAudio Member Join Date: Feb 2009 Location: Melbourne, Oz	In the olde days, it was common to use two dual diodes of lower voltage rating in a doubler configuration. The dual diodes in each valve were paralleled to cope with the higher current levels, and the advantage was that the diode voltage spec didn't have to be high, and the filter caps were placed in series and clamped to half HT. The disadvantage was you needed 2x 5V heaters. However it is sometimes difficult to design the capacitor for valve rectifier circuits, especially doubler, as the ripple current ratings are quite low for low uF electrolytics with high voltage ratings. The only simple workaround is to use larger uF caps of lower voltage rating in series. Many possibly don't check the capacitor ratings. Ciao, Tim

25th February 2011, 03:15 PM	#10
whitelabrat diyAudio Member Join Date: Dec 2006 Location: Maryland	How about a pair of 4B32's

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