suggestions for a rectifier

audio_moksha · 24th January 2008, 04:23 AM

Hi folks,

I have a 375-0-375rms power transformer that I want to use for an EL34 SE in triode mode (w/6SL7 driver). Using a capacitor input filter PSU, I need 420V while each EL34 pulls 70mA (140mA total).

Could somebody suggest a decent rectifier that would drop 110V at 140mA?

Thanks

oshifis · 24th January 2008, 09:56 AM

You need a serial stabilizer to drop the excess 110 V that can dissipate at least 15.4 Watts. But I guess you can not avoid using rectifier diodes of >1200 V and a capacitor of 630 V before the stabilizer.

Rewinding the transformer seems an easier solution...

SunRa · 24th January 2008, 10:37 AM

TV damper diodes maybe? These could suit... Search for 6cj3, Svetlana 6d22s

ray_moth · 24th January 2008, 10:56 AM

If you use 3.3uF for C1 and 100uF for C2 with a 5H choke, you should get about 420v. this is using either 5AR4 or 6D22S rectifier. Try it using PSUD II

kevinkr · 24th January 2008, 04:05 PM

You didn't mention whether this amplifier will use cathode or fixed bias, in the case of fixed bias you would be dissipating ~30W in each EL34 which is just a bit too high.. With cathode bias assuming an effective Vp of about 390V this would equate to about 27W - also imo "on the edge" - with modern tubes despite what the ratings say in triode connection I would not exceed 25W for reasonable tube life. (There's not much margin even at 25W.)

audio_moksha · 25th January 2008, 01:56 AM

I'm using cathode bias with a 440R resistor at approximately -31V Vgk.
I simply followed the EL34 data sheet and approximated a Se configuration from the data given for the triode Connected PP which is rated at Va=400V, Ia=70mA with Rk=440R and Ra=5k. I've had a similar amp running for a year now with SS rectification and so far its not given me any problems......And am I not running the tubes at 24.4W since P=I^2*R = (70mA)^2 * 5k = 24.5W?

audio_moksha · 25th January 2008, 02:05 AM

Ray_moth, I tried PSUD but I get VR1 = 426V but it is listed as RMS. I need 420V pk to get 400V on my EL34 plate. I used this for PSUD:
Transformer: 375Vrms
C1 : 3uF 2R
L1 = 10H, 80R dc (Hammond 193J)
C2 = 100uF 2R
R1 = 5k

ray_moth · 25th January 2008, 02:24 AM

I'm not sure what you mean. VR1 is DC, not AC.

audio_moksha · 25th January 2008, 02:39 AM

For Vr1 we have min, max, diff, mean and RMS columns. I was referring to the last column that states Vrms=426V. But if the other columns are all VDC then what does the Vrms stand for?

24th January 2008, 04:23 AM	#1
audio_moksha diyAudio Member Join Date: Oct 2006 Location: Los Angeles	suggestions for a rectifier Hi folks, I have a 375-0-375rms power transformer that I want to use for an EL34 SE in triode mode (w/6SL7 driver). Using a capacitor input filter PSU, I need 420V while each EL34 pulls 70mA (140mA total). Could somebody suggest a decent rectifier that would drop 110V at 140mA? Thanks

24th January 2008, 04:05 PM	#5
kevinkr diyAudio Moderator Join Date: Sep 2004 Location: Boston, Massachusetts Blog Entries: 6	You didn't mention whether this amplifier will use cathode or fixed bias, in the case of fixed bias you would be dissipating ~30W in each EL34 which is just a bit too high.. With cathode bias assuming an effective Vp of about 390V this would equate to about 27W - also imo "on the edge" - with modern tubes despite what the ratings say in triode connection I would not exceed 25W for reasonable tube life. (There's not much margin even at 25W.) __________________ www.kta-hifi.net

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24th January 2008, 09:56 AM	#2
oshifis diyAudio Member Join Date: Mar 2004 Location: Budapest, Hungary	You need a serial stabilizer to drop the excess 110 V that can dissipate at least 15.4 Watts. But I guess you can not avoid using rectifier diodes of >1200 V and a capacitor of 630 V before the stabilizer. Rewinding the transformer seems an easier solution...

24th January 2008, 10:37 AM	#3
SunRa diyAudio Member Join Date: Aug 2004 Location: Romania	TV damper diodes maybe? These could suit... Search for 6cj3, Svetlana 6d22s

24th January 2008, 10:56 AM	#4
ray_moth diyAudio Moderator Emeritus Join Date: Jan 2004 Location: Jakarta	If you use 3.3uF for C1 and 100uF for C2 with a 5H choke, you should get about 420v. this is using either 5AR4 or 6D22S rectifier. Try it using PSUD II

25th January 2008, 01:56 AM	#6
audio_moksha diyAudio Member Join Date: Oct 2006 Location: Los Angeles	I'm using cathode bias with a 440R resistor at approximately -31V Vgk. I simply followed the EL34 data sheet and approximated a Se configuration from the data given for the triode Connected PP which is rated at Va=400V, Ia=70mA with Rk=440R and Ra=5k. I've had a similar amp running for a year now with SS rectification and so far its not given me any problems......And am I not running the tubes at 24.4W since P=I^2R = (70mA)^2 5k = 24.5W?

25th January 2008, 02:05 AM	#7
audio_moksha diyAudio Member Join Date: Oct 2006 Location: Los Angeles	Ray_moth, I tried PSUD but I get VR1 = 426V but it is listed as RMS. I need 420V pk to get 400V on my EL34 plate. I used this for PSUD: Transformer: 375Vrms C1 : 3uF 2R L1 = 10H, 80R dc (Hammond 193J) C2 = 100uF 2R R1 = 5k

25th January 2008, 02:24 AM	#8
ray_moth diyAudio Moderator Emeritus Join Date: Jan 2004 Location: Jakarta	I'm not sure what you mean. VR1 is DC, not AC.

25th January 2008, 02:39 AM	#9
audio_moksha diyAudio Member Join Date: Oct 2006 Location: Los Angeles	For Vr1 we have min, max, diff, mean and RMS columns. I was referring to the last column that states Vrms=426V. But if the other columns are all VDC then what does the Vrms stand for?

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