PSU choke help please

gary h · 7th July 2008, 09:42 PM

Hi all,

I'm trying to figure out values for an LCLC(RC) filter section for my Aikido line stage preamp. I'm having a bit of trouble in PSUD2 due to not really knowing what I'm doing. John Brosky recomends a choke filtered B+. Anyway, having read and searched the forum I'm working with the following assumptions and questions:

Inductance of L1 is Vp/Ip. So around 300VDC after tube rectification to 4 6SN7s (10mA each) is 7.5H. Am I on the right track or does the capacitor pairing change this?

I have options for choke resistance (300-700 Ohms,) lower is better?

How much extra choke current rating is recommended?

Having read warnings about dual LC sections ringing, is this easily solved by making the L2 a higher value? If so, 10, 20H? Or just use one LC? (I'm hoping to maximize lower frequency, minimize high frequency noise, but am willing to lose some voltage.)

Thanks for the help, I hope to have the PSUD2 model working once I get these values within reason, so far I have been unable to successfully simulate.

Also,

how can I estimate the line section load for B+ in psud2 without having built it yet? Is it as simple as the speced plate resistence *4 (6,700*4=27kOhms?)

To model a full wave tube rectifier in psud2 it shows 2 tubes. I'm planning on using a 12X4. Can I just ignore this symbolic difference?

I better stop now before my head explodes. (And yours.)

Thanks in advance for the help.

gary

Serge66 · 8th July 2008, 12:49 AM

Hi Gary,
The choke size is correct.
The formula is V/(I*6*PI*f).

For the cap, I normally use 1uF per mA.

For modeling, you can use LTSpice also called Switchcad from LT.
The page is http://www.linear.com/designtools/software/
It is free. For tube models, visit Duncan's page:
http://www.duncanamps.com/spice.html

I modeled a choke first PSU with the above. I had to add a snubber (47k+100nF) after the rectifier to eliminate HV peaks. I have yet to build it. Maybe next year. Sigh.

Have you got a copy of the Radiotron Designer Handbook? I don't remember the latest edition. Third, I think. It has been digitized (.pdf) and can be bought online from tube/audio magazines. I remember it is also posted free on the web somewhere. It has excellent info on the design of PSU. LC, 2 sections LC...

Good luck.

Serge

Serge66 · 8th July 2008, 12:55 AM

Fourth Edition, actually.
Here is the link:

http://frank.yueksel.org/other/RCA/R...ion/index.html

gary h · 8th July 2008, 02:34 AM

thanks Serge,

I've seen the small cap before the choke in other schematics, will this help mitigate turn on and turn off noise?

I'll check out the link,

thanks a lot.

gary

ray_moth · 8th July 2008, 09:28 AM

A small cap before the choke (0.68uF seems to be a favorite value) can be applied to reduce noise from the choke in a choke-input filter.

A 0.01uF 1,000vAC cap across the power tranny secondary can be used to suppress spikes for the protection of rectifier diodes.

7th July 2008, 09:42 PM	#1
gary h diyAudio Member Join Date: Apr 2006 Location: usa	PSU choke help please Hi all, I'm trying to figure out values for an LCLC(RC) filter section for my Aikido line stage preamp. I'm having a bit of trouble in PSUD2 due to not really knowing what I'm doing. John Brosky recomends a choke filtered B+. Anyway, having read and searched the forum I'm working with the following assumptions and questions: Inductance of L1 is Vp/Ip. So around 300VDC after tube rectification to 4 6SN7s (10mA each) is 7.5H. Am I on the right track or does the capacitor pairing change this? I have options for choke resistance (300-700 Ohms,) lower is better? How much extra choke current rating is recommended? Having read warnings about dual LC sections ringing, is this easily solved by making the L2 a higher value? If so, 10, 20H? Or just use one LC? (I'm hoping to maximize lower frequency, minimize high frequency noise, but am willing to lose some voltage.) Thanks for the help, I hope to have the PSUD2 model working once I get these values within reason, so far I have been unable to successfully simulate. Also, how can I estimate the line section load for B+ in psud2 without having built it yet? Is it as simple as the speced plate resistence 4 (6,7004=27kOhms?) To model a full wave tube rectifier in psud2 it shows 2 tubes. I'm planning on using a 12X4. Can I just ignore this symbolic difference? I better stop now before my head explodes. (And yours.) Thanks in advance for the help. gary

8th July 2008, 12:49 AM	#2
Serge66 diyAudio Member Join Date: Nov 2007 Location: Canton of Jura	Hi Gary, The choke size is correct. The formula is V/(I6PI*f). For the cap, I normally use 1uF per mA. For modeling, you can use LTSpice also called Switchcad from LT. The page is http://www.linear.com/designtools/software/ It is free. For tube models, visit Duncan's page: http://www.duncanamps.com/spice.html I modeled a choke first PSU with the above. I had to add a snubber (47k+100nF) after the rectifier to eliminate HV peaks. I have yet to build it. Maybe next year. Sigh. Have you got a copy of the Radiotron Designer Handbook? I don't remember the latest edition. Third, I think. It has been digitized (.pdf) and can be bought online from tube/audio magazines. I remember it is also posted free on the web somewhere. It has excellent info on the design of PSU. LC, 2 sections LC... Good luck. Serge __________________ 'I have no faith in prayer that's not electronically augmented' Philip K. Dick "A Maze Of Death" 'I have no faith in bimbos that are not surgically augmented' Serge66

8th July 2008, 12:55 AM	#3
Serge66 diyAudio Member Join Date: Nov 2007 Location: Canton of Jura	Fourth Edition, actually. Here is the link: http://frank.yueksel.org/other/RCA/R...ion/index.html __________________ 'I have no faith in prayer that's not electronically augmented' Philip K. Dick "A Maze Of Death" 'I have no faith in bimbos that are not surgically augmented' Serge66

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Choke rating for choke input duty	cbutterworth	Tubes / Valves	14	9th November 2007 04:43 PM
Swinging choke vs std. choke in PS	Curly Woods	Tubes / Valves	2	5th March 2007 08:30 PM
Swinging Choke or Smoothing Choke	danFrank	Tubes / Valves	4	11th February 2007 11:05 AM
L as a choke.	bogdan_borko	Solid State	9	9th September 2006 09:48 PM
SS PSU without choke	Mikael Abdellah	Tubes / Valves	29	15th January 2003 04:34 PM

8th July 2008, 02:34 AM	#4
gary h diyAudio Member Join Date: Apr 2006 Location: usa	thanks Serge, I've seen the small cap before the choke in other schematics, will this help mitigate turn on and turn off noise? I'll check out the link, thanks a lot. gary

8th July 2008, 09:28 AM	#5
ray_moth diyAudio Moderator Emeritus Join Date: Jan 2004 Location: Jakarta	A small cap before the choke (0.68uF seems to be a favorite value) can be applied to reduce noise from the choke in a choke-input filter. A 0.01uF 1,000vAC cap across the power tranny secondary can be used to suppress spikes for the protection of rectifier diodes.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read