6922 direct coupled to 2A3 - Page 2

gabriel611 · 15th March 2006, 08:03 AM

arnoldc,

could be why i'm reading only 260volts at the plate because of the 10k resistor. can i still get away with the needed voltage on the driver if i remove this resistor?

also, if i lower the cathode resistor on the 2A3, will i not be able to get the 45 volts to drive this output tube?

what are now my options with this mains transformer and said tubes? please suggest. thanks

arnoldc · 15th March 2006, 08:27 AM

i guess not. you lower your cathode resistor, you pull more current, which means your B+ is going down even further.

Why are you so stuck with this power supply? What's the transformer secondaries? What's the filtering topology? (CRCRC, CLCLC, LCLC, etc)

ps.

If you're stuck with that power transformer *and* using tube rectification, ditch the tube rectifier and use SS. You will get a higher B+

pps.

it's just not enough... if the 2A3 grid is 130V from the SRPP, you want the cathode to be 45V above that, 175V. 175V / 50mA = 3K5 ohms cathode resistor. But you actually need 4V + 130V + 45V + 250V = 430V

gabriel611 · 15th March 2006, 08:45 AM

my filtering section after the 5u4g tube is composed of 20uf cap then 10H choke then 220uf cap which gives me a b+ of a little over 350volts. will changing the caps give me a higher b+? sorry but im just a newbie. and thanks for the reply.

gabriel611 · 15th March 2006, 08:47 AM

btw, i dont want to spend more as much as possible so im trying for this transformer to work.

arnoldc · 15th March 2006, 08:49 AM

why sorry? we are all newbies here. Just wait when Sy, Thorsten, and Frank, and many others post in a thread

two options-

1. Use another power transformer

2. Ditch the 5U4, and go SS

gabriel611 · 15th March 2006, 09:07 AM

ok. please suggest what ss rectifier to use? can you help me with the power supply schematic? what will be its effect on the sound compared to tube rectifier? thanks

arnoldc · 15th March 2006, 09:25 AM

what is the secondary of your transformer?

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
capacitor coupled vs. direct coupled ouput	hugobross	Solid State	11	21st January 2011 01:56 AM
6sn7 direct coupled and transformer coupled	neazoi	Tubes / Valves	3	23rd May 2008 03:30 PM
6922 transformer coupled	Andersen	Tubes / Valves	12	9th April 2008 02:47 AM
My first amp - a direct coupled 2A3	Wardsweb	Tubes / Valves	51	3rd August 2003 04:22 AM
Can someone explain parafeed & direct coupled & a.c. coupled?	mwmitchell	Tubes / Valves	2	11th September 2002 01:10 PM

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

15th March 2006, 08:03 AM	#11
gabriel611 diyAudio Member Join Date: Feb 2006 Location: manila	arnoldc, could be why i'm reading only 260volts at the plate because of the 10k resistor. can i still get away with the needed voltage on the driver if i remove this resistor? also, if i lower the cathode resistor on the 2A3, will i not be able to get the 45 volts to drive this output tube? what are now my options with this mains transformer and said tubes? please suggest. thanks

15th March 2006, 08:27 AM	#12
arnoldc diyAudio Member Join Date: Apr 2003 Location: Makati	i guess not. you lower your cathode resistor, you pull more current, which means your B+ is going down even further. Why are you so stuck with this power supply? What's the transformer secondaries? What's the filtering topology? (CRCRC, CLCLC, LCLC, etc) ps. If you're stuck with that power transformer and using tube rectification, ditch the tube rectifier and use SS. You will get a higher B+ pps. it's just not enough... if the 2A3 grid is 130V from the SRPP, you want the cathode to be 45V above that, 175V. 175V / 50mA = 3K5 ohms cathode resistor. But you actually need 4V + 130V + 45V + 250V = 430V

15th March 2006, 08:45 AM	#13
gabriel611 diyAudio Member Join Date: Feb 2006 Location: manila	my filtering section after the 5u4g tube is composed of 20uf cap then 10H choke then 220uf cap which gives me a b+ of a little over 350volts. will changing the caps give me a higher b+? sorry but im just a newbie. and thanks for the reply.

15th March 2006, 08:47 AM	#14
gabriel611 diyAudio Member Join Date: Feb 2006 Location: manila	btw, i dont want to spend more as much as possible so im trying for this transformer to work.

15th March 2006, 08:49 AM	#15
arnoldc diyAudio Member Join Date: Apr 2003 Location: Makati	why sorry? we are all newbies here. Just wait when Sy, Thorsten, and Frank, and many others post in a thread two options- 1. Use another power transformer 2. Ditch the 5U4, and go SS

15th March 2006, 09:07 AM	#16
gabriel611 diyAudio Member Join Date: Feb 2006 Location: manila	ok. please suggest what ss rectifier to use? can you help me with the power supply schematic? what will be its effect on the sound compared to tube rectifier? thanks

15th March 2006, 09:25 AM	#17
arnoldc diyAudio Member Join Date: Apr 2003 Location: Makati	what is the secondary of your transformer?

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