Understanding load on triode and impedance matching - Page 6

johnsurnamerobinson · 12th June 2019, 08:37 AM

The use of load lines is invaluble when aiming for max power transfer.However as I posted before in your case you need to make sure the o/p transformer has ample iron so as not to saturate when passing anode standing current +max signal.A good transformer manufacture will work this out for you as it depends strongly on core material.BTW a class A push pull output stage is far more forgiving in this regard as standing current is cancelled in the transformer.

TonyTecson · 12th June 2019, 08:37 AM

powering headphones, you will actually see much much less power than the graphs showed...

btw, speakers that are nominally rated at 8 ohms is only 8 ohms at one frequency and goes all over the place with different frequencies, i suspect that headphones are not much different...

johnsurnamerobinson · 12th June 2019, 08:58 AM

More on output transfomers.Care also needs to be taken when including a CUSTOM o/p transformer in the negative feedback loop.Thats a whole new world of pain!!!!

Re your point about headphone amps. I am an old timer and over the years can recall seeing many designs for valve headphone amps in the UK hobby press.Since almost everything ends up on the net these days they should be out there.I am no expert on google you may need something more specific. As I recall most seemed to use small signal triodes with No o/p transformer they were cap coupled. Really sorry I cant provide links.

PRR · 12th June 2019, 05:32 PM

> intended loads of about 64-300 ohms, .... .... I can't decide between 5K:16 (17.7:1) and 5K:32 (12.5:1).

Use 5K:32.

itsikhefez · 12th June 2019, 05:37 PM

Thank you

Tubelab_com · 12th June 2019, 09:55 PM

Quote:

Use 5K:32.

Without actually testing anything, that would be my best guess too. Unfortunately I have been busy slinging asphalt and ripping one of the heads off my dead lawn mower lately.

I would get the amp working with the 32 ohm transformer using a cheap speaker as a (mismatched) load, then try the headphones. Once working you can play with resistors in PARALLEL with the headphones to adjust the load seen by the tube for the best balance of power and distortion. Something between 33 and 1000 ohms will be the best.

As I stated before, I believe that a 5K to 8 ohm OPT will be marginal at putting enough power into 300 ohm phones without getting the 45 too close to clipping. The 32 ohm OPT will have enough voltage on its output to feed the cans, and enough reserve power to feed a resistor, while keeping the 45 in its happy zone around half a watt or less on peaks.

itsikhefez · 12th June 2019, 10:06 PM

Thanks for the input George, much appreciated.
I will proceed with this and report my findings, but that will take a while.

rayma · 12th June 2019, 10:09 PM

Quote:

Originally Posted by cerrem

Graphical Constructions for Vacuum Tube Circuits: Preisman A: Amazon.com: Books
Electronic Designers Handbook: R.W. Landee: 9780070361102: Amazon.com: Books

Preisman and another book by Pullen are free here.
http://www.tubebooks.org/Books/intro_Preisman_graph.pdf
http://www.tubebooks.org/Books/Intro...onductance.pdf

johnsurnamerobinson · 14th June 2019, 10:15 PM

You are really lucky to have so many good people reply to your post.All of them have given sound advice. I do understand your desire to learn and can only say ¬ learning drives us all forward.

TonyTecson · 15th June 2019, 12:16 AM

learn by doing, less talking.....

12th June 2019, 08:37 AM	#52
TonyTecson diyAudio Moderator Join Date: May 2003 Location: Maybunga, Pasig City	powering headphones, you will actually see much much less power than the graphs showed... btw, speakers that are nominally rated at 8 ohms is only 8 ohms at one frequency and goes all over the place with different frequencies, i suspect that headphones are not much different... __________________ hard work erases ignorance.....

15th June 2019, 12:16 AM	#60
TonyTecson diyAudio Moderator Join Date: May 2003 Location: Maybunga, Pasig City	learn by doing, less talking..... __________________ hard work erases ignorance.....

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
Understanding load lines	merlin el mago	Tubes / Valves	86	6th December 2018 08:08 PM
EL34,KT66,6L6GC,KT77:who works better with high impedance OT load in SE Triode Mode?	ygg-it	Tubes / Valves	3	22nd May 2015 07:20 PM
Understanding load lines	tvrgeek	Tubes / Valves	20	18th January 2010 07:16 PM
Need help understanding transformer impedance ratios and impedance matching	percy	Tubes / Valves	5	28th February 2005 09:35 PM
Understanding OPT primary Z and load matching.	percy	Tubes / Valves	4	21st August 2004 01:30 AM

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


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

12th June 2019, 08:37 AM	#51
johnsurnamerobinson diyAudio Member Join Date: Nov 2018	The use of load lines is invaluble when aiming for max power transfer.However as I posted before in your case you need to make sure the o/p transformer has ample iron so as not to saturate when passing anode standing current +max signal.A good transformer manufacture will work this out for you as it depends strongly on core material.BTW a class A push pull output stage is far more forgiving in this regard as standing current is cancelled in the transformer.

12th June 2019, 08:58 AM	#53
johnsurnamerobinson diyAudio Member Join Date: Nov 2018	More on output transfomers.Care also needs to be taken when including a CUSTOM o/p transformer in the negative feedback loop.Thats a whole new world of pain!!!! Re your point about headphone amps. I am an old timer and over the years can recall seeing many designs for valve headphone amps in the UK hobby press.Since almost everything ends up on the net these days they should be out there.I am no expert on google you may need something more specific. As I recall most seemed to use small signal triodes with No o/p transformer they were cap coupled. Really sorry I cant provide links.

12th June 2019, 05:32 PM	#54
PRR diyAudio Member Join Date: Jun 2003 Location: Maine USA	> intended loads of about 64-300 ohms, .... .... I can't decide between 5K:16 (17.7:1) and 5K:32 (12.5:1). Use 5K:32.

12th June 2019, 05:37 PM	#55
itsikhefez diyAudio Member Join Date: Aug 2015	Thank you

12th June 2019, 10:06 PM	#57
itsikhefez diyAudio Member Join Date: Aug 2015	Thanks for the input George, much appreciated. I will proceed with this and report my findings, but that will take a while.

14th June 2019, 10:15 PM	#59
johnsurnamerobinson diyAudio Member Join Date: Nov 2018	You are really lucky to have so many good people reply to your post.All of them have given sound advice. I do understand your desire to learn and can only say ¬ learning drives us all forward.