A Audio and hi-fi forum. AudioBanter

Go Back   Home » AudioBanter forum » rec.audio » Vacuum Tubes
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

Replace plate load resistor with plate choke



 
 
Thread Tools Display Modes
  #1  
Old March 9th 17, 07:15 AM posted to rec.audio.tubes
Jimmy[_8_]
external usenet poster
 
Posts: 11
Default Replace plate load resistor with plate choke

HellO!
I've read posting on other forum and it draws my attention.

IS the DCR of the plate choke should be equal to the resistive value of the plate load resistor if considering replacing the resistor with the plate choke?

Example: if the current plate load resistor is 1000 ohm, should I use plate choke with DCR 1000 ohm??

A plate choke is a different impedance (reactance) at each frequency, increasing its value as frequency goes up.

Thanks!
Ads
  #2  
Old March 28th 17, 07:40 AM posted to rec.audio.tubes
[email protected]
external usenet poster
 
Posts: 1
Default Replace plate load resistor with plate choke

On Thursday, March 9, 2017 at 5:15:58 PM UTC+11, Jimmy wrote:
> HellO!
> I've read posting on other forum and it draws my attention.
>
> IS the DCR of the plate choke should be equal to the resistive value of the plate load resistor if considering replacing the resistor with the plate choke?
>
> Example: if the current plate load resistor is 1000 ohm, should I use plate choke with DCR 1000 ohm??
>

Unfortunately, you have not mentioned the tube type, or any of the operating B+, Eadc, Vac conditions, so none of us can answer your question properly..
Please specify ALL working conditions in future.

But let us suppose you have an anode resistor of say 10k0 which has 20mAdc to feed an EL84 in triode mode, where Ea = 250Vdc ( Vdc between anode and cathode ) The 10k will have 200Vdc across it, and there may be Rk = 515r, with Ek = +10.3Vdc, and B+ will then be 10.3V+250V+200V = 460.3Vdc.

Do you understand this fully so far?

Let us assume you want the bandwidth to be 20Hz to 20kHz.
Now this would be easily achieved by the EL84 triode with 10k0 load only, and no shunt C or L anywhere.

Let us assume you wish to replace the 10k0 with a choke.
The choke's dc wire resistance can be any value providing the heat generated in the winding wire does not cause the choke to overheat. So a typical value of Rw might be 470r, and so 20mAdc gives Pw = Isquared x R = 0.188W..
But the Vdc across L = 9.4Vdc, so the Ea across tube will increase to exceed +400Vdc, and the Idc will increase, and soon there may be a CLOUD OF SMOKE from your bench, and then you might blame us for the wrong advice.

So, DO NOT just remove the 10k0 and instal a choke; you NEED to understand a whole lot more about WHY you have asked us about a choke replacing the R.

The safe way to replace the 10k0 with a choke - assuming we want better Vac operation with less THD than with the R, is to keep the Ea nearly the same with choke as for without it.

You need to understand the properties of the tube involved, say EL84 in triode, with Iadc = 20mAdc.

Its Ra will be about 2k2. if you insist on bandwidth down to 20Hz, it means the F response is -3dB at 20Hz because Ra = L reactance XL = 2,200r.
This means the L must be at least 17.5 Henry. This leads us to wonder about core saturation and and air gap size and a whole lot of other L, C and R properties of the choke and so we can safely say there could be up to 7 items to be used in several equations to arrive at a design for the choke which will lead to the desired outcome of better result compared to having a 10k0.
  #4  
Old April 5th 17, 06:23 AM posted to rec.audio.tubes
Patrick Turner
external usenet poster
 
Posts: 3,964
Default Replace plate load resistor with plate choke

On 2017-03-28, > wrote:
> On Thursday, March 9, 2017 at 5:15:58 PM UTC+11, Jimmy wrote:
>> HellO!
>> I've read posting on other forum and it draws my attention.
>>

[snippety snip Jimmy's and further posts from Peter Wieck and Patrick Turner]

Jimmy, Peter and Patrick,
your discussion is appreciated but may I politely ask you guys to limit
your lines to 78 characters. Help us all to read your posts by giving
your lines a break ;-)
Thank you and cheers
Eike

I refuse to limit my posts here to 78 characters. So YOU won't here much from me. To reduce your ignorance, Read my website at www.turneraudio.com.au
  #5  
Old April 12th 17, 02:43 AM posted to rec.audio.tubes
Jim Candela
external usenet poster
 
Posts: 6
Default Replace plate load resistor with plate choke



I was thinking the same thing Pat until I realized he said 78 characters per line, and not for the entire post!

Jim
Wd5JKO
  #6  
Old April 12th 17, 09:34 AM posted to rec.audio.tubes
Patrick Turner
external usenet poster
 
Posts: 3,964
Default Replace plate load resistor with plate choke


I was thinking the same thing Pat until I realized he said 78 characters per line, and not for the entire post!

Jim
Wd5JKO

Well Jim, It seemed to me someone was complaining yet again that my posts were too long. And of course I have zero idea how to control the length of lines at my end; I am somewhat unskilled in IT practice, but maybe not as unskilled as those who invent and present us with means of communication without full instructions about how to use it all.

I have found I cannot be a part of ****ter because it is restricted to 140 characters per post.

I find Farsepuke a complete mystery. I tried joining 4 years ago, and nobody contacted me for 18mths, so I quit the damn place, and deleted my profile..
Then recently I re-joined to be able to post to a guy about a health issue.
I was inundated by inbox messages saying I had notifications and messages so I'd login and find there was zero messages. I did manage to talk to the fellow who had posted. Nothing for month now. So, my last post at Farcepuke tells everyone ppl to simply email me with regular email, and not to try thru Farcepuke.
Nobody has, which indicates NOBODY can be friends; the idea of "friends" is just another bowl of puke at Farcepuke.

It seems to me that the best form of the news groups was once before Google took over Usenet Groups, and changed all the format.

Rec.audio.tubes in 2003 was an extremely lively place where I sometimes wrote to 20 ppl who asked questions about tube amplifiers et all.
It was not moderated, so it soon attracted the most vicious of people who enjoyed their silly word wars rather than enjoy the brotherhood of man. So slowly the thin skinned who expected politeness all vanished. I stayed, and to make matters easier for tube enthusiasts I created my website with those who didn't know very much in mind.

I am not sure the Internet is getting any better. Last monday night's ABC Four Corners program in Australia of 1 hour was all about Facebook, oops, I meant Farcepuke, and how everyone is tracked and watched, and targeted by ppl wanting to sell stuff, mostly crap. Then there's the fake news and the "viral spread of posts" which are often of -155% relevance to any intelligent person; the level of BULL**** has risen so high now.

So it seems humans never really progress while crowing about "progress" to state of worseness, while sometimes moaning about 78 characters.
For the last 8 years at least my presence here has dwindled; I think many fellows who built tube gear may have been stopped by the GFC in 2008, or else they all got old and lost interest. I made a business out of a hobby, and shared it all with everyone.
It wasn't very lucrative, so I was happy to quit business in 2012 and take the old age pension because it paid twice as much. Those many customers who said they really loved tube gear would not pay more than peanuts.
I wasn't bitter, because I'd worked hard enough in my 30s to pay off my house, so in my 50s I could afford to do a low pay job because I didn't have to pay rent.
Maybe that's enough background information from me; I try to not have a single malicious molecule within my humble self.

I'll try to have a good Easter, you should try that too.
I did have both knee joints replaced 7 weeks ago; Its probably true I have a high pain threshold. But I should get back in my bicycle next Saturday, and that will be heaven. I am not obsessed with the Internet, and I have other interests - called living.

Keep as well as Unkle Fate allows,
Patrick Turner.
  #7  
Old May 22nd 17, 06:26 AM posted to rec.audio.tubes
Jim Candela
external usenet poster
 
Posts: 6
Default Replace plate load resistor with plate choke

On Wednesday, April 12, 2017 at 3:34:20 AM UTC-5, Patrick Turner wrote:
> I was thinking the same thing Pat until I realized he said 78 characters per line, and not for the entire post!
>
> Jim
> Wd5JKO
>
> Well Jim, It seemed to me someone was complaining yet again that my posts were too long. And of course I have zero idea how to control the length of lines at my end; I am somewhat unskilled in IT practice, but maybe not as unskilled as those who invent and present us with means of communication without full instructions about how to use it all.
>
> I have found I cannot be a part of ****ter because it is restricted to 140 characters per post.
>
> I find Farsepuke a complete mystery. I tried joining 4 years ago, and nobody contacted me for 18mths, so I quit the damn place, and deleted my profile.
> Then recently I re-joined to be able to post to a guy about a health issue.
> I was inundated by inbox messages saying I had notifications and messages so I'd login and find there was zero messages. I did manage to talk to the fellow who had posted. Nothing for month now. So, my last post at Farcepuke tells everyone ppl to simply email me with regular email, and not to try thru Farcepuke.
> Nobody has, which indicates NOBODY can be friends; the idea of "friends" is just another bowl of puke at Farcepuke.
>
> It seems to me that the best form of the news groups was once before Google took over Usenet Groups, and changed all the format.
>
> Rec.audio.tubes in 2003 was an extremely lively place where I sometimes wrote to 20 ppl who asked questions about tube amplifiers et all.
> It was not moderated, so it soon attracted the most vicious of people who enjoyed their silly word wars rather than enjoy the brotherhood of man. So slowly the thin skinned who expected politeness all vanished. I stayed, and to make matters easier for tube enthusiasts I created my website with those who didn't know very much in mind.
>
> I am not sure the Internet is getting any better. Last monday night's ABC Four Corners program in Australia of 1 hour was all about Facebook, oops, I meant Farcepuke, and how everyone is tracked and watched, and targeted by ppl wanting to sell stuff, mostly crap. Then there's the fake news and the "viral spread of posts" which are often of -155% relevance to any intelligent person; the level of BULL**** has risen so high now.
>
> So it seems humans never really progress while crowing about "progress" to state of worseness, while sometimes moaning about 78 characters.
> For the last 8 years at least my presence here has dwindled; I think many fellows who built tube gear may have been stopped by the GFC in 2008, or else they all got old and lost interest. I made a business out of a hobby, and shared it all with everyone.
> It wasn't very lucrative, so I was happy to quit business in 2012 and take the old age pension because it paid twice as much. Those many customers who said they really loved tube gear would not pay more than peanuts.
> I wasn't bitter, because I'd worked hard enough in my 30s to pay off my house, so in my 50s I could afford to do a low pay job because I didn't have to pay rent.
> Maybe that's enough background information from me; I try to not have a single malicious molecule within my humble self.
>
> I'll try to have a good Easter, you should try that too.
> I did have both knee joints replaced 7 weeks ago; Its probably true I have a high pain threshold. But I should get back in my bicycle next Saturday, and that will be heaven. I am not obsessed with the Internet, and I have other interests - called living.
>
> Keep as well as Unkle Fate allows,
> Patrick Turner.


I hope your knees steadily improve as the surgery scars heal. I don't check here too often, so I am just now responding.

In front of me is a ham band radio receiver, the Mosley CM-1, circa 1961 I think. It is a 5 tube dual conversion set which only uses type 6AW8A for all functions. It is in dis-repair. Once working again, I plan on making a FWB power supply instead of half wave, which should raise the B+ to ~ 180v, and replacing the NE2H regulators with a pair of 33v zeners in series for each NE2H. Was also thinking obout triode connecting the Audio OP pentode section to lower Rp such that the tiny OP transformer might be less tinny. Then make Rk about 400 ohms to get 6v bias at 15ma cathode current. But then the decreased gain will need to be made up for....perhaps looking at a CCS plate load for the driver stage. Just thinking at this point.

Good to hear from you Pat.

Jim
Wd5JKO
  #8  
Old May 22nd 17, 11:38 AM posted to rec.audio.tubes
[email protected]
external usenet poster
 
Posts: 13
Default Replace plate load resistor with plate choke

OK Jim, I found a copy of the schematic. The cct is a variation on something somewhat common with old guys like us back in the day, convert down to the BC band & use an ordinary receiver to do the tuning. I did two of them, one for my old Ford car.

So the front end does a block conversion in this case & the 2nd IF does the tuning, a slick way to get good image rejection. The preselecter completes the job.

Given the cct constants a B+ of 180V seems unlikely, 140-150V is possible. The first filter cap is shewn as 50 microF & is a problem for the PT. The peak currents are limited only by the PT wdg R's. Better stuff in something like 100R in series with the PT HV secondary to limit the peak charging currents. It is the RMS current that heats & kills transformers, not so much steady currents.

I noticed somewhere on line 5W audio mentioned. I think one Watt more likely. Rather then surgery to do a triode output & driver,if there is space there should be some kind of suitable OPT that would improve the sound. Hammond has several designed for SE output. But rather expensive now.

If the NE2H neons are still working keep them in the cct as is. The B+ will be about the same as original, no need to complicate with Zeners. My own experience with zeners as the voltage increases so does the change with temperature. As the zener heats up the voltage drifts with it.

Looks like a very good radio.

Good Luck, John L Stewart
  #9  
Old May 23rd 17, 02:51 AM posted to rec.audio.tubes
Jim Candela
external usenet poster
 
Posts: 6
Default Replace plate load resistor with plate choke

On Monday, May 22, 2017 at 5:38:13 AM UTC-5, wrote:
> OK Jim, I found a copy of the schematic. The cct is a variation on something somewhat common with old guys like us back in the day, convert down to the BC band & use an ordinary receiver to do the tuning. I did two of them, one for my old Ford car.
>
> So the front end does a block conversion in this case & the 2nd IF does the tuning, a slick way to get good image rejection. The preselecter completes the job.
>
> Given the cct constants a B+ of 180V seems unlikely, 140-150V is possible.. The first filter cap is shewn as 50 microF & is a problem for the PT. The peak currents are limited only by the PT wdg R's. Better stuff in something like 100R in series with the PT HV secondary to limit the peak charging currents. It is the RMS current that heats & kills transformers, not so much steady currents.
>
> I noticed somewhere on line 5W audio mentioned. I think one Watt more likely. Rather then surgery to do a triode output & driver,if there is space there should be some kind of suitable OPT that would improve the sound. Hammond has several designed for SE output. But rather expensive now.
>
> If the NE2H neons are still working keep them in the cct as is. The B+ will be about the same as original, no need to complicate with Zeners. My own experience with zeners as the voltage increases so does the change with temperature. As the zener heats up the voltage drifts with it.
>
> Looks like a very good radio.
>
> Good Luck, John L Stewart


John, Thanks for the very thoughtful reply. The Mosley CM-1 has an interesting history. The designer, John Clemens, W0BD was interviewed in 2013 about his receiver. John was 90 years old then. Here is the video:

https://twit.tv/shows/ham-nation/episodes/129

Fast forward to 15:00 minutes...

Here is where I got to thinking about a triode audio output tube:

http://our-house.jp/6AW8/index.htm

Jim
  #10  
Old May 23rd 17, 12:17 PM posted to rec.audio.tubes
[email protected]
external usenet poster
 
Posts: 13
Default Replace plate load resistor with plate choke

On Monday, May 22, 2017 at 9:51:03 PM UTC-4, Jim Candela wrote:
> On Monday, May 22, 2017 at 5:38:13 AM UTC-5, wrote:
> > OK Jim, I found a copy of the schematic. The cct is a variation on something somewhat common with old guys like us back in the day, convert down to the BC band & use an ordinary receiver to do the tuning. I did two of them, one for my old Ford car.
> >
> > So the front end does a block conversion in this case & the 2nd IF does the tuning, a slick way to get good image rejection. The preselecter completes the job.
> >
> > Given the cct constants a B+ of 180V seems unlikely, 140-150V is possible. The first filter cap is shewn as 50 microF & is a problem for the PT. The peak currents are limited only by the PT wdg R's. Better stuff in something like 100R in series with the PT HV secondary to limit the peak charging currents. It is the RMS current that heats & kills transformers, not so much steady currents.
> >
> > I noticed somewhere on line 5W audio mentioned. I think one Watt more likely. Rather then surgery to do a triode output & driver,if there is space there should be some kind of suitable OPT that would improve the sound. Hammond has several designed for SE output. But rather expensive now.
> >
> > If the NE2H neons are still working keep them in the cct as is. The B+ will be about the same as original, no need to complicate with Zeners. My own experience with zeners as the voltage increases so does the change with temperature. As the zener heats up the voltage drifts with it.
> >
> > Looks like a very good radio.
> >
> > Good Luck, John L Stewart

>
> John, Thanks for the very thoughtful reply. The Mosley CM-1 has an interesting history. The designer, John Clemens, W0BD was interviewed in 2013 about his receiver. John was 90 years old then. Here is the video:
>
> https://twit.tv/shows/ham-nation/episodes/129
>
> Fast forward to 15:00 minutes...
>
> Here is where I got to thinking about a triode audio output tube:
>
> http://our-house.jp/6AW8/index.htm
>
> Jim


THX for the 6AW8 running as a pwr amp, very useful info. I see they shew that the pentode section running as a triode at 1/2 W output while on the 200V PS. There are nomographs included in several of the RCA Receiving Tube manuals that allow estimates of pwr at other operating conditions. With the existing PT in the receiver I got 0.48 X 0.5W, about 240 mW, still very usable on a good speaker.

I didn't hookup to the video. Surprisingly, even tho we are in a major metropolitan area here, HS iNet has not yet come to this area. I'm on a rocket stick that communicates with the local cell phone tower close by on a 6 lane, soon to be 8 lane highway. Ridiculous & very expensive.

Cheers, John
 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Replace projector globe with resistor? Andre Jute[_2_] Vacuum Tubes 17 April 1st 11 12:35 PM
BJT for plate CCS load Tom Schlangen Vacuum Tubes 15 December 8th 04 11:41 AM
A Black Plate Here, a Smooth Plate There, Here a Plate, There a Plate, Everywhere a Plate Plate... Crumb Vacuum Tubes 4 November 10th 04 12:54 AM
EMT plate vs. EMT plate impulse? Jay Levitt Pro Audio 13 October 26th 04 05:26 AM
Is plate dissipation really plate current x plate voltage? Claus Misfeldt Vacuum Tubes 12 September 1st 04 10:54 AM


All times are GMT +1. The time now is 05:42 AM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Copyright 2004-2017 AudioBanter.
The comments are property of their posters.