Tube failure - Page 2 - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

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
Reply
 
Thread Tools Search this Thread
Old 18th May 2003, 08:33 PM   #11
diyAudio Member
 
Join Date: May 2003
Location: Morton, Illinois
Default 100 ohm resistor

Yes, the 100 ohm resistor is in the signal path and definitely handles audio frequencies.

Unless the designer is trying to compensate for a weakness in the sound, I would find the best resistor, sonically, possible.
  Reply With Quote
Old 18th May 2003, 09:56 PM   #12
diyAudio Member
 
Christopher's Avatar
 
Join Date: Apr 2003
Location: Hamilton
Default Well the best sounding,

I dropped four different resistors on the floor, and I liked the sound the wire wound made the best.

Seriously, I'm not sure if you've been following the "Blind Listening Test" thread, but this little discussion has spilled over from that one. I am one who maintains that in most cases, one resistor actually sounds the same as another. (ie when you no longer know which resistor you are listening to ,you won't be able to tell a difference) although I'm open to any evidence to the contrary.

I have been doing a little research, "little" being the operative word here, and so far I have to agree with you and Frank on the other point though. It still seems to me that that resistor would be carrying audio. According to what I've read, about 1/10th of what the plate carries. Still, B.R. must have solid grounds for saying so, so my research continues.

In any event, even if that resistor was to be attenuating signal in a non-linear manner,(which in this application I don't beleive it is) as 10 times the current is going through the plate, the 'sound' should not be altered. Thus, the best looking resistor would be just as valid a choice as the best sounding.

Chris
  Reply With Quote
Old 18th May 2003, 10:01 PM   #13
diyAudio Senior Member
 
fdegrove's Avatar
 
Join Date: Aug 2002
Location: Belgium
Default To The Shredder...

Hi,

Quote:
Yes, the 100 ohm resistor is in the signal path and definitely handles audio frequencies.
Obvoiusly so.

Quote:
I've asked twice, and now B.R. has asked as well, what is the inductance of those resistors, and further, how would it affect the circuit?
You're being stubborn or downright stupid?

Go educate yourself before jumping to conclusions.
Learn how to read replies, it may help.

Quote:
Well I'm sure Bruce could explain his postition to me, can you explain yours?
Sure, his is economical, mine isn't.

Quote:
No one said the plate doesn't carry audio, what he said was the 100ohm resistor carried DC only. I had made the same assumption that you have,(that the resistor makes the screen part of the plate), but based on Bruces reply, there's something I missed, I'm going to try figure out what that was.
Well, yes you did.And in the same sentence you contradict yourself a few times already.
It would really come as a surprise if Mr.Rosenblit said any such thing for it it is absolutely incorrect.

Quote:
and now B.R. has asked as well, what is the inductance of those resistors, and further, how would it affect the circuit?
Really a novice to all things electronic or what?
The inductance of a 5W 100R will vary from one manufacturer to another.
More importantly, it was your mistake to assume all WW resistors had to be replaced in the first place.
How on earth can you jump to such conclusion from my reply...mind you your conclusion IS correct inductive components do not have a place in audio...unless you can put them to your advantage.

Quote:
As for the GA vs AR version of the OTL, I don't see any cut corners at all, perhaps you can point them out.
I can, but I'm not inclined to given your "friendly" attitude.

Quote:
Well don't keep us in suspense I'm sure that if you have some useful improvements, Bruce would most certainly appreciate your input, I know I would.
See above.

Quote:
As for the GA vs AR version of the OTL, I don't see any cut corners at all, perhaps you can point them out. Since you photocopied parts of the book, there was obviously something you could learn,
The only thing I learned from it is that in the US you can patent the way how you tie your shoelaces and that you don't have a clue what the patent is about.
Zener diodes my *ss.

Quote:
Square waves actually, and I did dig it up, it was a 2uf cap in parallel with an 8ohm resistor. Tougher than music I'd say.
Great, now you really got the message...ever looked at the impedance correction network at the output?

Need more hints?

No, you don't for you're smart and educated an rely on everything Mr.Rosenblit puts on paper, right?

Sorry, but you got yourself a very KIND reply both technically and personally.

You figured so many things wrong, hard to believe really...and I'm the bad guy?

Cheers,

P.S. And I always had the impression Canadians were open minded, hospitable people...
Sorry. cheap shot.
__________________
Frank
  Reply With Quote
Old 18th May 2003, 10:03 PM   #14
diyAudio Senior Member
 
fdegrove's Avatar
 
Join Date: Aug 2002
Location: Belgium
Default NO IT HASN'T

Hi,

Quote:
Seriously, I'm not sure if you've been following the "Blind Listening Test" thread, but this little discussion has spilled over from that one.
You wish it had...

Not with me matey...
__________________
Frank
  Reply With Quote
Old 18th May 2003, 10:14 PM   #15
diyAudio Senior Member
 
fdegrove's Avatar
 
Join Date: Aug 2002
Location: Belgium
Default ND I'M STILL P*SSED.

Hi,

Well,well we do come around?

Quote:
In any event, even if that resistor was to be attenuating signal in a non-linear manner,(which in this application I don't beleive it is) as 10 times the current is going through the plate, the 'sound' should not be altered. Thus, the best looking resistor would be just as valid a choice as the best sounding.
It's not just one resistor but more than half a dozen of'em.

I grant you this much, I want things to be as perfect as I can get.
My audiobandwidth runs well into the hundreds of kiloherz...
Ever asked yourself why?

And, I'll be the last to accept unnecessary commercial compromise.

You know, it's all about roll off and there's little point in having an OTL amp if you don't take that brownie along...

Cheers,
__________________
Frank
  Reply With Quote
Old 19th May 2003, 02:16 AM   #16
diyAudio Member
 
Join Date: May 2003
Location: Morton, Illinois
Default Resistor, screen, plate

Chris, I hope you don't mind as I am lazy.

I respect your opinion about resistors sounding the same, but If there was a sonic difference, that sonic difference will show up in full force on the plate.

The screen grid has great, nearly total control over the plate current, and how the screen goes (sonically), so goes the sonics at the plate.
  Reply With Quote
Old 19th May 2003, 07:49 PM   #17
diyAudio Member
 
Christopher's Avatar
 
Join Date: Apr 2003
Location: Hamilton
Default Ok let's see...

Hi Steve,

According to what I've read, there is about 10% of the overall current going through the screen grid in this configuration. Are you saying that connected in triode mode as the screen goes so goes the plate? Or were you speaking in pentode mode? I must admit I still can't figure out why Bruce would say that it is only DC going through this resistor, as I see no mechanism for this to be true, I may end up asking him.

However, in answer to the overall impact of inductive vs non-inductive I have learned the following. Anyone feel free to correct any assumptions I've made as this is pretty free form.

I had a really hard time finding any hard numbers, and I have a friend who has a good inductance meter who is going to do a measurement for me, but in the mean time...

I was able to find one data sheet that said the <5ohm values were <1uh. A quick calculation shows that at1uh and 1MHZ the reactance is ~6ohms. So that's 3ohms at 500Khz 1.5 at 250 and so on. So if you are really uptight about how linear your cathode resistors are at 250khz you do have a somewhat valid concern. Keep in mind this inductance in no way will limit the bandwidth, just change it's linearity a bit. Now from 5 to 50K(published BW of this design) these cathode resistors will change about .3 of an ohm. I would suppose that the natural variation in current throught tube would be greater than what the rise and fall of .3 ohms on the cathode would create. Further, since removing them altogether would lower the output impedence by about 10%, adding another .3 of an ohm changes that a max of .6%(in this case about 25 milliohms). Yes I know it's non-linear, but the important thing is what effect will this have on the performance of the amp? I can't see a non-linear swing in output impedence in the fractions of percent to be even remotely important when you consider how non-linear the load is in comparison. As for the 100ohm resistors, well given that it's 10% of the plate and even a 6 ohm swing is only 6%, numbers get pretty insignificant pretty fast.

More to come...


Chris
  Reply With Quote
Old 19th May 2003, 10:23 PM   #18
diyAudio Member
 
Join Date: May 2003
Location: Morton, Illinois
Default In triode mode....

Yes Chris, in triode mode it's the screen that nearly completely controls the plate current (signal). Thus, how the screen goes, the plate goes also, whether current or signal.
  Reply With Quote
Old 19th May 2003, 10:30 PM   #19
diyAudio Member
 
Christopher's Avatar
 
Join Date: Apr 2003
Location: Hamilton
Default closed minded and stupid, but I try...

Quote:
You're being stubborn or downright stupid?
A bit of both I guess, I just figured you would know off the top of your head, and I'd have to do a tonne of work, and since you maintained it was a bad practice, you could support that with some basic engineering, I suppose that was stupid of me to assume. See the above post, I answered the question to the best of my ability, feel free to correct the math or the assumptions or point out anything I may not have taken into account. I'm here to learn.

Quote:
Sure, his is economical, mine isn't.
Sorry, I wasn't clear in my question, what I meant was if Bruce says only DC and you say AC then I suspect he feels he can support that, or are you saying that he says it only carries DC for economic reasons?

Quote:
Really a novice to all things electronic or what? The inductance of a 5W 100R will vary from one manufacturer to another. More importantly, it was your mistake to assume all WW resistors had to be replaced in the first place.
Well, yes, well not quite, but it's already been established that I'm not strong in ciruit theory, but I'm learning, and I do have a fairly good capacity for understanding when someone explains something new to me. And I did say roughly and typically(when I first asked on the other thread that this didn't spill over from) Now one would assume that if you figure the screen resistors should be non-inductive, then for god sake man, get them off the cathodes! And that's all of 'em in this case. Vary from one manufacturer to another? Really, that's not much help. You could have done a worse case scenario, at least it's a place to start.

Quote:
Zener diodes my *ss.
Ok, now that's funny. Just so we're all clear on this, you don't think the zeners have anything to do with what makes this OTL special (or at least on par with a new shoelace tie) BTW it is a rather common misconception that anything can be patented. But that's another discussion.

Quote:
My audiobandwidth runs well into the hundreds of kiloherz...
Ever asked yourself why?
No, but I have asked myself how.
If Bruce publishes the BW to be 5 to 50Khz, you must have a few pretty nifty tweaks up your sleeve.

Rolloff? I've put my best effort out there for all to review/critique, how do you suppose the choice of these resistors affects the rolloff? If you are willing to explain it I'm willing to learn.

and finally.....

Quote:
No, you don't for you're smart and educated an rely on everything Mr.Rosenblit puts on paper, right?
All things in moderation I suppose, but as for taking all my info from Bruce? Hardly. So far, he is one of the few I've read in this buisness that talks any sense at all. I have to admit, that the DC comment really caught me by surprise, and so far all the research and critical thinking I've done certainly doesn't support it. One of the reasons I'm so often willing to take him at face value, is I've wondered about all kinds of little things that seem to make no sense (cable direction, cable choice, biwiring and on and on) and he comes along and say he thinks it's dung and then goes on to support it with some pretty solid arguments. That just immediatley endears a guy to me. OTOH when someone just comes along and says 'no that's wrong' and then backs it up by saying, 'and if you weren't so stupid and uneducated you wouldn't be saying such a thing' well I tend to be suspicious of anything he has to say.

Compensation network? Are you saying he did something with the AR version that makes it less stable than the GA version(into inductive loads), or there was a way to stabilize the amp without using the network but he couldn't be bothered? I'm sorry but figuring that out for myself would take about a week, and even then I'm not sure I'd be right. BTW there's something I've been just dying to ask, do you biwire?

Oh yeah and one thing I did learn while I was trying to get inductance numbers for the WWs. These things kick ***! They are rugged, have the best temperature coefficient, last forever, take more heat, drift over time is virtually non-existant. Pretty good stuff for a piece of gear yes?

So far, the WW looks good to me.

Chris
  Reply With Quote
Old 19th May 2003, 11:51 PM   #20
diyAudio Senior Member
 
fdegrove's Avatar
 
Join Date: Aug 2002
Location: Belgium
Default OKIDOKI.

Hi,

Not that many people here understand OTL amps which is probably why you mainly depend on me and quite likely SY...
Sorry if I left someone out.

Quote:
I just figured you would know off the top of your head,
'Course not and it ain't that simple either...basically you need to avoid stray inductance for it creates resonant circuits.
Whether these resonate within or outside "your" audioband or not is irrelevant...thing is they resonate.

Just keep in mind it's an additive effect, the more the worse it gets.

Quote:
Sorry, I wasn't clear in my question, what I meant was if Bruce says only DC and you say AC then I suspect he feels he can support that, or are you saying that he says it only carries DC for economic reasons?
That resistor carries both AC and DC, where you derive that 10% figure from is a mystery to me.
Economics only come into play when the type of resistor is concerned, after all when we consider 5W'ers a run of the mill inductive one is cheaper.

Oh, and there are no cathode resistors in the output stage...they are only there for measuring purposes and to protect the valves from back EMF...
Again, using inductive WWs is going to falsify measuements to some extend.

Quote:
Well, yes, well not quite, but it's already been established that I'm not strong in ciruit theory, but I'm learning, and I do have a fairly good capacity for understanding when someone explains something new to me.
Fine, I have no problem with that...just keep in mind that there's is nothing mysterious about OTLs other than you always have an innate imbalance between the anode and cathode followers...

Valves just don't come in complementary pairs, you see?
Other than that, a lot of semiconductor amps rely on the same basic circuitry.

Quote:
Ok, now that's funny. Just so we're all clear on this, you don't think the zeners have anything to do with what makes this OTL special
They don't have anything to do with the patent, they are likely to degrade the sound ...hence my remark that the GA circuit has much more potential.
And I can only confirm that the latter sounds good, has TPs built in and is a good basis for you to understand how an OTL works.
Not to mention the fact that zeners are noisy and to add insult injury the whole shebang is in the feedback loop...

Quote:
Rolloff? I've put my best effort out there for all to review/critique, how do you suppose the choice of these resistors affects the rolloff? If you are willing to explain it I'm willing to learn.
It's not only that handful of resistors, it's the entire design that contributes to it...
50kHz is not bad but you can easily have an OTL running linearly into the almost 1/2 Mhz range...helps phase linearity alot.

Quote:
I'm so often willing to take him at face value, is I've wondered about all kinds of little things that seem to make no sense (cable direction, cable choice, biwiring and on and on) and he comes along and say he thinks it's dung and then goes on to support it with some pretty solid arguments.
Seems you're vulnerable to the easy way out kind of explanations for most of that makes sense to me...and I do involve in comparitive listening...
Those topics are really very old hat to me anyway.

Quote:
Compensation network? Are you saying he did something with the AR version that makes it less stable than the GA version(into inductive loads),
Yes and no, it's an impedance compensation network and no it won't necassrilly compromise the amps stability...it will, however make the amp change response with different loads.
And, if I may say,make your tests seem odd if you're unaware of its' presence.

Quote:
BTW there's something I've been just dying to ask, do you biwire?
As a matter of fact I use tri-wire....what about it?

Quote:
Oh yeah and one thing I did learn while I was trying to get inductance numbers for the WWs. These things kick ***! They are rugged, have the best temperature coefficient, last forever, take more heat, drift over time is virtually non-existant. Pretty good stuff for a piece of gear yes?
Yep, nothing against them here...if it weren't for their...well, you guessed it...

May you rock for ever,
__________________
Frank
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

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

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Tube rolling causes failure... Zap Tubes / Valves 10 3rd August 2008 03:04 AM
TIP35C Failure Peter1960 Solid State 6 19th August 2005 11:43 PM
Tube Failure jwatts Tubes / Valves 11 12th February 2005 06:54 AM
Amp failure .. . DilutedImage Car Audio 11 23rd August 2004 08:40 PM


New To Site? Need Help?

All times are GMT. The time now is 12:11 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2