Heater Wiring

[5string]

Hello,
In the Library I was just reading ‘Servicing Fender Amps’ and read this regarding Heater System Basics, wiring:

*Pin two on the last (6V6) power tube goes to pins four and five on the (12AX7) pre amp tube that is closest to the power tubes. Pin seven on the last power tube goes to pin nine on the pre amp tube. The 6.3 vac winding continues down the line in a twisted pair fashion to the rest of the pre-amp tubes.*

I’ve added the parenthetical tube numbers above for clarification.

I understand the phase issue and the need for consistency in the wiring but, I’m wondering about the pin relationship between the 6V6S and the 12AX7s. Does this pin relationship always hold true or, can pin 2 of the last power tube go to pin 9 on preamp tubes and pin 7 of the last power tube go to pins 4-5, as long as all the wiring continues down the line in the same fashion?

Asked another way - is the relationship between the 6V6 and 12AX7 always pin 2 to pin 4-5 and pin 7 to pin 9? Can it be pins 7 to 9 and pins 2 to 4-5? 

I hope my questions make sense.

Thanks,
Joel

[sluckey]

There is no phase relationship.

[pdf64]

I’m happy to be proved wrong, but there’s a vast amount of such technobabble tosh, a fair amount of it even predating the internet.
I’m sure that the author meant well in representing the consensus of this tosh, but in doing so proved his technical incompetence.

Please be advised that for tubes operating in push pull there’s a slight benefit of heater hum cancellation if their heaters are all wired with the same phase going to the same pin.
But the benefit is limited by how much heater hum can break through into the signal path at the power tube stage (answer is ‘very little’).
For the rest it doesn’t matter at all, hence the use of the same green wire for both phases.
It may be appreciated that first and foremost, Fender had a common sense, practical approach to design and manufacturing matters; if they thought such ‘heater phasing’ was an issue, surely differing wire colours would have been selected for each phase?
It may be noted that British manufacturers did tend to use differing wire colours for each heater phase but I don’t read anything into that.

[pdf64]

Hello,
In the Library I was just reading ‘Servicing Fender Amps’ and read this regarding Heater System Basics...

An internet search doesn't seem to bring up a book with that title?
Who is the author?

[5string]

I'm the author of this post and pdf64 is correct; I am technically incompetent.  I'm an old retired aircraft mechanic, who's built three amplifier kits (that work) and I can't make sense of the conflicting information I read.  It's dreadfully confusing and there's so much I don't know. 

For example, I didn't know my post was representing technobabble and tosh.  What I do know is that gratuitous, patronizing comments about a poster's competence are not helpful and won't encourage people like me to ask questions on this forum. 

If my original questions don't make sense, please explain why to me. If the questions are in inartfully constructed, let me know and I'll try again.  I the questions are built on a false premise, tell me where I'm getting it wrong. 

As I noted in my original post, the Library on this forum: https://el34world.com/charts/fenderservice4.htm, as well as the instructions in the kits I've built, go to great lengths to establish and maintain the pin-to-pin relationship between the tubes.

I'm trying to understand why, and if it matters and hope someone can give me a kind and informative answer.

[dbishopbliss]

An internet search doesn't seem to bring up a book with that title?
Who is the author?

I think you were thinking "Library" as in a place where books are kept. The original poster seemed to be referring to Doug's library: https://el34world.com/charts/fenderservice4.htm

[sluckey]

The only reason Fender may have specified connect pin 2 of the 6V6 to pin 4/5 of the 12AT7 was so Rosalita could string the filaments with consistency. Rosalita was a minimum wage employee who was good at soldering and could follow simple instructions with a minimum of mistakes. She neither cared nor needed to know why a wire went where, she just needed to know that it did. Very efficient on an assembly line. She cranked out 100? amps per day and they all were wired the same. Well, maybe 95% of 'em. 

[Joel in Texas]

Hi 5string.  pdf64 should definitely speak for himself if I have any of this wrong.

But when he said "I’m sure that the author meant well in representing the consensus of this tosh, but in doing so proved his technical incompetence."

...I do not think he was referring to you when he said "the author". 

I think he was talking about the author of "Servicing Fender Amps", the text you quoted.  And you are not the author of that text, right?

I just thought I should share this perception, since it might help with further communication on this thread.

[shooter]

gratuitous, patronizing comments

you'll find with time, EVERYBODY here, wants to help, be helpful and encourage, but you can't look at an inch and discern well what a mile looks like.
hang in there, you'll see I'm correct about 12% 

[PRR]

...I didn't know my post was representing technobabble and tosh.  What I do know is that gratuitous, patronizing comments about a poster's competence are not helpful and won't encourage people like me to ask questions on this forum. ...

It seems to me that pdf64 was disagreeing with the words you quoted, not YOU.

Note he says "predating the internet", so clearly not all aimed at today's discussion.

Which means he disagrees with Doug Hoffman, a VERY successful amplifier builder, and owner of this forum.

FWIW, I also disagree with Hoffman. Heater phase has no effect that I can picture.

Yes it works for Hoffman. And it makes superficial sense. It is not clear he tried the other way. I do know that Hoffman does very meticulous layouts. And consistency is a virtue.

[5string]

Thanks to all who pointed out a different perspective of pdf64’s comment. I didn’t read it that way but, can see I was wrong.  For that I apologize to all.

And more especially, my apologies to pdf64. I’ve learned way more than I expected from this post.

[Willabe]

I'm an old retired aircraft mechanic, who's built three amplifier kits (that work) and I can't make sense of the conflicting information I read.  It's dreadfully confusing and there's so much I don't know.

Yes, a royal pain in the butt!          

Too many 'experts' on the internet.   

It takes time to sort through all of what you need to know. I'm still reading.

This forum is about as safe a place to hang out as you can find.

There's been a couple of times when I 1st read a response I thought was not very nice. But after thinking about it a little while, I could see that maybe I just misunderstood what they meant?

Many of us are not the best 'writers' and often in a hurry or have other things on our mind, so we don't always take the time to say/write things are clearly as we should?

And if anyone jumps on someone here, guys will not sit back and let it go on.         

[Willabe]

Oh yeah, forgot to say.............    Welcome!        

(Watch out for Jim and Silvergun.  )

 

[pdf64]

An internet search doesn't seem to bring up a book with that title?
Who is the author?

I think you were thinking "Library" as in a place where books are kept. The original poster seemed to be referring to Doug's library: https://el34world.com/charts/fenderservice4.htm

Oops, apologies to Doug and 5string for my poor wording, no offence was intended.
The 'incompetence' was indeed directed at the author of heater wiring guidance (which turns out to be Doug, to whom we all are in debt), rather than towards 5string.
It was meant in the technical sense, that the author was writing beyond their competence (ie qualification), rather than in the colloquial sense (eg as a synonym for bumbling fool).
Whatever, a poor choice of word with a much more abrasive effect than I intended, and I take it back.

[nandrewjackson]

   I also thought the "incompetence" was a jab at the question poster, but I've only had 2 cups of coffee yet today.


It does make much more sense that it was referring to the information from which the OP was quoting.


This is electricity. 1 in every 2 linemen died from electrocution in the early days,  and homes had flip-up outlet covers so the electricity wouldn't spill out into the room.


I would absolutely "love" to be a tube (valve) expert, but I drown in the math or find questionable references every time I dive in.


I've always kept my heater wires "in phase" and I imagine I always will. Whether or not there's any science behind it. 


 

[Willabe]

Our host Doug has great info on this forum, just scroll down to the bottom of any page in this forum.

This is Sluckey's web site, great info there. If you click on the globe on any of Sluckey's post's it will take you there. 

http://sluckeyamps.com/index.htm

Here's a few solid tube amp info web sites, if you haven't found them yet.

Merlins web site, he is a member here and pops in every now and then;

http://www.valvewizard.co.uk/

Rob Robinette's web site, he is also a member that pops in from time to time;

https://robrobinette.com/Amp_Stuff.htm

And here's Aiken's web site;

http://www.aikenamps.com/index.php

[Willabe]

.......... and I can't make sense of the conflicting information I read.  It's dreadfully confusing and there's so much I don't know.

Yes, 1 guy/group insist you do it this way and another guy/group says NO!, you have to do it this way.   

Now of course we're always correct here. 

Just get the basics down and don't worry about any magic bullets. You can branch out and try other things latter if you want. (I know your just trying to sort out conflicting info, you will.)

Some of the mods and 'tricks' don't really do a whole lot and are not absolutely necessary as some proclaim. Some of them you might not hear any difference at all. Also depends on how good your ears are.

If you build an amp and it works, it's not noisy, and you like the sound of it, what else do you need?     

I do wire my heaters in phase with 2 different wire colors. I don't think it's necessary, but as long as I'm in there, why not? But then again, I like to elevate my heaters with a standing dcv of 70 to 80 dcv and I like to use a humdinger pot on the heater string. Again, not necessary but it can be helpful at times if you get a tube that has a mis aliened heater/cathode sleeve, ie, a noisy tube. Now you can use that tube.     

If your building from a kit and not from scratch then just learn how to solder well, learn good/practical lead dress, learn good grounding and learn how to read a schematic and not just a layout diagram.

[PRR]

I must point out ONE case where 'heater' connection matters. Beach radios had battery heated naked filaments. THESE have + and - marks on the filament pin-out. Because the heater is also the cathode, and has 1.5V of DC drop along it, you must connect heater battery correctly to get the designed grid-cathode bias.

There is another larger class of naked filament tubes intended for AC heat. 2A3, 300B. These are typically power tubes with *large* grid swing. Hum is a problem. You center-tap the AC so the average cathode potential is near zero. Also these are usually low-voltage filaments and high signal voltage; like 2.5VAC (1.25V each side) heat and 30V grid drive.

All of these filament tubes fell out of favor with the introduction of indirectly heated heater-cathode tubes. Another name is Uni-Potential Cathode. The filament is bunched-up and slid inside a Nickel cathode sleeve. What happens in the filament stays inside the cathode, has "no" effect on the operation of the valve. This allowed AC heat of sensitive tubes; also avoids a maze of C- bias batteries (because we can cathode-bias without interacting with heater power).

Hemmingway said a writer needs a good BS detector. Internet writers mostly do not know Hemingway's teachings, and do spew BS. Be careful where you step.

Some sources are low-BS. The now-dead men of RCA and GE and Philips knew their stuff (their jobs depended on it). The tube books do not indicate a 'phase' for the heaters of the tubes we use.

Some sources, listen but verify. Electronics mags from 1930s-1960s published a lot of material, sometimes hum tips. Yes, sometimes the authors were résumé-polishing, and sometimes editors were not practical engineers, so don't trust too deep. And I don't have a bibliography of hum articles. But in my massive reading I do not recall any "heater phase" suggestion (in context of the tubes used in g-amps). Valley Wallman 1948 has nothing on the topic.

An interesting side-note: most 1950s+ 12AX7 use helical heaters, most 6L6 etc use folded heaters. Both are tightly packed into the cathode sleeve. I can't see how either type has a "side", or how to correlate folds against twists to say "this is the same 'phase'". 

Another path is to try to logic it out. "Cancellation" implies two equal but opposite signals. It seems unlikely that hum in a low-level stage and hum in a high level stage can cancel without added fuss. Especially since the gain between is usually variable (volume and tone knobs). We do observe hum-null in some amps: there is hum in second stage with Volume full down, as we turn up to maybe "3" the hum reduces (1st stage hum balances 2nd stage hum), then at higher Vol setting the 1st stage hum dominates. Sweet, except this Vol setting is rarely the gain we want to work at. (The opposite case, hum worst at half-way, is electrostatic leakage into the wire from the pot wiper, not heater hum 'phase'.)