Exactly Tony.
For numerous decades, manufacturers produced consumer products with tubes that lasted for ages.
I've restored 1929 floor radios with 'still good' original tubes.
Certainly those old sets were mass-produced and had wide tolerences in manufacturing.
How the hell did they hold up so well?...... they were 'designed' well.
Yet today, we've got hoardes of onliners, worrying about trivialities that never before needed worrying about.
And they insist on handing out justifications because of obsession-worry based on someone with an obsession, etc.
In other words, they want to argue that the way to enjoy a beverage is through a tiny hypodermic needle, instead of a straw.
"JoJoBigfoot online says I need to eliminate that .00000004% variation of a Nanovolt because it might hurt my dog's ears."
and i remember many of the carbon comps resistors back then had 20% tolerance and no one complained....
and recently, one was chasing down ppm distortion in his amp and in the end, it was the dummy load stopping the march to ppm distortions...very funny.....
Because I'm at the low end of the spec. 11.4V is the lowest voltage allowed for a 12.6V tube. Using a bridge instead of FWCT, I'd have 10.8V.
As far as voltage swings, I have no idea what WOT is on about.
I've had hundreds of old customer radios (among other consumer products) on my shop bench through the decades.
Every brand you could think of, American, Japanese, German/European...etc, even the newer Chinese stuff.
It's imperative to be widely versed / diversified as to handling/servicing these, and particularly important with the rare and valuable models, some are treasured family heirlooms.
You mention 20% tolerance resistors, I'll add the capacitors too, which all of those old sets managed to function quite well - up to a point.
A 220K plate load resistor may have aged enough to increase into close to a 1 meg over the decades before performance would noticeably suffer.
Of course, these got changed out, as was anything that I determined as a poor design choice.
Because some factories at times used what they hand in stock that "just made the set work".
Thus the dislaimer often added to Service Manuals and Owner Manuals - "Design/Specifications subject to change without notice".
That's the dividing wall between hobbyists and the professional crowd.
Tubes have been fondly known in the industy as being "forgiving" components, ages before the internet was ever born.
They were designed with specific operating specifications and conditions, some critical, others quite flexible.
In fact, a lowly 12AV6 1st audio tube used in millions of table radios, etc, is known to perform better with reduced filament voltage in some situations.
In other products like stereo amplifiers, 12AX7's filaments used as front-end and phono service were wired in series and were fed their DC filament voltages from the output tubes cathode bias voltage, which fluctuated dependant on operating conditions.
And these same products eventually became famous for their performance.
As Tony T mentioned - "and no one complained".
Somehow, for various reasons, discussions on the internet have become stomping grounds of critical thinking and debates, with such extreme sensitivity towards narrow deviations of a given property.
I can understand the desire for wanting to be precise about some things, as I've been called "highly detail oriented" by my customers, and I can appreciate accuracy and neatness in design and appearence, but I'm not so drawn into the strict/obsessive behavior that has seemed to evolve in some discussions.
I look at that phenomenon as being overblown hyper-overthinking and worrying over trivialities.
Yes. I even have a Belcor receiver that uses the phono tube heaters as cathode bias for the output stages.
For me, it's a trade off. I either run 11.4V or I would use a 24VCT instead of 18VCT and waste the extra power in resistors.
The simple thing I'm trying to get across here is that with the same transformer I can go bridge or FWCT, and the latter works better for me.
To the OP's original question? No. It doesn't make a lick of difference to the end user as long as the output is as expected.
For me, it's a trade off. I either run 11.4V or I would use a 24VCT instead of 18VCT and waste the extra power in resistors.
The simple thing I'm trying to get across here is that with the same transformer I can go bridge or FWCT, and the latter works better for me.
To the OP's original question? No. It doesn't make a lick of difference to the end user as long as the output is as expected.
Tubes 'waste' heat due to their natural design.
They are inefficient devices compared to transistors.
So a couple of wasted watts for a filament dropping resistor isn't a design-killer in my opinion.
In fact, if the filaments are run on DC, that resistor allows a final filter cap to be used to further smooth the DC.
Millions of consumer "All American Five" table radios with their 5 tubes used a dropping resistor both as a fuse, and a cushion while the set was heating up.
The often stated "for use on 110 to 125 volts" meant a wide range of compatability to whatever location it was used at.
Those old AA5 radios didn't care if it was AC or DC either 🙂
The power wasted in those radios was nothing compared to wasting something like 30 watts to drop 3 volts @ 10A... Just saying. This is why I switch my phono stage tubes (all 8 of them!) in when it's being used instead of lighting them up all the time.
This is also why most of my designs use a 12V SMPS instead. You get the full 12V with a way smaller footprint, and way less waste heat. Oh and the TCO (total cost of ownership) is about 10% of the linear supply I build. For the cost of just the filter caps for my linear supply (Six of these: https://www.mouser.ca/ProductDetail/United-Chemi-Con/ELBV250ELL153AM40S?qs=GBLSl2AkiruwIR9GO8hNZQ== "For Airbag Module" ), I can buy 2 SMPS complete.
The power wasted in those radios was nothing compared to wasting something like 30 watts to drop 3 volts @ 10A... Just saying. This is why I switch my phono stage tubes (all 8 of them!) in when it's being used instead of lighting them up all the time.
This is also why most of my designs use a 12V SMPS instead. You get the full 12V with a way smaller footprint, and way less waste heat. Oh and the TCO (total cost of ownership) is about 10% of the linear supply I build. For the cost of just the filter caps for my linear supply (Six of these: https://www.mouser.ca/ProductDetail/United-Chemi-Con/ELBV250ELL153AM40S?qs=GBLSl2AkiruwIR9GO8hNZQ== "For Airbag Module" ), I can buy 2 SMPS complete.
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Eight tubes for a (stereo) phono stage?
Overkill to me.
When fine-performing RIAA preamps used only 1 or 2 and satisfied audiophiles for decades.
Again, it's like insisting that I sip my beverage through a tiny sterilized hypodermic needle with multiple filtering attached, instead of directly though a much more convenient straw.
Overkill to me.
When fine-performing RIAA preamps used only 1 or 2 and satisfied audiophiles for decades.
Again, it's like insisting that I sip my beverage through a tiny sterilized hypodermic needle with multiple filtering attached, instead of directly though a much more convenient straw.
LOL I wouldn't say any phono tube stage with only one ot two tubes is a fine anything except a fine example of crap. Eli's modified one excepted but if it wasn't crap to begin with he wouldn't have needed to ad a MOSFET source follower.
I did a quick search through this thread and didn't find a single match for the string "reverse", so I don't think this has been mentioned yet. If it has, I apologize.
A four-diode bridge has the advantage that no diode sees a greater reverse voltage than V_DC_OUTPUT. Not even during a mains surge. So if your transformer secondary is 30VAC loaded, 39VAC loaded, the DC output voltage is always less than 39*1.414 = 55.2 volts. None of the diodes in the bridge will ever see a reverse voltage more than 55.2 volts. It would be perfectly safe to use diodes rated for 80V in this application. There's no need to act macho and buy 600 volt diodes for this bridge. Which is helpful if you tend to prefer Schottky diodes like I do. Schottkys are plentiful below 150 volts and comparatively rare above 150V.
A four-diode bridge has the advantage that no diode sees a greater reverse voltage than V_DC_OUTPUT. Not even during a mains surge. So if your transformer secondary is 30VAC loaded, 39VAC loaded, the DC output voltage is always less than 39*1.414 = 55.2 volts. None of the diodes in the bridge will ever see a reverse voltage more than 55.2 volts. It would be perfectly safe to use diodes rated for 80V in this application. There's no need to act macho and buy 600 volt diodes for this bridge. Which is helpful if you tend to prefer Schottky diodes like I do. Schottkys are plentiful below 150 volts and comparatively rare above 150V.
And yet.... through the decades, plenty of picky audiophiles were delightfully satisfied with their Harman Kardons, their Fishers, their Stromberg Carlsons, Marantz's....etc.
Reviews back then, and my own personal conversations with customers all justify that.
But here I have to read your unhappy 'high horse' comments to the contrary of Public Opinions.
Sorry that you're so extremely disgusted with the (crap) technology that sufficed people in the past, and still do today.
I have to conclude that you're another one of those obsessed-with-perfection types that never seem to find the never-ending search of the Holy Grail of audio.
Because their isn't one.
I've tossed several customers out of my shop that insisted that I go to extreme measures to provide them with 'their' idea of how I should service their equipment, specific internet-gotten modifications, and what I should charge for the service.
Thankfully, it was only a couple of bozos that pulled that crap on me, while 99.99% of other customers kept me in business for decades.
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Oh dear WOT is ramming his personal opinions down everyone's throats again. This thread is done for.
Oh please!
It's not about my personal opinions, it's what MY CUSTOMERS think and where THEIR preferences are at.
I'm on a roll today..... adding more to "The List".
Want to be added?.....
Kodabmx could get as much as an extra volt in his filament supply by using 40V Schottky rectifiers - that's not nitpicking obout tenths of a volt, if you ask me.
Wow. High Horse? Seriously?
Get a grip, please. Don't be insulted by the FACT that two 12AX7 don't make a particularly good phono stage. Instead embrace the evolution of electronics. Do you really think the RCA textbook 12AX7 based phono is the end all and be all?! You're insane if so.
"I want my old POS to work again for no reason but nostalgia. Can you fix it?"Oh please!
It's not about my personal opinions, it's what MY CUSTOMERS think and where THEIR preferences are at.
I'm on a roll today..... adding more to "The List".
Want to be added?.....
The price of something brand new and "better" specification wise? Why fix it other than nostalgia*? Honest question - not trolling.
*Ok, keep it out of landfill.
MJ sez that Schottky are kinda rare above 150V - they're also not that great, as when you get up to 200V PIV, there's not that much advantage in voltage drop using a 200V Schottky as opposed to an equivalent ultrafast diode. At voltages of 100V or below, it's a different story, especially when you dip below 60V. I work in the commercial realm, and 80% derating for PIV is considered sufficient.
i suggest that you look at how the Dynaco engineers did the filaments in the PAS3 preamp....that should tell how how it was done...
you do not look at filament voltages without looking at the primary line voltages as well, and if i were you i will take this primary voltages into high consideration too....
what is the filament voltage at when the line is at its lowest? that is where i will focus my efforts at...