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John L Stewart John L Stewart is offline
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Smile All Triode PP UL

Here is something to puzzle over in your quitter moments!

Cheers to all, John L Stewart
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Doug Bannard Doug Bannard is offline
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"John L Stewart" wrote in message
...

Here is something to puzzle over in your quitter moments!

Cheers to all, John L Stewart


+-------------------------------------------------------------------+
|Filename: Triode UL.jpg |
|Download: http://www.audiobanter.com/attachment.php?attachmentid=361|
+-------------------------------------------------------------------+



--
John L Stewart




That's neat John! Have you done any breadboarding yet to try it out?


All the best : Doug


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patrick-turner patrick-turner is offline
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Default All Triode PP UL

On Tuesday, 12 November 2013 20:40:29 UTC+11, John L Stewart wrote:
Here is something to puzzle over in your quitter moments! Cheers to all, John L Stewart +-------------------------------------------------------------------+ |Filename: Triode UL.jpg | |Download: http://www.audiobanter.com/attachment.php?attachmentid=361| +-------------------------------------------------------------------+ -- John L Stewart


Doug asked, in so many words, "have ya built it?"

Anyway I doubt it has much in common with any UL circuit where the screens of OP tetrodes or pentodes have a fraction of the anode signal voltage applied so that the OP tubes get a fraction of the NFB that is available in a full triode connection or a real triode without a screen.

The Schematic JS tenders to us has ONLY triodes used. There are "UL taps" on OPT which feed the anodes of the driver triodes with cathodes direct coupled to OP triode grids.
Of course one would have to bias the secondary of IST and do other things to make the circuit shown more than a smoke producung tube buster.

But ANYWAY, the OPT primary "UL taps" provide some NFB shunt FB to the signal applied to the OP tube grids via the Ra of driver tubes, and field effect of anodes on electron flow. But I doubt the amount of NFB is effective enough to make it worthwhile to hurry to the patent office, even if you could travel back to 1946 when patenting some desirable gadget was like printing money in your shed legally.

The thing about *most* output triodes is that they have been designed to be easily drivable with most loads, typically needing between 20Vac and 50Vac and having gain of about 3.5 to 6 while having Ra low enough to always be usefully lower than the anode load, thus ensuring a good damping factor, and all manner of trickery such as UL connections and pentodes, tetrodes and cathode are not needed if it is found the triodes give sufficient power.

A normal triode amp with pair of trioded KT66/6L6/EL34/KT88/KT120/6550/KT90 or real triodes 300B driving RLa-a 10k0 in class A is a kind of gold standard. There are easier ways to effectively apply NFB than using an IST and FB via UL taps, and anodes to OP tubes.

But I could be wrong.

Where are all the working voltages and Vdc, Idc RL values et all? I would ask "where are all the details of circuit operation including distortion measurements and what is bandwidth, stability, and R-out, etc, etc, etc?"

Of couse JS probably would need to spend a day or three wiring it and testing it.
He should have the time with snow now laying around his house and too cold to ride a bike anywhere.

I'm up to my neck in keep busy doings, so I won't be trying JS's schematic.

Patrick Turner.
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John L Stewart John L Stewart is offline
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Talking

Quote:
Originally Posted by patrick-turner View Post
On Tuesday, 12 November 2013 20:40:29 UTC+11, John L Stewart wrote:
Here is something to puzzle over in your quitter moments! Cheers to all, John L Stewart +-------------------------------------------------------------------+ |Filename: Triode UL.jpg | |Download: http://www.audiobanter.com/attachment.php?attachmentid=361| +-------------------------------------------------------------------+ -- John L Stewart


Doug asked, in so many words, "have ya built it?"

Anyway I doubt it has much in common with any UL circuit where the screens of OP tetrodes or pentodes have a fraction of the anode signal voltage applied so that the OP tubes get a fraction of the NFB that is available in a full triode connection or a real triode without a screen.

The Schematic JS tenders to us has ONLY triodes used. There are "UL taps" on OPT which feed the anodes of the driver triodes with cathodes direct coupled to OP triode grids.
Of course one would have to bias the secondary of IST and do other things to make the circuit shown more than a smoke producung tube buster.

But ANYWAY, the OPT primary "UL taps" provide some NFB shunt FB to the signal applied to the OP tube grids via the Ra of driver tubes, and field effect of anodes on electron flow. But I doubt the amount of NFB is effective enough to make it worthwhile to hurry to the patent office, even if you could travel back to 1946 when patenting some desirable gadget was like printing money in your shed legally.

The thing about *most* output triodes is that they have been designed to be easily drivable with most loads, typically needing between 20Vac and 50Vac and having gain of about 3.5 to 6 while having Ra low enough to always be usefully lower than the anode load, thus ensuring a good damping factor, and all manner of trickery such as UL connections and pentodes, tetrodes and cathode are not needed if it is found the triodes give sufficient power.

A normal triode amp with pair of trioded KT66/6L6/EL34/KT88/KT120/6550/KT90 or real triodes 300B driving RLa-a 10k0 in class A is a kind of gold standard. There are easier ways to effectively apply NFB than using an IST and FB via UL taps, and anodes to OP tubes.

But I could be wrong.

Where are all the working voltages and Vdc, Idc RL values et all? I would ask "where are all the details of circuit operation including distortion measurements and what is bandwidth, stability, and R-out, etc, etc, etc?"

Of couse JS probably would need to spend a day or three wiring it and testing it.
He should have the time with snow now laying around his house and too cold to ride a bike anywhere.

I'm up to my neck in keep busy doings, so I won't be trying JS's schematic.

Patrick Turner.
Hey Patrick, you can do better than that! You actually touched on the reason that circuit does what it does in your response. And I’m surprised that Phil has not chimed in with his ideas.

Here is a hint to give you a lead to the operation of the circuit. You can find enough information in the RCA Tube Manual RC-14 to get you going. Don’t think you will find much to help in RDH4.

The IST has nothing to do with the circuit other then as a phase invertor. It will run well from any common power amp front end. Even your favourite. So go back & take another look!

Not much biking these days, altho I got out for a little more than 50 km yesterday. Busy with the log splitter & otherwise getting the place ready for winter. I will soon trade the bike for skis. The weather to turn cold & snow this week.

Not much electronix this summer either. Lots of yard work on 4 ½ acres. Had to chop up five large trees that came down in storms. And the electrical boxes I put way out in the yard after 35 years the wood was shot. I put 110/220 volts underground the full length of the property when we built here. Very handy, but lots to repair as everything seems to wear out. Me too!!

In the meantime, here is something else to get your mind around.

Cheers to all, John
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patrick-turner patrick-turner is offline
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Default All Triode PP UL

Hey Patrick, you can do better than that!

Ah, well, probably I could, but I am a retired self taught amp-worker person who may have already published enough so that if anyone needed to known what I think, ( or that I think at all, or used to think, ) it could be gleamed by the fact I've not experimented with a whole range of amp topologies and stuck firmly to those that gave me good enough measurements better than most text books indicate is a good enough standard. I sold amps to ppl, and every amp I sold was different to the last, but had within it the same mental approach, and this for eg, did not include ISTs, because of their BW limitations, and THD injections to the signal path. I did allow myself to use of choke feed to driver stages, but always with a series resistance between end of choke and anode to isolate the ugly behavoir wound items can cause in audio amps.

You actually touched on the
reason that circuit does what it does in your response. And I’m
surprised that Phil has not chimed in with his ideas.

Well, perhaps he saw no mutual benefit in responding. The purpose of discussion groups sensibly conducted is that posters exercize their mind as well as readers. My experience here since 2001 has surely exercised my mind at least.

Here is a hint to give you a lead to the operation of the circuit. You
can find enough information in the RCA Tube Manual RC-14 to get you
going. Don’t think you will find much to help in RDH4.

RDH4 and all other books I have don't have your circuit you posted.

The IST has nothing to do with the circuit other then as a phase
invertor. It will run well from any common power amp front end. Even
your favourite. So go back & take another look!

OK, I will, but seems like triodes were like FB resistors, but I have to return to make sure. I've got 101 projects to complete - very happy now without audiophile customers to drive me broke and snd me insane.

Not much biking these days, altho I got out for a little more than 50 km
yesterday. Busy with the log splitter & otherwise getting the place
ready for winter. I will soon trade the bike for skis. The weather to
turn cold & snow this week.

Opposite here, warming up, early mornings good on bike, but have a bout of back trouble rite now. Maybe a week or two off bike, its always good to quit for a week or three each year when I have averaged 12,000km. I just have a house to care about, hedges, lawns, wysteria, and plumbing, draining, electrical et all -been 35 years since I needed to hire a tradesman, because I am one.

Not much electronix this summer either. Lots of yard work on 4 ½ acres.
Had to chop up five large trees that came down in storms. And the
electrical boxes I put way out in the yard after 35 years the wood was
shot. I put 110/220 volts underground the full length of the property
when we built here. Very handy, but lots to repair as everything seems
to wear out. Me too!!

I'm having a good run with my work with very few repairs needed, and am reaching the stage when house begins to fall down around me and I don't hafta give a **** about it, I ain't tryna keep up with the Jones's and I like frugality, fine music played live, bicycles, socially cheerful companions, and farnarcling around with primitive electronics, and the rest of the world is forgiven for their stern faced determination to make a lotta mistakes.

In the meantime, here is something else to get your mind around.

Yeah, The pear seems at ease with its connections. So few of them, wheras a bunch of grapes is needed to represent the carp in box of modern electro-junkery.
Patrick Turner.

John


+-------------------------------------------------------------------+
|Filename: Feedback Pear A.jpg |
|Download: http://www.audiobanter.com/attachmen...tachmentid=362


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patrick-turner patrick-turner is offline
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Default All Triode PP UL

On Tuesday, 12 November 2013 20:40:29 UTC+11, John L Stewart wrote:
Here is something to puzzle over in your quitter moments! Cheers to all, John L Stewart +-------------------------------------------------------------------+ |Filename: Triode UL.jpg | |Download: http://www.audiobanter.com/attachment.php?attachmentid=361| +-------------------------------------------------------------------+ -- John L Stewart


I've had another look at the schematic file in http://www.audiobanter.com/attachment.php?

The cathodes of "driver triodes" are direct coupled to OP triodes. So therefore we are left to assume the OP triodes are drawing grid current, because if they are not, the driver triodes would have no Ia and no Ik so would not drive anything.
The use of IST is "incidental" and not necessary, and any balanced input signal will drive the circuit. Unfortunately, I see extremely little detail in your schematic, no tube types, no Vdc, no Vac basically no bloomin nuthin..

But lets assume driver triodes could be a pair of 6SN7 parallel wired, we put 15k cathode resistors on to a negative rail, maybe -150Vdc, and maybe they'd be Ik at about 10mA each. Assuming OP triodes have negative bias with no grid current, then Ra looking into anodes of 6SN7 would be Ra + [ (U + 1) x Ra ] = 320k, so that any if OPT tranny UL tap voltage = 100V, then 0.315mA of feb back current flows in 320k, so in fact the cathode drive voltage would have 15k x 0.315mA = 4.7Vac, and if THD = Vd at OPT tap, then 0.047Vd appear at OP grids, and this is amplified say by 3.5, in OP tubes are 300B and error signal at 300B anodes = -0.146Vd, which does very little to reduce the +2 x Vd at anodes. To be useful FB, you need the error signal = maybe -10Vd, so that the THD reduction factor = 0.2.

Pardon me for the boring reasoning, but how come you didn't include a reference to what someone else has thought about the detailed workings? If there is a mistake in my figurings, perhaps you'd like to point them out to me.

Right now now I have completetion work on an oscillator I begun 2 months ago.

I wanted to include a Schmitt Trigger square wave circuit to make a reliable good looking square wave even at 2MHz, the top F for my new wien bridge oscillator. I have tried many types of two transistor schmitt triggers, and seems its very difficult to get an acceptable square wave above 500kHz, for +/- 10pk volts. I made a nice voltage amp with bjts, gain 4, symetrical pnp and npn circuit, only 6 bjts, and easily got 0.3Hz to 12MHz at 7Vrms.
I tried C-mos 4093 and although it has stability and works up to 1MHz, the rise time is slow, ie, the harmonic content of the square wave is no more than 3MHz, and I want 10Mhz.
So I am trying more things, including small package switcing mosfets to get better HF performance that the 4093 data sheets don't mention, - because it is so poor. I figure its easy to amplify a square wave with +/- 2.5Vpk to get the final voltage I want, and to get the F content to survive going through attenuator network and output buffer to get 50 ohms Rout for this gene.

I have to say the variation of F with tuning caps is smooth and jitter free, and so much better than using any pot.

So, I am occupied, while being useless to ppl wanting dirt cheap masterpiece amps. NOW, they all must learn a lot and build their own, because none of them want to pay anyone proper wages for hundreds of hours of work.

Two things in life give it meaning - Usefullness, and Happiness. and the first is not very possible, leaving me only the second issue to get right, and its enough to occupy me.
Maybe none of us ever figure out why Existance exists, or what is Infinity, or Eternity, although we think we know these exist.

Somehow the Speed of light seems very slow. Because how does one end of the Universe ( that we know of, could be many more ) know what's happening at the other end of Universe RIGHT NOW? It implies stuff moves at speed = SOL raised to power of infinity, or some incomprehensible speed. God does not play dice, but whatever God is, then It hides itself easily maybe because our gear is far to slow to detect the really quick stuff going on.
But if I get a really good square wave at 1MHz ( with H up to 10MHz from 2 transistors then I'll let you all know via my cluttered web-site.
Patrick Turner.
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