Voltage amplification questions .01V to 5000V

[LazyDoorMan]

I’m building a custom Voltage amplifier that will be amplifying  “pure” sine waves from a signal generator. Input signal will range from .01V to 1V and will be a set frequency ranging 500-5000hz.

I’m new to tube amplification. I was originally going to wing it and just use a 5f1 but thought I’d maybe put some more thought and not just outright waste money blindly. So I bought a book “Amplifying With Vacuum Tubes” by Carl Gauss. I’ve read and reread it about 4 times, and I’ve learned quite a lot, but I’m still short on knowledge in a few places.

Currently I don’t have any parts other than a signal generator and an o scope on the way.

The signal generated by the signal generator .01V-1V (it’s a cheap FeelElec FY8300) needs to have a final amplification factor that will bring the signal to 5000v or more. This signal out is a broadcast antenna Containing multiple coils in series. I’d like the final sine wave signal to have as least distortion as possible.

Here is my custom design I’ve designed. It includes cathode biasing, 1M pots all over to help refine the signal. I’ve included a similar B+ filter as the 5f1 however I’m not sure of the C7,C6,R15,R14 values. I think I’d prefer to use a choke filter instead bc I’m under the impression it will aid in less distortion, but I don’t know how to determine values of L1, C55B.

I believe with the 12AX7 and 6SN7 I should be able to achieve a 250V signal and then amplify it through a microwave transformer at a conservative 1:20 ratio to achieve 5000V. I’ll be using the 5Y3 rectifying tube. The OT is me thinking outside of the box to achieve my goal..... is the coupling at C5 as well as the 1M Pot load at R13 going to be sufficient to ignore the usual impedance requirements that are necessary to work around with most OT and still allow strong low distortion voltage gain though the OT.

Lastly, I’m not afraid to start the design over from scratch I’m just a newbie and this is my newbie design in dire need of external input from those who know much more than I do.

As a side note.... I’ll be building 3 of these units, so cost is a factor within reason, but I understand the need to spend what’s necessary.

Thanks

[LazyDoorMan]

The design:

[PRR]

Welcome.

> frequency ranging 500-5000hz.

Steady tones or complex signal?

> ...signal to 5000v or more. This signal out is a broadcast antenna Containing multiple coils in series.

You are going to try to radiate audio fields? How much power (how far)??

[LazyDoorMan]

They will be steady tones

To clarify more, i will be running the signal into an induction motor. The coils of the motor will act as antenna... so I guess it’s not necessary for the signals to travel more than a yard from the coil.... but the full length of wire (antenna wrapped inside motor) will be atleast 10 meters. I’ve found parameters of a similar induction motor by driving it and pulling out what the motor is generating. I’m under the impression from those results that anywhere from 50-500mA at 5000v will be ample power. However I will not know for sure until a test is done.

Grand plan: experiment that uses 3 phase RF signal at high voltage to drive a motor.

[PRR]

> 50-500mA at 5000v

This works out to 250 Watts @ 100,000Ω to 2,500 Watts @ 10,000Ω.

This is far past a "newbie"s first design, or almost any guitar amplifier.

Most motors run at line frequency. Jack that to 10 times normal line frequency, it will spin 10 times as fast. For even small 3-phase motors that tends to be 18,000RPM.

I am reminded of trashcan-size tubes used for induction heating of plywood glue, crankshaft journals, and precision metal melting. {Off-topic} OMG: they are still there in Rancocas.... Inductotherm. I was there in ~~1969, before I-295 opened. Henry Rowan did good.{/Off-topic}

Unless I've misunderstood your goal, I think you are in the wrong place.

[acheld]

I know nothing about induction motors, but I have to ask:

Why would you build a valve amplifier for a 21st century application?    Valves in our world distort -- very nicely often enough -- but nonetheless distort your signal which I would think is exactly what you don't want.

I'm guessing that we don't know enough about your design requirements.  It does sound like an interesting and ambitious project!

There are some veteran radar experts on the forum who will likely offer germane advice.

[LazyDoorMan]

I did a bad job explaining I think. I’m most curious if I could produce a 5000v “smooth/clean” -for lack of a better word- sine wave with little to none distortion from the design I made. Is the transition from the 6sn7 tube to OT going to turn into a fireworks show and blow my tubes? Is the step up microwave transformer going to distort the signal beyond what I desire? Would I benefit from a choke filter vs cap resistor cap B+ supply? ......Or should I take another approach and have it signal>preamp>Driver>power tube and try and amplify with tubes all the way to 5000v and change my b+ accordingly to around a 7000v And couple the signal using a 1:1 transformer that leads straight to the coils of my experiment?

The experiment is not dependent upon power. I know that sounds bizarre, but I’m solely looking for precise voltage amplification.

I would be okay with most any amount of power that is produced as a byproduct of voltage amplification  however the least amount possible is preferred. I believe 5w or any value less at the target 5000v would be fine but again, I’m not trying to produce power I’m trying to produce precision voltage.

[LazyDoorMan]

I know nothing about induction motors, but I have to ask:

Why would you build a valve amplifier for a 21st century application?    Valves in our world distort -- very nicely often enough -- but nonetheless distort your signal which I would think is exactly what you don't want.

I'm guessing that we don't know enough about your design requirements.  It does sound like an interesting and ambitious project!

There are some veteran radar experts on the forum who will likely offer germane advice.

Texas Instruments has a controller that runs an induction motor using RF signal. However, their programming will max out at 600v and 1500hz ish. Reverse driving the motor and pulling out it’s parameters displays a direct need for frequency at voltage all the while using mere mA. Sooo.... i thought I’d do an old fashioned thing and do a dangerous experiment in the name of discovery and see what happens. This “sonic “ motor is utilized all over every day but it’s limited by the voltage and frequency of its controller. So I’m building my own extremely high voltage controller piece by piece with age old technology.

[Willabe]

Sooo.... i thought I’d do an old fashioned thing and do a dangerous experiment in the name of discovery and see what happens. This “sonic “ motor is utilized all over every day but it’s limited by the voltage and frequency of its controller. So I’m building my own extremely high voltage controller piece by piece with age old technology.

Why? For what? Just to experiment? 

5000 to 7000vac is not a dangerous experiment, it's an EXTREMELY DANGEROUS experiment! 

Not worth it. I think your in over your head with this, you need to rethink this. 

[PRR]

> Texas Instruments has a controller that runs an induction motor using RF signal.

Pointer? Part number? App-note?

Is this a VFC?

[shooter]

these two tube drive/PA would do 500W CW at 64Mhz into an inductive load.  we pulsed them for 25Kw
not a home brew I would attempt.

[1blueheron]

It sounds as if you are attempting to replicate some of the experiments performed by Tesla in 1901-1907.  All fine but don't forget he took out "the grid" on occasion and was deemed anything from "eclectic" to mentally insane. 

The results of your experimentation could be rather shocking.

The more modern Tesla model S uses an updated version of Teslas polyphase induction motor. Perhaps it might serve as a study aid?

How did you intend to make the motor spin, as a amplified sine wave radiated wirelessly would energize all fields of the "antennae" in the motor simultaneously.  Therefore, In a wireless application there would be no push/pull effect.  You would need many of these amplifiers with some type of focused beam and a complex switching mechanism to make it spin rather than melt.

Some of our "Hi-Fi" tube brethren are very much into low distortion amplification.  Guitar amplification today is all about useful distortion, or as we like to call it, "tone".

Have you investigated the use of a magnetron for your application?  Readily available from a dumpster near you in a discarded microwave oven.

What is the significance of your chosen frequency range, and a fixed frequency in particular.  Usually a variable frequency drive is implemented for motor control.

Kudos to you for thinking "outside the box" but recognize that the further from the box you go, the smaller the box becomes in sight.  At some point, the box is lost from sight and you find yourself all alone, homeless and without as much as a box   .

[HotBluePlates]

Sounds great!  Go for it!

[PRR]

Have you investigated the use of a magnetron for your application? 

Magnetron is fixed-frequency (essentially). Like a whistle, the dimensions set the pitch. It may bend a percent or so, but LDM is looking for a decade (3 octaves).

[LazyDoorMan]

Have you investigated the use of a magnetron for your application? 

Magnetron is fixed-frequency (essentially). Like a whistle, the dimensions set the pitch. It may bend a percent or so, but LDM is looking for a decade (3 octaves).

I’m not sure I understand how a magnetron is “essentially” fixed frequency. What makes a magnetron different from a regular transformer other than it being a step up and having a rather large iron core. Would a toroid step up transformer with a 1:20 Not have a fixed frequency? And produce less distortion?

[LazyDoorMan]

HotBluePlates,

It appears that many people are insisting on misinterpreting my project.

I’m not in search of producing power. My ONLY objective is precision amplification of of single tone sine wave signal to a value of 5000v. Again, I’d prefer the Least amount of amperage out.

So, say a final signal out at 5000v and 50mA would mean an output of 250v at 1A at the output of a 6sn7 bc 1A/20 =50mA at 5000v. But to clarify further..... I would be okay with a lesser current than THAT even. So, a signal out of the 6sn7 of 250v at 200mA would be OK which would result in a 5000v at 10mA etc etc.

You say that I’d need a B+ value for the 6sn7 of 450v. Is that the voltage out of the 5y3 rectifier before the filtering or is that the voltage taken prior to the point of R9 and R12?

[sluckey]

My ONLY objective is precision amplification of of single tone sine wave signal to a value of 5000v. Again, I’d prefer the Least amount of amperage out.

The neon sign transformer in my '67 Tesla coil science project puts out a clean 12KV 60Hz sine wave. Use a variac to knock it down to your 5KV objective.

[HotBluePlates]

Sounds great! Go for it!

[premiumplus]

My ONLY objective is precision amplification of of single tone sine wave signal to a value of 5000v. Again, I’d prefer the Least amount of amperage out.

The neon sign transformer in my '67 Tesla coil science project puts out a clean 12KV 60Hz sine wave. Use a variac to knock it down to your 5KV objective.

And please realize that 5,000 volts at VERY low current will still reach out and grab you. Back in the '80s I worked on copiers and those kind of voltages will knock you clean across a room. I've seen it happen. I've worked around high voltage a lot and you have a lot to learn, grasshopper. And if you're designing this you are in way over your head. I'm not being disrespectful, I'm telling you the truth. High voltage is very, very dangerous. 15 mA across your spinal cord is sufficient to kill.

[PRR]

A KEY specification on any amplifier is the LOAD.

Which you repeatedly fail to quantify in any meaningful way.

You have suggested "no current" but there is capacitance everywhere and it all sucks. Even at a mere 5KHz.

It is typical to estimate 30pFd at every node of a tube amp. It may be much more. It might be less with great care.

Let us be generous and assume this is the *only * load.

30pFd at 5KHz is 1Meg reactance.

5000V sine is I assume RMS. This is 7000V peak. 7000Vpk in 1Meg is 7mA. 7000V at 7mA is 49VA of power. Without resonance or complex switchers, this is going to need over 50 Watts of final stage DC power. Very likely over 300 Watts.

Or a transformer, as you suggest..... except a tranny to get to hundreds of Hz will be a large lump of iron and copper and will have a self-capacitance in the Hundreds of pFd. You have to get above 100kHz to reduce the total mass and self-capacitance. So the idea of "transformer step-up" does not fit the situation.

If you kept the 5000V but scaled-up the load conductance 1000X to say 7Amps, it would cost a lot more but the impedances are more manageable. A 35KVA load is costly but not absurd to drive: any big-city broadcaster is in this range.

This below will NOT work. Gain is "cheap" but the output is grossly distorted because it can't pull-up even minimal 5pFd capacitance.

https://frank.pocnet.net/sheets/127/6/6BD4.pdf

[LazyDoorMan]

HotBluePlates

I was misinterpreting the term magnetron as a microwave transformer. I am fully aware and I understand they are two separate components now.

I am a young grasshopper with lots to learn and no offense taken there. Any current at 5000V is dangerous and is mathematically going to be a significant amount of power.

(Side note: if anyone has tube suggestions that would be better suit to replace 6sn7 I’m open ears)

From the 6sn7 data sheet max current output of 20mA. Say I revise the circuit to bring more power to the 2nd stage voltage amplifier[someone mentioned 450v To get anywhere close to 250]and can indeed Amplify to my 250v mark and maximize the current flow at 20mA. Am I right to math:>>250v @20mA (that’s 5 watts I believe) send that through the primary of a microwave transformer an get 5000v @1mA (that’s 5 watts still) but there will be loss of course.

I’m gonna botch the wording on this but is there a cutoff current at which a microwave transformer requires to effectively induce current in its secondary winding? If so how would I go about finding the value? If I were to make my own 1:20 OT using a torus core. What would be the best core material for the torus, taking into consideration that frequency of 500-5000hz but most predominant in the range 3000-5000hz. I’ve been reading up on audio transformers and a lot of the information is Mainly for VHF and UHF and above and that’s way outside the scope of my needs. When winding a secondary with a 1:20 ratio, does it need to be sectioned?


As far as load... I’m waiting on the motor in the mail

[shooter]

2 computers ago I had a file from the web that used a driver tube to feed the guts of a micro-wave to create a multi-KW Morse-code transmitter.  took some digging, the plans/design were solid.  I gave up and went with an off shelf, under the table, 1KW linear amp for CB guys.  Transmit that into a 6db antenna (load) that wouldn't melt, you'll be close to your "design" albeit at 27MHZ.
the point, you need lots of surf time, maybe in the shadier spots of the web.  Happy hunting 

[sluckey]

LazyDoorMan, what is your electronic background, education and experience?

[HotBluePlates]

Sounds great!  Go for it!

[Willabe]

As far as load... I’m waiting on the motor in the mail.

No your not. 

You don't buy a motor on line without knowing it's voltage, current draw and it's speed. Those specs are all online with the sale post listing.

[EL34]

Lazy Door manIs this post for real or are you trolling?

[LazyDoorMan]

2 computers ago I had a file from the web that used a driver tube to feed the guts of a micro-wave to create a multi-KW Morse-code transmitter.  took some digging, the plans/design were solid.  I gave up and went with an off shelf, under the table, 1KW linear amp for CB guys.  Transmit that into a 6db antenna (load) that wouldn't melt, you'll be close to your "design" albeit at 27MHZ.
the point, you need lots of surf time, maybe in the shadier spots of the web.  Happy hunting 

Sounds like you’ve had some pretty high power ideas. Unfortunately the concepts are out of my scope. I’m really determined to keep within my frequency range mentioned prior and the higher the frequency the higher the power by default which Id like to minimize. Also, keep in mind the goal is to sync 3 of these out of phase. I have no idea where to start or if it’s even possible to make a 5khz version of a magnetron let alone synchronize it’s pulse. Not that I’m against the idea. Lastly I may be wrong but I thought burst static Morris code (spark gap) devices were illegal since the early 1900’s.

As far as background your own guess from my postings is probably spot on. >> did you know that Christopher Columbus had know knowledge of sailing across vast oceans yet.... the queen chartered him to do so and in the end he succeeded? Fascinating stuff right? Too bad she altered the fine print of the contract otherwise he’d be one of the wealthiest lineages in the world possibly The Wealthiest!

Mr. Willabe, I’m entertained by your comment. I have to say it made me chuckle a bit. A wise man might suggest to you that maybe the windings and the wiring are going to be redone in a new fashion? Therefore, the specs available would be incorrect? Sometimes when you try and strong arm someone you end up looking dumb and the people who didn’t go to college all look at each other and say man I bet he went to college and learnt a lot

[LazyDoorMan]

El34, yes it is for real I’m not trolling. I’m just out trying to learn and find a way to actually do my experiment safely and seeking alternative ideas and suggestions

[Willabe]

Your either an uninformed goof who wont humble himself enough to listen, want to play with 5Kacv just for an experiment, or your just a shady trouble maker. Either way somethings wrong with you and should seek counsel from someone with some wisdom that will help you. 

This forum is for dealing with audio circuits, tube and solid state.

You should look for answers somewhere else.

[acheld]

Well I knew you for real.  I sounded just like you when I was young -- that's not a complaint or a dis -- just how it is.   And yes, I'm going to sound like your grandfather now.   I'm ok with that.  I hope you can listen, because I get the feeling you want to do something worthwhile.

Couple of observations:

1) I think you may underestimate the team around Columbus, as well as his own preparation for his journeys.  It took him years to get the financial support, as well as his own preparation as a mariner, along with the accumulated knowledge of the European sea faring nations.  The main reason the Spanish funded him was to a)get rich, and b)convert everyone to Catholicism.  His idea to sail west around the world was not new.   Yup, he was audacious enough to try it.   My main point here is that there is a background to Columbus' project, and a lot of people helping him.  Kind of like what Elon Musk is doing with Tesla.

2) One of the main lessons we take home every day on this forum is that context and planning matter.  You need to know where you are attempting to go, first and foremost.   If you want help from forum members, you must communicate what you want to do, and what your plan is.  Getting piecemeal advice does not work (aside from simple factual bits of advice).   When you engage us, we become part of your team, so to speak.

3) A bit of advice:  high voltage can and does kill.  High voltage guitar amps can be dangerous, but you are talking of a device that is using voltage 10 times higher than what guitar amps are designed for.   Some of the folks on this forum are accustomed to working on military radar and other commercial applications and do know the danger to the uninitiated.  Take this to heart.

4) While I don't know much about induction motors, they ARE really interesting.  Listen to Sandy Munro (he's all over YouTube) discussing the differences between VW, Honda, Ford and Tesla motors.   The control of these modern motors is based on clever engineering of the inductive elements in the motor as well as the precise control of the energy fields.   In my opinion, tubes are ill suited to this precise level of control.  Forget the cost.  Silicon rules, tubes drool.   

[66Strat]

2 computers ago I had a file from the web that used a driver tube to feed the guts of a micro-wave to create a multi-KW Morse-code transmitter.  took some digging, the plans/design were solid.  I gave up and went with an off shelf, under the table, 1KW linear amp for CB guys.  Transmit that into a 6db antenna (load) that wouldn't melt, you'll be close to your "design" albeit at 27MHZ.
the point, you need lots of surf time, maybe in the shadier spots of the web.  Happy hunting 

My dad used to build linear CB booster transmitters back in the late 60s. His were about 1KW. The priest of the local Catholic church came by one afternoon and asked dad if he could hold off on broadcasting between 11AM and Noon on Sundays and 5 to 6 PM on Saturdays. It seems that dad was bleeding over on the church PA system. It was a bit distracting to hear "breaker one nine, what's your twenty?" during the reading from the Gospel.

[shooter]

Sounds like you’ve had some pretty high power ideas.

part of my career was fixing high power TX stuff, I spent ALOT of time sitting in class, learn'n NOT to fry my asterisks off 

(spark gap) devices were illegal since the early 1900’s.

I didn't spent any time in class lern'n law, no jail time lern'n law either

[LazyDoorMan]

This forum is for dealing with audio circuits, tube and solid state.

You should look for answers somewhere else.

Mr. Willabe, I don’t understand why you have been so adamant at poking me and giving discouragement since I started this thread. I can’t think of a better forum to look for answers at bc I’m building an audio signal amplifier. It’s just not going to be audible or used with a guitar. And I’m using tube amplification to do so. Tubes that are very common at that as well.

 I didn’t start a topic to ask permission I asked for advice and suggestions that would make my experiment function and from the feedback from people I’ve learned a bit more of what to do and what not to do and understand better as a whole what I’ll be working on.

I’ll never understand why people need to jut in not once but twice and thrice when you have nothing to offer besides negativity. You don’t even bring an alternative to the forefront. You’re just being noisy.

Acheld, right on man. I would like to say that I chose tubes bc of their high voltage capability but an alternative means would suffice. I had only seen electronic chips as an alternatives as well as boosters and stuff that required programming knowledge. I may have misjudged but I’m knee deep in tube education and I feel like with some trial and error it will get the job done.

[Willabe]

I’ll never understand why people need to jut in not once but twice and thrice when you have nothing to offer besides negativity. You don’t even bring an alternative to the forefront. You’re just being noisy.

Yep, he's a     troll.

[HotBluePlates]

... I don’t understand why you have been so adamant at poking me and giving discouragement since I started this thread. ... I’ll never understand why people need to jut in not once but twice and thrice when you have nothing to offer besides negativity. ...

Sounds great!  Go for it!!

[LazyDoorMan]

Back to the topic I’m going to do some ordering and get back with the results in a few weeks wish me luck peeps

[PRR]

Good luck! Go for it!

[acheld]

LDM, re-read my post.  I guess was being too subtle.

You are out of your depth.

[shooter]

IFF you live after the 1st multi-kv poke, you'll find humility a good thing 
books will have value AND knowledge you might have overlooked prior to electrocution


save up a couple $$'s for a 25kv probe so you don't fry-a-fluke