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Author Topic: Will New Power Transistors End the Need for Tube Amplifiers in the Future?  (Read 20729 times)
G3RZP
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« Reply #30 on: January 26, 2012, 12:06:09 AM »

Say I'm 60 years old, and have a good tube amp with ceramic tubes in it, and spares that are cycled round every two years, why would I want to buy a SS amp? The tube amp will quite likely outlast me.

Next question: is possible yet to do a 600 watt or 1000 watt amp solid state, with the same performance as an Ameriton tube amp, for the same price?  If not, what has got to drop in price to enable that?
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G4ZOW
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« Reply #31 on: January 26, 2012, 01:17:31 AM »

A new S/S amp project being put together that might interest some of you: http://www.nikkemedia.fi/juma-pa1000/

I don't see heat as the problem with good designs as efficiency numbers are slowly climbing and good wind tunnel designs heat is the least of your problems.

Good protection circuitry I would of thought being most important.

The broadcast industry with 24/7 operation (AM & FM) are now pretty much all fully S/S and the 1kW & 1.25kW devices are already being used in production equipment.

Personally I like the look of the BLF578XR from NXP: http://www.youtube.com/watch?v=8ziYqjMQGEQ

Don't listen to all the anti-S/S brigade going on about pulse power  Grin

Our amplifiers albeit for the FM broadcast industry exceed FCC specs and have full certification with an ID number on every unit we ship to the US up to and including our 1kW model.

David G4ZOW
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KE5JPP
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« Reply #32 on: January 26, 2012, 03:36:24 AM »

A new S/S amp project being put together that might interest some of you: http://www.nikkemedia.fi/juma-pa1000/

I don't see heat as the problem with good designs as efficiency numbers are slowly climbing and good wind tunnel designs heat is the least of your problems.

Good protection circuitry I would of thought being most important.

The broadcast industry with 24/7 operation (AM & FM) are now pretty much all fully S/S and the 1kW & 1.25kW devices are already being used in production equipment.

Personally I like the look of the BLF578XR from NXP: http://www.youtube.com/watch?v=8ziYqjMQGEQ

Don't listen to all the anti-S/S brigade going on about pulse power  Grin

Our amplifiers albeit for the FM broadcast industry exceed FCC specs and have full certification with an ID number on every unit we ship to the US up to and including our 1kW model.

David G4ZOW

You are giving examples of amps that are used on (relatively) fixed frequencies.  It is quite a different design problem with amps that have to work from 1-30 or 1-50 MHz.

Gene
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KE5JPP
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« Reply #33 on: January 26, 2012, 03:45:47 AM »


Personally I like the look of the BLF578XR from NXP: http://www.youtube.com/watch?v=8ziYqjMQGEQ

David G4ZOW

Very interesting.  They are using a liquid cooled copper block for transistor cooling.  I wonder how cold the coolant is being pumped through the copper block?

Gene
« Last Edit: January 26, 2012, 05:26:10 AM by KE5JPP » Logged
VE7RF
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« Reply #34 on: January 26, 2012, 03:47:39 AM »

A new S/S amp project being put together that might interest some of you:

http://www.nikkemedia.fi/juma-pa1000/


Our amplifiers albeit for the FM broadcast industry exceed FCC specs and have full certification with an ID number on every unit we ship to the US up to and including our 1kW model.

David G4ZOW

##  Than Finnish 1 kw output ham amp  uses a  SINGLE  freescale device.  Notice the heat sink is like a tunnel ram, below the chassis.    No imd specs yet.


##  there is an outfit in Halifax canada that makes a 52 kw CCS  SS FM amp.  It uses  up to 52 x 1 kw modules.  So it can be configured from 1 kw  up to 52 kw.   The rf modules can also be hotswitched off line..then the remaining units take up the slack.  Each module has it's own switching supply.  The switching supplies can also be hot switched out.   The cleaning lady can maintain a set up like this.  One unit bites the dust, who cares, the remaining units crank out a bit more .  Somebody goes up the hill in the springtime, when the snow melts..and swaps out the odd unit.

##  I saw AM broadcast  TX..back in the 70's..that used 2 x 25 kw output amps..and one combiner. These are tube types.  If one bit the dust, you are only down 3db.  That was a common set up.

##  $4000.00 for a yaesu VL-1000...with it's rf deck + switcher supply  + kw rated auto tuner is a bit much $$  to spend imo.  I don't think you can buy the VL-1000..minus the auto tuner either.  Great, you have just traded in.."tune and load"...for ... "C1 and C2 on the kw ant tuner.  You can run a tube amp with out an ant tuner... but it's tough with a ss amp..unless the swr is low. The tube amp doesn't require a mess of LP filters either.

Jim  VE7RF
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N3OX
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« Reply #35 on: January 26, 2012, 07:22:14 AM »

Personally I like the look of the BLF578XR from NXP: http://www.youtube.com/watch?v=8ziYqjMQGEQ

Don't listen to all the anti-S/S brigade going on about pulse power  Grin

Quote from: KE5JPP
Very interesting.  They are using a liquid cooled copper block for transistor cooling.  I wonder how cold the coolant is being pumped through the copper block?

They are barely generating any heat at all in that test.  Watch that video very carefully and keep an eye on the DC power supply each time they show it. (around 3m 20s is good)

The open circuit test shows 55V at 2A for a time averaged total circuit dissipation of just 110W  (no power can be delivered to the open circuit).  The short circuit test shows 55V at 9.4A for a total dissipation of 517W.   They allow that condition to persist for what, ten to twenty seconds on a solid copper water block?

At least this is almost exactly the device dissipation that would be seen for 1200W operation at 70% efficiency... but that's only a couple times where the device is operating at a reasonable keydown-type dissipation for a  few seconds during that whole video.  It happens during the short circuit tests and during the variable-SWR test.  It is not left that way for very long and it's water cooled.  

It looks to me like the amp is running at just 55V and 0.23A input under normal operation which is like a 1% duty cycle even if the sucker had 100% efficiency!  Maybe they hadn't turned the source on but it looks to me like it's running at 55V and 0.23A and then they uncouple the dummy load and current rises to 2A.  I wouldn't be surprised if the bias in a ham amp would dissipate as much as the operation at "1200W" in this video does.

They are babying it in that test heat-wise.  It doesn't matter how cold the fluid is they're running through the block.  That block probably wouldn't rise to more than "somewhat warm" during these tests even if it was just a thermally isolated, half-hollowed-out copper block with no cooling.

People have also been very impressed by the "ruggedness" shown in this video.    I know I was at first.  Look at how they abuse it with no protection circuitry! But then you look at the current in the short circuit test.  The power dissipated in the short circuit test is suspiciously close to the power dissipated in 70% efficiency keydown operation at 1200W and the current drawn in the short circuit test is LESS THAN A THIRD of what you need to get 1200W keydown out at 70% efficiency.

My guess is that the power supply current limit and pulse duty cycle in that video are tuned carefully to put things at conservative safe dissipation during the short circuit tests and I bet you would kill the part in seconds (if not blow it up in plausible scenarios) if you short circuited the output with 1200W average power going out.  
I also don't know if this part is even linear enough for SSB, etc.  No IMD specs.

Anyway, I think there's great promise in some of the nice linear high power devices that are out there but this kind of marketing video needs to be taken for what it is: a flashy demonstration that isn't really stressing the device like what would happen if you weren't careful in your home lab.  You buy one of these things along with a 50V 40A telco surplus power supply and duplicate these tests and you might end up with a paperweight  (and hopefully not an face full of expensive transistor bits)  

Of course it's not reasonable to use an expensive transistor like this without fast protection circuitry but it's important that hams, especially home experimenters, understand how easy they were taking it on the transistor in this test.  This was NOT an "antenna shorts across the tower during a  RTTY transmission" sort of abuse test.  This was not a "short the output while you're holding the key down" test.  It was  test specially tuned so that the continuous device dissipation operating into a short circuit was a safe level comparable to 1200W CW output, and even there they didn't demonstrate that their water block lashup could keep it cool in steady state at that dissipation.  

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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
W6RMK
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« Reply #36 on: January 26, 2012, 07:51:23 AM »

Say I'm 60 years old, and have a good tube amp with ceramic tubes in it, and spares that are cycled round every two years, why would I want to buy a SS amp? The tube amp will quite likely outlast me.

Next question: is possible yet to do a 600 watt or 1000 watt amp solid state, with the same performance as an Ameriton tube amp, for the same price?  If not, what has got to drop in price to enable that?

Performance measured how?
The inexpensive Ameritron tube amps have manual plate tuning controls and very little internal protective circuitry, if any, which works on a tube in the hands of a human operator who will make mistakes, but would almost certainly result in instant death for RF transistors when mistuned.  So SS amps use broadband designs and output filters.

What has to change?
The market for amplifiers. As you pointed out, you expect to use your tube amp til you die, so you're not a customer for a SS amp.  And I suspect you are typical of much of the potential market. 

Eventually, new hams will come into the market, want an amplifier, not be interested in tubes, buy a SS amp as currently constituted, complain about the performance(measured however), and the mfrs will respond with new products.  No/Auto tune amps are a lot easier to use, and I don't think the somewhat arcane and esoteric skill of tuning up a tube amp brings a lot to the operator. The reason they dominate now is that there's a lot of manually tuned amps in existence, and they're cheap, not because people love to turn the knobs.  It's not like manual vs automatic transmission, where there is some benefit from the manual transmission.  Given a choice between a top of the line autotune tube or no-tune SS amp and a low end manual everything, I'll bet most hams would choose the former (hmm, look at those contest stations and the DXpeditions... They love them their big Alphas)
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G3RZP
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« Reply #37 on: January 26, 2012, 07:59:22 AM »

Because of the low impedance, doing an HF tuned high power SS amplifier isn't that easy anyway, so relatively wideband is the way to go.

But what has got to drop in price to make the protected, filtered, 1 or 1.5kW SS amp comparable in price to an Ameritron in terms of output power and IMD - especially high order IMD?

IIRC, Rohde and Schwarz had a BC FM tx some 20 odd years ago with liquid cooling of all the modules. I don't know if one can have awkeard electrolytic corrosions there: possibly using copper throughout the cooling system is necessary, or at least desirable.
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W4VR
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« Reply #38 on: January 26, 2012, 08:28:38 AM »

The answer is a simple "yes"
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KB1GMX
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« Reply #39 on: January 26, 2012, 09:03:02 AM »

I'm with some the cost of the current crop of SS amps is rather high.

The other issue is IMD, Most of the devices I've played with can do very well, but the
current crop of radios put out a lot of trash.  Some of the best radios the IMD is so
poor (even when not over driven) that an amp with -25db IMD won't make it
much worse. (the TS2000 and K3 as examples).

Then again I grew up with both tubes and transistors but strongly remember getting
hit by the  HV of a RCA CARFONE base (500W low band FM) because some dork did
a "whats that?" and added me to the circuit.

Sure I can build a amp using 2 or 3 4CX250s or a pair of 3CX800s but they will still need
a boat load of cooling, protection and they will not be small.  The thought of that HV puts
me off.

There are no shortage of high power devices and complete amps.  A local group GEMOTO
was selling retired Larcan TV block amps.  Imagine 1KW out on 6M and bullet proof too.

My current amp for 432 was a retired Comark 100W driver.  Very clean and also resilient
and that isn't even FET it's 15-20 year old bipolar parts. 

I'd add the efficiency comments are mostly red herring.  ALL amps will be more efficient at some
power than another.  If you understand the arithmetic it real simple power in divided by power out.
Tubes we ignore the heavy 20 to 50W of filament power but it's there.  Generally it's not an issue
save for the power not put out is heat.  In any case the number for full power will rarely not be good
compared to say 1/5th power.  If they are it's biased Class A, it's rare to find tube amps biased
that way.

As to tubes being more rugged, I've seen what happens to a VHF amp (pair of 4cx250s) when the blower fails.  They don't last long and the components around them suffer significant heat damage.  A local
managed to fry (killed the transformer and tube) a CommanderII amp so it can be done.

The biggest difference I see in commercial and ham is that commercial they design against faults
the system can see due to failures and those induced like Lightining.  TV and FM stations do not QSY or change antennas often.  Ham, they have to protect against overdrive, bad antennas, bad cables, wrong frequency, and the I want to run full power RTTY on a intermittent duty amp.

I'd ask the same question for tube or transistor users.  IF you blowing them up, what are you
doing wrong?   The rest it's may be things like the the particular radio and there are more than
a few that blow up due to cooling fails (dead fan or horribly clogged) or assembly faults
(bad soldering).


Allison
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KD8MJR
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« Reply #40 on: January 26, 2012, 09:37:35 AM »

The answer is a simple "yes"

Agree Smiley
But most of these guys will have to have the tubes pulled out of their cold dead hands before they would go SS.
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M0HCN
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« Reply #41 on: January 26, 2012, 09:55:40 AM »

Part of the problem is that proper protection costs real money, and that it is invisible most of the time.....

Lets see, to do the job right you need:

Airflow and heatsink temperature (Both because that air also cools the output filter and power supply).
Transistor temperature (per device ideally).
Over current.
Over voltage.
Reflectometers at both input and output of the LPF (The input to detect wrong band setting).
Imbalance detection if using multiple PA blocks.
Drive power (and some fast way to fold it back, a relay or ALC will not suffice).

The airflow should be filtered to keep fluff from eventually coating the internals and stuffing up the cooling.
Also careful sequencing so that nothing is ever hot switched.

This is not simple and not particularly cheap, but is basic to most good quality commercial service amps, you seldom see all of it in a commercial ham amp because the cost is just too high.

All this in addition to a well designed PA block with enough margin to start with, and enough heatsink to ensure it works properly in a 40 degree C equipment rack.

Also there is a lot of inertia behind the tube amps, and sometimes a poor understanding of the SS ones (The care and feeding is different).

Regards, Dan.
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K1DA
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« Reply #42 on: February 04, 2012, 07:27:50 PM »

   One key  observation...the writer had to get an "expert" to fix his Tokyo High Power amp (good company BTW) while MANY hams can look at a dark 3-500 or 811 and draw the proper conclusion.  Low voltage may be safer, but a lotof people have done themselves a lot of harm fooling with car batteries. 
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W8JI
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« Reply #43 on: February 04, 2012, 07:36:30 PM »

Personally I like the look of the BLF578XR from NXP: http://www.youtube.com/watch?v=8ziYqjMQGEQ

Which is, very obviously, a very low duty cycle pulsed power test.

Quote
Don't listen to all the anti-S/S brigade going on about pulse power  Grin

That's right. Look at the video, and see it first hand.

Quote
Our amplifiers albeit for the FM broadcast industry exceed FCC specs and have full certification with an ID number on every unit we ship to the US up to and including our 1kW model.

FM service is single band, and non-linear. It has controlled drive levels, tons of protection, lots of reserve dissipation because size and cost are no object, and it has good steady loads.

It is nothing at all like Ham stuff.   
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W6RMK
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« Reply #44 on: February 05, 2012, 09:05:57 AM »

   One key  observation...the writer had to get an "expert" to fix his Tokyo High Power amp (good company BTW) while MANY hams can look at a dark 3-500 or 811 and draw the proper conclusion.  Low voltage may be safer, but a lotof people have done themselves a lot of harm fooling with car batteries. 

People have been professionally building, using, and fixing tube amps for almost 100 years, and solid state amps for a bit less than half that.  Hams are running somewhat behind that.. I would say that the fraction of hams who have built and modified and fixed solid state amps is perhaps a few percent of those who have done the same with tube rigs.

In another 30 years, I suspect it will be different.
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