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This is an AM modulator which I would love to have but the 304TL only has a MU of 12 and loads at 6.6k in PP at 2500v. A pair of these and you can build a nice 1500 watt PP tube amp if someone could wind an output transformer the size of Vermont.
"If it measures good and sounds bad, it is bad; if it measures bad and sounds good, you have measured the wrong thing."
- Daniel R. von Recklinghausen
Follow Ups:
304TL is an interesting tube. It has four plates in parallel. Supposedly, it is four 100TL's in one envelope. And the filaments are divided into circuits, so you can run them at 5V/25A or 10V/12.5A.
There's also a 304TH, same but with a MU of 20.
two 152tl in parallel.
Link below:
it is proof that the Religious Fanatic prohibitions against paralleling tubes is BS!
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
Worse yet... if you run the filaments in series you also have 2 of those parallel plates at 5V less bias than the other two.
dave
one end of the cathode is biased at 10V from the other?
And the venerable RCA 10? Biased 7.5V different, one end of the cathode to the other?
And yet...
Did you know that simply running only the filament will melt solder?
Now, add the plate current to that.
I once built a good sounding S.E. amp out of one-- until I realized that a good 2A3 or 45 outperforms it. It made a nice transmitting tube-- I've replaced a lot of them in Mil.Spec. transmitters.
Guess what? Dull Cherry-Red is what the plates like. Run an old one at the same temperature, and you'll get nothing! (In a transmitter). They have to be "sharp".
For practical purposes, it's another outdated antique. Today, we have 100% solid-state transmitters with autotune.
---Dennis---
x
with a PP 304TL amp that filled(and warmed) up most of the room.
One of THE best sounding systems is pictured above, 5 way Ale compression driver horns driven by a custom made SE 304tl mono-blocks.
Seem to recall that a lower voltages (1000-1200) the plate resistance of this tube would be pretty low requiring only a 2.5K to 3.5K output transformer. Likely work fine with something designed for an 845 or GM70.
I've go about a dozen of them somewhere in storage, was thinking of using 'half' of one for a SE amp build, kind of a poor man's 152tl amp.
Run 600 VDC across the tube. Decide your loading and plate current, and drive requirements based on that.
The 304TL is plenty linear-- so what is practical works just fine-- no need to morph this thing into a monster. Use a LOT of forced-air cooling.
I was in the room you show at RMAF. This system sounded good, warm, friendly, with low distortion.
Compared to the "ultimate"-- whoever that was-- it scored maybe a 9.3-- of a possible "10".
It's best quality was an effortless ease. What little it lacked was not enough extended highs, and it was slightly euphonic-- not in a necessarily bad way. A good feature which it had was bass that was real--not bloated, and not recessive or peaky.., but which underlaid the music in a positive way-- not overbearing. This shows good woofer cone-control and good execution of speakers in the demo room..
Could one live with this system over a period of years? YES, I think you would keep it.
The Von Gaylord room sounded good also, with their oil-cooled ceramic-triode amps. Von Gaylord demo rooms should always be attended at an audio show, no matter who you are or what you represent. I always make it a point to visit them as well as most others.
---Dennis---
Were these guys at RMAF?
Looks like he was influenced by the old Altec/WE single driver technology.
There is a thread started on High EF forum about them.
n
Are those your Western Electric speakers?
"If it measures good and sounds bad, it is bad; if it measures bad and sounds good, you have measured the wrong thing."
- Daniel R. von Recklinghausen
Former and possibly current ALE distributor Kevin Brook's home system from about a decade or so ago.
Some of the best sound in a home system I've ever heard!
I heard he now likes Lowther based system more than the monster horn installation on the picture.
That horn system sure too up a lot of room in the parlor!
Just guessing that Kevin is no longer an ALE dealer, which might explain it as well.
Sure did sound good!
My friend who has his Lowther honeymoon (Don't we all at some point in this hobby? Mine was ~5 years ago..;) talks frequently with Kevin.
Surely , well integrated Lowther system is almost maintenance free which can't be said about huge 5 way Ale system.
Rgrds. W
What's the maintenance on a 5-way ALE horn system?
OK, once it's set up properly.
Those magnets are pretty stable as long as you don't drop them.
too big for me
The smaller tantalum anode stuff is quite enough to run well up to the limits of good OPT performance. The big stuff needs enough dissipation to run the anodes up to gettering temperature. Even two of those in Class A is huge by OPT capability. Dave and Jeffrey have found a few ways around this to good effect though...:) and SE no less...
Their plate resistance is quite low thanks to the gm afforded by what is basically 4 75TL's in parallel...mu of 12 is quite adequate.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
The 12 mu is fine..Not everyone agrees but even 6L6gc running in triode have a mu of about 6 as I recall.
You have to love to two anodes and two grids. Just keep the Tantalum hot enough to getter by pretty much running it to red.
"If it measures good and sounds bad, it is bad; if it measures bad and sounds good, you have measured the wrong thing."
- Daniel R. von Recklinghausen
It's four 75tl in parallel.
Cathodes/filaments can be wire as all four in series at 10V or series/parallel at 5V.
This would allow, if one so chooses, to run HALF the tube, with 5V at 12.5A filaments.
At about 1000V and 100ma, this might be somewhere between an 845 and a 211 in plate resistance.
I found ten of these 304TL tubes at a garage sale a few years ago. I suspect a problem with ultra high power audio transformers is producing a full range and flat high frequency response. The stray capacitance and insulation spacing in between the windings would be huge.
What would a 2.5KW audio transformer weigh? 75lbs?
Jim
The audio transformers we use in the AM modulators handle the HV well but we also have a much higher impedance secondary. I would guess it's in the 75lb to 125lb range.
"If it measures good and sounds bad, it is bad; if it measures bad and sounds good, you have measured the wrong thing."
- Daniel R. von Recklinghausen
I do like the efficiency of class C RF plate modulated finals.
Guitar amps as well.
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