SET? Go big or go home?

[W9TR]

Got some directly heated triodes. Thinking that a big SET amp would be killer.

 

[THD+N]

Could be... what is your plan? High wattage good quality SE iron is not cheap (if that matters) and the power supply can be quite formidable.

 

[W9TR]

I was having a bit of fun on a slow Monday.

They’re from an amateur radio HF Amplifier I just finished restoring. You’re right - the magnetics is would be more than challenging!

A pair of Eimac 3-500Z’s running 1.5 kW output. 3000V on the plates. Ip=800 mA.
Filaments are 5.0 V @ 14.5A, each tube.
Forced air cooled, 13 cfm each tube.

The power supply is a 2400Vrms xfmr feeding a SS fwb to a resonant choke filter tuned to 120Hz. 8Hy choke in parallel with a 0.1 mfd 5000v oil filled cap. Filter is a 20 mFd 5000 oil filled cap. Bleeder is 3 20k 100W resistors.
Whole shebang weighs 125 lbs.

 

[Selmerdave]

Toasty...Honestly I'm surprised only 125 lbs. Sounds like the user needs their own sub-station to run it...but certainly cool.

 

[kward]

Go over to DIYAudio and read about @Maxamillion's "Midlife Crisis" amp to get some ideas of what would be involved. Most people just buy a red sports car or something but the guys who are really serious build really big SE amps

https://www.diyaudio.com/community/threads/the-midlife-crisis-my-833c-amp-build.232484/

 

[THD+N]

Go over to DIYAudio and search for @Maxamillion 's "Midlife Crisis" amp to get some ideas of what would be involved. Most people just buy a red sports car or something but the guys who are really serious build really big SE amps

Hey, I resemble that remark... I had two red sports cars, now have one and two 833A's still icthing to do something with.

 

[W9TR]

Toasty...Honestly I'm surprised only 125 lbs. Sounds like the user needs their own sub-station to run it...but certainly cool.

I will be running a 240V line. Key down full power it draws 24A @ 120V. Those big 833 Amps are really something.

 

[Lavane]

Got some directly heated triodes. Thinking that a big SET amp would be killer.
View attachment 2783604

And heat and light the room at night!

 

[Maxamillion]

The Midlife Crisis amps took me almost a year to complete, and are still going strong. They drive my big Infinity RSIIb speakers effortlessly.

PS: I bought a red sports car anyway, a 2019 Challenger Hellcat, 717HP, 6-speed manual. Drove it for 3 years and sold it...the amps are a longer lasting thrill.

 

[W9TR]

The Midlife Crisis amps took me almost a year to complete, and are still going strong. They drive my big Infinity RSIIb speakers effortlessly.
View attachment 2783855
PS: I bought a red sports car anyway, a 2019 Challenger Hellcat, 717HP, 6-speed manual. Drove it for 3 years and sold it...the amps are a longer lasting thrill.

That is way cooler than a Hellcat. Anybody can own one of those. But 833 based SET amps - that takes true skill and dedication! Enjoy them in good health.

 

[W9TR]

And heat and light the room at night!

Glad we live in cool country. Turn on the power switch and your dissipating 320W of heater and bleeder power. Key the amp to transmit and you've got another 420 watts of plate dissipation before you make a watt!

 

[trainbuftony]

Radio shack.
It was a retail store but also the old gaffers who played with big power radios put them out in a shack where the heat didn't heat up the whole house up to uncomfortable levels.

 

[turnitdown]

What frequency is your station broadcasting on? Hahahahahahahahaha

 

[santa]

813 can get it done relatively safely and sound great.

 

[santa]

The Midlife Crisis amps took me almost a year to complete, and are still going strong. They drive my big Infinity RSIIb speakers effortlessly.
View attachment 2783855
PS: I bought a red sports car anyway, a 2019 Challenger Hellcat, 717HP, 6-speed manual. Drove it for 3 years and sold it...the amps are a longer lasting thrill.

What is the plate voltage present on those?
What output transformer are you using?
And lastly, have you taken any measurement data you can share?

Your system is pretty awesome and I’m sure quite enjoyable to listen to.

 

[Maxamillion]

What is the plate voltage present on those?
What output transformer are you using?
And lastly, have you taken any measurement data you can share?

Your system is pretty awesome and I’m sure quite enjoyable to listen to.

Plate voltage is 2.3kV, running at 160mA. Output transformers are Monolith Magnetics S-833, with amorphous double-C cores and Teflon interwinding insulation. Each OPT weighs about 62lbs.

All the measurements are in the thread linked above, as well as schematics and LTSpice and PSUD2 simulations.

 

[Maxamillion]

Here's a picture Monolith Magnetics sent me of one of my OPTs under construction, before potting. That's an ECC83 tube next to it for reference.

 

[Selmerdave]

"Monolith" sounds about right. Amazing.