Today? Resistors. I spent a couple hours scrounging the surplus market for suitable dummy loads for The Next Generation of Stupid Power Tube Amp Power Supplies. My current huge bank of 4.3k/20W sand boxes wasn’t going to be enough. What I needed was going to end up being over $200 no matter where they came from, piecing together values needed for all 3 power supplies. Then I finally gave up and just looked up Mouser. $20 a pop for 225W Ohmites. At 2.5k ohms, just put up to 6 in parallel, and trim with whats on hand. Done. They are on their way.
See what happens when you have too much time on your hands?
See what happens when you have too much time on your hands?
Attachments
Those will run really, really hot at full power. Be sure to mount them horizontally, well away from any flammable material,
and in full free air circulation. There are accessory steel mounting brackets (not included) that fit in the ends.
And they break in half very easily if dropped or subjected to a sharp impact. There are noninductive versions available.
and in full free air circulation. There are accessory steel mounting brackets (not included) that fit in the ends.
And they break in half very easily if dropped or subjected to a sharp impact. There are noninductive versions available.
Last edited:
I Usually mount an array of those on a sheet of plywood using my own mounting brackets, with a box fan blowing on them. Tests wont be crazy long duration - 10, 20 seconds at a time measuring voltages under load with the various taps and winding configurations on the transformers till I get my target voltages. Inductive, non inductive doesn’t matter for DC load. My array of 20 watters I normally use for load testing tube amp supplies was just coming up short for testing a supply for an 800 watt amp in development. They may run for longer when I go to measure temperature rise of the transformers, but the immediate goal is to get the unloaded/loaded voltages dialed in. I do this all the time when doing custom trafo winds.
I have an array of 33 ohm, 500 watters and two pair of 5 ohm 225 watt I use for dummy loads for speakers or solid state amp supplies. But 284 ohms wasnt enough here. Those often run all afternoon and I know about HOT.
I have an array of 33 ohm, 500 watters and two pair of 5 ohm 225 watt I use for dummy loads for speakers or solid state amp supplies. But 284 ohms wasnt enough here. Those often run all afternoon and I know about HOT.
Tube amp? I bow to.
We had a guy - the vendor was doing power supply "burn-in" or some sort of reliability test - where multiple supplies were resistively loaded. He figured out a way to convert the power supply outputs back into AC, feed current back into the mains, while still providing the necessary current load the resistors would have. I suppose at the scale they were running, it saved or would have saved an appreciable amount of energy - otherwise up in smoke.
Been brewing for a while. An 800-1000 watt solid state amp isn’t a challenge anymore. Been there done that bought the T shirt. There will be a few smaller steps along the way - I built 200 watt monoblocks a few years back using standard components so I’m not starting from ground zero with no idea what I’m doing.
I guess you can always power a grid tie inverter with a power supply, and feed it back or otherwise usefully use the energy. At least run the company coffee pot. Sort of the opposite of plugging a UPS into itself and letting the battery slowly go down.
I just needed load resistors that won’t turn into fuses while I’m tweaking up transformer turns ratios and taps. Simulate it - yeah right. Unless you have a model that includes leakage reactance you don’t model the voltage drop under load accurately at 500+ watts. You measure it, plain and simple. I need 700 volts at 1.6 amps to make 800 watts with my OPT and tube complement. I put a 437 ohm load on the supply, and see where I need to go to get there. It will be made from some yet to be built 600 VA toroid that will provide heater power and the first 150-200V for the screens, with a 480V industrial control trafo stacked on top to get the rest of the voltage. It has taps from 380 to 480V. Tweak till I get the voltages I need. If I can get closer to that magic kW that’s fine by me too.
I guess you can always power a grid tie inverter with a power supply, and feed it back or otherwise usefully use the energy. At least run the company coffee pot. Sort of the opposite of plugging a UPS into itself and letting the battery slowly go down.
I just needed load resistors that won’t turn into fuses while I’m tweaking up transformer turns ratios and taps. Simulate it - yeah right. Unless you have a model that includes leakage reactance you don’t model the voltage drop under load accurately at 500+ watts. You measure it, plain and simple. I need 700 volts at 1.6 amps to make 800 watts with my OPT and tube complement. I put a 437 ohm load on the supply, and see where I need to go to get there. It will be made from some yet to be built 600 VA toroid that will provide heater power and the first 150-200V for the screens, with a 480V industrial control trafo stacked on top to get the rest of the voltage. It has taps from 380 to 480V. Tweak till I get the voltages I need. If I can get closer to that magic kW that’s fine by me too.
this week I bought
Edifier R1700BT
Edifier T5 sub
2 IEMs (cheap Chi-fi) (CCA CRA and CCA Lyra)
1 dongle DAC for my Samsung S20
AK XB10 ( to add bluetooth capability to above 2.1 system consisting of Edifier R1700BT and T5 sub). XB10 will connect to the line-in of T5 and line-out will go to R1700BT.
Edifier R1700BT
Edifier T5 sub
2 IEMs (cheap Chi-fi) (CCA CRA and CCA Lyra)
1 dongle DAC for my Samsung S20
AK XB10 ( to add bluetooth capability to above 2.1 system consisting of Edifier R1700BT and T5 sub). XB10 will connect to the line-in of T5 and line-out will go to R1700BT.
These resistors. those are loads huh?
Can't you use something that is submersed in some oil... like the Ham Radio guys do when they're working testing their transmitters and don't want to hook it up to the antenna?
It'll be toasty in the winter, that's for sure.
I use banks of physical resistors so I can dial my loads in exactly, on the fly, without resorting to special cooling other than a fan. X ohms is what Y amplifier will draw off the supply or or transformer when it drops to Z volts. Do it for another project and the value needed changes. Re wire, trim with smaller units. I just didn’t have something BIG enough in the 400 to 600 ohm ranges for the latest batch of projects. Once I’m done with these projects they will find use in others. More tools in the box, not unlike buying another power tool from Home Depot.
What surprised me about the whole deal was the BEST prices I could find on the surplus market couldn’t beat MOUSER. I remember when I could get resistors like that for FIVE BUCKS. But even 20 isn’t particularly bad.
What surprised me about the whole deal was the BEST prices I could find on the surplus market couldn’t beat MOUSER. I remember when I could get resistors like that for FIVE BUCKS. But even 20 isn’t particularly bad.
And they just got here. The “mixed brand” lot of 6HJ5 ALL turned out to be the Raytheon type -regardless of whose name was screen printed on the bottle. Complete with the ”LYFA” mark etched into the glass. Score one for the good guys. Now enough of those on hand for the “350 watt 8 ohm” version, a complete retube, and spares.
Arriving today are 2 auralex pads to set my midbass horns on since they'll sit on installed shelving. Wednesday I got a large acoustic absorber for behind my seating (have to sit kind of close to rear wall), in the next few days I get a 6ch amp to continue adding active channels. Some JBL 2384 waveguides are on their way, and I'm crossing my fingers that the M2 comp driver (D2430k) isn't low-quality like so much of what JBL's been doing lately. The 2384s might need cleaning up but a little throat smoothing is easy to do.
SMSL D-6s Balanced DAC after seeing the ASR measurements. The Topping DX3 Pro+ can move to the desktop.
Aceclofenac - can be effective for asthma attacks as well.
"A little knowledge is a dangerous thing." Again 🙄
I sit about seven feet from the back wall so I put up a four foot CURVED front curio cabinet. The thing is like seven feet tall and four feet wide. It doesn't absorb sound, it scatters it very nicely without killing the room... really nice live sound without affecting the soundstage.
I have some tube traps up in the front, but the rug and the couches absorb enough that I didn't want to kill the sound of the room.
.
The LTSpice XVII simulator by Gilles Brocard, 748 pages
KiCad 6 Like a Pro by Peter Dalmaris, 548 pages
Will keep me busy for a while, started with the KiCad book.
The LTSpice XVII simulator by Gilles Brocard, 748 pages
KiCad 6 Like a Pro by Peter Dalmaris, 548 pages
Will keep me busy for a while, started with the KiCad book.
It's been... a lot lately. Yesterday after my post, I heard back from Assistance Audio... Getting some BMS coaxes too. Gonna find out who the 1.5" throat king of dual phragms is.
I bought an AMD 3800X processor from Amazon Warehouse deals - it arrived without the CPU, just a heatsink and fan.
Looks like someone bought it previously, kept the chip and returned it. The Amzn fellow working the sort on those returns must've looked at it, shrugged, put it back in stock. Dishonesty squared.