What the heck is it? Royal Device (loudspeakers) mystery box

... Rat's nest design that cost $1.5k...

Here is a hilarious translation (probably google):

http://modama.net/47lab/dac01_e.html

"Circumstance plug price being large amount, to open the wallet, it was something where courage is."

"The hot water of the potato it divides Shigaraki DAC, With, it seems that stops wanting to murmur absentmindedly with the dense eye"
Wow.

"There is no 'leg' in we"

There is no "quality" in construction, either. Looks like a couple of pounds worth of off-the-shelf components, and probably a circuit design lifted straight out of the application notes from the manufacturer of the DAC chip.

Though maybe, just maybe, they were taking distant construction-technique inspiration from "dead bug" RF circuit prototyping -- e.g., http://www.opencircuits.com/Dead_bug_style -- and thought it would help with audio.

Doubtful, though. Mostly it looks like cheap hand-crafted bodgery.
 
Close to the edge I reckon. ;)

It looks like the two caps are two commonly derived but perhaps separate Vcc supplies according that schematic or maybe one for each channel.

I'd say the most expensive part of that phono stage is the stainless steel case, but it is an absolute work of art compared to 47 labs Shigaraki DAC pictured below:

View attachment 1118347

Rat's nest design that cost $1.5k...

Here is a hilarious translation (probably google):

http://modama.net/47lab/dac01_e.html

"Circumstance plug price being large amount, to open the wallet, it was something where courage is."

"The hot water of the potato it divides Shigaraki DAC, With, it seems that stops wanting to murmur absentmindedly with the dense eye"
They actually call it a "transretion."
 
I agree, and originally wrote a description about how you need to hit somewhere between the 27 volts DC required by the regulator, but ideally come nowhere near the 35 volt limit of the power supply caps. 20 volts AC inpuhint, 20 VAC * 1.41 - 2 * 0.7 = 26.8 VDC and assuming some load, will be just a hair below the minimum required to achieve regulation and thus may be unstable. Unless it was intended to run on a 21 volt adapter -- unusual -- the next step after 20 volts in common adapter availability is usually 24 volts. At least one other (very similar) Royal Device phono preamp is 24 VAC.

Then I deleted that from my post, figuring it would just add confusion.

Electrolytic caps should be run at approximately 50% their rated voltage, for maximum life. 17 volts DC is below what will regulate, so I wonder if the two filter caps are in series (voltage rating is then additive) or it was simply designed a bit close to the edge.

Do you think this will do it, Dave? Or not enough amps?

https://www.ebay.com/itm/U-S-ROBOTI...e=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649
 
I shoulda studied more in school. The spec sheet says "Power Consumption: 1.5watts"

And I found this conversion chart

How to convert 1 amp to watts
How to convert electric current of 1 amp (A) to electric power in watts (W).

You can calculate (but not convert) the watts from amps and volts:

1A to watts calculation with voltage of 12V DC
For DC power supply, watts are equal to amps times volts.

watts = amps × volts

watts = 1A × 12V = 12W

1A to watts calculation with voltage of 120V AC
For AC power supply, watts are equal to the power factor times amps times volts.

watts = PF × amps × volts

For resistive load without inductors or capacitors, the power factor is equal to 1:

watts = 1 × 1A × 120V = 120W

So if I have:



watts = .500a x 20v = 10w?

of course it says "without inductors or capacitors" so what do I know. I just hope it works. I bought it. :)
 
I agree, and originally wrote a description about how you need to hit somewhere between the 27 volts DC required by the regulator, but ideally come nowhere near the 35 volt limit of the power supply caps. 20 volts AC input, 20 VAC * 1.41 - 2 * 0.7 = 26.8 VDC and assuming some load, will be just a hair below the minimum required to achieve regulation and thus may be unstable. Unless it was intended to run on a 21 volt adapter -- unusual -- the next step after 20 volts in common adapter availability is usually 24 volts. At least one other (very similar) Royal Device phono preamp is 24 VAC.

Then I deleted that from my post, figuring it would just add confusion.

Electrolytic caps should be run at approximately 50% their rated voltage, for maximum life. 17 volts DC is below what will regulate, so I wonder if the two filter caps are in series (voltage rating is then additive) or it was simply designed a bit close to the edge.


I re-read your post and I'm still completely confused.


Sorry, guys, I keep reading "DC output" and "AC voltage". What should I be feeding this preamp? I bought one tranformer that puts out 20VDC and one that puts out 20VAC (yes, I did actually order TWO because I got so confused. :()

So which damn one should I plug into it?

:bs:
 
The external plug on the device expects AC power.

The power supply stages are the external plug, the rectifier (inside the unit), the filter capacitors, and finally the voltage regulator. The rectifier inside the device turns AC into pulsating DC. The filter capacitors turn the pulsating DC into smooth DC, and voltage regulator further smooths and regulates the DC to power the preamplifier.

The voltage regulator emits 24 volts DC. It expects 27 or more volts DC as input. The filter capacitors' maximum DC rating is 35 volts, but you want to keep the voltage well below that to extend the life of the capacitors.

Therefore, we need to determine what AC voltage needs to be supplied to the device to wind up with 27 volts at the input of the voltage regulator, as follows:

The pulsating DC voltage that will come from the rectifier and be supplied to the voltage regulator will be the AC voltage at the external plug times 1.41 (to convert RMS AC measurement to DC peak) minus the voltage drop of the rectifier which is roughly 2 times 0.7 because each silicon diode inside the full-wave rectifier has a voltage drop of roughly 0.7 volts, and two diodes will be in series with the supply at any time. Thus, given an AC voltage of 20 volts at the external plug, the DC voltage going into the regulator will be 20 times 1.41 minus 2 times 0.7, which is 26.8 volts DC.

In other words, a 20 volt AC input to the device will produce 26.8 volts DC at the input to the voltage regulator. That's just a smidge below what the regulator requires according to its data sheet, but it's well below the voltage limit of the capacitors and so it will probably be fine.

In short, the device should work with an external AC power supply of 20 volts.
 
Last edited:
The external plug on the device expects AC power.

The power supply stages are the external plug, the rectifier (inside the unit), the filter capacitors, and finally the voltage regulator. The rectifier inside the device turns AC into pulsating DC. The filter capacitors turn the pulsating DC into smooth DC, and voltage regulator further smooths and regulates the DC to power the preamplifier.

The voltage regulator emits 24 volts DC. It expects 27 or more volts DC as input. The filter capacitors' maximum DC rating is 35 volts, but you want to keep the voltage well below that to extend the life of the capacitors.

Therefore, we need to determine what AC voltage needs to be supplied to the device to wind up with 27 volts at the input of the voltage regulator, as follows:

The pulsating DC voltage that will come from the rectifier and be supplied to the voltage regulator will be the AC voltage at the external plug times 1.41 (to convert RMS AC measurement to DC peak) minus the voltage drop of the rectifier which is roughly 2 times 0.7 because each silicon diode inside the full-wave rectifier has a voltage drop of roughly 0.7 volts, and two diodes will be in series with the supply at any time. Thus, given an AC voltage of 20 volts at the external plug, the DC voltage going into the regulator will be 20 times 1.41 minus 2 times 0.7, which is 26.8 volts DC.

In other words, a 20 volt AC input to the device will produce 26.8 volts DC at the input to the voltage regulator. That's just a smidge below what the regulator requires according to its data sheet, but it's well below the voltage limit of the capacitors and so it will probably be fine.

In short, the device should work with an external AC power supply of 20 volts.


Thanks, Dave. Very informative. I appreciate it. Today I learned something!
 
Why did I know I was going to end up with $25 worth of adapters that didn’t work. So the plug on the DC output you and it fits, but the plug on the correct AC output unit does not fit. God I hate adapters. So can I cut the plug off the DC adapter and splice it on the AC adapter or is everything going to go boom!




 
Yes, you can cut the plug off the DC adapter and graft it onto the AC adapter.

No boom.


Sir, no boom. Thank you for your help. Green light, as you can see. Been playing for a few hours and sounds quite nice. It came alive after about 30 mins of warm up and I am pleased, although I don't have much to do a shootout with. My first dedicated phono preamp! A happy poor audiophile. And now I shall reveal -- per the spirit of Audiokarma -- I paid $2.99 cents for it at the thrift store. Who prices something labled "finest hand-made Italian audio..." two dollars and ninety-nine cents? Anyway, thank you, Dave. I didn't want to wreck it!




 
Last edited:
Back
Top Bottom