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

Get a pretty good idea once you find the regulated PS within and see what voltage size the capacitors are. I 'm betting its opamp based.
 
bridge rectifier implies AC input. The 3 legged TO-220 case device is probably the voltage regulator. Whats the voltage on the big caps? Whatever it is, divide by 1.4 and thats the max AC input it could possibly be.

4 transistors per channel, could still be phono preamp.
 
It does look like a phono pre. As for the screw, maybe it was left handed threads to throw you off. :naughty: Maybe try something like 18v to start with? I keep a couple wall warts around with voltage selectors and different power jacks. One goes from 6v to 24v
 
It does look like a phono pre. As for the screw, maybe it was left handed threads to throw you off. :naughty: Maybe try something like 18v to start with? I keep a couple wall warts around with voltage selectors and different power jacks. One goes from 6v to 24v


I guess. I wonder what voltage would be typical in Italy? :angel:"

Well, phono pre is a good find, as I currently don't have a dedicated one. I must say the components sure look a little "budget." Cheap Taiwanese "Elite" caps. Ehhh?
 
chadbag: Uhm, why don't you simply identify the voltage regulator?

Greetings from Munich!

Manfred / lini
 
Please post whatever is written on the body of the component I've circled in red. It is (likely) a voltage regulator, and identifying it will help determine the minimum AC voltage needed to run the unit.

unit.jpg
 
I must say the components sure look a little "budget." Cheap Taiwanese "Elite" caps. Ehhh?
They're power supply filter and bypass caps. Premium components in that role wouldn't make any appreciable difference.

The unit as a whole looks like typical consumer-grade electronics in a chunky case.
 
So some good researchers over at the Steve Hoffman Forum found this!!!

ROYAL DEVICE - BLUE EYES PHONO STAGE

COMPLETELY NO FEEDBACK even locally SINGLE ENDED CLASS A Junction FET PASSIVE RIAA PHONO STAGE.

BEfonoBottom.jpg


The Blu Eyes RUBINA is derived from the professional RUBINA PHONO STAGE. It features a smaller cabinet in shining stainless steel BUT NO Step-up neither OUTPUT transformers. Suites to all MM and MC cartridges with an output level above 1 milliVolt, and it can drive even power amps with at least 0,5-0,6 volt input sensitivity. If connected to a preamp the possibility to drive also cartridges with output level of 0,5 millivolt is possible instead. The reason to use a JFET circuitry instead of tubes it is due to the high gain obtainable without the use of Feedback, still keeping a very low noise. Moreover, with discrete JFET circuitry we can afford valve sound without entering the microphonicity problems. Metalized polypropylene 2% capacitors used onto the PAssive RIAA circuit. Only discrete components. No ICs or SMD used at all. Please see schematics hereafter.


Phono Input: MM/MC high level

Input Impedance: MM/MC high level 47 Kohm

Frequency Response: 25Hz to 20,000Hz +/- 0,3 dB; SUBSONIC PASSIVE FILTER - 2,5 db @ 20 Hz

Harmonic Distortion: less than 0.2%

MM Sensitivity: 1 mVolt input for 0,5 Volt output @ 1 KHz (54 dB)

Total MM gain: 54 dB

Output impedance: minimum 600 ohm load - suggested above 1500 ohm

Maximum Output Voltage: 2,9 Vrms on 600 ohm load - 5 Vrms on 1500 ohm load

Amplification: Two stages JFET Single Ended NO FEEDBACK even locally - grounded source modality.

MC S/N Ratio: 89 dB S/N measured in respect to max output

Power Consumption: 1,5 W

Dimensions (W x D x H): 150 x 75 x 50 mm

Weight: 1,3 Kg - 3 pounds

Chassis Finish: SHINING STAINLESS STEEL Die casting 4 mm or SMOOTH STAINLESS STEEL

Remarks: Inputs for MM and MC high level cartridge - PASSIVE RIAA - Any channel and stage with completely separated internal power supplies - RIAA with ALIANTE AUDIOCAP polypropylene capacitors 2% and 1% resistor - HIGH-END Connectors - External p.s.u. transformer

BLUEYESfonoschema.jpg


DONNA <<<<< This is the link to the Wayback Machine webpage for this. It may take a little longer to load. (Thanks to Ham Sandwich)
 
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24volts AC is a bit too high. That will result in approximately 33.5volts after rectification and a diode drop- close to the limit of the caps.

around 19.5-20v is better.


Lenovo makes a 20v 1.5a AC adapter. What do you think of that supply being safe? Thanks!
 
It would be safe, but I'm not a big fan of SMPS (switched mode power supplies) near a high gain, fet input phono stage.

Go linear (transformer) - you may find at a thrift store a nice little plugpack/wallwart from a christmas tree lighting set for a dollar, they often have 20v AC. You don't need much current.
 
24volts AC is a bit too high. That will result in approximately 33.5volts after rectification and a diode drop- close to the limit of the caps.

around 19.5-20v is better.
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.
 
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...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...

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:

shigaraki 47labs.JPG

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"
 
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