XPR-1 lights: a measure of instantaneous voltage?

[etc6849]

I'm curious about the internal workings of what exactly the LEDs indicate?

There are 12 vertical LEDs, does each light consist of an equal voltage range?  E.g. if voltage is <2x but > than 1x, does that mean two LEDs will light, and if so, what is the voltage value for x?

I wouldn't think the arm7 processor would be calculating instantaneous power?

PS: I'm not asking about peak mode, but normal mode where transients seem to light up a bunch of lights very fast, and then they quickly turn off as the music gets quieter.

[leonski]

Sounds reasonable to me!
If you hooked a 'Scope to your speaker terminals you'd see voltage peaks IN TIME to the Ladder LED Display. No magic computer circuitry needed. Maybe a voltage divider net composed of 1% resistors?

[leonski]

Like THIS circuit:

I see OPAMP versions which have VERY high input impedance and Should have NO audible effect.
The link here is for a 'cheap-o' version which might have adverse sonic impact.


Basic resistor type power indicator:

www.redcircuits.com/Page102.htm

[stiehl11]

Dec 10, 2015 23:23:56 GMT -5 etc6849 said:

I'm curious about the internal workings of what exactly the LEDs indicate?

There are 12 vertical LEDs, does each light consist of an equal voltage range?  E.g. if voltage is <2x but > than 1x, does that mean two LEDs will light, and if so, what is the voltage value for x?

Lonnie has said in the past that the LEDs are logarithmic in scale. I've assumed a base of 1 when looking at my LEDs.

[DavidR]

I guess I've had it wrong all these years. I always thought it indicated wattage in a linear form; e.g. 100 watts rms per channel and 10 LED lights per channel, each light would indicate 10 watts.

[leonski]

If it is a voltage indicator, the 'power' indicated will depend very much on the IMPEDANCE of the speaker in question.

That would be 1watt= 2.83 volts @ 8 ohms.
For 4 ohms? The same 2.83 volts is 2 watts.

If the lights are distracting, put TAPE over 'em.
LISTEN for distortion and don't get too wrapped around the axle with 'power'. In general, (very general) you may get a real loud stereo with 20 watts RMS. At that point? you MIGHT have 200 watt PEAKS.
That's a 10db 'crest factor'.

If you tell the user that the lights are in Watts? Who cares? If the 1 watt light lights with 2.83 volts into an 8 ohm resistor, that's about as good as it will get. REAL speakers are all-over the place, impedance-wise.

[etc6849]

Thanks guys! So it appears it is using voltage, but scaled using a logarithmic function. Makes sense.

I agree on the listening for harshness/distortion. I heard some of that before on very dynamic recordings at their peaks. Not anymore though since I added the XPR-1's! I'm pretty sure they will never clip or have rail sagging even though my speakers have some nasty impedance dips.

[novisnick]

Mar 12, 2016 23:51:45 GMT -5 etc6849 said:

Thanks guys! So it appears it is using voltage, but scaled using a logarithmic function. Makes sense.

I agree on the listening for harshness/distortion. I heard some of that before on very dynamic recordings at their peaks. Not anymore though since I added the XPR-1's! I'm pretty sure they will never clip or have rail sagging even though my speakers have some nasty impedance dips.

Clip,,,,,,,thats for toe nails!!,,,,,,,,,he,,,,,,he,,,,,,he,,,,,,,,

[leonski]

Mar 12, 2016 23:51:45 GMT -5 etc6849 said:

Thanks guys! So it appears it is using voltage, but scaled using a logarithmic function. Makes sense.

I agree on the listening for harshness/distortion. I heard some of that before on very dynamic recordings at their peaks. Not anymore though since I added the XPR-1's! I'm pretty sure they will never clip or have rail sagging even though my speakers have some nasty impedance dips.

20 amp circuit for the XPR-1s?    To get the rated power OUT of this amp, that's what it'll take.