Power Meters on Gen4 Amplifiers - Please

[ttocs]

Jun 22, 2020 17:06:14 GMT -5 audiobill said:

ttocs, the bias is the dc grid voltage that "biases" the tube into a controlled state of cathode emissions to the plate. The AC musical signal "rides" on this DC voltage, and causes changes in the plate voltage as a result of varying cathode emissions, thereby amplifying the signal.

For your M125s with four output tubes, your bias at 1vdc is correct, and you shouldn't expect to see a lot of variation from your input signal, it hasn't really been amplified at this point.

Bill

Thanks Bill!
I really didn't know what to expect, hence the interest in experimenting, however, I was thinking that the bias would change with power level - somehow.

These amps are Class AB, correct?

[audiobill]

Yes, AB

[ttocs]

leonski, excellent links, thanks again!

[emotifan]

I'm still using the XPA-2 gen2 and I find the meters look so silly I turn them off. When they are on they're jumping so far towards maximum output at moderate volume levels that I doubt they're even accurate. And what good are they without reference numbers to see what power they are displaying?

[vcautokid]

I always wondered about the meters too. You want at least more gradation or a range that goes green yellow and then red at least if no markings are going to be used.

[markscho]

I find the XPA2 GEN2 Meters to give a good ballpark of output of the AMPs and the sound output. I do run sensitive speakers so that may have something to do with it as three blues spheres solidity lite up and few more flickering and it is extremely loud and the neighbors complain a few houses down

KeithL >. Make some meters happen for us with the DR1s GEN4 or at least a special option if technically and financial feasible for EMO . Analog Meters - Return of the Blue Spheres - Bars - whatever your choice.

[405x5]

Jun 11, 2020 22:29:29 GMT -5 markscho said:

Hi All

It would be great to get power meters on the XPA DR1 Gen4 when they come.  Analog or digital.  Even an option to custom order amps with Power Meters would be good with the same power meters that came on the XPA1 Gen2 to save cost & complexity of manufacturing  for Emotiva. I run a pair of XPA2 Gen2s Vertical Bi-Amped and have held out for new amps with power meters.  I would gladly pay up for some meters 


Thanks and Thoughts 

Don’t hold your breath....those days are over, me thinks

[ttocs]

Here's your meter!

[DavidR]

Or in Emo Blue

[markscho]

[dragonV]

youtu.be/HKTR07n0YTo

Oled meters

[leonski]

Meters above marked as VU, not power in watts. You might be able to hook them up in some low level circuit, than adjust to audible distortion, then back off with the meter just 'flickering' to +3db......
That may be nice to watch but certainly not what I'd call useful.

Might Keith or Lonnie chime in on the difference between a VU meter and a Power Meter?

Just a thought, but a good, fast, DVM set for AC volts would work. IF you knew the max output voltage of the PS.....But you are still NOT addressing speaker distortion which trumps output power.

[donh50]

Power meters usually display average power in Watts. Actually, they usually display voltage or current, converted to watts by the meter's scale, so impedance is assumed. Some do display true power since there are chips (ICs) that will do that for you now. A log scale is almost always used as that corresponds better to our hearing and as others said makes the meters bounce more.

VU is actually a 1940's-era (I think) standard -- the volume unit. It was (and is) pretty much the standard used in broadcast studios and the like. IIRC, a reading of 0 VU is technically 1.228 Vrms across a 600 ohm load (+4 dBu -- 0 dBu is 1 mW into 600 ohms) at 1 kHz. Edit: Here's the original paper - www.aes.org/aeshc/pdf/chinn_a-new-svi.pdf - I was able to pull it up without logging into the AES site. I have a vague memory that the original meter was based on a 200 uA coil but don't quote me on that.

As discussed previously by others, the bias current ideally will not change in normal operation, and so is not any fun to watch except when you are setting the bias of the amp. Actually, it's not really fun then, just a chore to be done before the music starts and the real fun begins. BTW, tubes are thermionic devices, so let them warm up a good long while 30 minutes or more before setting the bias.

FWIWFM - Don

[leonski]

I can't imagine ANY 'power meter', even with a 'chip', being anything close to accurate in displaying real power. MAYBE if the speaker manufacturer would provide the impedance / phase data on a flash drive to be downloaded INTO the chip in the amp so the correct conversion could be done.
This is nutty, of course, since many manufacturers don't have that data and even many speakers rated at a given impedance would more properly be another value....

Even transistors should be given time to get to a stable temp. If the amp has a cover or case, USE IT, since that materially effects the amps temp...

I LIKE the bias meter, which is fine ona high bias amp. Those 10 or so watt 'in class A' amps could easiy be seen slipping toward A/B as the bias started 'wiggling'....IMO? More useful than power which is Meaningless, except as a number maybe to be compared and bragged over.

The last point is one of meter ballistics. I'd bet that was part of the standards. My meters on my Tandberg 3000x Reel-to-Reel are to the standard ON PLAYBACK and substantially more 'lively' during record.

More important than VU or Power is WHERE in the circuit they are used and potential comparison of benefits if properly used.

[donh50]

The power monitor chips measure voltage and current on the fly so can get a "true" average power level without knowing the impedance. Not sure they have much bandwidth, however, not my area.

[audiobill]

Jul 3, 2020 20:23:41 GMT -5 DavidR said:

Or in Emo Blue

Not possible - McIntosh has a trademark on that specific shade of blue.

Maybe "Wannablue" instead?

[leonski]

I'd suggest paying BIANCHI a royalty to use their trademark color.......Celeste. Named after the daughter of the founder.
This is an amazing green color and apparently varied some over the years......


veloaficionado.com/blog/when-the-new-dog-digs-up-the-old-dog-part-4

[markscho]

Anyone have any thoughts on when the XPA / DR Gen 4s will be released. Assuming next year as think that will be year 6 of the Gen3s - Suppy Chain issues not withstanding

[Boomzilla]

Power meters? REALLY? The standard VU meters aren't accurate. They take away $$$ that could be spent on sound quality instead. I'd rather have a silver color option than to have meters. Black is just so blah on amplifiers... The silver color would also serve to identify the Emotiva Generation 4 amplifiers from their predecessors. Want meters? Get that app that displays meters on your TV screen.

[klinemj]

Dec 21, 2021 13:42:57 GMT -5 Boomzilla said:

Power meters? REALLY? The standard VU meters aren't accurate. They take away $$$ that could be spent on sound quality instead. I'd rather have a silver color option than to have meters. Black is just so blah on amplifiers... The silver color would also serve to identify the Emotiva Generation 4 amplifiers from their predecessors. Want meters? Get that app that displays meters on your TV screen.

Who cares if they are not accurate? The bouncing bliss of seeing the needles move is all most people need! As for me..."meh, one more think that could break". "Whatev's..."

Mark