hi friends,
glad to come back after a long interruption. I start with a smooth project. I have 4x 8ohm non inductive resistances. It gives me idea of an audio dummy load with wattmeter, something like sencore PA81.
For dummy load part, I think of
for wattmeter I think of something around AD637.
advices are welcome and if something exist, I don't want to reinvent wheel
glad to come back after a long interruption. I start with a smooth project. I have 4x 8ohm non inductive resistances. It gives me idea of an audio dummy load with wattmeter, something like sencore PA81.
For dummy load part, I think of
- 4 to 8 ohm switch with extra contacts for correct display value
- thermal switch for fan
- DC protection warning
- BNC output
for wattmeter I think of something around AD637.
advices are welcome and if something exist, I don't want to reinvent wheel
Attachments
Plug your amp into something like this.
Many functions.
Panel mount version also.
Was $30 or so here.
I believe he is talking about a watt meter for amplifier output into speakers not the power used by the whole amp. That’s the idea behind the 4 and 8 ohm load resistors.
Agreed. On the other hand these AC-power-input meters are very useful as well, a must-have imho
yes, it's audio watt meter inspired from sencore PA81 audio analyzer.
Switching power resistors is the first problem to resolve: Mecanical, relay,... ?
with 4 x 8R resistors I would like to get
-stereo 8 ohm 500W
-stereo 4 ohm 1000W
-mono 8 ohm 2000W
LTC1966 with 6KHz BW seems correct for line measures but not enough for audio. May explain lower price.
Switching power resistors is the first problem to resolve: Mecanical, relay,... ?
with 4 x 8R resistors I would like to get
-stereo 8 ohm 500W
-stereo 4 ohm 1000W
-mono 8 ohm 2000W
LTC1966 with 6KHz BW seems correct for line measures but not enough for audio. May explain lower price.
For the watt meter, it is simple subtraction of amplifier losses from total input.
For true RMS output measurement, you need a complex integrating unit, very expensive.
There is a thread here somewhere about it.
Not new.
For true RMS output measurement, you need a complex integrating unit, very expensive.
There is a thread here somewhere about it.
Not new.
I am a little bit concerned about the LTC1966 - the BW being independend on the input level is surely a nice feature, but if you check the datasheet to almost the button there is a graph showing the lineary around 0.
It is shown for 3 representative units and as I read it the linearity is unpredicable below 2mV input - and the "Electrical Characteristics" also states that minimum input is 5mV rms.
This device seems to be aimed at applications using a default 200mV display.
If used this way the usable range is not going lower than 2.5% of full range
The AD637 can be a lot better in comparison.
BTW: the lower price is likely based on the different technique used for the RMS conversion - the AD637 is laser trimmed to achieve its accuracy, whereas the precision of the LTC1966 is inherent in the conversion method (Delta-Sigma).
Cheers,
Martin
The bandwidth of the 1966 falls off, but is useful out beyond 20 kHz. That's not where you'll find significant audio power or none of us would have tweeters. The low level performance might or might not be an issue. I can't see much interest in very low level power measurements, but my desire for elegance makes the lack of performance down there annoying. I've used AD637 in the past, but it was way cheaper back then. Might look at AD737 too. That's about $11.50 from Digikey. Note that all these converters have some limitations at the extremes.
thanks for sharing these informations about lt1966.
I also found low priced boards like :
https://www.velleman.eu/downloads/0/infosheets/k8098_uk.pdf
May be not interesting to develop something...
Dissipation of 1KW need efficient workflow. A tunnel with two fans on each side was my first idea. But someone may have better solution ?
I also found low priced boards like :
https://www.velleman.eu/downloads/0/infosheets/k8098_uk.pdf
May be not interesting to develop something...
Dissipation of 1KW need efficient workflow. A tunnel with two fans on each side was my first idea. But someone may have better solution ?
If it helps: I'm using the LTC1968 in the autoranger. Wideband and reasonable accurate.
You probably don't need to be accurate to the mW anyway.
Jan
You probably don't need to be accurate to the mW anyway.
Jan