Also, I think You got mixed up the file names.
The kaiser win. File shows 0.000097% and not the other way around..
The kaiser win. File shows 0.000097% and not the other way around..
It's too bad there wasn't tighter integration with the RTX unit and application controlling it. When I'm working with an amplifier, I have to connect a meter to see how much output voltage I have to determine what power the amp is delivering. That's one thing the old 339A does well, you can read the oscillator level and the input level. From there the exact gain is easy to figure out. Not with this solution.
-Chris
-Chris
The RTX is factory calibrated, as long as you know where you are relative to dBFS and the range it is pretty easy to figure out what the output voltage fed to the amplifier is. Should be equally true for inputs as long as gain/attenuation at the input of the instrument is known.
There may eventually be software that can use the I/O attenuator API directly which would make things easier.
As with anything new there is a learning curve/accommodation.. I still have rather a long way to go, but I am at this point a casual user..
Most of the measurements I use this for are relative.. Frequency response measurements, gain measurements, and thd distortion relative to the fundamental. Mostly not very sophisticated stuff.. I've not yet tried a multitone test on anything other than loop back.. I'm not repairing anything and use it mostly as a design aid, and it produces output that I can compare directly with my simulations.
There may eventually be software that can use the I/O attenuator API directly which would make things easier.
As with anything new there is a learning curve/accommodation.. I still have rather a long way to go, but I am at this point a casual user..
Most of the measurements I use this for are relative.. Frequency response measurements, gain measurements, and thd distortion relative to the fundamental. Mostly not very sophisticated stuff.. I've not yet tried a multitone test on anything other than loop back.. I'm not repairing anything and use it mostly as a design aid, and it produces output that I can compare directly with my simulations.
Hi Kevin,
Yes, you can calculate what level you are actually seeing, but it is faster to simply measure it. You also don't make a silly mistake doing that.
-Chris
Yes, you can calculate what level you are actually seeing, but it is faster to simply measure it. You also don't make a silly mistake doing that.
-Chris
I was just wondering, all the measurements here use 1KHz, wouldn’t a sweep show more information?
You can change the vertical scale to dBV, and display the signal amplitude directly without calculation, provided you’ve done the calibration.
If you don’t even want to bother with the calibration procedure, with RTX it’s very convenient, you simply enter the factory calibrated values in mV and you’re good to go (that’s what I usually do, takes no more than 10 seconds)
Most software analyzers can be calibrated for the voltage levels at the "soundcard" inputs and outputs. My software can work with the exact voltages present at the inputs and the outputs. I would be very surprised if ARTA can't do that.
I get the impression that you're a bit disapointed with your new toy. I'd be happy to buy your RTX6001 if you would like it to find a new home 😀
mrbrennwa, I feel slighted now, you beat me too it.
Chris, I understand your frustration.
George, That may be true, and Chris does have a point.
In prior history (including the "big dog" of instruments in Nord Amerika ist A.P. for measuring THD, THD+N, etc.
I am here to report there is bias people.
When I got my little QA400 (before the QA401) and after RNMarsh posted that we should all agree to use the flat top window for the THD and THD+N measurements. I read through the attachment he made of AP recommendations.
After I read the AP recommendations, I mentioned no, we need to use the Hann window for it and stated that it was in the AP Manual. Well who was I to tell the powers that be...so everyone agreed to use the Flat Top window (because of bias) and the numbers were lower on measurements.
Much of the work on the HP339A was done using FlatTop.
However, somewhere along the line after the HP339A threads they got religion and changed over to the proper window, that being Hann.
I can't comment on the newer Kaiser7, other than it sounds Russian. Oder Oesterreichen auch. I don't have umlots on this keyboard either. Es tut mir lied. But I can say this and most should understand it.
Trink I (EEE) ein Bier! Sauf Aus.
Cheers Mates,
Chris, I understand your frustration.
George, That may be true, and Chris does have a point.
In prior history (including the "big dog" of instruments in Nord Amerika ist A.P. for measuring THD, THD+N, etc.
I am here to report there is bias people.
When I got my little QA400 (before the QA401) and after RNMarsh posted that we should all agree to use the flat top window for the THD and THD+N measurements. I read through the attachment he made of AP recommendations.
After I read the AP recommendations, I mentioned no, we need to use the Hann window for it and stated that it was in the AP Manual. Well who was I to tell the powers that be...so everyone agreed to use the Flat Top window (because of bias) and the numbers were lower on measurements.
Much of the work on the HP339A was done using FlatTop.
However, somewhere along the line after the HP339A threads they got religion and changed over to the proper window, that being Hann.
I can't comment on the newer Kaiser7, other than it sounds Russian. Oder Oesterreichen auch. I don't have umlots on this keyboard either. Es tut mir lied. But I can say this and most should understand it.
Trink I (EEE) ein Bier! Sauf Aus.
Cheers Mates,
The single-frequency tests provide considerably better signal-to-noise ratio. The sweep methods provide the general picture of the distortion throughout most of the full spectrum, but the signal/noise ratio is probably insufficient for the kind of tests that were shown here in the past few posts (I haven't tried it though).
Hi mbrennwa, cwtim01,
No, I'm just very accustomed to using self contained instrumentation. My biggest issues were that there are no knobs to twist. Getting past that is huge for me. The true power of this kind of instrument would be if scripts could be written so it would run tests automagically.
I will confess I forgot about the calibration, I think I did that when I first got the instrument. I'll run through it again. Earlier I did have it setup to read in voltages, but the dB scale is more convenient to use. Knowing the voltages is more important when setting amplifier output levels as I do measure at various common power levels. My normal points are at 1 watt and 50 watts (2.83V and 20V) across 8 ohm dummy loads. I will do full power measurements if there is a concern or request for that level.
Some of this is getting use to doing things a new way, but I think that an AC meter will always be needed to set output levels accurately. Not a deal killer as I had already considered this.
-Chris
No, I'm just very accustomed to using self contained instrumentation. My biggest issues were that there are no knobs to twist. Getting past that is huge for me. The true power of this kind of instrument would be if scripts could be written so it would run tests automagically.
I will confess I forgot about the calibration, I think I did that when I first got the instrument. I'll run through it again. Earlier I did have it setup to read in voltages, but the dB scale is more convenient to use. Knowing the voltages is more important when setting amplifier output levels as I do measure at various common power levels. My normal points are at 1 watt and 50 watts (2.83V and 20V) across 8 ohm dummy loads. I will do full power measurements if there is a concern or request for that level.
Some of this is getting use to doing things a new way, but I think that an AC meter will always be needed to set output levels accurately. Not a deal killer as I had already considered this.
-Chris
Yes I have the AC voltmeter (and a fine one with true rms) always attached at the output.
Also smelling the load for heat dissipation. No smell no joy..
Sometimes fantastic results can be obtained without load 🙂
Ciao, George
Also smelling the load for heat dissipation. No smell no joy..
Sometimes fantastic results can be obtained without load 🙂
Ciao, George
Hi George,
That is so true. Unloaded the output stage is a lot more linear. By the same token, measuring on 4 ohms or lower really degrades the performance.
-Chris
That is so true. Unloaded the output stage is a lot more linear. By the same token, measuring on 4 ohms or lower really degrades the performance.
-Chris
Hi Sync,
Links work - thanks.
Did Ap use an offset for the lower FFT? Also, that is a mighty good notch filter they have!
-Chris
Links work - thanks.
Did Ap use an offset for the lower FFT? Also, that is a mighty good notch filter they have!
-Chris
Avoiding ground loops
Let's say someone uses the RTX to test an amplifier. The amp has RCA inputs only, and it has a three-pronged mains connector that connects the audio GND to safety earth. The RCA input of the amp is connected to the RTX using the RTX BNC connector or using an XLR-to-RCA converter on the RTX XLR connector. In such a setup, the chassis of the RTX and the amp are connected to each other (1) via the shield of the RCA cable and (2) via the safety earth connections of the mains cables. This is just another way of saying there is a ground loop.
What is the best way to avoid this ground loop and the associated noise/hum that will enter the test setup?
Let's say someone uses the RTX to test an amplifier. The amp has RCA inputs only, and it has a three-pronged mains connector that connects the audio GND to safety earth. The RCA input of the amp is connected to the RTX using the RTX BNC connector or using an XLR-to-RCA converter on the RTX XLR connector. In such a setup, the chassis of the RTX and the amp are connected to each other (1) via the shield of the RCA cable and (2) via the safety earth connections of the mains cables. This is just another way of saying there is a ground loop.
What is the best way to avoid this ground loop and the associated noise/hum that will enter the test setup?
Hi mbrennwa,
Use the positive phase for signal, and the negative phase (180°) for the common RCA ground. You do the same with measuring the output if the amplifier. That should break the loop nicely.
I already connect to the outputs that way and I have to make some custom cables in order to do that with an RCA type connector. (like a preamplifier or signal processor)
-Chris
Use the positive phase for signal, and the negative phase (180°) for the common RCA ground. You do the same with measuring the output if the amplifier. That should break the loop nicely.
I already connect to the outputs that way and I have to make some custom cables in order to do that with an RCA type connector. (like a preamplifier or signal processor)
-Chris
Also good for connecting to home brew breadboards.
Quicker, easier and cheaper.
GLS Audio XLR-M to RCA Patch Snake Cables - 3ft Colors Home Studio Series - 6 Pack
Be careful and order cables with both genders of XLR’s.
DT
Won't these cables connect the XLR "cold" pin to the chassis pin and the RCA shield like an XLR-to-RCA adapter?
At $25.99 US each pak, they aren't a bad price. They are sold out. Now, if they come back at list, they can keep them!
I wonder if they ship to Canada, and will they use USPS?
-Chris
Looks like they won't ship to Canada. The only country you can select in shipping is the USA.
I wonder if they ship to Canada, and will they use USPS?
-Chris
Looks like they won't ship to Canada. The only country you can select in shipping is the USA.
FALSE ALARM
These cables are not wired as #17 in the Rane note.
XLR Pin #2 is connected to the tip of the rca. Pins 1 and 3 plus the XLR shell are connected to the grounded shell of the rca.
GLS Audio XLR-M to RCA Patch Snake Cables - 3ft Colors Home Studio Series - 6 Pack
DT
These cables are not wired as #17 in the Rane note.
XLR Pin #2 is connected to the tip of the rca. Pins 1 and 3 plus the XLR shell are connected to the grounded shell of the rca.
GLS Audio XLR-M to RCA Patch Snake Cables - 3ft Colors Home Studio Series - 6 Pack
DT