I recently finished my BA3 build and I was curious about setting P3 for minimum distortion. Not having a distortion analyzer I looked at the TrueRTA which I had heard people talk about on the forums.
The free version is 1 octave and useless for this application, so I went ahead and picked-up the 1/24 octave version, my signal generator was a cheap Chinese one anyway. For me, it was $100 well spent as it allowed me to adjust my BA3 and my F5T for the lowest distortion.
Setting up the software to use with my Asus Xonar soundcard was straight forward, the first photo is with P3 misaligned and the second photo is after adjusting for minimal distortion. With P3 set at the midpoint, the distortion reading wasn't too bad, but I adjusted it out more so it would illustrate P3 working.
I've also included a picture of the distortion measurement of the Whammy and one of the Bottlehead Crack. I did the crack just to see the noise floor and as I expected it increased and the second harmonic distortion was more evident.
For my BA3 I used a TPS7A3301 dual power supply that I bought from Owen when he was selling his Wire headphone amp boards.
I found this software to be a useful tool, I'm not sure if it would have been possible to use the 1/3 or 1/6 octave software which they sell for less money to accomplish these adjustments? I'm guessing it wouldn't be very effective.?
The free version is 1 octave and useless for this application, so I went ahead and picked-up the 1/24 octave version, my signal generator was a cheap Chinese one anyway. For me, it was $100 well spent as it allowed me to adjust my BA3 and my F5T for the lowest distortion.
Setting up the software to use with my Asus Xonar soundcard was straight forward, the first photo is with P3 misaligned and the second photo is after adjusting for minimal distortion. With P3 set at the midpoint, the distortion reading wasn't too bad, but I adjusted it out more so it would illustrate P3 working.
I've also included a picture of the distortion measurement of the Whammy and one of the Bottlehead Crack. I did the crack just to see the noise floor and as I expected it increased and the second harmonic distortion was more evident.
For my BA3 I used a TPS7A3301 dual power supply that I bought from Owen when he was selling his Wire headphone amp boards.
I found this software to be a useful tool, I'm not sure if it would have been possible to use the 1/3 or 1/6 octave software which they sell for less money to accomplish these adjustments? I'm guessing it wouldn't be very effective.?
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That one looks like it does a nice job. Does it work using a PCI sound card or do you need to use the USB interface?
I haven't used this type of software before but I was impressed with the ease of using TrueRTA, I didn't need to buy the USB interface or make up a dummy load. I just used BNC to alligator clips and used the headphones for a load on the Whammy and the Crack.
I'm guessing with one of the USB interfaces the noise floor would be lowered a little bit, but for my application, it worked fine using the ASUS sound card.
I haven't used this type of software before but I was impressed with the ease of using TrueRTA, I didn't need to buy the USB interface or make up a dummy load. I just used BNC to alligator clips and used the headphones for a load on the Whammy and the Crack.
I'm guessing with one of the USB interfaces the noise floor would be lowered a little bit, but for my application, it worked fine using the ASUS sound card.
Nice! I am interested in doing this, but will use different hardware and software. Can you describe how you connected the amp to your sound card? (i.e., to avoid damaging the sound card)?
You need to first set-up the sound card or USB interface with the software using a jumper going from the output to the line-in and doing the line-out and line-in calibration.
I went directly from the output on the soundcard and used the output of the BA3 directly to the line-in on the sound card using RCA's to 3.5mm stereo jack.
I just found it easy to use and thought I would share it with people that wanted to set-up their BA3's or other PASS units.
The one that Ben shared looks to do the same thing albeit with a little more effort.
I went directly from the output on the soundcard and used the output of the BA3 directly to the line-in on the sound card using RCA's to 3.5mm stereo jack.
I just found it easy to use and thought I would share it with people that wanted to set-up their BA3's or other PASS units.
The one that Ben shared looks to do the same thing albeit with a little more effort.
I don't know whether a built-in sound card will work with REW, but if the sound card has line out and line in, it could possibly work. Since REW is free to use, you can install it and try it.
I like REW because it is simple to use and it gives numerical values to the harmonic distortion levels.
I like REW because it is simple to use and it gives numerical values to the harmonic distortion levels.
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