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Post by Blackdawg on May 20, 2020 0:11:03 GMT -6
I didn’t realize that was your interface loopback. Yeah, that doesn’t seem right at all. Is it better at a much lower level, like -30 dBFS? Same pretty much.
Edit: same shape of curves I should say. The overall levels of distortion are about 20dB lower but the percent is higher like 6.8%.
Have you checked your TAF connector? Nothing touching in there? Have you tried different channels? |
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grantb
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Post by grantb on May 20, 2020 0:17:36 GMT -6
Same pretty much.
Edit: same shape of curves I should say. The overall levels of distortion are about 20dB lower but the percent is higher like 6.8%.
Have you checked your TAF connector? Nothing touching in there? Have you tried different channels? Yes and yes. Tried all in and out channels and four different cables (all made by me with the good stuff but I double checked the pinouts, pin 2 hot 3 cold 1 gnd). Tried battery power also, same but slightly lower output and worse bass response. |
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Post by Blackdawg on May 20, 2020 0:36:41 GMT -6
Have you checked your TAF connector? Nothing touching in there? Have you tried different channels? Yes and yes. Tried all in and out channels and four different cables (all made by me with the good stuff but I double checked the pinouts, pin 2 hot 3 cold 1 gnd). Tried battery power also, same but slightly lower output and worse bass response. Huh curious. I'll try to get mine from work and measure it to see if it's similar. |
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Post by Blackdawg on May 20, 2020 10:18:33 GMT -6
Here is my Digi192 for reference. Older converter but still solid.   |
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grantb
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Post by grantb on May 20, 2020 13:11:29 GMT -6
Here is my Digi192 for reference. Older converter but still solid.
That is more like the distortion I was expecting to see from mine, sub -100. I'm curious about other MixPre 10s, if you or anyone else gets a chance to test. Thanks to you and dogears for your thoughts!
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Post by Blackdawg on May 20, 2020 13:16:51 GMT -6
Here is my Digi192 for reference. Older converter but still solid.
That is more like the distortion I was expecting to see from mine, sub -100. I'm curious about other MixPre 10s, if you or anyone else gets a chance to test. Thanks to you and dogears for your thoughts!
I'll try to get mine here in the next couple of days. Working from home but plan on going in this week so will grab it. Also I believe Guitar has one maybe he'd be willing to try as well. |
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Post by Guitar on May 20, 2020 13:31:43 GMT -6
This is really cool! Glad to see Peterson dumping knowledge bombs as usual. I will dig into this later, yes, maybe try to do some tests.
I have a MixPre 6 series 1. Also have a Zoom H6, and a Sound Devices 302, as well as some other bits, like an H1n, and an AT825 stereo mic that runs on battery power, etc. Building up my mobile rig has been such a good experience.
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Post by Blackdawg on May 20, 2020 13:35:05 GMT -6
This is really cool! Glad to see Peterson dumping knowledge bombs as usual. I will dig into this later, yes, maybe try to do some tests. I have a MixPre 6 series 1. Also have a Zoom H6, and a Sound Devices 302, as well as some other bits, like an H1n, and an AT825 stereo mic that runs on battery power, etc. Building up my mobile rig has been such a good experience. My Mixpre's are also the gen 1. But yeah it's cool to measure stuff. I've enjoyed it. |
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grantb
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Post by grantb on May 28, 2020 19:00:49 GMT -6
Sound Devices got back to me. They ran their own tests with their AP and were able to get similar results, so my unit is not broken. I think I just have to accept that while it's a cracking field recorder, it is not quite up to being a piece of precision test equipment. In calibrating my CAPI FC526XFMR, I also noticed that it can not drive some transformer inputs very well. Anyway I've got workarounds so I'm still planning on running some eq curves at some point.
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Post by EmRR on May 28, 2020 21:47:01 GMT -6
In calibrating my CAPI FC526XFMR, I also noticed that it can not drive some transformer inputs very well. . Please go into detail. It should drive just about anything. |
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Post by Blackdawg on May 28, 2020 22:32:18 GMT -6
Sound Devices got back to me. They ran their own tests with their AP and were able to get similar results, so my unit is not broken. I think I just have to accept that while it's a cracking field recorder, it is not quite up to being a piece of precision test equipment. In calibrating my CAPI FC526XFMR, I also noticed that it can not drive some transformer inputs very well. Anyway I've got workarounds so I'm still planning on running some eq curves at some point. Surely you have another interface though? I really like the Mixpre's but I would never use one as my center piece for a studio. |
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grantb
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Post by grantb on May 28, 2020 22:46:40 GMT -6
In calibrating my CAPI FC526XFMR, I also noticed that it can not drive some transformer inputs very well. . Please go into detail. It should drive just about anything. The calibration starts with feeding a signal at -30dBu and measuring signal level through a series of test points in the path. With the MixPre outputting 24.49mV, when connected it drops to 19.6 mV across the inputs. This reduces the level at all test points and throws off the calibration procedure. I solved this by buffering the signal through a CAPI ML2 at 0dB gain. I could have just increased the level of the test signal to compensate, but I was attempting to get the right dBu numbers out of and in to REW. Reading the rms voltage with my meter and converting to dBu has proved much more useful.
Keep in mind that this "interface" is primarily a battery powered field recorder. I'm sure compromises (like output current limitations) have to be made in the name of power consumption, and that some of those are in effect even when I am powering it with a power supply. I am a little surprised that it droops driving 4k5, but I went to some trouble to verify that this was the case, including removing the input relay and the input transformer. All that's left after that are the three input resistors, a 2k2 for each line across 165R. |
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grantb
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Post by grantb on May 28, 2020 23:00:54 GMT -6
Sound Devices got back to me. They ran their own tests with their AP and were able to get similar results, so my unit is not broken. I think I just have to accept that while it's a cracking field recorder, it is not quite up to being a piece of precision test equipment. In calibrating my CAPI FC526XFMR, I also noticed that it can not drive some transformer inputs very well. Anyway I've got workarounds so I'm still planning on running some eq curves at some point. Surely you have another interface though? I really like the Mixpre's but I would never use one as my center piece for a studio. Haha studio, I wish! I haven't worked in a studio for years. I have a home office crammed with gear and parts. These days I am just a crazy audio-obsessed person who likes to build stuff and make noise for fun.
I had been using an Apogee Duet, but I built a fast hackintosh and the string of adapters to get all the way back to firewire has become too long. I hoped that the MixPre would be sufficient for my little home setup and also allow some field recording for creative purposes, but it turns out I'm going to have to buy that Lynx after all  |
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Post by jaymz168 on Jul 13, 2020 8:00:45 GMT -6
I did a bunch of these for my AML EZ1073 a couple years ago when I built it but it's with an old version of REW. I could redo them and post measurements here if you'd like. Also check out Open Sound Meter, it's a free open source tool similar to SMAART: opensoundmeter.com/ It does live transfer function measurements unlike REW so you can any input signal, even music, and see what your gear is doing to it live. |
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Post by Blackdawg on Jul 13, 2020 9:58:31 GMT -6
I did a bunch of these for my AML EZ1073 a couple years ago when I built it but it's with an old version of REW. I could redo them and post measurements here if you'd like. Also check out Open Sound Meter, it's a free open source tool similar to SMAART: opensoundmeter.com/ It does live transfer function measurements unlike REW so you can any input signal, even music, and see what your gear is doing to it live. Nice! I think REW will do that now actually via the Scope function. Maybe that's a new thing since you last used it? Would love to see the EZ1073 stuff. Those are on my list of units to get and build. |
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