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The BA-3 as preamp build guide
The BA-3 as preamp build guide
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Old 10th February 2019, 05:50 PM   #1351
MEPER is offline MEPER  Denmark
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The other channel I was able to adjust just a fraction better.

THD = 0.0035%, THD+N = 0.0084%

Here 2nd and 3rd are almost equal. If I leave it there for now I don't hope the small channel difference will destroy the "imaging" or make it sound bad...….

Should it be possible to zero out the 2nd harmonic completely?
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Old 10th February 2019, 05:53 PM   #1352
6L6 is offline 6L6  United States
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The BA-3 as preamp build guide
0.00anything is really, really good.



A cleaner signal generator will likely do nothing, it’s the relationship between H2 and H3 that you are looking for. (And you found it very well!)
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Old 10th February 2019, 05:53 PM   #1353
6L6 is offline 6L6  United States
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The BA-3 as preamp build guide
You cannot null it completely away. Just set the relationships.
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Old 10th February 2019, 06:02 PM   #1354
MEPER is offline MEPER  Denmark
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It was a wrong image on the last one. Here are for both channels.
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Old 10th February 2019, 06:02 PM   #1355
Russellc is offline Russellc  United States
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The BA-3 as preamp build guide
6L6, I'm dieing to know, what is change up after listening to low distortion for a while? This info is great, When I started P3 measurement for the average hobbyist thread, it was BA3 I was interested in working with! (Both FE version and full BA3 power amp. Please carry on!

Russellc
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Old 10th February 2019, 06:05 PM   #1356
Russellc is offline Russellc  United States
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The BA-3 as preamp build guide
MEPER, is it possible to show your entire hook up routine using the Focusrite with BA3? I still haven't gotten beyond installing ARTA and would like to get all the bits together as you have.

Many thanks,

Russellc
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Old 10th February 2019, 06:26 PM   #1357
MEPER is offline MEPER  Denmark
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Yes, my setup looks like that on the picture. When you use Arta with internal generator the signal comes out at the back of FocusRite. From the back I connect to the input of the pre and the output from pre I connect to the input of the FocusRite. Then you have to find the right amount of internal damping of the test generator (I set to -3dB) combined with the right amount of monitor, input sensitivity of FocusRite and Volumen control of the pre :-)
Before that you have to find adapters that works so you can connect to RCA from FocusRite. I have spend some time with that and also playing with Arta and loopback test. First step is to be able to make a loop back test and play with Arta (spectrum analyzer) and learn how it works. I will say now after measuring that it is mandatory to adjust P3 as before that the distortion was 5-10 times higher than after the adjustment. Will see after a listening test if I can hear a difference. Then later I can adjust to more dominant 2nd harmonic…….if I want.


I did not recheck bias and offset.....maybe P3 could change these settings……?
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Old 10th February 2019, 06:35 PM   #1358
Russellc is offline Russellc  United States
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Thanks, I will ask more when I get all the stuff. what did you need to get cable wise to hook this up?

I may as well order them while I am sitting here.

Thanks!

Russellc
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Old 10th February 2019, 06:59 PM   #1359
MEPER is offline MEPER  Denmark
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I use jack to RCA on both input and output of FocusRite. They comes in many variations. The one that worked for me is a "mono jack" to RCA. Something like this (but it was not actual that one…..but will probably work as I think these can be wired in only one way).
Monoprice 1/4in (6.35mm) TS Mono Plug to RCA Jack Adapter, Gold Plated (Yellow plastic center) - Monoprice.com
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Old 10th February 2019, 10:33 PM   #1360
Russellc is offline Russellc  United States
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Thanks, I may have stuff to cobble them, if not these look great. Post your results, I understand the predominate 2nd order distortion adds some meat to the bones, other way quick and clean, but a "thinner" balance.

Thanks again,

Russellc
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