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Measurements and comparison of isolation transformers and DI boxes

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dominikz

dominikz

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Was it mentioned anywhere in the article what DI stands for?
There are a few interpretations of the acronym "DI", but often it is said to stand for "direct injection".

It is a device used to connect high impedance, high level unbalanced sources (like e.g. passive guitar pickups) into low impedance, low level balanced inputs (e.g. microphone preamplifiers). Very common (and useful) device in recording studios as well as on stages (live sound).
 

pseudoid

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I hate ground loops.
Not even 'gremlins' can publicly admit that they "love" ground-loops.;)
202204_XLRisolatorFloater.jpg

This arrangement of grounding flexibility seems to be about the most useful.
 

nagster

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DI was measured.
There are two DIs each, but since there was no difference at the time of the FR and THD ratios, we are measuring one each after that.
DI_j48_type85_tritech_02.jpg

The DI output is connected to the analyzer via apx1701. For phantom power. Input impedance is fixed at 20kohm. I didn't use a 9V battery.
Bypassed apx1701 only when measuring FR with a load of 600 ohms.

The voltage applied to DI in HF IMD and 32tone measurement is half the voltage when 1kHz THD ratio is -60dB.
However, tritech stopped at -100dB, so I applied the maximum voltage of the AP generator.
 

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  • DI_SMPTEsweep.png
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nagster

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Countryman type 85 (Active type. 9V battery or 48V phantom power.)
type85_01.jpg
 

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  • type85_32tone.png
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nagster

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Radial J48 (Active type. 48V phantom power only.)
j48_01.jpg
 

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  • j48_thdvsG.png
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  • j48_32tone.png
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nagster

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Tritech DB-LL1 (passive type. lundahl LL1530 1:7 connection)
tritech_01.jpg
 

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  • tritech_thdvsG.png
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  • tritech_19+20.png
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  • tritech_32tone_10V.png
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nagster

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@nagster That's really amazing work, thanks a lot for contributing!
If you don't mind I'll add links to these posts at the end of post #1, so people can find them more easily.
Is it a link? No problem at all. I'll leave it to you.
Thank you for posting an interesting review.
 
OP
dominikz

dominikz

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morillon

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maybe he would be welcome, if not already done (?), to measure some active or passive options from aes to spdif or vice versa?
;-)
 
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