Re: [Avid-L2] OTish: Audio Level Converter? Pyle Premium Direct Injection Audio Box - 2.36" x 4.09" Passive DI Unit Hum Eliminator w/ Input Attenuator to Connect Guitar & Bass, 1/4'' Impedance Transformer Connector to Balanced & Unbalanced XLR

TLDR Nerd alert.

I started as a sound man.  My favorite old school text is a tome known as "The Audio Cyclopedia" by Howard M. Tremaine.  It also works as a boat anchor, should have been in multiple volumes. (1,800 pages)

Audio Cyclopedia amazon.com

First off.  When I hear people talking about shorting pins it always bothers me.  New gear "gets by" with having one side shorted due to higher source impedence, but it's better to do an attenuator, designed for going from Balanced to Unbalanced, less likely to introduce distortion because 1/2 the source being shorted to ground.  Do this to tube gear and it can be sonically bad news. Back in the day you had to match impedance between devices.

Here is a great summary of building an attenuator (pad) for going between balanced and unbalanced devices:

Build your own attenuator pads uneeda-audio.com

On the subject of Positive and Negative, I like to think more from the idea of In phase and out of phase.  The two "hot" leads are part of a pipe pair, where the flow is always opposite between sides.  The whole purpose of balanced is that when you get outside interference (mostly AC line voltages) that in a balanced circuit the interference is introduced in opposite amounts on the hot leads, automatically cancelling out the noise at the receiving device.  The minute you attach one of those leads to ground, you are also likely to introduce hum.  The above bridge resistor network is the best way to deal with going from Balanced to Unbalanced.

I personally like resistive pads better than active devices, less likely to introduce audio artifacts due to additional stages of amplification/transformers.

Also, plus one on the wiring of XLRs being inconsistent.

My audio kit always also includes several ground lifting plugs.  The other issue with unbalanced gear is multiple paths to ground.  Ground Loops.

Ground loop (electricity) en.wikipedia.org

Nerdman out.

Dave Hogan

Burbank, CA

On Oct 14, 2025, at 1:18 AM, Tony Quinsee-Jover via groups.io <tony=hdheaven.co.uk@groups.io> wrote:

In the context of audio waveforms the convention of hot and cold comes from that a positive deflection of the diaphragm in a microphone should result in a positive voltage (ie the top half of the waveform). 

All pretty esoteric I agree. And yes, I agree with you - much balanced equipment appears to not be so balanced under the hood. 

T. 

Sent by magic over t'interweb

On 14 Oct 2025, at 03:10, John Moore via groups.io <bigfish=pacbell.net@groups.io> wrote:



I hear what you are saying but to nerd it up a bit.  Given the balanced outputs are generating an AC signal what does hi and low or hot and cold really mean.  I know in household AC the neutral is generally considered to be 0 volts relative to ground, although floating and iffy neutral connections can change this.  Here's a quick Google:

Standard 3-pin XLR configuration (Balanced Audio)

The standard wiring for professional balanced audio follows the AES (Audio Engineering Society) convention, often called "Pin 2 Hot". 

 

Pin	Function	Proper Term
Pin 1	Ground / Shield	Ground: Connects to the cable's braided shield to provide electrical grounding and protect against interference.
Pin 2	Positive / Hot	Hot: Carries the audio signal with positive polarity.
Pin 3	Negative / Cold	Cold: Carries a second copy of the same audio signal but with its polarity inverted.

 

Since the signal from a dynamic mic is an alternating current signal pins 2 and 3 alternate their polarity don't they?  Electrons run negative to positive so for the current to alternate that means the polarity of the pins have to reverse.  I suppose just like speakers  can be out of phase so can a microphone.  When the air pressure pushed the mic diaphragm, voice coil (in dynamic mics) or backplate (in condenser mics) forward the speaker cones should move forward as well, shouldn't they?  So the hot and cold have more to do with phase than actual polarity of the connection or am I just over thinking this?

 

I do recall at ABC I had to take an XLR TimeCode signal into the RCA TimeCode input of a Sony BVU-800.  I shorted Pins 1&3 and got nothing.  I then found the Timecode XLR Source was mis-wired switching pins 2&3.  I've seen some behavior on Behringer mixers that make me think that their "balanced" inputs are really unbalanced under the hood.  Could it be there is a global conspiracy of unbalanced inputs and outputs masquerading as balanced?  That might explain this whole thing.  ;-)