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Author Topic: The Marriage of Heaven and Hell (A+D)
fractile
Propellerhead
Posts: 161
fractile
Post Re: The Marriage of Heaven and Hell (A+D)
on: November 4, 2014, 21:20

I was at the grocerystore and this came on: http://www.youtube.com/watch?v=F3qvosHHcWc
John Lennon - Instant Karma-Offical Video-HQ
The drums jumped out and wow, that's what drums sound like at Abbey Road. The 2010 remastering probably has to do with it sounding like the first time to hear it. It was written and recorded the same day. More here: http://www.beatlesbible.com/people/john-lennon/songs/instant-karma/

fractile
Propellerhead
Posts: 161
fractile
Post Re: The Marriage of Heaven and Hell (A+D)
on: November 4, 2014, 22:30

That thing about EMI/Abbey Road reminded me that they don't allow impulse response maps to be made in their studio(s). One thing lead to the next and...
I downloaded the FreeVerb3 VST plugin collection. It has a lot of processing options that are unique (from what I've seen) to it, in addition to making your own IR convolutions. Available for compiling on your favorite *NIX or as Windows and Mac OSX VST plugins.
http://www.nongnu.org/freeverb3/

Guest

Posts: 3
Post Re: The Marriage of Heaven and Hell (A+D)
on: November 19, 2014, 02:17

In a continuous attempt to discover the Why of all the Do's and Don't's, I'd like to post some notes on utility mains power supply. This wondering began after trying to understand why the voicecoil in a woofer got fried a while back when I was first testing the new-to-me Bryston amp. It has a frequency response beginning at 1 Hz. The situation was the amp was being fed with analog line out of a computer that was plugged into the unbalanced (120vac to Ground) mains circuit, instead of the dedicated, balanced (+/-60vac with Grounded center-tap) mains supply I have on the other circuit (of the total two supply circuits). My guess so far is there was a D.C. offset that was fed into that voicecoil.

I'd been using an optical output on the computer's audio... luckily I was smart enough to use a spare pair of speakers to test with instead of the main monitors.

Ok, let's outline the basic situation(s) and associated cautions that people will generally be faced with when supplying mains power. I'm not a licensed electrician, so consult your personal electrician for anything beyond standard installations. (1) If electric outlets are in the same room it is not guaranteed that they are on the same circuit.

For 120vac (single-phase) feeds it's (not un-)common to bring in 240vac two-phase "from the pole" and split the legs into two 120 volt circuits. These two legs are 120 degrees out of phase with each other. The full deck is 480vac 3-phase called delta, or Y configuration. 3x120=360 degrees or 480 volts. To exacerbate the problem, in residential circuits (commercial? check the NEC codebook) the low/cold white wire is connected to Ground at the premises source input. So instead of having 2 or 3 out-of-phase floating a.c. voltage sources, they're pinned to ground at one end, with the center of the Y here seen as ground and the legs the 3 phased vectors of 120v.

Comparing two circuits on two different mains circuit legs, it's possible there's a DC voltage offset between them, due to the physically separate, even if very similar paths to ground. The simplest fix for this would be isolation transformers on each, with a center-tap on the secondary winding of each connected to a common Ground point. A Variac autotransformer could work well, with the right Ground configurations. Plus the voltage can be dialed up to around 125vac. The raw voltage around here is around 110vac; with a voltage regulator it goes up to 123v on a good day. That could add up to increased dynamic range of about 10% on eqpt with standard transformer power supplies.

News Flash: From the product description of the Neumann Battery Supply BS 48 i (for the U47fet, etc. mics): "...The audio output is dc-free. Therefore, no transformer is needed when connecting to unbalanced inputs..." Another cautionary perspective on connecting into unbalanced inputs. It might be best to use a transformer or servo-balanced conversion on unbalanced signals, especially on vintage-type gear they may have become sketchy over time.

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