equalizer?

[homme_de_terre]

Just connect the return signal (pin 3) to ground (pin 1)

Manfred

[whitebroncoii]

Just connect the return signal (pin 3) to ground (pin 1)

Manfred

Although Europe has always configured an XLR-3 with pin 2 hot and pin 3 cold, US audio products were mixed. Older Altec electronics were pin 3 hot. In the big picture this is not an issue because it will not physically hurt anything. However, grounding pin 3 on a pin 3 hot circuit will invert the phase and there are audiophiles among you that may not be able to sleep knowing the phase is reversed. I simply think it is a good idea to check the data sheet for the "hot" pin and ground the "cold" pin when connecting RCAs to balanced inputs.

[techmecca]

terminology

balanced connections will have a hi, lo, and ground
hi can also be called +, or ?+ or hot ...
lo can also be called low, -, or ?- or cold ...
ground can also be called C, or common, or shield ...

unbalanced connections will have one signal wire and a ground or common
signal wire can be called hot, or tip, or ?
ground as above can be called C, or common, or shield ...

pin and terminal are used here interchangeably

with xlr's - on gear with balanced in and out the signal hi and lo wires will be on pins 2 and 3 but when pin 2 was eventually standardized to be + or hot it took a while for manufacturers to conform and there was no magical wave that went out and converted all the pin 3 hot devices to become pin 2 hot... so it's case by case with anything old... though older gear from usa was mostly pin 3 hot and older gear from europe was pin 2 hot... and in newer gear some manufacturers never changes because they had already sold a zillion SM57's or whatever wired pin 3 hot and were not going to change - screw the standard. Anyone remember the AES show where they were handing out the little cardboard spinner wheels with 3,2,3,2,3,2,3,2 around the circle and the arrow you spin to decide the wiring standard? further back anyone remember the bikini clad dbx girls and Larry Scully handing out packs of rolling papers with his phone number printed as if penned in on the inside flap - ah those wuz the days - the Waldorf - when swag was swag.

anyway...

connections

unbalanced sources to balanced inputs are easy - the unbalance signal goes to the balanced hi pin (or terminal) and the unbalanced common goes to BOTH the balanced low pin and the common pin... this works almost universally with both active balanced input and transformer balanced inputs. If you have the phase wrong it still works.

balanced outputs to unbalanced inputs can me more problematic...

transformer balanced outputs can have the balanced hi output terminal going to the unbalanced signal pin (tip or whatever) and the balanced signal low and common terminals would go to the unbalanced common... if you have the phase wrong it still works. Note that since unbalanced inputs are often high impedance you may need to have a terminating resistor across the (transformer) balanced signal pins (hi and lo) to provide some loading and reduce a HF peak or resonance in some outputs... most transformer outputs were designed to look into 600 ohms - I find that 1000 or 1200 ohms works fine with some gear and other gear really does not need to be terminated... depends on the amplifier and transformer combo so YMMV (Your Mileage May Vary)

now... here's where it can get messy. Active differential balanced outputs feeding into unbalanced inputs can be more difficult especially in some gear with poorly designed output amplifiers. Active balanced outputs will have an amplifier driving each output pin - one drives the hot pin "phase +" and the other drives the low pin "phase -" - same signal but fase phlipped. Decently designed gear will have a cross-coupled feedback that will sense when the one or the other signal pin is shorted to ground and remove some feedback from the amplifier driving the un-shorted pin so that the level remains constant... in well designed gear this circuit is completely symmetrical so either hi or low pin can be shorted and the remaining pin will retain level relative to ground. HOWEVER in other gear the feedback and level comp thing only works if low pin gets shorted to ground... and sadness will result if you have the phase wrong. In BOTH cases the amplifier driving into the shorted pin will not turn off - it will drive distorted audio to ground, as current, so if your ground is not solid and draining off this current you will get some of this distorted audio popping up elsewhere in your system as crosstalk and not very clean crosstalk at that. In stereo systems the effect is that of cluttering up your imaging, among other things - and it's just not clean. So, if you terminate an active signal pin to ground, the level may stay the same, but you do run the risk of introducing some distortion and crosstalk into your system. Furthermore YET OTHER active balanced outputs actually CAN'T have the low signal short to ground because that low side amplifier is driving the high side amplifier - which is inverting and driving the hot pin... I've seen this in some gear and it's really annoying (old old old Wheatstone consoles for one).

In any case when - even if your level compensates and the output amplifier is really groovy and symmetrical and your ground is good and drains all the distorto audio away, and all that, you WILL loose 6 dB of headroom in that output.

Now... IF you have some gain down stream and can afford to loose 6dB in level you can choose NOT to short the low side pin of your active balanced output and just connect your balanced output hot pin to your unbalanced input signal pin and your balanced output common/ground pin to your unbalanced input common/ground pin and leave the balanced low pin hanging free and not driving distorted audio current to ground and alls good - you will have 6dB less level and 6dB less headroom but as long as you can make it up later you are fine... and in most stereo playback systems you will have more gain than you need downstream.

okay - so I hope that was readable and useful

have a nice day

[just me now]

i like my white 4400s w/ no trannies/crossovers....
4400 - Retired Product - White Instruments Div. C Van R, Inc.

perhaps a purist would prefer the 4000 ( i think??? could be wrong) series
(if not, i meant the cut only versions)



they do pick up hum/noise from close electrical components (read amps) though...
requires some distance from other equipment IME....

or i can run it in the loop of a Urei 1620 preamp/DJ mixer and it seems quiet too...

good luck,

try to audition other friend's gear, if at all possible, is all i can say!




*EDIT*
darn, posted after reeading only a page of posts...
sorry for the repeat!


parametrics are nice too. agreed!

[magnarc]

John

Thanks for your posts, very informative and useful.

Do Shure still sell the 57 pin 3 hot?

Nat

[techmecca]

current product - according to the literature - is pin 2 hot

I just looked on the interwebs and my previous statement needs to be modified or corrected

Back in '90-'92 when this was happening I remember Shure and others making the case that with so many units in the field and users expecting consistency across time that they were in a bind, but I can see that current literature states that positive pressure on diaphragm makes positive voltage pin 2 with respect to pin 3. 1992 was about half my career in audio ago and many many other things have gone by since. I was not on the standards committee and I am no expert on the history of what all happened - though I do remember Shure was one of the manufacturers that was being mentioned.

The best thing to do, really, is not to assume anything. You need to test and verify so you really know.

There are various ways to do this

One way is to put up a new mic that is stated to be pin 2 hot and compare this to others just by placing them side by side pointed at a common source and seeing if they add or null when you bring them up on a mixer and sum them? you can use music or use a tone like 400Hz or so that has a wavelength that is pretty long so that having the diaphragm of one mic ahead of another by an inch or so is NBD and just test you mics against each other - and of course your cables and mixer inputs should all be right and no phase reverse buttons down, EQ out and so on.

Off the shelf phase testers exist? they are none of them flawless but they do work under controlled conditions. You want a two piece system with a transmitter box that has a little speaker in addition to electrical output connectors for mic and line level and a receiver with a microphone in addition to connectors for mic and line level.

Mine is from Galaxy Audio. I see these from Rolls and Alphaton and I am sure there are others

You can DIY this as well - I've seen various DIY projects so with a little search these will turn up.

BTW when we went through all the mics in the studio we just changed them as needed while testing, verified the correction and moved on - I did not take notes? roughly a third needed to be changed and I can't remember specifics - some were tube mics and others were dynamics and some were Shure and sone were EV and some were Altec and so on.

For electrical absolute phase test you can make barrel connector with diode in it connected with cathode to pin 2 and anode to pin 3 so that it clips off the positive peaks (works at levels around +4 - not at mic level) This is really rude but with a scope it's pretty easy to see if the flat top stays on top. There is a BBC stereo test signal that clips the top off the left channel only so you can do channel ID as well but I digress

this thread was about EQ - right? well we are well off the track now...

so to further complicate things on the absolute phase front I will open a whole other can of worms and leave with this? (running as fast as I can)

be vary careful about using these phase checker boxes on speakers like, oh, say Klipsch Cornwalls and immediate relatives? and many horn based systems including Altec. Absolute phase is NOT going to be consistent across all the drivers especially in systems where the acoustical centers of the individual drivers are not aligned - which is most speakers but especially more so in horn-based systems

You'll find the individual driver polarity in an absolute sense is not maintained because it is more important to have phase alignment driver to driver at the crossover points. Passive crossovers induce phase shifts and designers, if they are thinking about this, will work crossover points, phase shifts and speaker polarities to obtain smoothest response across the crossover points

I'm sure this has been discussed here somewhere

now I will quietly sneak out of the room

[Panomaniac]

Oh yes, I remember the great pin 2, pin 3 debate from the early 90s. Glad to see that it has mostly worked itself out.
Smart move testing and fixing all the mics, bravo!

BTW, active crossovers also cause phase shift. All crossovers do. Just FWIW.

[techmecca]

BTW, active crossovers also cause phase shift. All crossovers do. Just FWIW.

point taken - though phase shift and the linearity thereof varies with topology, number of poles etc.

many EQ's phase shift as well and some more than others - I did say 'can of worms'

digital crossovers do not have to have phase shift and can introduce delay in each band to time align everything

so back to the EQ thing...

I use analog parametric's for room tuning smaller systems

my first choice - Meyer CP-10 but those are pricy for a lot of people who do this for a hobby

Orban 622B (B's are quieter) can be had for around $250... I've picked them up for as little as $100 and one I got for free because it was dead and they come up pretty often on eBay and don't sell for $350... there are three of them up right now. I recommend cleaning these up, and as with most older gear, that you recap them... and that is another topic. I'm not saying these are great EQ's but I've known them a while and they can be fixed up so they work okay.

Ashly SC-66 is a good one but they do not come up as often. I picked one up for $75 once and felt this to be an extreme deal. These are loved so they don't pop up as often and tend to get snatched up quickly - they made some other models

Actually there are hundreds of parametric EQ's up on eBay... hmmm - wow - all kinds... Phase Linear Model 1100, SAE 2800, the aforementioned Meyer CP-10 at not a bad price considering how well they are made and how much they go for new, more Orban models than I remember, some Rane... and so on... I generally go with what I know. I'm also biased against some of the newer commodity gear because it's made so cheaply and is unserviceable. I am also leaning against gear that offers things like "tubessence" and other such colorizers - I'd rather have tube gear and iron for that.

and of course if the speaker system is well designed and the room is good you shouldn't really NEED EQ... but most rooms are too small and not ideal and the question there is - have I done all I can with the acoustics?

Electronics is easy. Acoustics and transducer systems ... I guess it's easy if you have a lot of money, some land, lots of time and a tolerant spouse but in the real world you end up running out of gas on acoustics ("gas" being available space, money, time, expertise, spousal and family tolerance and simple physics) so you get an EQ... and like I said, with a parametric you can zero in more specifically and apply just what you need where it's needed

...and I guess I should add the obvious - some things can NOT be fixed with EQ, like a phase cancellation CAN'T be filled in so any narrow band notch'y looking things have to be addressed some other wise - if you are pushing the boost up full to fix something then you are fixing it the wrong way.

so really - acoustics first, speaker placement IN the room, then maybe look at crossover network for general tonality correction... some give you some adjustment there... and after that EQ if you still feel a lack of joy

BTW I'm down with Lyme disease and bored out of my mind... my posts (other forums) are generally verbose and wandering anyway... but also tend to be infrequent since I stopped moderating (other forums) a few years back. I actually read the entire alnico recharge thread this morning ... I actually started to research how to build a recharger but then I stopped... and I think I better hobble down the the bench now and see if I can get some work done and stop thinking about such things

acoustics first / EQ last

[mah]

John K. Commiserations re your medical problem. You seem to have a good attitude toward it. Did you know George W. Bush has this malady? I think a few Board members have immuno-system and/or nervous system problems that may be difficult to diagnose and difficult to manage. Keen interest in something(e.g. Altecs) can certainly provide some relief(speaking from experience).

Welcome aboard.

Regards, Marshall.

[techmecca]

yeah - well this is the fourth time I've had this. First time I had no idea why I was feeling like crap and I went off to work way way upstate NY at Mutt Lange's studio (the man calls and you go - this was 1996 - he's moved to Switzerland since) and THEN it hit me full force. I had a crew with me so I was working three hours and going to my room to sleep and sweat for three hours - rinse and repeat for three days... awful and stupid. Got back and went directly into hospital for an IV drip of fluids and antibiotics - got better. Now I know what it feels like coming on and the Deer tick population is fierce this year - little buggers - so no hospital after first time but it still kicks my ass every time. I have never gotten the circular rash or any visual signs.

Lyme is treatable and is not a chronic thing for MOST people but in some it digs in to places antibiotics can't get in to or gets very aggressive and messes up joints, eats connective tissue... it can get pretty grim. We've been lucky. Everyone in the house has had this at least once. It's worth reading up on if it's endemic to where you are and or plan on going to.

In other places people have poisonous snakes coming into their houses - we have these stupid little ticks . I'll take those over King Brown's.

...anyway the good news - for me is - these golf-ball sized antibiotic capsules are doing the job and I am feeling a LOT better. I'm going to Vermont for a few days and I'll be back to normal work mode next week... which is good because too much time on the internets and I start getting these crazy ideas like trying to build a water powered car or a speaker magnet de-magger/re-charger or buying a 1962 Lincoln Continental convertible and restoring it in my driveway... it's bad enough that I have now THREE pairs of 604's in cabinets, not to mention the Cornwall's in my kitchen and so on