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Audio phasing




 
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N3WWL
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« on: June 05, 2010, 02:59:18 PM »

I just retired a Behringer Ultra Voice Pro in favor of a Symetrix 528E.  I have always experienced an out of phase waveform from my Ranger until I engaged the phase inverter on the Behringer.  The Symetrix has a switch labeled Voice Symmetry.  I assume it's a form of phase inversion.  I am unable to correct the phase using this switch.  In fact the only difference I see is a slight bit more PEP but no visible difference on the scope.  I remember my old DX-100 had a similar problem which was easily correctable by switching the plate caps around on the modulator tubes.  I have tried to take the center conductor on the audio cable and switch it from hot to ground with no success.  How can I easily correct the audio phase?  My Flex 3000 and Kenwood 870 do not exhibit and out of phase wave form...only the Ranger.  I am using an Electro Voice RE-27 fed with balance audio cable into the Symetrix, then coming out of the Symetrix unbalanced to all 3 rigs.  I experience no hum or any other issues.  Any advice appreciated...it's driving me nuts :-)
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WBear2GCR
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« Reply #1 on: June 05, 2010, 03:26:39 PM »

Jay if it is a 3 pin XLR connector, do not move the ground.
swap the other two. that will flip the phase.

That phase corrector thingie, I suspect but do not know, is one of these magic "real time phase flipper" circuits. In which
case you need to flip phase the output wire from the Symmetrix to the rig.

Or you could flip the plate caps on the modulator tubes, if they have any...

Not sure if this is what the situation is or not, but flipping the phase on the mic and using the phase corrector won't
change much, afaik.

                            _-_-bear

PS. the standard on XLRs is pin 1 is Ground. dunno why they ended with that, I'd rather have pin 2 ground myself... but whatever...

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nq5t
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« Reply #2 on: June 05, 2010, 03:27:14 PM »

The Symetrix has a switch labeled Voice Symmetry.  I assume it's a form of phase inversion.  I am unable to correct the phase using this switch. 

The purpose if this function in the 528E is to improve the symmetry of the speech waveform.  It is not a phase inverter.

Grant/NQ5T
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W1RKW
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« Reply #3 on: June 05, 2010, 04:19:48 PM »

When you change the polarity on the signal isn't that just flipping the signal amplitudes, ie. negative to positive and positive to negative vice phase?  changing phase is changing the signal in the time domain.  yes/no?
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Bob
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flintstone mop
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« Reply #4 on: June 05, 2010, 07:11:56 PM »

Remembering QSO's with you, Jay, during the Raytheon dayz and the Flex dayz, your voice has good characteristics to get a lot of pos peaks. Very asymmetrical voice. That control on the 528 is useless. Didn't do anything for me.
Rather than get complicated trying to get the Ranger happy with your new processor, when two other devices are good, just switch the plate caps on the mod tubes of the Ranger.

Phred
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Fred KC4MOP
N3WWL
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« Reply #5 on: June 05, 2010, 09:11:16 PM »

i would love to do that fred but there are no plate caps on the ranger
it uses 1614's
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K1JJ
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« Reply #6 on: June 05, 2010, 10:29:28 PM »

Jay,

Since it will be a semi-permanent thang, pull off the cabinet. You can reverse the Ranger's driver transformer input or output connections (phase) or do the same with the modulation transformer in or out leads.  


For a long time I plugged the RE-20 into a little box that had a double throw, 2 pole toggle switch that switched phase for the two balanced leads.  Since you have balanced mic cable, that wud work.  Hopefully the 528 doesn't kill this polarity bias. I used to have a 528 and thought it worked OK, however.

There's a few ways to do it if you don't want to switch it within the audio chain. I'd agree that you have the perfect voice to optimize phase.  Positively the lowest Kio Rio Voice in America, caw mawn.


T
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Frank / WA1GFZ says when he's working near high voltage, as a warning he sings this song by Jay and the Americans: "Come a little bit closer, you're my kind of man, so big and so strong, come a little bit closer, I'm all alone and the night is so long."
w4bfs
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« Reply #7 on: June 05, 2010, 10:45:12 PM »

Jay,

..... You can reverse the Ranger's driver transformer input or output connections (phase) or do the same with the modulation transformer in or out leads.   

T

it will take a bit more since the Ranger uses a mod transformer winding for negative feedback as I recollect ....
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k4kyv
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« Reply #8 on: June 06, 2010, 12:46:09 AM »

When I had a Ranger years ago I disabled the negative feedback. Its purpose is to allow the modulator stage to be used as a class B driver for the Johnson Kilowatt. Beam power tetrodes make very poor class B drivers if neg feedback is not used. If you are only using it as a modulator and not as a driver stage, the feedback is unnecessary.

I disabled mine because the Ranger has some rather large capacitors across the modulation transformer windings and IIRC in the low level sp. amp stages, that cause the highs to begin to roll off above about 2 kHz.  I removed those "hyellowfying" capacitors, but that resulted in about a 3 kHz audio squeal from the modulator.  I figured out that the el-cheapo audio iron in the Ranger has a serious phase shift problem at 3 kHz and higher, turning the negative feedback into positive feedback and thus causing the oscillation when the rig was modified to have significant response at that frequency.  By disabling the feedback I was able to operate without the capacitors with no self-oscillation.  That improved the high frequency response tremendously.

I increased the low frequency response by increasing the values of coupling capacitors, and taking the DC off the primary of the driver transformer.  I converted the driver stage to resistance coupling by adding a 10K or 30K (don't remember which; it was 35 years ago) plate resistor to the 12AT7 plates, and coupling the audio from the plates to the driver transformer primary through a 1 mfd capacitor.  Of course, the plate resistor dropped the plate voltage to the driver stage to less than half the proper value, so I returned the resistor to the +HV supply (the same one that supplies plate voltage for the final and modulators) instead of to the low voltage supply. The voltage drop in the resistor brought the plate voltage back down to about the right value.  I would recommend a little experimentation; use the value of plate resistor that brings the measured plate voltage at the driver stage back to the same value it was with the stock circuit.

The Ranger sounded very good with the mod, even with the stock mod transformer.  The stock audio is nowhere near flat, but steadily rises to a peak at about 1500~ and then begins to roll off at higher frequencies beyond that. After the mod, it was flat from about 100~ to 5K or more. I disabled the feedback simply by disconnecting the feedback winding from the circuit.

If you reverse the grid or plate leads to the modulator tubes it will turn the negative feedback to positive.  Just reverse the polarity of the feedback winding or disconnect it from the circuit entirely.

I then went a step further with the modification.  I removed the driver transformer from the rig, disassembled it, and restacked the laminations so that there was no gap in the core, but stacked like a power transformer.  The gap is not needed when the plate current to the driver stage is not flowing through the primary winding of the transformer.  Removing the gap effectively increases the amount of iron in the transformer and thus the low frequency response.  Of course, low frequency response is still limited by the mod transformer, but the rig sounded satisfactory without further ado, and the audio quality didn't suffer as a result of the absence of negative feedback.
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K1JJ
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« Reply #9 on: June 06, 2010, 11:50:06 AM »

Whoops, that's right - I did forget about the negative feedback in the Ranger. Glad to hear Johnson considered  it back then... :-)

As Don says, there are a couple solutions to it - disconnect it or reverse it with the other winding to properly change the phase..

Maybe the DPDT toggle switch after the mike is the easiest method at this point. Also consider a phase switch on the balanced output of the 528. Like my Berhinger 9024, maybe it will handle bal to unbal loads without a problem and let you control things after the 528, as you wish.

Let us know what you finally come up with, Jay.

T
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Frank / WA1GFZ says when he's working near high voltage, as a warning he sings this song by Jay and the Americans: "Come a little bit closer, you're my kind of man, so big and so strong, come a little bit closer, I'm all alone and the night is so long."
WA3VJB
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« Reply #10 on: June 06, 2010, 10:27:48 PM »

Jay,

It's worth one more check that all your hookups from the microphone to the 528E have Pin 2 "hot," which means the leading waveform curve swings positive from positive pressure on your microphone.

Quote
I have tried to take the center conductor on the audio cable and switch it from hot to ground with no success.

There are three wires from the 528E to feed a balanced load. 528E's Ground = Ranger's Ground.  Which of the other two did you pick as "hot" ??

I'd try the "other" one, and if you see an improvement from thus switching the output leads of the 528E, maybe make a dedicated interconnection cable as the easiest way to normalize the Ranger to the rest of your transmitters.  

(also, check the manual -- there's a chance the 528E does not like to see an unbalanced load)

Along a balanced path, I utilize a barrel XLR connector that has two dip switches in the case. It's placed in line with a connector for the mic, line or output for testing.  One switch lifts Pin 1 (ground lift) the other swaps Pins 2 and 3.  I use it a lot, even though my cables don't change around that often.

Gary/INR used to notice his headphones were out of phase, sometimes, even when NOTHING else had changed in his setup.  So maybe there's some Phase Phantoms roaming around.
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W3GMS
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« Reply #11 on: June 07, 2010, 09:03:13 AM »

Hi Jay,
I pulled my 528E schematic out and this is what you can do to fix the phase issue. 

A few comments are in order first however.  The unbalanced output is dedicated to one of the balance output drivers so your stuck with the phase that presents itself from that driver unless you flip the phase at the microphone. For reasons mentioned below, in your situation with multiple rigs your better taking care of the phase issue at the output of the 528E where you have both phases available to drive various transmitters.  You can use the balance output in your favor. To get the balanced output, two op amps are used but each one is 180 degrees out of phase with each other.  Pin 2 of the XLR is the same phase as the unbalance output so that one is no good for you with the Ranger.  Pin 3 however is 180 degrees out of phase compared to pin 2.  Since you may have rigs that require a different phase, you can easily pick up either phase A or phase B right on the balanced output connector.  Phase A we will call it would be pin 2 of the XLR and phase B would be on pin 3 of that same connector. Again always pickup ground on  pin 1 of the XLR.

Hope that helps!

Regards,
Joe, W3GMS   

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WD8BIL
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« Reply #12 on: June 07, 2010, 09:43:20 AM »

Jay, just makeup a short 1ft audio cable that flips the phase. Stick it in the Ranger jack and attach the present audio line. No need to open anything up.
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N3WWL
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« Reply #13 on: June 07, 2010, 10:11:05 AM »

Thanks for all the advice thus far.  I've tried switching the unbalanced leads at the audio cable end at the Ranger jack.  Hot to ground and ground to hot.  This line is coming from the unbalanced output of the Symetrix.  I had no audio this way at all from the Symetrix.  I then tried to make up a balanced cable.  I used pin 1 shield and tried to use pin 2 hot and pin 3 cold which still had an out of phase waverform.  I switched the hot and cold leads and then I had no audio at all.  That should work, right?  Im rather confused... it doesn't take much   Shocked
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WD8BIL
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« Reply #14 on: June 07, 2010, 11:38:47 AM »

Quote
I used pin 1 shield and tried to use pin 2 hot and pin 3 cold which still had an out of phase waverform.  I switched the hot and cold leads and then I had no audio at all.  That should work, right?  Im rather confused... it doesn't take much   

That's cause the Ranger input is unbalanced. When you switched the hot you grounded it at the Ranger. Guess a li'l balanced transformer is in order. I got a Collins 600ohm balanced to 15K unbalanced one ifn ya want it.
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W3GMS
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« Reply #15 on: June 07, 2010, 11:56:27 AM »

Jay,
The 2 audio signals off the balanced XLR are out of phase when compared to pin 1 which is ground.  That gives you 2 unbalaced output with each one being out of phase to the other.  Ground must remain ground and it can't be used to flip the phase, otherwise you will short the output of the op-amp when you ground the signal line, hence no audio.  Its not like the transformer days where you can ground either side of a transformer coupled balanced output to make it unbalanced.  If what I mentioned above does not solve the problem then something within the Ranger is not allowing the phase difference to be observed.   
Regards,
Joe, W3GMS   
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flintstone mop
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« Reply #16 on: June 07, 2010, 02:02:00 PM »

I think Buddly is on to something.
You will need a transformer just before going into the Ranger to flip the phase without grounding out the audio from the Symmetrix. The symmetrix needs to be isolated from the Ranger. The "out" side of the transformer dosen't care which wire touches ground.

Fred
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Fred KC4MOP
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« Reply #17 on: June 07, 2010, 03:07:26 PM »

Fred,
2 out of phase signals in reference to ground are already supplied from the 528.  So simply pick the phase thats correct.  One of the drivers is an inverting amplifier and the other is configured as a non inverting amplifier depending if you pick pin 2 or 3 reference to pin 1 on the XLR.
Regards,
Joe, W3GMS 
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flintstone mop
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« Reply #18 on: June 07, 2010, 03:29:25 PM »

Fred,
2 out of phase signals in reference to ground are already supplied from the 528.  So simply pick the phase thats correct.  One of the drivers is an inverting amplifier and the other is configured as a non inverting amplifier depending if you pick pin 2 or 3 reference to pin 1 on the XLR.
Regards,
Joe, W3GMS 
Very nicely put........FB Joe!

Fred
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Fred KC4MOP
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« Reply #19 on: June 14, 2010, 08:34:02 AM »

Thanks for all the advice. With Joe, W3GMS's advice, and Dave, K3ZRF's explanation, I used an XLR connector at the rear of the Symetrix and only used one of the two balanced lines along with the shield to pin one.  I forget which pin I ultimately used. It worked perfectly....thanks again.
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WD8BIL
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« Reply #20 on: June 14, 2010, 08:49:33 AM »

You da man, Dave!
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flintstone mop
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« Reply #21 on: June 14, 2010, 04:22:46 PM »

You da man, Dave!

DAVE?HuhHuh??
Dave's not here..........door slams
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Fred KC4MOP
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« Reply #22 on: June 14, 2010, 06:05:36 PM »




          Dave (ZRF) was on a different channel!

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73,  Ralph  W3GL 

"Just because the microphone in front of you amplifies your voice around the world is no reason to think we have any more wisdom than we had when our voices could reach from one end of the bar to the other"     Ed Morrow
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« Reply #23 on: June 14, 2010, 10:49:14 PM »

                                                        .


* Yes Dave.jpg (27.07 KB, 412x412 - viewed 411 times.)
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« Reply #24 on: June 15, 2010, 10:21:49 AM »

                                                        .



Forgot about that DAVE!!!!
I was on a Cheech and Chong channel
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Fred KC4MOP
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