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EQUALIZERS FOR AUDIO




 
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Author Topic: EQUALIZERS FOR AUDIO  (Read 10608 times)
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ve6pg
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« on: February 17, 2005, 03:08:06 PM »

HI AGAIN FROM TIM....I WOULD LIKE SOME INPUT ON USING A STEREO EQUALIZER FOR TAILORING MY AUDIO TO MY VIKING 2. I HAVE 2 DIFFERENT ONES,A RADIO SHACK 12 BAND EQ,AND A TEAC EQA-5. THE RADIO SHACK IS A "12 BAND EQ",THE TEAC IS 10 BAND PER CHANNEL.
 BOTH UNITS ARE YOUR TYPICAL EQ FROM YEARS AGO,TO CHANGE THE SETTINGS OF YOUR TAPE DECK,ETC...THEY BOTH HAVE LEVEL CONTROLS,WHICH INCREASES/DECREASES THE OUTPUT..SO IF YOU ARE USING SOMETHING LIKE THIS,AND HOW YOU HAVE WIRED IT UP FOR GOOD AUDIO,PLEASE LET ME KNOW.
  THANKS ES 73...TIM...SK..
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...Yes, my name is Tim Smith...sk..
KL7OF
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« Reply #1 on: February 17, 2005, 05:36:21 PM »

tim ...what are the input and output impedances on the equalizers that you have...?  I have a 10 channel eq that has a 50k ohm balanced and a 50k ohm unbalanced input..... The outputs are 50k ohm unbalanced and a 600 ohm balanced ...  I have used this downstream from a mic amp with the eq's 600 ohm output going to the audio input of a broadcast transmitter...worked very well........Most of the stereo eq's that I have seen are for use downstream from a stereo hi fi amp and they have 4-8 ohm in and out....I haven't tried any of these types yet...I too am curious about the results others have had using these types of stereo eqs......Steve
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Jack-KA3ZLR-
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« Reply #2 on: February 18, 2005, 04:46:04 AM »

Good Morning Fellas,

 Here's a Very nice web sight and Very Nice Ham who provides a very good treatize about audio and Hooking things together..

http://www.nu9n.com

I'd give julius W2IHY' sight a look over and pay special attention to his IBox it has helped many a ham with mix and matching issues and you can build it yourself...

http://w2ihy.com

Reading about these things helps alot...Hope it helps out...


de jack ka3zlr
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Paul, K2ORC
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« Reply #3 on: February 18, 2005, 08:44:19 AM »

Hi Tim.  You don't say whether your Viking II is stock or whether you or someone else has modified the speech amp to allow for transmission of a wider range of audio frequencies.  A stock Viking II has a rather limited audio range and the response drops off rapidly above 3000 Hz and below 800 Hz (I'm going from memory on these figures but I believe they're in the ballpark).   What I'm driving at is that using an EQ with a stock Viking II might not produce the results you are hoping for.  

If you'd like to widen the audio response of your transmitter's speech amplifier, take a look at the audio mods for the Viking II, two examples of which can be found on the AM Window Tech page under Modifications.   Here's the URL:

http://www.amwindow.org/tech/htm/mods.htm

Another way to get a Viking II producing wide audio is to bypass the speech amp completely and feed balanced audio to the grids of the 807 modulators through an line to grid audio transformer.   Ken, W2DTC does this with his Viking II and  Bill KC2IFR does it with his Valiant, just to cite two examples you can hear on the bands here on the east coast.  The audio produced by these two gents is fabulous and the direct feed probably produces the best results.   Getting a transformer that will do the job is the trick.  The Hammond 841 fits the bill, but last I looked I think it ran somewhere around $75-80 new and was a special order.  You can do some research and get the figures you'll need to do the mod and then start searching for a transformer.  

If you really want to delve into the audio mods and different problems inherent to some of the stock components in the Viking II, they have been discussed in articles that appeared some time back in Electric Radio.  You can check the ER website for info about an independent website that features a searchable index of back issues of Electric Radio.  There's a link to ER's website from the main index page of the AM Forum and you can purchase the back issues directly from ER.  

Good luck and enjoy the Viker II!

Additional notes:  

Paul, VE7KHZ has a website that includes some info about his mods to a Viking II.  He used the audio to modulator grids method and he discusses what he did and shares some photos.  Here's the URL to the page on Paul's website that shows his Viking II audio mods.

http://www.qsl.net/ve7khz/VikingII.html

Highly recommended too are articles on the AM Fone "East Coast Sound" page, including Mike W2ZE's excellent introduction to audio entitled "Processing 101".  Here's the URL:

http://amfone.net/ECSound/index.htm
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Jack-KA3ZLR-
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« Reply #4 on: February 18, 2005, 06:08:05 PM »

Paul,

Now this is where i lose it, the 841 i find sez P-P Plates to line here at this URL.

http://www.hammondmfg.com/560.htm

Ok so the deal is to put this, audio feed to line and plates to the Grids...Via 47k resistor... I'm misunderstanding something here...
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Steve - WB3HUZ
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« Reply #5 on: February 18, 2005, 09:12:32 PM »

Or avoid the mile long URL and the pass through of the Netscape site and go straight to the source.


http://www.nu9n.com
http://w2ihy.com/



Quote from: Jack-KA3ZLR-
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Jack-KA3ZLR-
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« Reply #6 on: February 19, 2005, 07:06:13 AM »

I will effect a repair Steve, that's inconsiderate of me...Whoops... :-P
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VE7 Kilohertz
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« Reply #7 on: February 19, 2005, 02:03:36 PM »

Well, QSL seems to be down this morning but here is what I did on my Viking II. There is no need to use the exact Hammond xfmr, it's just what I had on hand. The critical parameter is the impeadance ratio. Use one as high as possible, ie 600 ohm to 50K or sometimes you will find 150 ohm to 50 or 100K. That is what you need to use. Other change needs to be to the modulator tubes. They need to run Class AB1, no grid current flows, hence, no power consumption. This is simply a bias change IIRC. I used to build tube audio amps in a previous life and the long tail pair is a classic diff amp configuration. Can't remember if this is what I did or not either. :Huh:

The xfmr is connected so that your audio gear drives the 600 ohm input and the 50K or plate or P-P grid connection goes directly to the grids of the 807s, bypassing all of the restrictive circuitry in the Viking II. You will need to connect 50-100K resistors to each grid from your bias source, or you can just connect one to the center tap of the secondary of the transformer to feed both tubes at once. Set the bias so that there is about 35mA in each 807. That should put you well into AB1. I think I put a feedback loop around the whole xmfr 807 stage but it's probably not needed, especially if you don't get the max Z ratio xfmr. You need as much drive as possible going into this, +4dBm or thereabouts. You may not be able to drive it from "consumer" gear and may need a broadcast mixer or similar balanced source, or a high gain audio amp to get that sort of drive.

Once QSL is back up, I will revisit my page and see if any more gray matter springs back to life. I don't want to pull the Viking II of the shelf and dismantle it.

Cheers and GL

Paul
VE7KHz
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KL7OF
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« Reply #8 on: February 19, 2005, 04:05:27 PM »

Paul.....We haven't heard that viker in quite a while..You should get it down off the shelf.... I might be tempted to get mine off the shelf as well...  ( The one with audio from the radiotron speech amp)......Steve
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Bacon, WA3WDR
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« Reply #9 on: February 20, 2005, 11:51:52 PM »

Once you get the system talking you will probably find you need to pull the 200 Hz range down a few dB and push the 2-4KHz range up a few dB.  Mileage will vary depending on the microphone and audio mods.  An unmodified rig would probably not need the 200 Hz cut, but would need tremendous 2-4KHz boost.

You will want a mike preamp appropriate to your particular mike, because lower-Z mikes generally have lower output, and crystal and ceramic mikes need much higher load impedances.  Because of its low-Z and high output, a cheap electret mike directly into the EQ might work well enough to make some evaluations, though.
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Jack-KA3ZLR-
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« Reply #10 on: February 21, 2005, 05:58:26 AM »

I like all the possible Mods that can be done... I like to try them and Note the differences..But I like to know the whole procedure before attempting them...
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