The AM Forum

Can someone give me some friendly advice on setting up the compressor and gate?  I got a DBX 266xl. I spent a half hour pumping the audio into my Eton XM1 monitor rxer on the line in jack.  Then Into the Globe king 500C and dummy load.  I think I have the concept down pretty well. When I bypass, I have about 75% mod.  When its on, I have right at 100% and the percieved loudness more then doubles. My voice jumps out at you..

I am using mostly default factory settings. I understand the gate threashold.. I turned it up just until the fan noise went away. I dont understand the Ratio for the gate or the compressor ratio. I read the manual 5 times.

My understanding was that the unit would keep audio levels equal even if I leaned back in chair or turned my head to look at the meters ect.. This effect is not really shown.  If I get closer to the mic, I am louder. If I back off, I am softer. Should a compressor not clamp and boost to give you a constant avg output?

Thanks for any advice!  The unit really sparked up the audio!  I got great reports saying that I am louder and clearer with the unit on.. So I guess its doing something.

Clark

A.  Look at the Bird when you're adjusting it.  The "perceived" loudness you hear people telling you about is actually an INCREASE in your avg power output.  This must be done on the AVG scale.  I triple my avg output when I put my compressor / gate / etc. chain inline I sent to you, while the PEP output stays the SAME!  You can also see this with an oscope.

B.  The compression ratio is the amount of dynamic range you want to LOSE.  You can crank them to 20:1, but you really sound like a monosylabic idiot.  I use a multiband (5 bands and a 3 band), so mine sets up different than your's.  HOWEVER, what you want is enough compression that your avg power is pretty much maxed (if your not using the SB220!!!  The Xformer in it won't handle super levels of 'talk power'), PEP maxed, and you have no negative excursions beyond 100 percent, or better, 95 percent.

After that, it's all in eq and getting on the air reports from PEOPLE YOU TRUST to have a good ear.  Getting an audio report from someone running > 100 percent + and - isn't in your best interest, find someone running hifi and have them help you.... They'll have the RECEIVER to do it, more than likely.  Getting someone that likes to run slopbucket only in contests probably isn't in your best interest, either.

And then when you get that audio chain completely correct, feed it into the 440 / 2 meter station!  I did, and it's FUNNY to get responses from people like WTF, that's not communications audio.  Guys up on 2 have NO idea about hifi audio!

--Shane

Mike - W2ZE has written a great tutorial on audio processing.

http://amfone.net/ECSound/processing101-1.htm

The gate ratio (sometimes called expansion ratio) on some mic processors can be adjusted from maybe 1.5:1 up to 10:1. You already know what adjusting the threshold does, what the gate ratio sets is how much the audio is muted when the gate kicks in. At 10:1, the processor will completely kill audio when gated off, at 1.5:1, there's more of a slight "ducking" effect. You'd use the higher number when broadcasting from an extremely loud location when you really wanted the audio to clamp down between words or sentences. Does that make sense?

A properly adjusted gate can be a huge advantage when dealing with feedback from a modulation transformer rattling. I have that problem here.

A compressor itself can't keep your audio level the same from a whisper to a shout, 15 to 20 db of compression is the top limit. For decent audio, hold the compression to maybe 15 db. If you try to compress too much, you'll pick up background and breathing noises and sound like mush when you close-talk the mic. Learn how to work a mic, like many DJs do. You have to talk at a similar level at similar distances to the mic.

No compressor is going to give you the ultimate improvement in loudness. They just work too slow. If you want to get louder, you need a fast peak limiter or clipper after the compressor. Classic clippers include the CBS Volumax 400 or 4000. Or the late-70s vintage Orban Optimod 9000 or 9100. Or you can build one. As opposed to the slow action of a compressor, a clipper works on each cycle of the audio waveform. Many clippers allow you to manually select the 'loudest' audio polarity, or they will flip the polarity automatically for you.

That is the classic AM broadcast setup. A compressor/mic processor/EQ followed by a final clipper/peak limiter.

Remember a processing rule of thumb: Just as a little salt is essential to a good meal, too much will ruin it.

Clark,

>My understanding was that the unit would keep audio levels equal even if I leaned back in chair or turned my head to look at >the meters ect.. This effect is not really shown.  If I get closer to the mic, I am louder. If I back off, I am softer. Should a >compressor not clamp and boost to give you a constant avg output?


I don't know anything about that DBX in particular.   Sounds like the performance you are looking for is what you get with an extremely tight peak limiter.  You need not a studio limiter but one used on AM broadcast rigs, that will clamp a certain level and prevent over modulation.   But first, it's a good idea to have a scope, dummy load and separate receiver to hear yourself with before you start working with outboard audio gear.  It's also a good idea to run the audio equipment output through an isolation transformer in the line to the tx if ur having any hummm.  I'm also assuming the last audio box before the tx is somewhat matched to the audio input Z of the rig and the tx is passing audio flat from around 20 hz to up beyond your high frequency cutoff and ur rx or diode detector-->AF amp has a flat rx response.  An AF signal generator is nice to have too, to work all this out.      

Okay.  With a real tight limiter riding herd over your audio, you can scream into the mic but you won't overmodulate yet you can back off and let the compressor boost your low level sounds.  Of course you can dramatically reduce your dynamic range and wind up with a lot of processed sounding density if you overdo the compression.   Back off on the compression and let the limiter curb your peaks.  The CBS Labs audimax/volumax combos did that too and were the secret behind the old 1960s loud rock stations like WLS.  Anyway, if you have good modulation and linearity you should be fine.  So, the cheapest broadcast limiter I know of is the Inovonics 222.  You can sometimes find them on eBay for around $500; maybe less.  They used to be cheaper, as low as $100 used, but part 15 AM broadcasters discovered them and drove the prices up.   The 222 gives as much as -12 dB extremely fast gain reduction, up to 130% pos. modulation and in most models a 10 KHz low pass filter.  If the 500C doesn't like that you can always dial in 100% pos and neg.  the filter isn't of much use to hams since we probably tx out around 5 Khz or less from carrier but I've heard that Inovonics will supply components to give you a lower freq. cutoff.   I realize the money may seem like a lot for an audio box but for AM once you get one and start using it, you'll feel like you got a really good deal.  Happy testing one two three and don't rely on audio reports off air from other hams.  Listen to yourself (use a good pair of headphones Sennheiser HD280s are good cans) or get guys with good receivers to email you mp3 files of you taken off-air.  Dig around in here:  http://amfone.net/ECSound/  good audio advice in there from K1JJ et al.  it can be quite a revealing experience.  The first time I swept my rig I discovered it was no where near as flat on tx as I thought.  I also discovered I was hitting 100% on low freq. vowel sounds, wasting power on sounds that were rich but lacking in intelligibility.  Make sure ur GK is flat, ditto for ur rx audio gear then start adding in the outboard processing boxes.   the limiter should be the very last box before ur rig. 

73

Rob K5UJ  

Thanks to all

Gate:
After playing with the unit more with the use of headphones, I can really see how the gate works.  A carefull balance is hard. I can hear the Gate turning off and on. Maybe this cannot be heard over the air though.  The fan noise in the room is pretty high.  Its nice to have the noise gone.. But its not nice to have it PUMP on and off between words. I think I will end up using very little GATE and let the ambient noise come in at times.

Compressor:
I figured out that If turn the compression threashold knob to -10 the over all signal drops 10DB. I can see that on the meter. But if I then Set the output control to +10, I get all that back plus about double.  With this set, in normal talking I see about 6DB to 10 DB on the compression meter.  When I go to bypass my overall sound is MUCh lower.  I am using the Overeasy feature (soft knee) which is much smoother on the ears with my voice.

I found a ratio of 2 to 1 seems to work well.  If I run less its not enough and I have run more it seems like to much.

Attack and release:   I use the AUTO feature.  This enables the DBX system and I cant seem to improve upon it.




 

Sorry for the double post.. But ever since I upgraded to a new PC with Windows Vista, This forum is a major pain to use. I can type TWICE the speed the forum software will except and if I type more then the one window, The text jumps up and down.. Anyone have a way to fix this?


Part Two of post:

The main thing learned was that the Compressor is removing signal and to get that compression, You then boost the output of the device. 

I find I am really missing the limiter function.. I see the 166XL model has the limiter.. Its another $100.  Should I stop now.. Return this Compressor gate and just buy the 166XL Compressor, gate, limiter?     

I say this because I was expecting to be able to set a hard output level. This way, I could NEVER over modulate the King.

Clark

Try recording your audio and playing back rather than listening to yourself in the cans while adjusting the setup.
You want to hear the sound through the audio chain, not the combination of the audio chain plus direct conduction through your head .                         Ian VK3KRI

Clark,

I just thought of this--if the broadcast limiters mentioned are too expensive you could try a negative peak limiter circuit such as this:  http://www.classeradio.org/3-diode.jpg

I have not tried this -- I bought my broadcast limiter originally for SSB where a diode clipper won't work, and when I got into AM I decided to keep using it (I mean, it was designed for AM so why not  ;) ) but this simple circuit or something similar to it might limit your negative peaks in the Globe King and cost a lot less!

73
Rob K5UJ

Hi Clark
The adjustments you made in your last post are pretty close to mine. It should have a pleasant sound on the air without heavy processing. And the increased modulation will give you an edge when conditions are rough.

Fred

Why not try the virtual rack I sent you.  It has a De-Esser, De-Syballant 'machine', hard limiters, a simple compressor, 5 band compressor, 31 band eq, 3 band compressor, C-Quam stereo encoder, etc.  It even has studio echo and reverb, should you want that old style studio AM sound.

Once you fool with it (it has over 100 different machines you can add), go purchase something that does what you want, rather than sitting here throwing money away after something you're not sure you can get with what you got already.....

Try the rack on the computer.  I did.  Sounds just as good as the 'real rack', and only requires audio in and out.  I haven't used iso transformers, and have ZERO problems with it.  Matsushita caps work best, the 220uF being the smoothest coupling cap I've seen, as well as many of the ESSB guys (that's where I got the idea to try it).

--Shane

A clear demonstration of what I was saying in the previous thread on the subject.  It is AVERAGE power, not PEP, that determines the loudness and effectiveness of a clean signal, and therefore its interference causing capability.

The Bird 43 does not give a true average power reading for a complex, non-sinusoidal modulation envelope, but for what you are trying to do here, it gives a relative output indication, which is all you need.

EXACTLY!!!  I remember being laughed out of conversations when trying to explain what at the time was "my crazy theory" about talk power, etc.  Then, I was the first that got a 43P in my "group", and that pretty much ended the conversations.

And thanks, in retrospect, for the discussion before.  It would be interesting for someone to put something together about processing AND wattmeter dynamics, too.  I mean, this is a SERIOUSLY misunderstood phenomenon, just tune the bands and you can see that MANY people don't know how to adjust their processors, etc. to get them right.

Here's a ? for ya.  If you wanted to adjust your processing chain for max loudness, crispness, etc.  we know you can't do it on a single tone, or using a set of tones like an IMD test.  Think it's possible to create a 'complex waveform' (like someone did to pulse tune amplifiers on this reflector about a year ago) that WOULD allow us to do just that?

--Shane

Yea,.. everybody has them now,, Slopbuckets, AM.ers,, Regular Hams,, CBers on sideband using Amateur Gear..Yea it's contagious Audio Processing.....

Now it's Become the Norm of Amateur Radio, all across the bands, Lotsa Audio Processing going down...

73
Jack.

One basic rule needs to be mentioned.

The louder your audio, the more you push it to the edge, the lousier it will sound.
You need to pick the appropriate tradeoff point- "Loud enough" and clean vs. DX pileup audio, mush and distortion.

I have decided more and more that I need a limiter.  The one in the globe king is not working for some reason. I dont like it anyways. Its not adjustable.

I would like to limit my outbound modulation to 100%. Then, Use the compressor up against the limiter. I think this will make for the best punch and sound. 

Shane, I dont have that program anymore. What was it called? I can try it out. I just need some cables. I can run it through the effects loop on the mixer.

I would rather just use a D104.. LOL.  But on my Globe king, You cant get above 80% audio when you run into the First Preamp tube. It does not have enough kick to move the rest of the chain.  If you drive the second tube with the mixer, I can go 125% easy.

Thanks for all the help!  I will try recording and playback today!

Clark

If you'd like to hear a decent system, on 27.025 there is a gentleman called Prime Minister.  He's running a direct injected Flex radio, with another system set up with ProTOOLS audio processing.  This runs into a 3CW40K, so should be NO problem hearing him when he is transmitting.

The audio quality of that system is just short of amazing.  Guess when you are a professional recording artist, the sky's the limit. 

MANY of the guys on the 'superbowl', so to speak, have been watching the amateur boards, direct grid feeding their boatanchors, flex radios, etc.  I've made, and another gentleman is making modulator boards allowing direct fed audio into ANY transmitter, for HiFi AM / collector modulation.  So far, we've got neg peak clipping, hard limiting, switchable controlled carrier AM, etc. 

Anywho, you are correct, the processing bandwagon is wide open...  Shoot, there are guys on 2 meters now with processing!

--Shane

I'll resend you email I sent, it had the effects rack in it.

The programs I use are Adobe Audition 3.0 as well as Reaper.  MANY of the superbowl guys are on ProTOOLS now, since it costs more than anything else, it must be better, right?

Anyway, I'll get the effects rack.  I use it with my D104, and it works great for me.  I put an RCA on the side of my Silver Eagle, and I still use it for PTT, etc.  Audio just wraps through the computer.

--Shane

That depends on how you do it, and whether or not you are exceeding the headroom at any stage along the audio chain.  Then it depends on the type of "processing" you are using.

The purpose of processing is to keep your average audio level as close as possible to the point of overmodulation or to the saturation point of the weakest link in the audio chain on voice peaks, without actually reaching that point.  It usually consists of some form of agc to keep the average level more steady, followed by some form of peak limiting or clipping to take care of errant peaks.  When done properly, it can produce minimal distortion of the signal. Don't expect to achieve a 10 dB increase in "talk power".

Anything that alters the voice waveform to make the audio sound "louder" for a given percentage of modulation, inherently produces distortion.  Every human voice has a characteristic peak to average ratio.  Anything you do to alter that ratio is, by definition, distortion.  Some forms of distortion are more objectionable than others.

The simplest and dirtiest method of generating "loudness" is simply to turn the mic gain clockwise, to hell with the distorted sound it produces and the splatter that results.  You hear plenty of this during any slopbucket QuaRMtest.

Email is sending now.  It's 10.7 megabytes.  I sent it to your newer email addy, not the one that's decades old...  Lemme know if you need it split up, and I'll do that.

Instructions to install are included in my email.  Lemme know if you need more.

--Shane

You know, I used to show that to guys in the shop as well.  Put the Bird meter inline, and start turning the Auto Mod Control to disable it.

It would result in an increase in the AVG Pout UP TO A POINT....  And then all of a sudden, the OScope would start to pinch off, and the AVG power would start to DROP, while the PEP stayed the same or would continue to increase.

Was easy to convince truckers that clipping the modulation limiters was NOT the best idea after showing them that test.

Also won many a 6 pack of beer with that bet :)  I'd even let them bring in their own radio to show them.

--Shane

You might want to install the famous "3 diode limiter" in the modulator, to prevent baselining no matter how hard you drive it? A good idea, even if you prevent overmod via an external limiter... the info is sitting around here on a link probably to the amwindow site...

           _-_-bear

Shane,

First of all I didn't Know The Flex Rigs are able to operate on Chicken Band...LOL....that's a piece of news to me.  

And this Direct Injection System.,,? that's feeding the Balanced Modulator Directly right, as I understand it I don't do it so I'm just working on a wim here. There are some benefits to that, ESSB..


73
Jack.

Part of my job is to design the parameters of the Omnia AM broadcast audio processors.  I start with about a 2.5:1 ratio slow wideband AGC leveller, followed by about a 3:1 ratio multiband compressor, and thats followed by a brick wall limiter.  Hit the limiter with about 2 to 4 db hard limiting.  A gating function can be applied to both the slow AGC and the multiband compressor.  I adjust the gate to "freeze" the gain changes whenever the input audio drops below a user set threshold.  That avoids pumping.  Also, some mic processors also have a compression, downward expander, and gating function (such as a Symmetrix 528).

The key to generating a dense but not overblown punchy processed voice signal is to apply brick wall limiting ONLY at the final stage of the processor, immediately before the transmitter audio input.  Also, the flatter the response of the transmitter, the more you will be able to utilize aggressive processing.  For amateur radio use, set about a +6db shelving boost starting at about 1.8 kHz, and sharply filtering out anything above about 4.5 kHz.  If you have a lot of room noise, close talk the microphone to keep the ambient noise level down.

When you listen to your audio as you are adjusting it, you will find the point where adding processing does little to add loudness, and too much makes it sound more compressed and/or distorted.  Set your final adjustments to where you just approach the "sweet spot" where loudness maxes out, and excessive distortion has not set in.

73
Ted  W8IXY

That explains why we haven't heard Dale on 75m in a while - he's moved up the bands!   ;D

Thanks to everyone and to Ted.

I just wanted a simple Compressor limiter. It appears I purchased the wrong unit. I am going to return it today and by the unit that has the adjustable limiter.  Then I can set a hard limit.  I dont like pushing the old King 500 to hard. The mod iron is known to fail.

Thanks for all the tips on the adjustment procedure!  I got a great report last night from some guys that know audio. So the compressor is helping. The gate is nice as nobody can hear the fans running in the room.

Shane, Thanks for the link. I will play around with that software!

Clark

Shane,

First of all I didn't Know The Flex Rigs are able to operate on Chicken Band...LOL....that's a piece of news to me.  

And this Direct Injection System.,,? that's feeding the Balanced Modulator Directly right, as I understand it I don't do it so I'm just working on a wim here. There are some benefits to that, ESSB..

73
Jack.
[/quote]

We started out using Kenwood radios, and feeding the BM directly.  Then we discovered it was MUCH cheaper to use a single pass transistor, a audio amp IC and modulate the final / driver of a 4 watt type radio.  At that point, HiFi became a reality, for about 80 dollars, complete.  3 total transistors, a 39 dollar radio, and an audio amp IC.  Add about 6 caps, a variable resistor, 2 diodes and you're about done.

The system I did up used a CB radio chassis, the 148.  It feeds the audio chain directly, into the BM for SSB hifi use (although you get a LOT better tonal quality, it is NOT HiFi, as the TX chain goes through a xtal filter on XMIT and RX) and directly into the audio amp for AM.  It is a high level transmitter (albeit at the 16 watt PEP level, it modulates the driver and final directly in one guys, mine runs the final in Class AB at full voltage, while the driver is modulated.  Mo PEP power this way).

You can't do SSB RX HiFi with that radio, since it's using a xtal filter on ssb as well, but the AM filtering is pretty wide...  Tapping the volume control will produce a LOT better rx, and if you tap the center detent, it's line level.

That's about it....  I'll answer anything else, but probably better off list, as this isn't a CB reflector.  It IS nice to be able to play with HiFi on 10, though, with nothing more than a 70 dollar EBay special Cobra, though :)  I can't wait for HiFi 10 meter playing... C'MON SUNSPOTS!!!!

--Shane

I'm not sure who Dale is.... BUT, here is a semi list of stations here on the west coast you can listen for.

Prime Minister (Mostly FLEX driven, with a 60 inch display!!, but also has every Johnson made)
Doc Adams (Johnson's and Barker N Williamson Xmitters, Collins rarely used)
Radio Station West Side (tube homebrew transmitter)
Radio Station MotorMouth Maul (His Homebrew modulator into a solid state Cobra 148)
1-800 Toll Free (My homebrew Modulator with Cobra 148)
GhettoWay Driver (My Homebrew Modulator with a Cobra 148)

Small list, for those on the east coast.  Doc Adams, Prime Minister and MotorMouth are all running ProTOOLS.  1-800 runs Adobe Audition or Reaper, Ghettoway Driver is using Reaper.   There is a MULTITUDE of others, but by listening to these guys, you can actually hear the differences in the computer software..  They are MINUTE, but there, even when you have Ghettoway Driver and 1-800 using the SAME plugin software (Izotope), but different "processing" software itself.  And every one here but the Flex driven station is running high level mod. 

On the West side, listen for 2112 in Georgia, he's running a Flex system, as well, with Reaper.  Most of the other guys over on that side of the US are using ProTOOLS, so 2112 can give you the biggest difference in software sound.

All these guys run tubes with handles, so QRM/N would not be a big problem :)

--Shane

LMAO!!  ;D ;D ;D

http://www.circusmobile.com/waves/Prime_bump-it-down.wav (http://www.circusmobile.com/waves/Prime_bump-it-down.wav)

Very funny stuff!

Look up his song about the Johnson Vikings.. 


Clark

If their audio is clear enough to understand what they are saying, they are not real CBers!   ;)  What's this world coming to.

Well seemingly there's quite a bit of use of Computer Audio Software, and to me that would be somewhat more cheaper than buying up these audio processors, much more ease of use, more choices on Audio Processing, an Less cabling issues, I could be wrong.

73
Jack.

Dale is/was a VE3 station who identified himself as the Prime Minister and had access to a lot of big iron. He actually ran a business for a while dealing in old BC transmitters and the like, but the prices tended to be outta this world, getting an email response was unheard of, and he eventually went out of business and disappeared. Last time I heard him was a year or two back, pissweak on 75m one night, getting laughed at by the guys on the air because he was running a 706 mobile as his primary (and only) station.

He and Irb were inseparable.  ;D

That's the first tape.  Circa 1999, released at a big break in Arkansas.

Since then, he's also released "Great Big Johnson"...  "Cuz a woman loves a man with a great big Johnson", "I need an 18 wheeler to haul this great big ol johnson...  Armed and Dangerous Gettin on down" (running a valiant in his 18 wheeler into a 16 transistor amplifier), etc.  He released another song in between, "Ain't no 'Scuses on the SuperBowl", lastly followed by "The Hammah Hits Hard".  The last two songs where released to help recover the costs of nationwide breaks the 'cb club' he belongs to administers...

--Shane

AHHHH

I know exactly who that >>clown<< is.

I have one of a pair of Harris RF-103's he sold to, actually, the guy Ghettoway Driver, mentioned above.

Both where supposedly 100 percent working when they left, as advertised.

When the new owner in San Diego got his amplifiers, one didn't even have a tube and chimney in it.  He ran it for about 2 months, and one of the diode stacks in it blew (K2AW style).  He called me up and gave it to me..  I couldn't make the trip to San Diego fast enough!

Prime Minister on CB is NOT named Dale...  I know him personally....  Funny, though, Prime Minister ALSO runs an equipment company :)

--Shane

I got the 166Xl from DBX. This has an adjustable hard or soft peak limiter, expander/gate and compressor. It is a much nicer unit than the 266.  

Now, have the King set exactly at 100% and no matter what I do with gain or even screaming into the mic, I cant go over 100%. I actualy backed it down a bit more to go easy on the old girl.

I have about 6DB of compression set it with a peak of 10DB.  I can drive the input up and my voice rides the soft peak limiter. No sign of distortion but I am now very loud on the air. The difference is amazing really. My RMS Bird meter is going forward when I talk slightly.

Talk power and a wide full sound is what I gained.  Finally.. A Globe king with AUDIO.

Any king owners should consider this route. That first Preamp tube is pissweak and will never run the ring up to its potential.

Thanks to all that have helped me!

Clark

I Actually Like the DBX 286A
http://www.dbxpro.com/286A/286A.php

and it has RF Proofing built in nice little plus there.


73
Jack.

Rumour has it that the Prime Minister has/had only "Basic" Qualification.  He always seemed technically knowledgeable enough to qualify for the "Advanced" Qualification, though.  Maybe this was before the code test was eliminated, which I think occurred before the US did it.

I haven't heard Miss Piggy on the air in a coon's age.

I did not care for that one jack.. It has no adjustable Peak limiter. 

I have learned something very important today.  You should start with NO EQ settings into the compressor/limiter.  Then set the amount of compression you want.. Then set the output and peak limter.  After this you should use the EQ to CUT freqs you dont want rather then BOOST freqs you want.  Otherwise, the boosted freq might activate the compressor way before other freqs in the range.

ONce my EQ was flat, I got a tremendous about of talk power while staying under 100% peak mod. 

Clark

And then give yourself a 3 or so dB bump from 1 to 3.5 kC for slopbucket.  Simple to make that adjustment, and will be about the same as going to the Heil DX HC element.

You're right, start with the EQ VERY limited.  With processing, until you learn what EACH control will do to the overall tonal quality of your TX signal, LESS IS BETTER!  After you get the hang of them, then you can REALLY get that sound quality you want.

--Shane
 

This setup is just for the globe king.  I run a hand mic on the Icom pro or deck mic on the 1000d for the limited amount of SSB. 

I run a D104 on the Globe Champion.  Nice and simple and probably sounds better or as good as the outboard audio Globe king.. LOL

If I ever redo the room, I will set this gear up in the middle and run cables out to each radio. It would really clear out the clutter.. I have about 8 microphones setup here.. LOL

Clark

Then why not fix that mic preamp stage and save all the hassle?    :D

That's good info to know about the mic amp stage. Wonder why World Radio messed up on that one? I would have guess the driver stage first. I just bypassed all the internal audio stages on my Globe Champ and went straight to the grids of the modulators. But that was because I was lazy.  ;)

No rumor involved Don, all true from what the guys up north of the border tell. IIRC, he upgraded later when requirements changed, but disappeared in recent years. Last time I heard him on, he was using a 706 in his car, was pissweak, and said something about going back to nature. Maybe Tim the flying squirrel will chime in with better info.

If it's the person that sold this pair of Harris amplifiers, then yeah, he only had a basic qualification license.

He disappeared, actually, pretty much right after these amplifiers where shipped.  When they arrived, one missing a tube, chimney, plate cap, and a couple other things, he tried to call "Minister"...

No answer.  The call that ordered these amps was the last time my friend was able to get ahold of anyone at that number.

--Shane

And I will steve.. But for right now, This is my Big radio.. LOL.   When the big transmitter is done, I will move the audio gear to that rig and I can figure out a tube replacement for the Kings preamp. SOME modulators had TWO second tubes.. Mine has ONE.  So maybe the saw this and fixed it..But currently if you use that first tube, The audio is weak at best.

Clark

I hear ya. Once you have something working, you wanna use it.

Interesting about the mic preamp stage.  I would have  guessed it to be due to the modulator.  They run 1800 volts on the 4-250 (or is it 4-400?), but only about 1000 volts on the modulator stage.  The mod xfmr has a step-down ratio of about 1.2:1.  So, in the best of all worlds, it would be a wonder to get 100% modulation out of the thing.

My suggestion would be to beef up the modulator power supply voltage and perhaps replace the 811A's with 572B's, along with a better audio driver stage - maybe a pair of 6B4's or 2A3's, or as Derb said, a quad of 12B4A's.

http://www.circusmobile.com/waves/Prime_bump-it-down.wav


Man, that's a great rap!


"Look at that swing - Prime Minister's bumping that thang."

"And I put a choke chain on the duck pluckers...."

"I put a 25K slug deep in the corner."

"And try to get me in-between keys and I'll bury your ass..."


(I think we might hear some of these riffs on the air soon)


T

Its a 4-400.  Mine runs about 2000 volts. Solid state diodes, 14MF worth of cap.
My mod deck has 10MF of cap and 1550 volts. Preamp stages are running 450 volts or so. 

I get 125% mod out easy.

The trouble Don is the FIRST preamp tube.   If I use it, I get 80% max and crapy peaky audio.  Here is the schematic.

Clark

Jussa buncha dum CBers :)

Keep listening...  On one of the tapes, you hear Mr.  Toll_Free on the "watergate".

"Cuz when I put this maul down, around your Seattle Town, Minister, Can't NOBODY else get down.......  And yo Toll_Free Hi Fidelity Injected Modulation Base station down around these killin fields got down".

Small tubes that day, but it's there, on the last tape.

Blah blah blah... My claim to fame, making it on a rap tape about CBers, because I ran clean audio and a tube with some handles on it.  :)

--Shane

Funny raps. They were doing that stuff back in the 70's, long before the so-called music rappers of recent years. What's old is new again.

I like listening to that style rap.

This whole "I can kill you, your family, and everything around it, because I'm hard, and I've done more drugs than you.... All my homies are badder than you, foo" stuff has to go.

I mean, HOW many times do I have to hear what a bad ass you are, riding around in your Mother's Lexus while wearing your A & F 'gear'.

--Shane

Don.. I just heard you on 3885 in arizona. Nice audio.  30 DB over.  Could not come back as the king was set on 40 meters and I was listening on an ICom Pro.. 


Clark

Same guy. Very prolific. Very funny. He likes big butts.

http://www.youtube.com/watch?v=xvE3SkiYqlU&feature=related (http://www.youtube.com/watch?v=xvE3SkiYqlU&feature=related)

The whole "big butts" thing was in response to covermodels of the late 80s and early 90s.....  And the way the "black posterior" was NOT getting it's ample "airtime", so to speak.

He is now the man behind the music, so to speak, in anything Microsoft.

--Shane

Yea,.. it's always been a thing on the Forum,,... Lack of Big Black Butts, Rapen it up.... 8)

Man what a rip....lol

73
Jack.

 

WTF?  Isn't this the Technical forum?  For a moment I was thinking maybe I was in a state of confusion and had erroneously clicked on QRZ.com.

Just an update after using the Compressor limiter for a few days. I have a big increase in audio with out overmodulating or splattering. 

I have had very good comments on the air.  Most say my Audio is much louder and cleaner then my signal would normaly have. I am enjoying this.

Last night I listened on 3885 for a hour. Don and some guys where talking.  Don had 40 DB carrier but audio so low that it was hard copy. Some QRM but not much. The Tone is great.. But NO punch and NO clearity for DX. I am sure if he was in town it would have sounded nice and smooth. The other station had a 30DB carrier but could not copy any audio as the bass was so boosted on his signal so much.

A little later, A station with a Valiant and a D104 came on with less over all signal but CLEAR audio in the speech pass band so I could hear every word he said even when he faded down in the noise.  Remarkable.

This means alot to me because when a 150 watt station running 10DB to 20DB over is twice as inteligable over stations with 30 to 40DB over I wonder what the point of the big stations are?  Rag chewing with a focus on Great Wide band audio? OR Communications over DX.  I am starting to realize that alot of these mods and lack of COmpression, and or Speech passband limiting is probably a big negative for any kind of dx. 

Thoughts?

Has anyone had this experience? 

Spent ALL day fixing the Mic preamp stage Steve.  Your post bugged me.. so I set aside the day to fix it.  I found a cathode resistor that was supposed to be 2.2 that measured 500K. I replaced it. I found a short on the Grid pin to ground. I also found the Suppressor grid was hot hooked up correctly.. Due to me not following instructions. I found my mistake and fixed it.

Now, the D104 works and sounds well.. Like a D104.  I can get 80% mod out before the 6Sj7 starts distorting. Typical GK500 fashion..  I need more gain to go higher.  But, Its fixed, I can run the D104 now. Or, I can run the outboard audio and run 100%.

Clark

Cool. Now you have the best of both worlds. Just don't squeeze the D-104 too hard.   ;)

Steve.. Found that If I run a Powered D104, I can run the king down at 2 on the mic gain control. Then run the D104 preamp up a bit. The result is clear D104 sound with 100% mod.  Why this radio wont modulate a non powered D104 to full out is something I dont know.

Clark

I never like the 6SJ7 mic amps. Two stages of a 12AX7 alway seems to work better. That pentode should have a lot of gain, but I guess it doesn't have enough.

Yeah... Not enough..  But when you put the powered D104 in, You have plenty.  Just spent an hour talking on 7293AM. right at 100% audio. Great reports.  Nice D104 sound.  I wonder if there is another tube that would drop in with more gain?

Clark

Hello,

Speaking for the D104's non-amplified have you tried different heads on the unamplified stand. Not all heads are equal...and those elements can be tuned by simply changing the type of gluing arrangement whether plastic rubber or synthetic was used on the crystal element..it's fun to experiment on the heads to see the responses change..

On Older Heads the glue breaks loose at points output drops tone changes etc. need to get better involved with your D104's there's alot to learn about them and it's fun .....


73
Jack.

I tried 7 different D104 heads.  New and old.  I agree. That they all have a different sound. The one I selected has the most midrange and bass. 

Clark

I have a couple of "vintage" heads, that are a full 1" thick instead of the more common 13/16".  I can swear the thicker heads have better sounding bass than the thin ones, using otherwise identical elements and mounting hardware.

But I'm not sure how much I am being fooled by the placebo effect, the same effect that makes "hospital grade" power cords, wooden volume control knobs and "broken in" speaker cables improve the quality of sound from home stereo systems.
 
I use pieces of adhesive foam insulation strips to mount my D-104 crystal elements.  It looks to be about the same stuff as what the factory used originally.  I am afraid that hearing discernible differences between types of glue used for adhesive between the foam pads and the bakelite case of the crystal microphone element may be veering dangerously close to the realm of audiophoolery.

I was worried about the sound from my D104 so I Stapled Acoustic Foam all over the walls, Ceiling, Floor and tables.  Then I suspended the Globe king, reciever and tuner from the ceiling with Bungee cords.  Finaly, I hung myself from the ceiling with a harness.  This way, There can be no resonance anywhere in the room.

Seriously though.. Good point don.  Its is interesting on how the elements have a distict sound.

Clark

 " Finaly, I hung myself from the ceiling with a harness."

Oxygen free harness???


klc

 More modifications.. I deciede the Spring coil that held my harness up was imparting some resonance in the 2.25k range.  After 8 hours with a real time analyzer, we got the room flat!

Clark

No, I mentioned nothing about the foam pads Don, I am referring to the different glues that were used in different periods of time with the D104 on the metallic surfaces.

73
Jack.

The very early elements must have been screw mounted instead of using the foam pads.  My old 1" thick heads each have a big screw centrally located right in the middle of the rear plate.  The only thing attached to the screw inside the head is a nut holding the screw in place.  I suspect the original design used that screw to secure the element, and when the element was replaced with one of the later design with the foam pads, a nut was attached to maintain the screw in place and fill the unused hole.

The two smaller screws under the big one hold the bracket that secures the mic cord.  The early D-104's had no plug at the bottom of the head.  The cord was permanently attached internally.