The AM Forum

32v2 users: What microphone do you feel is a good choice for the 32v2. The manual does not really say what impedance mic is suggested for best performance. I have used the rig on CW for years but would like to put it on AM now.

Are the EV-638 or the D-104 good choices?

What sounds best over the air with an unmodifed rig?

thanks :)

 A D104 does a fine job on my V1 and V3.  However to sound best it requires changing the grid resistor on the first audio stage to 5 M ohm, or larger.  Now this isn't that big of a mod and can be done by sliding the transmitter about 3 inches forward in the cabinet to access the audio stage from the side. 

For a stock radio, I don't know.

Thanks, I beleive that is a 1Meg resistor now.

I put an 8 meg in my 32v2' but then used a mpf 102 source follower anyway in front of that.  The FET follower placed into the base of the mike where the two stage stock transistor amp resided before.   Used all the same switching and 9 v batt., but left pot in not connected.

Several older threads about all this on amfone including variations on the FET follower.

If the D-104 has a good crystal element the last thing needed is another amp stage.

A 4.7M input resistor load is fine and altho mo is often mo betta it can lead to stage instability. The V Line can also benefit from other audio changes unless you prefer the factory restricted passband.

I got so-so reports with my V2/D-104 and 4.7M before turning it upside down for changes which havent been completed yet.

Carl

I like the EV638 with the collins rig.  One tip I learned here was to put heat shrink over the 5 meg resistor, then cover that up with some RG58 coax braid to shield that resistor.  It will pick up hum.  Works like a charm.

C

what a great simple method of shielding the input resistor. THank you, I will try that.

Carl,  re: "last thing needed is another amp. stage."

The MPF102 follower does not have gain.  It is simply a very high impedance transformation to a typically lower impedance, say the 1 meg. input on common tube transmitters of 50's era.

 If you've been raised on transistors then 1 meg. sounds extremely high but from a crystal mike element it is low....   believe it or not, heh, heh.   I asssumed you knew that the D104 had lots of presence at mid to high audio freqs. but very llittle bass into a one megohm load.  Bass is much enhanced at loads of 5 to 10 megs. so that it approaches low end response of a typical dynamic mike.

The circuits described in this board or "The AM window" show phase switching, bass or treble enhancement, etc. along with simple impedance matching -- and all with one simple FET. 

Wouldn't changing the grid resister be a lot less trouble than building an active and extra stage? Hmmmm

Thats what I thought when I read all that stuff quite awhile ago....seems a lot of work. Ive nothing against SS when it makes things work better or its easier to implement.

If and its a BIG IF, the driver and mod xfmrs have enough iron to handle the lows then the 4.7M resistor is step one with a D-104, thats basics from the 50's. If the stage is stable then 10M is fine....triodes are usually OK.

After that its the usual component value changes to actually boost the bass as well as reduce stage gain if necessary when using a D-104.

Since the 32V is notorious for poor audio and power transformer insulation its not a rig that needs much in the way of enhancements. Run the 4D32 on the Low tap and dont try for any fancy audio processing.

Carl

Don’t mix apples and milk bottles. The source follower circuit is intended to be built into the TU base of the D-104 mic. This will allow use of the D-104 on any transmitter regardless the input impedance. It is not a mod specific to the 32V but one allowing greater versatility for the D-104.

Sure, you can use it on your 32V and any other transmitter. It doesn’t matter if it’s more work than changing the grid resistor, it results in more utility, so it’s worth it, in general.  It's probably easier just to change out the grid resistor, but not much when you consider the weight of the 32V!   ;D  That said, if the focus is solely the 32V than anything external is irrelevant.

The stock 32V produces audio quality equal or superior to the Viking I and II. The DX-100 might be marginally better (of the modulation is kept to about 90%) and the stock Apache usually worse (depending on the setting of the clipper). The driver and modulation transformers in the 32V are larger than those in the Viking I & II (especially the driver tranny which is very PW in the Vikings).

Agree when you only have one mike ;)



Unless the owner bought a restoed one rather than work on it himself. In the latter case it needs to come out of the cabinet anyway. Its not a rig to be doing a lot of lifting with.


But the others dont short out from just normal use as do the 32V's, just ask the rewinders. The Vikings are OK in stock form if you dont run beyond about an 80W carrier and audio to match; otherwise the driver iron folds up.
I didnt notice much difference otherwise in bandwidth and distortion between them....both need TLC.

The advantage of the D104 over most dynamic microphones is the pronounced rising high frequency response characteristics.  It naturally equalizes the voice in a favorably.  Many dynamic mikes lack this built in EQ, or  have it to a lesser degree.  The extended bass of a D104 when presented with a hi impedance load is a bonus.

Sounds like the source follower is a great idea if the owner doesn't want to modify the radio.

I always liked the sound of a stock 32V.  I think the Ranger is the only common vintage radio that sounds better.  I am looking for a HV transformer for one of 32V1's coincidentally.

The stock iron in the 32-V is more than capable, especially the driver. Rob, W1AEX recorded me on my modified 32V-1 late one winter afternoon last year.. The modifications followed most (with some changes) of the published ones on The AM Window..

Mods-

http://www.amwindow.org/tech/htm/32v.htm

32V-1 with an RE-20 into a a mic-pre (no processing) into a Shure mixer using the mic output transformer coupled.
Been running the high tap for 14 years, no crap outs , all original iron..

Recording-

http://dl.dropbox.com/u/17340243/32V-1%20Stock%20Iron.mp3

I agree with Charlie and Steve that the stock 32V sounds clean in stock form, and with SIMPLE mods starts to shine..

Hey, that recording stopped just when you were talking about your 1967 Firebird!  I want to hear the rest!!!  The audio with the mod's did sound nice.

Joe, W3GMS

By that I take you mean it doesnt have objectionable distortion....to which I agree.

But it still has the ARRL mandated restricted bandpass in stock form as does every other make and model from the mid 40's onward. The only postwar ham TX Im aware of that is unrestricted is the HT-9 which didnt stick around long and was replaced by the even scarcer HT-20

The 32V distortion specification: Audio distortion is less than 8% at 90% modulation with a 1000 cps input frequency.

We could argue endlessly as to whether that number is objectionable or not. Also, remember that that many receivers of that era produce that much distortion. To my ears, almost every stock 32V I've ever heard sounded better than any stock Viking I/II. It's usually not even close. YMMV.

So 8% at 90% is considered good? What about at 95 or 99%?

The Vikers are OK at 80W as Ive already stated, at 100-120W they sound like hell without several mods.

If you want a good low distortion receiver read Jays list

http://www.w1vd.com/BAreceivertest.html

Even some of the poor ones can be helped with minimal work.

Something as simple as a 1M resistor from P to P of audio driver and output tubes and a 47uF cap at the cathode of the driver can make a noticable improvement in distortion; Ive used a 100uF in the driver in a HQ-150 to get a better balance from lows to highs using BCB music (a local Hispanic station which has excellent variety) and talk shows. Also changed the two 1000pf high end rolloff caps to 270pf.

See Jays HRO-60 review for links to more audio improvements.

And surprisingly even the 1939 HQ-120 has excellent audio as built and its easily improved too.

No worries. If your distortion is higher than 8 percent just tell everyone it's your friend's transmitter.

Let's take a look at Jay's list. How about the venerable SX-28, a supposedly "good" sounding receiver. Here are the distortion specs.

Mod%  100 Hz  200 Hz  400 Hz  600 Hz  800 Hz  1 kHz  2 kHz 
90%     18%    18%     16%     14%     14%     14%    14% 


A transmitter with 8% distortion is more than acceptable with such a receiver.

Not everyone considers the 28 a good working receiver, its main claim to fame is its looks.

OTOH its another that can be much improved with some work.

I used a EV-638 with a HT-37, which has a similar input Z, and it sounded very clean and was well balanced.

My B&W 5100 sounds great with an non amplified D104, due to the 10M input-Z.  Also, much to my surprise, it sounds great driven directly from my Symetrix 421's unbalanced line out.   I had expected to have to do some sort of matching to make them play together well, but didn't.

If you are not hung up on Collins and just want a great sounding desktop 100W AM rig, trade it in for a 5100, which sounds better, is much more reliable, and is considerably easier to work on.

73 Jack KZ5A

BTW the EV-638 sounded like bovine flop on the 5100.

they all can be improved with some work. We're talking about stock radios here.

Old tube radios, at that. And casual 'amateur' use, not contesting or professional lab grade operation.


Exactly what I was thinking, Charlie. The Ranger is hard to top for good sound without modifications. The 32V is a close second. Collins tended to move more toward communications audio as time progressed, to get through the noise. Yet even on SSB in the 80s I would get positive audio reports using a KWM-2A, compared with the more prevalent Yaecomwood gear. I even had OTs comment something like 'you must be running a Collins rig'. Go figure!


That's a bit misleading. You're assuming today's conditions as 'normal' and applying them to a 60 yr old transmitter. This leaves out the obvious problems involved with aging components, aging insulation, and elevated line voltages. The low voltage transformer is the biggest issue with the 32V series today, having the sizzling 5Z4 and regulator sitting half an inch away with today's elevated line voltage doesn't help. And as you mentioned, Vikings and others have similar problems. Using a different mic or tailoring the audio won't roll back the years. And pounding the snot out of a stock old rig is more likely to cause failure.


Huh? What power did the ARRL have to mandate anything beyond their offices and membership? Numerous transmitters from that time frame seem to prove otherwise. Sounds like a UFO sighting to me. Show us some proof, big guy.  ;D

To the original question - a D-104 with a known-good crystal element, as discussed on here numerous times, is tough to beat for an off-the-shelf, good sounding mic. It mates up nicely with many old tube transmitters with zero mods including the 32V, and can sound even better with some simple changes to resistors and caps. There's a reason it's been around so long and used by so many. Max results with minimal effort. You can always go nuts if audio is your thing.

One can certinly run a crystal element directly into an unbalanced mic cable and into the super hi-Z of an input grid circuit, but then you've got a hi-Z source terminated by a hi-Z destination.  On paper, all is well.  But that hi-Z mic line can then be prone to noise and buzz.  Ever connect a hi-Z crystal mic into a hi-Z input of a tube-based PA system?  Just kick the mic cord and see what happens. 

One benefit of the FET as a source-follower is that it's output is low-Z, generally set by the value of the source resistor.  This can help reduce noise on the mic cable.  For long unbalanced mic cables, take the extra step and treat the cable as a quasi-transmission line and terminate the destination into the same Z as the source Z. 

Paul, W9AC

Long cords can also roll of the highs in a hi-z situation.

I tend to question that SX-28 result but Jay would have to comment on what was done to it first.


Its far from misleading as all BA's have to follow the same path. Some survive at 120-125VAC input and others dont. With all the visibility given to bucking transformers I have a hard time understanding why so many play Russian Roulette. I cant speak for the 32V1 but the later ones are known for audio iron, filter choke plus the LV transformer failures. That one I picked up at Nearfest had replacements in it from decades ago plus good spares were includes.

I said absolutely nothing about Viker iron failures, with good filter caps they seem to last just fine. Now, some bozo trying for extreme audio is asking for the mod iron to sizzle but thats not Johnsons fault.


 


Very simple my uninformed friend...they controlled who could run ads. This was when they became fanatically pro SSB and were reacting to all the overwide signal complaints about AMers. So manufacturers were pressured to narrow the bandwidth to, I believe, 3KHz per SB iffn I remember.
The Viking 1 was delayed in delivery because the audio section had to be redesigned.....maybe that pathetic driver iron was part of it

Start by reading all the old CQ's for more info, most cant be found in index searches.

Carl

Pure bunk. The ARRL was not going to turn down ad money. Name the companies that made hi-fi transmitters or non-ARRL approved transmitters that weren't allowed to advertise.

Sure ya did:


See? I don't think running them at their rated output could be considered 'extreme'. I'll bet if you cut back the 32V to 75-80w you'll have fewer failures of original components too. It just stands to reason due to the things mentioned previously about elevated line voltage, etc.


Don't need to - there are already ample examples of this theory being inaccurate too. Not that the ARRL wasn't eventually pro SSB, we're all certain of that. But as I pointed out in a thread in the QSO section, SSB had yet to become an issue when some manufacturers like Collins were restricting bandwidth on their own, to create more audio punch and sell more radios. Simply a business decision. The KW-1 sold back in the early 50s and started off with much broader audio than it ended up with. If your conspiracy theory is true, why wouldn't they have started with restricted audio from the get-go in 51-52, instead of waiting until half way through the production run? And the Ranger is known for having broader audio out of the box. Did Edgar not get the ARRL memo until the Valiant in '56? What about the Eico 720 from the late 50s/early 60s?

I wasn't there, but everything I've read and heard from others back then says it was merely a case of it being Amateur radio, not broadcast AM. Communication was the goal, so the more punch your audio had and the less wasted in extra lows and highs, the better your chances for being heard. Who wanted to sell a transmitter that sounded wonderful but got lost in the noise?

"It was the one armed man!!!"  ;D

They didnt lose a penny since it wasnt a sudden decision. The manufacturers had time to react with maybe Collins leading the pack.

Name me one hi fi transmitter after 1950-51. Maybe the real low volume ones werent bothered but CQ had many ads that werent in QST.

If you want to be an ARRL apologist and not do any research thats your choice.
I do know you werent old enough to go to the ARRL conventions in the 60's and hear Halligan and others speaking up in the hospitality rooms at night but I kept my ears open.

Folded up doesnt mean failed, I thought you knew more about the teriminology.  Also Im still trying to get it thru your thick bean that the later 32V's had problems before AM died off and yes 125VAC doesnt help these days. But the Vikers dont seem to be bothered nor do most other transmitter brands. Ask Gary what he thinks about Collins iron, I forget his call. http://members.tripod.com/tubes_tubes_tubes/transformerrewindingservice/




What examples? All Ive seen so far is chatter.
As far as Collins the obvious answer is that they phased into it rather than scrap costly iron. Im sure the ARRL had agreements. Who cares about the KW-1, they didnt make enough to count anyway.

The Ranger is known for WHAT? Do you have a plotted bandwidth handy or does it just sound better because iron isnt being stressed into saturation?
The Eico 720 was a CW rig for crying out loud and the seperate 730 wasnt anything special as designed, what is its BW? Did the 730 ads run in QST for the years it was offered or was it more a catalog and store item?


Not there but you believe everything you hear 3rd hand and more. The fact is that the punch became accepted with the help of many QST editorials and articles drumming it in.

The deep lows were a waste of power and highs didnt affect the talk power, it was bringing up the average percentage that gave the punch. Highs took up some BW but even they were chopped off in many receivers by 1955 or so
Even the fine sounding phasing rigs were restricted to around 3KHz but sounded a lot better than 2.4 to 2.7KHz filter rigs.

When I kick my TS-950SD to about 3300Hz on AM or SSB it also sounds much better.

I didn't think you could name any manufacturers. As I said pure bunk on your part. Next you'll be telling us NASA never went to the moon and it was all the ARRL's fault. What load.

Do some research and get back to us when you have some facts. I'm not interested in conspiracy theories.

YAWN

Kiddies sure have little ability at basic research :o

Ooooo, that's a harsh generalization there. It's like saying all old fudds are easily confused between opinion and fact, or fantasy and reality. Next thing you know, you'll be watering the house plants with shampoo and someone will be setting all those nice radios out on the curb. Tick tock.  ;)

Maybe the reason people are so curious about your claim is because others have indeed done research and no one has every found anything to it. Folks would still love to see the actual proof of this technical conspiracy you allege. You've offered your fond opinion, but no real facts. You know what they say about opinions.

The interest is there. If you can ever turn up any real documentation, there's a thread in the QSO section referencing your previous mention of it, or you could always start a new one. Since the Technical section is for technical discussions and not conspiracy theories, and since this thread was about the best mic to use with the 32V transmitter before being hijacked, I guess we're done here.