[Johnson] Viking 1 "gotchas" ?

[Bry Carling]

Thanks Richard,

Maybe I will use one of my low-z vocalist mics with a transformer. 
They have a pretty pleasant sound for the human voice and might give me
some nice high fidelity audio on AM!

Bry AF4K

On 22 Feb 2013 at 10:24, Richard Knoppow wrote:

Send reply to:  	"Richard Knoppow" <1oldlens1 at ix.netcom.com>
 
> ----- Original Message ----- 
> From: <tbs50a at aol.com>
> To: <bcarling at cfl.rr.com>; <burnsguitar at yahoo.com>; 
> <patrick at ae1pt.com>
> Cc: <Johnson at mailman.qth.net>
> Sent: Friday, February 22, 2013 7:53 AM
> Subject: Re: [Johnson] Viking 1 "gotchas" ?
> 
> 
> > Hi Brian and Bry,
> > One the V1 a few thinks come to mind. Bry mentioned the 
> > final toob.Oringinally it used a 4D32 but at one time they 
> > where very expensive is Johnson came up with a mod to use 
> > a 829B.The output is a little less abt 85wt vs 120wts. The 
> > 4D32 was abt $100 vs $10 for the 829B. In the 1990's a 
> > bunch of the 4D32's hit the surplus market at $20.\
> > Always make sure that you have grid drive to the final 
> > before you apply the HV. Originally the V1 didn't have a 
> > clamp toob so you can wasted the final.
> > Three things come to mind on the electronics.The voltage 
> > divider resistor R13? 15K 50watts Usually open..When open 
> > you won't have screen grid voltage on the mod & final 
> > Clean the meter switch really well. And pull out the 
> > roller inductor and clean it too.
> > Bry, On your D-104 I read somewhere that in the cartige 
> > there is a diaphragm with a pin in the center of it. That 
> > pin has a wax seal on it. Use heat to reflow the wax on to 
> > the pin. That should fix your low fq problem. Long time no 
> > chat OM.Have been in bed all week with a bum back. If you 
> > could say a few words in prayer that would be wonderful!!
> > GL&GB
> > Terry N3GTE
> >
> 
>      Most crystal microphones and headphones, at least the 
> ones with diaphragms (there is another kind) drive the 
> diaphragm with a pin. I would be very careful of using heat 
> because heat can destroy the crystal element.  They are 
> sensitive to heat and moisture.  One of the features of the 
> Astatic crystal mics was their method of sealing the element 
> to prevent moisture damage.
>      The D-104 does not have a lot of low end; this one may 
> be normal. I would compare it to another to be sure.  The 
> D-104 was designed for voice communication purposes and has 
> a steeply rising response curve with a fairly sharp peak at 
> about 4 khz. It can sound metallic or tinny.  Also, the load 
> impedance has a very strong effect on the response of a 
> crystal mic; the element looks electrically like a capacitor 
> so any parallel resistance makes it a high pass filter. 
> Crystal mics want to work into a very high impedance, the 
> closer to infinite the better, but a megohm or more anyway. 
> Many mic pre-amps present too low an impedance causing the 
> low end to roll off. Since the D-104 does not have a lot of 
> low end to begin with it becomes very tinny.  Putting a 100K 
> resistor in series with it may help.  Also cable capacitance 
> is important; excessive capacitance rolls of the high end 
> and reduces the output level. Short cables of 
> low-capacitance co-ax are necessary.
>     You can probably do better with another kind of 
> microphone. Crystal mics were popular because they were 
> relatively inexpensive for the quality and because they put 
> out very high levels. The latter was of importance when 
> electronic amplification was expensive.  The construction is 
> simple compared to a moving coil or ribbon dynamic mic but 
> the usual conical metal diaphragm limits the quality.
>     Long ago "sound cell" type crystal mics were available 
> where the crystal element was directly exposed to the sound 
> waves. These had quite high fidelity and extended 
> high-frequency response but very low level.  Brush 
> Development and some other companies made sound-cell mics 
> for measurement purposes and occasional use in sound 
> recording. They are essentially obsolete now.
>     FWIW, I have two D-104's, both sound exactly alike and 
> both sound tinny to my no longer very good hearing. 
> Currently, I am using an Electro-Voice 664, which gets good 
> reports.  There are newer mics with similar characteristics.
> 
> 
> --
> Richard Knoppow
> Los Angeles
> WB6KBL
> dickburk at ix.netcom.com 
> 
> 
> 
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