[Kenwood] Matching transformer for mike

[Steve H]

Thanks Rich, yes, its got a mike and line level option and inside the 
compressor on the main board there is a switch that changes the output
from line or mike. I was told to put that into the mike position, which I 
did, and it made a huge difference and eliminated alot of humm
and artifacts from the signal.

This is the mike I am now using:
https://www.newark.com/stellar-labs/cm-2250/studio-condenser-cardioid-microphone/dp/53Y1921

Since its designed around needing phantom power, and the 528E can supply it, 
figured it was a good match. When I tried it with just my headphones 
monitoring the output of the compressor, it really did sound great.

But no matter what I did last night with it set like that, could not get a 
whole lot of modulation into the Kenwood where it was an upgrade over the 
MC50 Kenwood mike. If I put the mike gain on the Kenwood past 3, I get lots 
of distorting and oscillations without even speaking into the mike. I can 
cut the mike gain control or the main level out from the 528E down to 
eliminate it, but at the cost of the percent modulation decreasing way down 
so its nearly unreadable.

So far the MC50 mike sounds way better than what I can get from this setup 
and it seems like more mike gain would get me more % modulation, however
as I get it better and hit 3, it just distorts. If I put the Kenwoods built 
in compressor on, I can get past 3 and modulation will improve as I go up, 
but even with the mike gain at max, the modulation % is just not very robust 
at all.

Steve Hearns
KA2PTE

----- Original Message ----- 
From: "Richard Knoppow" <1oldlens1 at ix.netcom.com>
To: <kenwood at mailman.qth.net>
Sent: Thursday, July 09, 2020 11:18 PM
Subject: Re: [Kenwood] Matching transformer for mike


> Level are important. If the output level of the processor is high you need 
> a resistive attenuator which will also serve to match the impedance.
>  In general, American practice is to state microphone input impedance as 
> the expected source impedance, usually there is no need to match 
> impedances because the source is a voltage source not a power source. For 
> instance, in historical broadcast equipment and sound equipment designed 
> to work from low impedance microphones the the typical input impedance was 
> on the order of 5K ohms or more while the source impedance was on the 
> order of 150 ohms. For equipment that runs at line level the impedance is 
> usually a terminating impedance, source impedance can be the same or 
> sometimes not.
>  See if the processor is meant to drive a microphone input or a line level 
> input. If a line level input you need an attenuator to get the level down 
> to mic level, maybe as much as thirty db. The exact impedance is not 
> critical.
>
> On 7/9/2020 7:53 PM, Steve H wrote:
>> I am trying to hook up a Symetrix 528E voice processor to my Kenwood 
>> Hybrid 830S and was told that the mike input is about 150 ohms
>> to the rigg and the processors output is 600 ohms.
>>
>> Other hams I think use a matching transformer, I guess 4 to 1? Anyone out 
>> there have any experience selecting a matching xfmr for the Hybrids?
>>
>> Steve Hearns
>> KA2PTE
>>
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> -- 
> Richard Knoppow
> 1oldlens1 at ix.netcom.com
> WB6KBL
>
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