[AMRadio] Speech processing technologies and methods?

FRANK HUGHES hughes frsahu0003 at embarqmail.com
Thu Dec 19 15:05:49 EST 2013

Hi Todd, 
I really like the idea of leaving the 32V-2 alone, and doing another fun project to build an exciter for the big amp! 

I run the 32V-2 on a Variac @ 115vac input, and the 32V-2 lo/hi voltage switch is set in "Low". 
A small fan is installed inside the case next to the 5Z4 and transformer that melts, so hopefully this will prolong the 32V-2 life. 

The 5Z4 currently installed is an RCA metal type, don't know if that runs any cooler than the glass version or not. 

I am planning to buy a Flex 3000 in a couple of months at the Orlando Hamfest to play with as a distraction from all the 'anchors. 

The Flex can drive the amp until I can find plans/parts/time to build an exciter. 

Must keep focused on finishing the amp first! 

"Pants first, THEN shoes" is my guiding motto. 

Photos of the big amp progress are posted on QRZ. 
----- Original Message -----

From: "KA1KAQ Todd" <ka1kaq at gmail.com> 
To: "FRANK HUGHES hughes" <frsahu0003 at embarqmail.com> 
Cc: "Discussion of AM Radio in the Amateur Service" <amradio at mailman.qth.net> 
Sent: Thursday, December 19, 2013 11:47:19 AM 
Subject: Re: [AMRadio] Speech processing technologies and methods? 

On Thu, Dec 19, 2013 at 6:26 AM, FRANK HUGHES hughes < frsahu0003 at embarqmail.com > wrote: 

I would like to learn about the speech processor options/techniques to improve what I am presenting the 32V-2 input with. 
Should I start by asking Ray @ ER if he has any back-issues addressing the subject? 

I would add to what Rob said here, there's really not a lot the 32V series needs to sound decent. They sound pretty good right out of the box. Like other rigs of the day they are somewhat restricted. 

The mic you're using sounds like a dynamic, not the best mate for the 32V. Simplest improvement you can make and IMO the best bang for your buck is to use a plain jane D-104 with a *good* crystal element. If you want to make a simple modification to improve the audio further, change the mic amp grid input resistor which, IIRC, is around 1 meg. Change it to something around 5 megs or more. 

Beyond that you'll be pushing the boulder uphill, a lot of work for minimal return. 

On 3885 I hear many folks discussing their signal processing methods, and can see that it would be fun to learn more about it. 


Keep in mind that many of these guys are using homebrew transmitters, not 32Vs or Apaches. The biggest weakness in the 32V is the LV transformer that gets baked by a combination of elevated line voltage and a sizzling hot 5Z4 half an inch away that will take the skin off your fingers if you grab it before it's cooled off. It's likely not too dramatic to say that it's just a matter of time until you fry it if you use the transmitter a lot - especially if you started modifying and driving the snot out of it. I have a stock 32V-2 that has only seen service as a 100 watt peanut whistle station and it has tar seeping out of the transformer. The best thing you can do for the transmitter is work to cool off the LV section. 

But first, I have to finish my first attempt at a homebrew amp, then on to new technical horizons. 


I'm with others here: if you're building an amp along the lines of 'DTC, don't bother driving it with a 32V. Keep that as a daytime transmitter for 75/80 meters, or 40m use. Build yourself a little Class E transmitter, a little tube exciter, or run a Flex or something along those lines with the amp. You'll be pleased with the results and the 32V will be forever thankful. 

BTW, you probably already know that, along with your other amps, the 32V doesn't do 160 either. 

~ Todd, KA1KAQ/4 

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