Enhanced Apache TX-1 Audio

[rayfri]

Just my two cents worth....   My own curiousity I might say ... NOT 
denigrating anyone, please understand that up front.
"To each his own as Mrs. Murphy said as she kissed the cow 
goodnight"....    HI HI.    Now, that said .....

I think many many many of the suggested improvements and modifications 
for these older rigs are great and beneficial.   However, many times I 
shake my head at what appears to be attempts now days (especially among 
the NEW generation of hams who are not adverse to coming right out and 
admitting it) to get "better audio," which usually translates to 
something like "I want my rig to have broadcast radio or studio quality 
audio."   Modifications .... use of WAY expensive Senheiser microphones 
and elements, equalizers ... and other things like that, just to sound 
like our local radio station  HI HI.

Some of these attempts to get studio quality audio end up costing more 
than the rig did when the company first manufactured it.
I've heard price quotes for the Senheiser microphones or elements that 
are more than the Apache cost when Heath first introduced it.

FOLKS ... this is HAM RADIO ... this is COMMUNICATIONS ...  this is NOT 
broadcasting.   We are not broadcasting the New York Philharmonic 
Orchestra.  We are having a conversation.   WHY do you want to have 
studio quality audio during a communications procedure?  Personally, as 
long as I can understand what  youre saying, I dont particularly care or 
notice whether youre tonsils are
giving forth with that beautiful bass tonal quality or you have the 
falsetto voice of a pubescent teenager...    HI HI.  
And, if it's a DX or other contest, we've only said three words to each 
other before we are history and a mere log entry to each other.

Again ... just my own idle curiousity...  not a complaint or criticism.
Ray  WA7ITZ


Robert & Linda McGraw K4TAX wrote:

>Borrowing from the excellent work others have previously done, I have taken the audio system one step further forward toward "better audio".  I used 0.056 mfd 400 volt paper or Mylar capacitors because they were available.  Any reasonable close value works, however 0.1 mf units may be overkill and increase unwanted low frequency flicker noise.
>
>For preservation, I left all original components in place.
>
>Starting with the input 12AX7 and the .005 to pin 2, add a 0.01 mf across that component.  This capacitor is basically in "mid air" between the component terminal board on the edge of the chassis and the tube socket.  Don't worry about the "spring" shield around the lead of the other cap.  Just hang the new one in mid air between the two points.
>
>*To the 510 pf capacitor electrically between pin 1 and the top end of the GAIN CONTROL, add a 0.056 mf.  This is located on the component terminal board.
>
>*To the .005 between the arm of the GAIN CONTROL an pin 7, add a 0.056 mf.  This is located on the component terminal board.
>
>*To the 510 pf between pin 6 of the 12AX7 and pin 2 of the 12AU7, add a 0.056 mf.  This is located on the component terminal board.
>
>*Lift the end of the 100K ohm resistor B+ that goes to pin 6 of the 12AU7.  This is located on the component terminal board.
>
>*Connect a 0.056 mf capacitor between pin 1 of the 12AU7 and the top end of the LEVEL CONTROL.  Blue wire.  This added capacitor can be located between two points on the component terminal board.
>
>*Add a 47 mfd 35 V electrolytic across the 2 mf capacitor in the cathode circuit of the 12BY7.  A wee bit hard to get to but worth it to improve the low frequency response.  
>
>*Pull the 6AL5 from the socket.  It is no longer needed.
>
>*Adjust the LEVEL CONTROL for about 50% rotation and leave it there.  Modulation is controlled by the front panel GAIN CONTROL. 
>
>These changes nicely improve the low frequency response down to about 150 Hz and open the top end to over 5 KHz.  You may desire to run some external EQ or processing to further enhance overall modulation level and control of such.
>
>One noted comment is that the OB2 VR tubes that regulate screen voltage were observed to fire on positive peaks thus limiting the amount of positive modulation as screen voltage is clamped at 210 volts.  Change them to 0A2 {150 volt} VR tubes.  This will require resetting bias and clamp controls for CW and SSB operation.  It should be noted that the changing of the screen regulators will allow the screen voltage to go to 300 volts and this is 50 volts above the recommended value for class C plate modulated conditions.  At the same time, I have not experienced any failures of 6146 or 6146A tubes.
>
>If you have any questions, ask.  I think you'll be pleasantly surprised how well and how effective and how easy these changes are to implement.
>
>-----------------------------------------------------------
>Products bought, sold or traded here is the responsibility of the
>parties involved.  This list and the City of Tempe are not responsible
>for losses or misrepresentations of any kind.  Buyer beware!
>
>-----------------------------------------------------------
>This list is a public service of the City of Tempe, Arizona
>-----------------------------------------------------------
>
>Subscription control - http://www.tempe.gov/lists/control.asp?list=HEATH
>To post - HEATH at LISTSERV.TEMPE.GOV
>Archives - http://listserv.tempe.gov/archives/HEATH.html
>
>
>  
>

-----------------------------------------------------------
Products bought, sold or traded here is the responsibility of the
parties involved.  This list and the City of Tempe are not responsible
for losses or misrepresentations of any kind.  Buyer beware!

-----------------------------------------------------------
This list is a public service of the City of Tempe, Arizona
-----------------------------------------------------------

Subscription control - http://www.tempe.gov/lists/control.asp?list=HEATH
To post - HEATH at LISTSERV.TEMPE.GOV
Archives - http://listserv.tempe.gov/archives/HEATH.html