[Premium-Rx] Wohler amplified speaker panels

[Terry O']

For those of you interested in the Wohler pro audio amplified speaker 
panels, I managed to obtain some schematics.  They are attached

I have seven units; two variants of the AMP-1, four variants of the 
AMP-2 and one AMP-.9.   As I wrote before, they are all modular inside.  
A picture of all seven units is attached.  Four of these have already 
been customized by me but you can see how similar all the circuit boards 
are.

All of these units that have a subwoofer have the 719006 low frequency 
amplifier board.

One of the AMP-1 units has the 719005A main amplifier board.  All four 
of the AMP-2 units have 719005A boards even though three of these are 
different versions of it.  The AMP-.9 has two of these boards.

The other AMP-1 uses the same amplifier circuitry on different boards.

Three of my AMP-2 units have meters in them.  The circuit boards are 
different than the attached 719017 bar graph meter schematic but use 
similar circuitry.

I don't have any schematics for the AES/EBU digital conversion boards.  
In two of my AMP-2 units, I removed the AES/EBU boards and used the 
space along the back of the chassis to add screw terminal strips for 
connection to my receivers.

I don't have schematics for the small phase indicator board used in all 
four of the AMP-2 units.

I made a mistake in one of my AMP-2 and blew out the bar graph meter 
board.  So here is my warning.  There are many four pin headers 
connecting the boards.  These connectors carry a mix of DC voltages and 
audio signals.  The meters have audio signals on the outer two pins, 
whereas many of the other boards have +24 VDC on one of those lines.  So 
be careful to remember which plug goes where.

One last note, these metal cabinets are slot loaded acoustic 
enclosures.  There is a 3/32" air gap around the entire back panel.  Do 
not fill this gap or modify the rear panel in a way that closes that 
gap.  I did that on the first AMP-2 I bought and sound was as bad as a 
stock Kenwood, Icom or even JRC NVA-88 external speaker.  There is also 
a crucial screw in the center of the top panel.  Leave that out and the 
top panel will buzz at higher volumes.

Of these seven Wohler's the most I paid was $40 for an AMP-2/DTR-2 
(still unmodified).  If you shop around they are out there for very 
reasonable prices.  They sound pretty good and I have yet to experience 
any failures not of my making.

Terry O'



On 12/30/2023 7:26 AM, Michael Melland via Premium-Rx wrote:
> Hi folks,
>
> I’m back on the list after a number of years off, having rehomed my radios during a move and build.  The shop and a man room is done so I figured it’s time to pick things back up.
>
> I’m curious what speakers you’ve found to work best with your receivers ?  In the past I used single Radio Shack stereo speakers… nothing fancy. I just acquired a WJ 8711A and will be setting it up with a bit more thought than normal ,lol. Thinking of trying a loop antenna… always used long wires in the past. Your thoughts on loop use would also be helpful.  I wish the archives were searchable… I’m sure they contain useful info…
>
> Mike, W9WIS
> Sent from my iPad
> ______________________________________________________________
> Premium-RX Mailing List Information
> Home:  https://mailman.qth.net/mailman/listinfo/premium-rx
> Help Page:   http://mailman.qth.net/mmfaq.htm
> Post to Group eMail:   premium-rx at mailman.qth.net
> Help Contact eMail:  73 at 73.am
> Web Home Page:  http://www.premium-rx.org/