MikesRadioRepair Reviews Asymod iii HiFi Board

[MadScientistElectron]

BM is only used in ssb radios

mmm's pdf attached

I realize that thiis an old topic thread but I wanted to clarify this statement made by Yeti. Actually a balanced modulator IS used for AM in some rigs... an example is the President Lincoln/HR2510/HR2600. Also some Ham rigs used the BM for AM. This is done by unbalancing the balanced modulator to let some carrier through and bypassing the SSB 10.695 filter via diode switching. I have done this as a mod to an RCI2950 and an old Cobra base station. Need to have a wider 10.695 filter switched in for AM or there will be a lot of spurious junk in the output. But it does make very nice AM. You have to make the SSB bias on for AM also to make the final linear. AM/SSB CBs switch the bias for AM/SSB, collector modulators are more efficient in Class C. Since the AM is now modulated at low level all stages after the balanced modulator have to be linear or the end product will be distorted. Of course you have to address the audio bandwidth to get "hi-fi" AM. This AM mod eliminates all crossover distortion from negative overmodulation and allows any amount of positive modulation desired. Just food for though for all of you who like to experiment. As a final point... if you're still using the standard diode AM detector that all CBs have any modulation above about 80% is distorted, getting increasingly distorted the higher the modulation level gets... so a better detector is necessary to demodulate "supermodulated" AM without distortion.

 

[Wire Weasel]

Fascinating Thread

 

[dave457]

Too bad alot of these guys don't post anymore or they just moved on

 

[Mustang 131]

Too bad alot of these guys don't post anymore or they just moved on

Well you do hear a lot more "hifi" stations now then when this thread started.

 

[Wire Weasel]

Well you do hear a lot more "hifi" stations now then when this thread started.

Likely because the tech evolved to pretty much accomplish the same sound without using an expensive add-on board.

 

[Onelasttime]

I think the device does what it is intended to do. Mike was a purist. The Lincoln/2510 line of radio's is one of his pet radio's I think he owns 8 NOS most recapped and aligned and still in the box. So putting this device in this chasis is asking for Mike to go on a rant. I did not watch the viceo I watched it live years ago.

If you like how Motor Mouth Maul sounds on the bowel this device is step one. The more powerful the output the more headroom you have when you dial things in.

As far as I am aware their are only two stand alone cards like this on the market. This one and the origanaly and 2nd decision Motor Mouth Maul Board MMM is the origanal. Good luck purchasing one they where forever out of stock decades ago. Then they Stopped making them and that is when Asymod came to market then a few years later MMM came back to market with his second design board.

These devices are the high water mark for an all in one device there is nothing better that you purchase on the market. All of the other attempts are combinations of other in radio modifications and direct inject with some form of audio software or hardware combined to produce the desired outcome just like what was used for decades in commerical radio before everyone went software driven.

 

[Onelasttime]

Likely because the tech evolved to pretty much accomplish the same sound without using an expensive add-on board.

There is nothing like this other than MMM board. This is the simplest and cheapest way to do this.

 

[nomadradio]

they Stopped making them

Seriously? John quit making his MMM board? Hadn't kept track.

I acquired a broken one years ago. Had been dipped in some kind of rubber like you use to dip a tool handle into. Peeled right off. Couldn't resist tracing down the schemo. Had exactly one conversation with John almost ten years ago. Told him I had a schemo. He sounded apprehensive and I assured him I had no intention of letting it into the wild, just wanted to satisfy my curiosity. So far I've been as good as my word, and kept it under wraps.

But if he no longer sells the thing that kinda changes the landscape. The circuit's not that tricky. Biggest aggravation was mounting controls and power supply in a cabinet and wiring them up to his board.

Had a few customers who kept blowing out the MMM's output transistor. Made them bigger and only the real fanatics would blow out a 25-Amp TO-3 transistor. Bought a couple of 150-Amp industrial-control transistors on fleabay a while back. Figured I'd put one of those in the next MMM that blew a tranny. Never got that 'round tuit'.

But if John has tossed that business overboard, sounds like it's up for grabs.

Hmmmm

73