Anytone AT5555 audio sounds bad when using amplifier

[Dereka5]

I've dug out my Maas DX-5000 which is the same as the Anytone AT5555, KPO DX5000, and others.

Without an amplifier, the audio sounds fine, but when I connect my B550P or KL505 the audio on SSB goes to shit.

I'm not overdriving the amps.

These are both Class AB amplifiers & sound absolutely fine on my other rigs.

I'm thinking these rigs might be poorly screened & susceptible to RF, but aren't sure.

Anyone else had this problem on their AT5555 or other rebadged variant?

 

[Shadetree Mechanic]

I used my 5555 with a kl203 on occasion. Power on the radio turned down all the way, it seems that the kl amplifiers need a really low drive. How much drive are you using?

 

[Dereka5]

I used my 5555 with a kl203 on occasion. Power on the radio turned down all the way, it seems that the kl amplifiers need a really low drive. How much drive are you using?

I've used drive as low as a couple of watts & as high as about 7W all with the same bad audio outcome.

I've tried these drive levels using other rigs, and they're all fine - so the problem would appear to be the 5555 being susceptible to RF feedback issues I think.

 

[Handy Andy]

These things are Dinosaurs when it comes to using better Pi-Network building - so yes, they are terrible at RF leaking in.

The thing uses 3 stages of predriver action - welcome to the world of harmonics.
Note the NC's - No Component - there's little to provide filtering all open gain too!
​

I've been fiddling with the AT-5555 for a while and have found very few avenues of reduction - this is really a TVI/RFI problem caused by the over-zealous desire to attain wattage in this footprint - its' why you have so many revisions from this chassis.

The Gain of each stage is not always properly neutralized and or controlled - Galaxy "Solve for X" problem is a similar vein to this very condition.

The amplifier stages are very broad banded and Quixiang techs have done little effort it controlling their gain into and out of the stages involved. They simply produce another chassis from the lessons learned in the earleir ones.

To obtain a clean signal into an amp No NPC-RC. Sorry.

And yes, AMC and ALC will need to stay in and the radio itself needs parts ADDED to the stages to reduce the stage-by-stage gain factors - using techniques much like Texas Star and Palomar use - NFB parts - to reduce the gain and get a grip on what's happening in the stage.

 

[Dereka5]

Excellent in-depth explanation as always there, Andy. Many thanks.

That 3 stages of pre-driver is absolute madness.

It's funny you mention harmonics; I failed to mention in my initial post - I intermittently get the "Hi SWR" warning popping up on the 5555 screen at odd times, primarily on SSB.

After further reading around the 'net, I've found other reports of compatibility issues with amplifiers & the 5555.

I might have a go at adding some decoupling Capacitors inside the rig, fitting ferrites on the mic' lead, etc', but if that fails I'll just pack it away.

 

[Handy Andy]

I'm sorry to have to give you such news, and to hear that you yourself could not find a way.

I was hoping somehow someone would provide some guidance for an otherwise good radio - just manufactured with issues that they learned from, yes, but did not bother to support the platform they learned from with some type of upgradable effort - even a kit or any form of communication (SIC) to help eliminate or alleviate this condition

(* as the laughter and guffawing in the Manufacturers Boardroom settles down to general coughing and mumbles...*)​

The FCC is totally useless in matters like this.

Now you know why I do get frustrated at the way Type-Acceptance and Accountability have disappeared as of late - too many foreign manufacturers have found loopholes in such matters to nearly put an end to the Radio Manufacturing business that originally the USA helped to create the demand and generate such a market.

In doing so, have now placed our dependence on newer technology, now more foreign to us than Radio itself - from places that once were not considered as viable sources.

We only have ourselves to blame.

To Add:

This "error" - is schematically and physically present in their radio...

I've amended this post to show a rather blatant error in Hi-Pass to Low-Pass configurations...using their data...

Their Band pass Filter uses RESITIVE elements as well as even fewer elements.
Uses similar Common Emitter but note the uses of the Emitter Resistor values
R values (At Emitter) for AT-5555 is 10 ohm 472 bypass cap
R Values (At Emitter) for CB typical is 22 ohms of same 472 Bypass Cap
Gain results are different - Base Biasing also allows AT-5555 for much more gain.
In the typical CB - uses 3 stages, 1 pre Driver stage
The AT-555 uses 3 combined.​

I'll let you explore and expose the rest.