Testing the DYC-817 Dynamic speech compressor

Hi Ed,
Yes, I’d like to do that test, but it will have to be some other day later. Difficult during the weekend, I’m afraid, and I’ll be entering to the hospital on Monday morning for my so long time expected surgery on Tuesday. It looks like I’ll finally get rid of my rectum cancerous tumour, so I’ll be quite in a “limp mode” for a while. After Tuesday operation I’ll try to show up here in the Reflector ASAP so you all will know I’m alive and kicking.
Cheers,

Guru

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Good luck with the Op Guru.

Remember, the recovery is a lot quicker if you don’t start doing things before you should!

73 Ed.

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Best wishes for the operation next week Guru. I hope and pray that it will be a complete success and that you recover quickly.

73, Gerald

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Hi all
My 817 option 46 is set at 50 and my SP seams to work great

Paul

My good wishes for a fast recovery, Guru.

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Mine too.
73,
Rod

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Best wishes Guru

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Best wishes, Guru…Cu soon!
73 Fabio, IK2LEY

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Best wishes Guru!!

73

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Hi Ed
The tests I’ve done here make a very substantial difference to the transmitted audio and to the average power level.

Is the dc supply from your radio the same as the design voltage?
Cheers
Andrew VK1DA/VK2UH

I think Andrew raises a good point - is the DYC-817 seeing +5VDC? If you have access to an oscilloscope, it’s a very simple circuit, basically one transistor, two trimmers and an SSM 2165 IC, whose data sheet is online. You should be able to easily confirm the input and output audio waveforms after confirming the IC has proper dc power. Note that trimmer P4 sets the compression ratio so it’s possible the compression level is set low.

I was very impressed with the DYC-817 back when I used it with my FT-817 seven years ago.

73, Barry N1EU

Ed,
Another thing to check is whether the microphone line from the radio has a dc component on it, for an expected electret microphone type.

The Yaesu mike is a dynamic and does not require a dc supply to the element. If the new rig provides that, it could well be affecting your results. It could be offsetting the operation of the compressor chip.

The two pots on the DYC board have different purposes. The first is to control the preamp gain, or rather the level of its output, [edit: actually it does change the gain as it is in the feedback loop of the op amp] which then goes into the MM2167 (corrected] chip which contains the compressor and noise gate circuitry. The second pot controls the compression level.

I did experiment with setting the compression level to zero, then adjusting the preamp level, confirming that the sound of the thing was basically the same as the microphone without compressor. Advancing the compression control to about 1/3 of its full range made a useful difference to the audio transmitted and the average power. (Setting it higher than that level on mine just added distortion and artifacts from the effects of speech wind onto the microphone and was a sound I didn’t want to transmit. )

So Ed you could try that approach. Identify from the instruction manual which pot is which, turn the compression pot fully anticlockwise and set the other pot to a level that gives you normal speech output to the radio. Then try the compression settings to say 1/3, 1/2 and 3/4 etc to see what you find. Monitoring the output using a second receiver, with the tx into a dummy load should work to let you try those options.

It’s night time in DL land so you won’t see this for a few hours yet. Hope this helps.

73 Andrew VK1DA /2UH

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Ed, I hope that turns out to be correct.
The DYC unit will expect the DC supply to be on one pin of the mike socket so if the connecting cable provides that on the right pin, the dc supply to the compressor is in place. But if the mike line has a dc voltage due to expecting an icom electret element, I think you just need a capacitor to isolate the voltage from the output of the compressor.
But now I am thinking “what about the pin connections”?. Have you made up a new connecting cable between the compressor and the Xiegu radio? The original was wired to suit the yaesu pinout. Icom and Yaesu won’t use the same connection pattern, or do they?
Keep plugging away, Ed, you’ll get there!
73 Andrew VK1DA/VK2UH

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My experience is that 95% of the time when people buy the unit as a kit and report that is does not work, it’s due to inadequate construction by the builder.

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In this case I believe Andrew may have hit the reason for the problem (I will know once I test my modified cable). I did point out that I am trying to use the (from Box73) kit in a different configuration to what was intended, so that is the risk that I took.

There is very little construction in this “kit”.

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I hope supplying 8V instead of 5V nominal voltage in your initial unsuccessful test didn’t damage the unit.
Richard @G3CWI, do you think there’s a risk for this.
Good luck, Ed!
73,

Guru

It uses an SSM2166 IIRC and Analog Devices say 4.5 - 5.5V supply in the data sheet.

EDIT: Absolute max ratings:

Supply Voltage 10V