The voice keyer chip includes a good sounding speech compressor, Ed.
73 Chris
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Neither dh8bqa nor the ISD7610 datasheet mention that. The ISD 7610 explicitly states that speech is stored uncompressed in analog memory. and that it has mic AGC.
I have never seen or heard one, so you may well be right - I am only going on these two references. Mic AGC can be a useful thing to have.
One trick with a voice store like this, would be to pre-clip your CQ message offline e.g. using VoiceShaper. Then that at least is louder, and people can get your callsign.
(I’ve always been tempted to get an ex yl to record my CQ calls. Her dulcet tones are reminiscent of of a chainsaw cutting through a rusty oil drum)
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Because some people have this and some don’t, I think it’s likely Microphone Proximity Effect is part of it. The mic becomes bassy and muffled if you are too close. And tone also changes as the microphone moves off beam eg if you hold it sideways.
Which is not to say that various replacements won’t be an improvement. BTW the MH31 has a steel lump inside that weight weenies will want to remove.
You should make sure you have the radio set up and using it best.
While I don’t like dropping my keks in public and showing off my inadequacies, for the first decade I had the '817, I didn’t realise zero bars == full power.
As other have mentioned the mic has a tone switch you need to set.
The SSB mic gain has to be set for your voice and mic - for me it is 100%.
Then you need to use the ALC meter when you are transmitting (see manual pg26)
You should watch the ALC and ride your speech volume to keep full power. The best way to turn a 5W radio into a 1W radio, is not talking loud enough.
(perhaps this is what the DH8BQA is doing for you with the ISD7610’s mic AGC)
My '817 has developed a fault over a long time, where it intermittantly no longer has enough TX gain to make the ALC operate. Unless you are tickling the ALC bars, you are not getting 5W.
BTW, I would like an RF clipper for it, it would probably be the single feature I’d most like added.
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Thanks everyone, I placed an order from sotabeams 
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Following this thread and in a drunken haze I’ve just ordered one too 
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Glad it’s not just me that does this 
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Don’t forget you have to set it up. Set up the 817/818 as per the manual for ALC etc. then you can insert the audio processor and listen on another radio as you adjust the processor for best audio and processing. Takes moments.
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I have done on-air tests with and without the DYC-817 compressor, listening to my signal on several remote SDRs. My signal is more readable at 0.5W and with the compressor (SSB mic gain at 25) than at 5W and without the compressor (SSB mic gain at 100). Around 10 dB gain.
I also have an old W4RT One-Big-Punch speech compressor built into a different microphone. It is better than no compression, but not as good as the DYC-817.
The things to look out for: feedback from RF entering into the compression circuit when the antenna is close to the unit. This has happened for both speech compressors. A little less so with the DYC-817. If you use the stock MH-31 mic, pay attention to the switch on the back and adjust for your voice and language type. Back off on the mic gain when using the compressor and use the ALC monitor as a guide.
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I have the FT8x7 speech compressor and while adjusting it I noticed the design appears to have a fault, namely that the first gain control pot merely adjusts the gain between microphone and the compressor chip, the second control adjusts the level of compression. There is no adjustment control on the output level sent to the 817 radio. There should be. Leaving the mike gain control at its uncompressed level in the 817 settings, the output of the compressor is higher than the standard level from the bare microphone. The switch that allows you to turn the compression on and off does not compensate for the net gain in the compressor unit making the comparison quite misleading. Some simple gain adjustments could be made to the circuit but would not necessarily be a neat change to the compressor. On balance then, it overdrives the 817 and some of the perceived increase in signal level is due to the gain in the compressor, not just the compression function. Presumably the quality of the transmitted signal is affected by this flaw.
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Andrew, a very helpful discovery.
I’ve always wondered why this compressor sounds so unpleasant compared to mine. I installed the internal chip in my MH31 and of course made the output voltage adjustable.
Doesn’t it help to turn down the mic gain on the FT-8x7?
73 Chris
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Chris, yes it probably would - but navigating config settings in the 817 isn’t what i want to do on a summit! The sheet for the chip does not have a preamp at all, but of course that depends on the output level from the mike level. Dynamics have fairly high output but if you replace the standard dynamic element with an electret, that may be even higher. For this reason a gain control pre-compressor chip is probably justified. It’s the output from the compressor that needs an adjustable control. For what it’s worth my 817 has a standard dynamic element and both pots are set to about 40%. Even then the output audio is rather harsh and is not as smooth sounding as the base 817 is capable of.
Microphone technique is responsible for most of the boomy bass sound of the standard rig. Overdriving the mike element itself results and it is flat topping from lower freq components in the stage before the microphone.
73 Andrew VK1DA/VK2DA
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