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Tuesday 22 May 2012

Speech Processor

I am going to put a PCB and parts together.

I'll post details to the blog later.

This was part of the thread on GQRP today...

Re: speech processor


I got this one from ok1cdj that did just that, he used the SSM2165 chip


I have one in a MH31 I use with the FT817 and it works great.

I'll email you the pdf manual if your interested.

The three connectors are in/out&power, there will be a ground too.

However the chip and the boards are not available any more a couple
others asked directly by email and asked could it be homebrewed.... the original
SSM2165 is not available but a newer SSM2167 is available, from Farnell part
2067797 (Digikey have it too but only in 1,000 units!)

The data sheet on the SSM2167 e.g.

The interesting stuff is on page 8...

Use a pot on pin 7 to adjust the effect on the lowest signals the data sheet

Input signals below VDE are downward expanded; that is, a −1 dB change in
the input signal level causes approximately a −3 dB change in the output
level. As a result, the gain of the system is small for very small input signal
levels, even though it may be quite large for small input signals above VDE. The
external resistor at Pin 7, RGATE, is used to set the downward expansion
threshold (VDE).

and pin 8 to adjust the compression, the lower the value of R the lower the
compression a 180K SMD resistor will do nicely... at 0R no compression at max R
the compression will be X10 (way too much but ho hum).

You could a similar layout to the original from from OK1DCJ (SSM2165 was SOIC8
this is 10 pin!)

Looks like a useful little project for fellow QRP SSB fans, anyone interested if
I put a PCB together and buy some SSM-2167 chips?



--- In, "Feri" wrote:
> HI Dear Friends,
> I need a small help. I would like to build a small speech processor into
> a microphone set. Only 5V is available for the unit. Do you have a
> working sematic with reachable parts?
> It could be very good to have when working with qrp in ssb modes.
> Thanks in advance!
> Feri -HA7BF-