Gamma Spectrometry Forum

Hi All,

Over the last few weeks, I have been doing some R&D on a new GS, it has some neat improvements.

Integral Sound Card
Yes, no need for the audio cable, the internal USB codec is recognised as a sound card (no driver required). The 3.5 mm jack plug is still there and delivers the same analogue output as before.

External Preamp Volume Control
It was always possible to adjust the preamp volume on the GS-PRO, but one had to open the case, so I have built this one with the trimmer pot on the side, so it can be adjusted without opening the case.

Pulse Shape Control
This is a new feature, it allows you to adjust the pulse length from zero to about 100µs. this feature could be handy if you are using a high sampling rate and want to tweak the settings for a maximum count rate.

BNC Connector for Signal
Now that the enclosure is a bit bigger it is no longer necessary to use the tiny SMA connector for the signal, so no special adaptor cable required.

Optional BNC or SHV Connector
It makes sense to supply this unit with SHV connector as a default for the bias voltage, but I made the board so it can also be configured with BNC as per image below.

New 5 Digit Display
The new 5 digit display shows the voltage in kV

TRRS Option
The 3.5 mm jack is a combined Mono, Stereo and headset jack, so I am trying to figure out is it is possible to have a dip switch or some option to switch between mono jack and headset plugs. This could be handy as many new laptops don't have a line in port.



The image below shows my first working prototype, silkscreen printing and final tweaks and price still to be announced.

Wow Steve, some very nice and useful improvements! Can hardly wait to get my hands on one... :)
Cheers, Tom

Interesting! What are the parameters of the integrated sound card?

Tom,

Can hardly wait to get my hands on one... :)

These projects always get better with every iteration and with so many enthusiasts out there I get good feedback with suggestions for improvements, so I am thinking of making a small batch of 5-10 units and offer them for sale at cost to guys like yourself, who can put them through the test.

Martin,

Interesting! What are the parameters of the integrated sound card?

I am using a Texas instruments PCM2900C USB codec, it's technically samples at 48kHz, but for some reason I can't explain, it produces a better spectrum on the 96 kHz setting in PRA. This is also evident by comparing the 48 vs 96 kHz pulse shape in Audacity. Comparisons between the PCM2900C and the internal sound card on my mac show no difference in resolution. Now that I know this works, I will talk with the experts at TI and find out if there are other options available.

Steven

Here is a sample spectrum recorded with Prototype V1.5

Great work, Steven!
Glad to see that you keep on improving the GS!
A couple of questions: does the USB interface allow to choose whether use the jack cable (PC sound card) or the USB cable (GS sound card) for the signal?
In this case, is it still possible to supply the GS from another source and not straight from the PC ? (This to reduce noise, for example...)

Thanks

Daniel,

Yes the analogue output is always active and functions just like the GS-1100-PRO, in addition to this you will have the option to connect via the internal USB sound card.

Obviously if the USB is connected to a USB battery you only have the analogue option available.

Note, that the GS-PRO-V1.6 has also been improved with a regulator and filter before the preamp power, so noise in the USB power should be much less of an issue.

Steven

Thanks Steven,
very clear.

I am thinking of making a small batch of 5-10 units and offer them for sale at cost to guys like yourself, who can put them through the test.

I volunteer! :-):-):-)

Thanks Steve, looking forward to taking one for a test drive. Please keep us updated on the details. Tom

Thanks for your confidence, I'm pleased to let you know that the boards and enclosures have been ordered. I expect it will take a few weeks, so stay posted.

Steven

Great job Steve, my compliments, will certainly be a great tool.

Dario