[digitalradio] Re: Sound Cards
Hi Skip and others. I bought the other USB sound card dongle: http://www.geeks.com/details.asp?invtid=CL-USCM2cpc=SCH I was disappointed with it. The microphone input was noisy and A/D resolution was far lower than 16 bits. I do not remember exactly, I think it was either 10 or 12 bits. With the noise taken into account, the input resolution was probably about 8 bits. There are no decoupling capacitors on the earphone output. And I don't think that it is a switched class amplifier or bridge amplifier. The earphones are grounded to common ground. If the earphones were plugged, there was DC current flowing through the earphones. It seems the manufacturer simply saved money and space by sparing two capacitors. I dissected one and the second one is still on my shelf unused. 73, Vojtech OK1IAK --- In digitalradio@yahoogroups.com, kh6ty kh...@... wrote: Tim, have you tried the USB sound adapter? The low end noise that the standard SignaLink has is not there and you can just use VOX for PTT switching. It is also an external soundcard. For only $7.50, you can hardly go wrong! If you can handle tiny chips, there is also a PTT output that you can bring to the outside. http://www.geeks.com/details.asp?invtid=HE-280Bcat=SND 73, Skip KH6TY Thank you Peter. I've been looking at external sound cards to use with a laptop for portable work. The internal unit in my laptop doesn't work all that well and my thinking was if I use a good quality external unit it can move to a new laptop when I upgrade some day. Tim, N9PUZ _ -- *Skip KH6TY* http://KH6TY.home.comcast.net
Re: [digitalradio] Re: Sound Cards
Hi Vojtech, My experience with it was strictly anecdotal, and had no noticeable problems on the air on HF compared to the SignaLink, but I did not make any quantitative evaluation other than to notice the absence of the low end noise on the waterfall that my SignaLink has. I just checked it and do measure a 0.05 ma DC current through the earphones. Too bad - I wonder if the C-Media motherboard chips have the same problem. I finally gave up on clone motherboards - too many other problems! We were using it under Linux because there are too many hardware compatibility problems with Linux recognizing soundcards, but it sounds like even the SignaLink would be a better choice. Since then, we have come out with a Windows version of fldigi which has no problems recognizing soundcards. Thanks for the heads-up, Vojtech! 73, Skip KH6TY Vojtech Bubnik wrote: Hi Skip and others. I bought the other USB sound card dongle: http://www.geeks.com/details.asp?invtid=CL-USCM2cpc=SCH http://www.geeks.com/details.asp?invtid=CL-USCM2cpc=SCH I was disappointed with it. The microphone input was noisy and A/D resolution was far lower than 16 bits. I do not remember exactly, I think it was either 10 or 12 bits. With the noise taken into account, the input resolution was probably about 8 bits. There are no decoupling capacitors on the earphone output. And I don't think that it is a switched class amplifier or bridge amplifier. The earphones are grounded to common ground. If the earphones were plugged, there was DC current flowing through the earphones. It seems the manufacturer simply saved money and space by sparing two capacitors. I dissected one and the second one is still on my shelf unused. 73, Vojtech OK1IAK
[digitalradio] Re: Sound Cards
I would choose a sound card with the lowest THD% or Total Harmonic Distortion if you can find the specs. Also choose a sound card with a high SNR (signal to noise ratio) and you should be pretty happy with the card, Then make sure to use some extra ferrite on the audio lines to help keep any extra rf type of noise out, and you could go pretty extreme with some shielded audio cables. I have had 5 cards now and the only one I have been happy with was the Turtle Beach Santa Cruz which used a crystal chip set. It was a super clean card and low priced but, they do not support it anymore I can not run it on windows 7 Emoticon10.gif
