Aloha!
Most PC soundcards are really Hi-Z, even though the op amp driving the output may have a source Z of 66 ohms. My question relates to HAM radio audio interfacing, where the matched load at the radio will be un-balanced, and also high Z. And at varying ground potential, and subject to RF fields.
Most PC to HAM radio solutions use crappy transformers with not so flat impedence curves, and limited bandwidth, to the point that HAMs buy new gear and replace the transformers. BUT they use 600 to 600 ohm 1:1 ratio xfmrs with little regard to balance or frequency response. These also have low DC resistance.
My past experience in broadcast and pro audio was to always use a 1:1 transformer with unbalanced sources, like a PC sound card, or consumer audio gear but with at least a 10K to 15K impedence on both primary and secondary but still with a true balanced 1:1 ratio.
I'm asking this question since I've read a lot of articles recommending modifying a popular Ham radio soundcard by tossing the transformers and replacing them.
The product is the Tigertronics SignaLink USB, but also applicable to any good quality un balanced output sound card.
See: http://www.tigertronics.com/slusbmain.htm
Please see: http://www.mouser.com/ProductDetail/Triad-Magnetics/TY-304P/?qs=Fg5d7evCuakQ2%252bEGHCQnZQ%3d%3d as an example of a so called upgrade to this product. It looks like a junk piece to me.
Look also at www.frenning.dk/OZ1PIF_HOMEPAGE/SignaLinkUSB-mods.html for a full discussion of why many find the transformers in this otherwise highly regarded PC soundcard to Ham radio interface poor.
You might have a product here!
So finally, is my old received knowledge that a higher impedence 1:1, rather that a 600:600 xfmr Correct?
Especially in regards to distortion and gain structure. The soundcard I currently use is a Soundblaster Audigy, and I never get enough level from the line level radio to drive it to full level. The Ham digital modes are very sensitive ti IMD, as they are two tone in nature.
Mahalo,
Gary
Most PC soundcards are really Hi-Z, even though the op amp driving the output may have a source Z of 66 ohms. My question relates to HAM radio audio interfacing, where the matched load at the radio will be un-balanced, and also high Z. And at varying ground potential, and subject to RF fields.
Most PC to HAM radio solutions use crappy transformers with not so flat impedence curves, and limited bandwidth, to the point that HAMs buy new gear and replace the transformers. BUT they use 600 to 600 ohm 1:1 ratio xfmrs with little regard to balance or frequency response. These also have low DC resistance.
My past experience in broadcast and pro audio was to always use a 1:1 transformer with unbalanced sources, like a PC sound card, or consumer audio gear but with at least a 10K to 15K impedence on both primary and secondary but still with a true balanced 1:1 ratio.
I'm asking this question since I've read a lot of articles recommending modifying a popular Ham radio soundcard by tossing the transformers and replacing them.
The product is the Tigertronics SignaLink USB, but also applicable to any good quality un balanced output sound card.
See: http://www.tigertronics.com/slusbmain.htm
Please see: http://www.mouser.com/ProductDetail/Triad-Magnetics/TY-304P/?qs=Fg5d7evCuakQ2%252bEGHCQnZQ%3d%3d as an example of a so called upgrade to this product. It looks like a junk piece to me.
Look also at www.frenning.dk/OZ1PIF_HOMEPAGE/SignaLinkUSB-mods.html for a full discussion of why many find the transformers in this otherwise highly regarded PC soundcard to Ham radio interface poor.
You might have a product here!
So finally, is my old received knowledge that a higher impedence 1:1, rather that a 600:600 xfmr Correct?
Especially in regards to distortion and gain structure. The soundcard I currently use is a Soundblaster Audigy, and I never get enough level from the line level radio to drive it to full level. The Ham digital modes are very sensitive ti IMD, as they are two tone in nature.
Mahalo,
Gary
