You'll find those transformers have high distortion , note the lack of distortion specs ... also they are optimized for phone line service and need to be driven fairly hard, in other words they aren't for low level signals and lack in dynamic range .... you hit them with a -60Dbm signal and you see the frequency specs fall apart, this is a side effect of compromising the design to help eliminate core satuartion with large phone line level signals (The are line transformers not small signal transformers) ... you might try Hammond's 800 series line of braodcast quality transformers but I bet they cost as much as the Sowters or better Jensens ... I'm not saying those won't work, but I doubt you'll see much, if any gain over a good opamp
There is a reason a Sowter or high end Jensen transformers cost in excess of 100 bucks and also why the old Peerless/Lansing transformers are highly valued and sell used for over 100 bucks too .... there is also good reasons why the highest end recording desks use transformers over the active balanced circuits you see in the mid and low end mixers/mike preamps JR --- In [email protected], KD5NWA <[EMAIL PROTECTED]> wrote: > > I've been thinking about that for a long time but have never done > anything about it. Mouser has some transformers that I keep > book-marked in case I decide to order them. They are flat from 200Hz > to 100KHz with .5dB, it's hard to get any better than that. They cost > about $14 each and you would need two, I keep ordering things from > Mouser but I don't add them in because the are never in stock so it > would hold up my order. > > < http://www.hammondmfg.com/pdf/5c0042.pdf > > > I just looked at Mouser, I should have bought them before, now there > is a ten device minimum order. > > > At 12:58 PM 6/10/2006, you wrote: > >I've always been surprised that someone has placed a high quality > >Sowter mike transformer directly to the outputs of a QSD (And unless > >someone does it this summer, I'll be the first but using some old, but > >excellent Peerless/Lansing transformers) ... you get noiseless gain, > >excellent balance and phase and can follow it with a single ended > >opamp circuit with optimum noise impedance if more gain is needed > > > >Main drawbacks are size and cost ($100+ per transformer) > > > >JR > > > >--- In [email protected], KD5NWA <KD5NWA@> wrote: > > > > > > I think the clue is that it takes a analog signal in and outputs a > > > digital representation hence A/D. > > > > > > If one follows the same procedure as when designing a RF-amp then it > > > will be a good thing. Only enough gain to overcome the circuit noise, > > > then your dynamic range is much better. > > > > > > On Fri, 2006-06-09 at 05:31 -0700, FRANCIS CARCIA wrote: > > > > I use minimum gain in the op amps after the detector to get > >maximum dynamic range. > > > > BTW Sound card codec is an A/D. frank > > > > > > > > "wavelengths@" <wavelengths@> wrote: > > > > Alberto: > > > > > > > > Over at the very controversial group softrock40 group. I suggested > >once that they could add analog to digital convertors right after the > >quadrature detector and so they seemed to have took off on that idea > >for awhile. It seems like it was an idea some of them had also been > >previously pondering: I do not know. Anyways it seems like a logical > >evolution of the circuit ideas. > > > > > > > > I terms of software now. Would there be an advantage in using the > >A/D right after the detector in your view and could the signal still > >be sent through the sound card? I realize that this would one day mean > >a new kind of software. If it is not immediately advantagous to > >explore then we can just dismiss that idea till some other date. > > > > > > > > Anyways if the A/D idea is not something ready for SDR at this > >time then we need to focus on the analog output of the quadrature > >detector as it is and go from there. {Some are still fussing over what > >sort of technology to use as the local oscillator and bandpass tuner > >sections.} Yet some have looked at the idea now and so it will not be > >something new one day down the road. It seems however that some very > >fast digital radio communications could result from the idea. Yet, as > >with anything no doubt it will have its peculiar problems also. > > > > > > > > ka9rza > > > > > > > > __________________________________________________________ > > > > Call Anyone, Anytime, Anywhere in the World - FREE! > > > > Free Internet calling from NetZero Voice > > > > Visit http://www.netzerovoice.com today! > > > > > > > > > > > > > > > > > > > > > > > > > > > > [Non-text portions of this message have been removed] > > > > > > > > > > > > > > > > > > > > > > > > Yahoo! Groups Links > > > > > > > > > > > > > > > > > > > > > > > > > > > -- > > > > > > Cecil > > > KD5NWA > > > www.qrpradio.com > > > > > > > > > > > > > > > > > > > > > > >Yahoo! Groups Links > > > > > > > > > > > Cecil Bayona > KD5NWA > www.qrpradio.com > > "Windows the worlds most successful software virus" > ------------------------ Yahoo! Groups Sponsor --------------------~--> Get to your groups with one click. Know instantly when new email arrives http://us.click.yahoo.com/.7bhrC/MGxNAA/yQLSAA/ELTolB/TM --------------------------------------------------------------------~-> Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/soft_radio/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
