Freq. Independent Phase Shifter
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From: MooseFET on 11 May 2010 20:58 On May 11, 11:04 am, whit3rd <whit...(a)gmail.com> wrote: > On May 11, 10:27 am, whit3rd <whit...(a)gmail.com> wrote: > > > > > On May 11, 6:47 am, George Herold <gher...(a)teachspin.com> wrote: > > > > On May 11, 3:21 am, billmur...(a)protech.com (Bill Murphy) wrote: > > > > > On Mon, 10 May 2010 18:24:52 -0700 (PDT), MooseFET > > > > > <kensm...(a)rahul.net> wrote: > > > > >What are the two other channels making? > > > > > Same signal, all spearated by 120 degrees. Done in CoolEdit. > > > > > >If you have two signals at 90 degrees, you can get any other phase > > > > >and the same amplitude. > > > > The simple way is to mix them in a pot. > > > > Sine----+ > > > | > > > P > > > O<----output > > > T > > > | > > > Cosine--+ > > > > But this has an amplitude variation as you move the pot wiper around, > > > No, it doesn't! Just buffer that output and it's good to go. > > Oops, got that wrong; there IS amplitude variation, up to about 30 > percent; See my post for a circuit that makes the amplitude nearly constant.
From: George Herold on 11 May 2010 21:27 On May 11, 8:58 pm, MooseFET <kensm...(a)rahul.net> wrote: > On May 11, 11:04 am, whit3rd <whit...(a)gmail.com> wrote: > > > > > > > On May 11, 10:27 am, whit3rd <whit...(a)gmail.com> wrote: > > > > On May 11, 6:47 am, George Herold <gher...(a)teachspin.com> wrote: > > > > > On May 11, 3:21 am, billmur...(a)protech.com (Bill Murphy) wrote: > > > > > > On Mon, 10 May 2010 18:24:52 -0700 (PDT), MooseFET > > > > > > <kensm...(a)rahul.net> wrote: > > > > > >What are the two other channels making? > > > > > > Same signal, all spearated by 120 degrees. Done in CoolEdit. > > > > > > >If you have two signals at 90 degrees, you can get any other phase > > > > > >and the same amplitude. > > > > > The simple way is to mix them in a pot. > > > > > Sine----+ > > > > | > > > > P > > > > O<----output > > > > T > > > > | > > > > Cosine--+ > > > > > But this has an amplitude variation as you move the pot wiper around, > > > > No, it doesn't! Just buffer that output and it's good to go. > > > Oops, got that wrong; there IS amplitude variation, up to about 30 > > percent; > > See my post for a circuit that makes the amplitude nearly constant.- Hide quoted text - > I should/could have thought of the loaded pot, that's an easy way to get rid of some of the variation. (I learned that trick from Phil H's book.) But I've never seen postive feedback used like that before. I assume that this gives some gain that changes as the source impedance changes. Thanks, George H. > - Show quoted text -
From: YD on 12 May 2010 00:35 Late at night, by candle light, billmurphy(a)protech.com (Bill Murphy) penned this immortal opus: >On Mon, 10 May 2010 06:59:03 +0300, Paul Keinanen <keinanen(a)sci.fi> >wrote: > >>Since the OP only needed frequencies up to 2 kHz and was using COTS >>amplifiers, a cheap dedicated computer running a multiple (4-6) >>channel sound card running at 8-48 kHz sampling frequency would do the >>trick. >> > >What about a single card with 4.1 or 5.1 outputs? > >Either way, how would I generate the three 120 degree offset channels >in software? > >Thank you for your reply. > Try Visual Analyzer from http://www.sillanumsoft.org/ (freeware). It can generate separate signals in each channel, with phase added. Make up the third with a handful of opamps and resistors. You can lock the frequency settings so one adjustment alters both at the same time. -- Remove HAT if replying by mail.
From: YD on 12 May 2010 00:45 Late at night, by candle light, Jan Panteltje <pNaonStpealmtje(a)yahoo.com> penned this immortal opus: >On a sunny day (Mon, 10 May 2010 12:32:38 -0700) it happened Joerg ><invalid(a)invalid.invalid> wrote in <84r5apFvq9U3(a)mid.individual.net>: > >>Jan Panteltje wrote: >>> On a sunny day (Mon, 10 May 2010 09:19:56 -0700) it happened Joerg >>> <invalid(a)invalid.invalid> wrote in <84qq1hFobmU1(a)mid.individual.net>: >>> >>>> Bill Murphy wrote: >>>>> I am using a commercial stereo amp to output continuous wave test >>>>> signals in the low audio range, up to about 2KHz. However, I need a >>>>> third channel with a 120 degree phase shift. Is there a circuit that >>>>> will do this evenly across this entire frequency range? >>>>> >>>>> Is it possible to do same using an off-the-shelf transformer and >>>>> current subtraction? >>>>> >>>>> Any advice would be appreciated. >>>>> >>>> Paul's suggestion with multi-channel sound cards is a good one. But keep >>>> in mind that phase shifts in the very low range (tens of Hertzes) can be >>>> iffy on some cards, output cap tolerances and all that. Unless you want >>>> to go in there with a solder iron. >>> >>> It is too much, all you need is 3 EPROMS, a 4040 counter, and a 4046 PLL as VCO, >>> add a pot to set the frequency. >>> Add 3 R2R networks, or 3 cheap DACS. >>> I have made one variable sine wave generator like that in the long ago past. >>> Milliwats, and in a small box. >>> Mine had auto sweep too, so I could test filters. >>> Just an integrator and a FF, and 2 comparators added. >>> 256 point 8 bits sinewaves. >>> After al this is s.e.d. not 'alt.pc.sales' or whatever. >>> >> >>It all depends. When you do this for a living you need to weigh the time >>it takes to whip this up against the cost and installation time of a >>multi-channel sound card. When you are retired, different thing. But >>many of us aren't there yet. > >Well, if that takes so much time, say more then 2 hours, I think you >need more time to go shopping or order the soundcard thing. >Plus put it in a PC, plus write the soft, plus it is not real time adjustable >with a pot, plus it is not GREEN, it sucks power, plus well it is all so obvious. >Who knows, you may not reach your pension... may as well build it now! > > Doesn't take all that much time. The soundcard is usually there already, d/l'ing the sw is another few minutes (see my above post), the time to get used to it is about the same as fiddling with a real generator. Plus the sw comes loaded with a number of other goodies. - YD. -- Remove HAT if replying by mail.
From: Jan Panteltje on 12 May 2010 06:08
On a sunny day (Tue, 11 May 2010 18:27:34 -0700 (PDT)) it happened George Herold <gherold(a)teachspin.com> wrote in <918314d4-a88a-4bd2-8f4b-de3537d2f12f(a)e35g2000yqm.googlegroups.com>: >On May 11, 8:58�pm, MooseFET <kensm...(a)rahul.net> wrote: >> On May 11, 11:04�am, whit3rd <whit...(a)gmail.com> wrote: >> >> >> >> >> >> > On May 11, 10:27�am, whit3rd <whit...(a)gmail.com> wrote: >> >> > > On May 11, 6:47�am, George Herold <gher...(a)teachspin.com> wrote: >> >> > > > On May 11, 3:21�am, billmur...(a)protech.com (Bill Murphy) wrote: >> >> > > > > On Mon, 10 May 2010 18:24:52 -0700 (PDT), MooseFET >> >> > > > > <kensm...(a)rahul.net> wrote: >> > > > > >What are the two other channels making? >> >> > > > > Same signal, all spearated by 120 degrees. Done in CoolEdit. >> >> > > > > >If you have two signals at 90 degrees, you can get any other pha= >se >> > > > > >and the same amplitude. >> >> > > > The simple way is to mix them in a pot. >> >> > > > Sine----+ >> > > > � � � � | >> > > > � � � � P >> > > > � � � � O<----output >> > > > � � � � T >> > > > � � � � | >> > > > Cosine--+ >> >> > > > But this has an amplitude variation as you move the pot wiper aroun= >d, >> >> > > No, it doesn't! �Just buffer that output and it's good to go. >> >> > Oops, got that wrong; there IS amplitude variation, up to about 30 >> > percent; >> >> See my post for a circuit that makes the amplitude nearly constant.- Hide= > quoted text - >> > >I should/could have thought of the loaded pot, that's an easy way to >get rid of some of the variation. (I learned that trick from Phil H's >book.) But I've never seen postive feedback used like that before. I >assume that this gives some gain that changes as the source impedance >changes. > >Thanks, > >George H. Just use AGC. |