[sdiy] Passive Ring Modulator

[John L Marshall]

One technique to improve rejection is to use transformers with split
windings instead of center tapped windings. If the windings are bifilar, two
wires in parallel, then the inductance and capacitance will be nearly
identical. But if the windings are not bifilar, split windings will still
still help.

Where the center tap ought to be, put a small trim pot (50 ohms). Attach
each trim pot end to each winding and the wiper becomes the new center tap.
Do this for each transformer.

Adjusting for minimum feedthrough will be a challenge.

Take care,
John
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Pacific Northwest DIY Synthesizer meeting, July 20, 2002
See: www.sound-photo.com
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----- Original Message -----
From: <cyborgzero at comcast.net>
To: "Synth (E-mail)" <synth-diy at dropmix.xs4all.nl>
Sent: Friday, July 12, 2002 2:43 PM
Subject: Re: [sdiy] Passive Ring Modulator


> Yes, I am *definitely* interested in this two diode ring approach,
> since the key issue with passives is they fact that they have a
> problem with carrier rejection. Anything that would increase that
> would be good in my book. ;)
>
> Rob
>
> ----- Original Message -----
> From: "Steve Begin" <Steve.Begin at pwgsc.gc.ca>
> To: "Synth (E-mail)" <synth-diy at dropmix.xs4all.nl>
> Sent: Friday, July 12, 2002 12:29 PM
> Subject: RE: [sdiy] Passive Ring Modulator
>
>
> > Awesome!  I found a 42TL028 transformer on mouser.com hopefully that
> is the
> > same thing.  I will try to order a few. Thanks a lot!
> >
> > How is the second diode ring connected in the design you have?
> >
> > Steve Begin
> >
> >
> > -----Original Message-----
> > From: ian [mailto:deviant at custard.org]
> > Sent: Friday, July 12, 2002 12:55 PM
> > To: Steve Begin
> > Cc: Synth (E-mail)
> > Subject: Re: [sdiy] Passive Ring Modulator
> >
> >
> > Hi Steve,
> > I have a boxful of ringmods much like this sitting on my desk right
> now! I
> > haven't had a chance to try them out yet, but other people who have
> tried
> > them say they sound great. The design I have was given to me by a
> > colleague, and it comes from the Amateur Radio Relay League
> handbook. It
> > differs slightly from the one on sonicstate, as it has two diode
> rings,
> > which is supposed to provide better carrier rejection than the
> single
> > diode ring design. As for the transformers, the ringmods I have use
> one
> > from Mouser, marked TL028 down one side and 0109S down the other.
> > Ian
> >
> >
> > On Fri, 12 Jul 2002, Steve Begin wrote:
> >
> > > Hi, I'm new to the list, not new to analog (am I gonna get in
> trouble if I
> > > spell it like that?)
> > >  gear, but fairly inexperienced when it comes to circuitry.
> > >
> > > I've got a question, has anybody had any experience with a passive
> ring
> > > modulator design like this one?
> > > http://www.sonicstate.com/synthfool/ringmod.html
> > >
> > > I'm interested in it since it looks very easy to make and cheap
> and if it
> > > doesn't work as well as other designs it doesn't bother me that
> much.
> > > However,  I guess the stancor a-4713 driver transformers are no
> longer in
> > > production and I can't seem to find anything information on them
> at all,
> > let
> > > alone a reference to a part I could use as a substitute.
> > > I'd really appreciate it if somebody could give me any direction
> at all
> > > here.
> > >
> > > The other thing I was wondering about (and I'm sure it's probably
> > painfully
> > > obvious to a lot of you) was half or full normalled patch bays.
> When you
> > > split a signal doesn't it affect the impedance or something along
> those
> > > lines?  I thought it would be a bad thing to do but I haven't seen
> anybody
> > > mention any problems with that.
> > > How about combining signals without a mixer?  I'm almost positive
> you get
> > > problems doing that.
> > >
> > > Thanks!
> > >
> > > > Steve Begin
> > > >
> > > >
> > > >
> > >
>