<html><head></head><body><div style="color:#000; background-color:#fff; font-family:verdana, helvetica, sans-serif;font-size:13px"><div id="yui_3_16_0_1_1456691302939_7977" dir="ltr"><span id="yui_3_16_0_1_1456691302939_8031">There are many inexpensive software applications for measuring THD, THD+N, SNR, SINAD, etc... With respect to your interface, you could look into the Focusrite Scarlett family of USB audio interfaces, such as the Scarlett 6i6 or even a 2i2. Both have respectable specifications to do basic measurements. Software wise, SpectraLab, RMAA, etc. </span></div><div id="yui_3_16_0_1_1456691302939_7977" dir="ltr"><span><br></span></div><div id="yui_3_16_0_1_1456691302939_7977" dir="ltr"><span id="yui_3_16_0_1_1456691302939_9934">On a side note, when it was mentioned that the CA3080EZ was not longer manufactured going to be manufactured, I bought quite a few hundred of them. So I have a lifetime supply for me and other interested parties. </span></div><div id="yui_3_16_0_1_1456691302939_7977" dir="ltr"><span id="yui_3_16_0_1_1456691302939_8218"> </span></div><div class="signature" id="yui_3_16_0_1_1456691302939_7981"><div id="yui_3_16_0_1_1456691302939_7995"><font size="2" id="yui_3_16_0_1_1456691302939_8004">Sincerely, <br> </font></div><div id="yui_3_16_0_1_1456691302939_7980"><font size="2" id="yui_3_16_0_1_1456691302939_7991">Chris Juried <br>Audio Engineering Society (AES) <var id="yui-ie-cursor"></var>Member <br>InfoComm-Recognized AV Technologist</font><span class="postbody" id="yui_3_16_0_1_1456691302939_7979"><br><a rel="nofollow" target="_blank" href="http://www.juriedengineering.com/" id="yui_3_16_0_1_1456691302939_7978">http://www.JuriedEngineering.com</a> (Juried Engineering, LLC.)</span></div><div id="yui_3_16_0_1_1456691302939_7985"><font size="3" id="yui_3_16_0_1_1456691302939_7984"><font size="2" id="yui_3_16_0_1_1456691302939_7983"><br><br>This e-mail, and any attachments thereto, is intended only for use by the addressee(s) named herein and may contain legally privileged and/or confidential information. If you are not the intended recipient of this e-mail, you are hereby notified that any distribution or copying of this email, and any attachments thereto, is strictly prohibited. If you have received this email in error, please immediately notify me at (754) 300-9972 and permanently delete the original and any copy of any e-mail and any printout thereof.</font></font><br></div></div><div class="qtdSeparateBR" id="yui_3_16_0_1_1456691302939_9935"><br><br></div><div class="yahoo_quoted" id="yui_3_16_0_1_1456691302939_9939" style="display: block;"> <div style="font-family: verdana, helvetica, sans-serif; font-size: 13px;" id="yui_3_16_0_1_1456691302939_9938"> <div style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;" id="yui_3_16_0_1_1456691302939_9937"> <div dir="ltr" id="yui_3_16_0_1_1456691302939_9936"> <font size="2" face="Arial" id="yui_3_16_0_1_1456691302939_9940"> <hr size="1" id="yui_3_16_0_1_1456691302939_9945"> <b><span style="font-weight:bold;">From:</span></b> "sleepy_dog@gmx.de" <sleepy_dog@gmx.de><br> <b><span style="font-weight: bold;">To:</span></b> synth-diy@dropmix.xs4all.nl <br> <b><span style="font-weight: bold;">Sent:</span></b> Sunday, February 28, 2016 8:34 AM<br> <b><span style="font-weight: bold;">Subject:</span></b> Re: [sdiy] Using both OTAs in 13700 as one OTA<br> </font> </div> <div class="y_msg_container" id="yui_3_16_0_1_1456691302939_9943"><br><div id="yiv4648084526"><div id="yui_3_16_0_1_1456691302939_9942">
<div class="yiv4648084526moz-cite-prefix" id="yui_3_16_0_1_1456691302939_9941"><br clear="none">
Assuming you use windows, if you have a not too shabby ASIO
soundcard, it means a program can get sole ownership of the card
and windows mixer not polluting your output signal. So you could
do audio range SNR and THD measurements with looping the soundcard
output, going through your test hardware, back to the input, and
using appropriate software. In the confines of the distortion
& noise of the soundcard used itself, obviously, but I suspect
that DIY analog synth circuits will be noisier than a decent ASIO
soundcard / external USB audio interface, my Roland/Edirol UA-25ex
served me well enough.<br clear="none">
<br clear="none">
Other than using existing software, you could implement it
yourself, I forgot where, but there are some app notes by TI or
National explaining how to use an FFT and generated test signals
to measure this. I have done it, but am not sure how well I did it
as to let my crappy little program loose on you :-D Unless you
insist, hah.<br clear="none">
It was done on one weekend, though, using FFTW library C# wrapper.
So not too difficult. If you are into software dev that is.<br clear="none">
<br clear="none">
There is a better option: one nice, free of charge program which
does all those things, and generate frequency response curves etc
- If you are interested, I will ask my colleague next week,
because I forgot its name, alas.<br clear="none">
<br clear="none">
You would need some level conversion for testing synth hardware
that way, I guess. At least protection for the soundcard input.
But (warning, I'm an analog semi n00b) I guess that operating
typical synth circuits with inputs of only +/- 1V or whatever
comes out of a soundcard might not do the noise figures justice?<br clear="none">
<br clear="none">
I'm sure some of the experienced people here can comment on that,
how to best do this. I'd be interested myself, for I have not
build any test bench for synth DIY circuits in this regard
(interfacing with PC soundcard *the proper way*) myself, but would
like to.<br clear="none">
<br clear="none">
As for many circuits with LM13700 not using the diodes, I would
guess that many were designed for the CA3080 and when that became
unavailable, people dropped in the 13700 as-is? (please do correct
me ;) )<br clear="none">
<br clear="none">
Steve<br clear="none">
<br clear="none">
<br clear="none">
Am 28.02.2016 um 09:13 schrieb Quincas:<br clear="none">
</div>
<div class="yiv4648084526yqt6725808257" id="yiv4648084526yqt63137"><blockquote type="cite">
<div class="yiv4648084526moz-text-plain" lang="x-western" style="font-family:-moz-fixed;font-size:14px;">
<pre>Hi guys
This thread got me thinking a lot about LM13700 VCAs, so I went to the datasheet and noticed they suggest using the linearizing diodes to reduce harmonic distortion. So I breadboarded it, changed some values to fit synth levels and added a voltage to current converter as seen in Thomas Henry's VCA1. I don't have adequate tools to measure THD or SNR, but it sounds dead clean to me! No noticeable noise and no audible distortion using the nice sine wave from my Norton filter in self oscillation. Is there a reason none of the designs discussed above use the linearizing diodes? Here's my shabby hand drawn schem....
<a rel="nofollow" shape="rect" class="yiv4648084526moz-txt-link-freetext" target="_blank" href="http://s1070.photobucket.com/user/Quincas_Moreira/media/image_zpsu5cm6fz8.jpeg.html">http://s1070.photobucket.com/user/Quincas_Moreira/media/image_zpsu5cm6fz8.jpeg.html</a>
Sent from my iPad
</pre>
<blockquote type="cite" style="color:#000000;">
<pre><span class="yiv4648084526moz-txt-citetags">> </span>On 10/02/2016, at 6:57 a.m., Simon Brouwer <a rel="nofollow" shape="rect" class="yiv4648084526moz-txt-link-rfc2396E" ymailto="mailto:simon.o@brousant.nl" target="_blank" href="mailto:simon.o@brousant.nl"><simon.o@brousant.nl></a> wrote:
<span class="yiv4648084526moz-txt-citetags">> </span>
<span class="yiv4648084526moz-txt-citetags">> </span>Hi Mattias,
<span class="yiv4648084526moz-txt-citetags">> </span>
<span class="yiv4648084526moz-txt-citetags">> </span>I mean the circuit like this:
<span class="yiv4648084526moz-txt-citetags">> </span><a rel="nofollow" shape="rect" class="yiv4648084526moz-txt-link-freetext" target="_blank" href="http://www.bernacomp.com/elec/lockbox/lockbox_vca2.gif">http://www.bernacomp.com/elec/lockbox/lockbox_vca2.gif</a>
<span class="yiv4648084526moz-txt-citetags">> </span>
<span class="yiv4648084526moz-txt-citetags">> </span>
<span class="yiv4648084526moz-txt-citetags">> </span>So, no.
<span class="yiv4648084526moz-txt-citetags">> </span>
<span class="yiv4648084526moz-txt-citetags">> </span>Best regards
<span class="yiv4648084526moz-txt-citetags">> </span>Simon
<span class="yiv4648084526moz-txt-citetags">> </span>
<span class="yiv4648084526moz-txt-citetags">> </span>
</pre>
<blockquote type="cite" style="color:#000000;">
<pre><span class="yiv4648084526moz-txt-citetags">> > </span>Op 10 februari 2016 om 12:31 schreef Mattias Rickardsson <a rel="nofollow" shape="rect" class="yiv4648084526moz-txt-link-rfc2396E" ymailto="mailto:mr@analogue.org" target="_blank" href="mailto:mr@analogue.org"><mr@analogue.org></a>:
<span class="yiv4648084526moz-txt-citetags">> > </span>
<span class="yiv4648084526moz-txt-citetags">> > </span>
<span class="yiv4648084526moz-txt-citetags">> > </span>Simon,
<span class="yiv4648084526moz-txt-citetags">> > </span>
<span class="yiv4648084526moz-txt-citetags">> > </span>what about the temperature dependencies in the transistor case?
<span class="yiv4648084526moz-txt-citetags">> > </span>Is that control circuit more sensitive for temperature variations?
<span class="yiv4648084526moz-txt-citetags">> > </span>
<span class="yiv4648084526moz-txt-citetags">> > </span>/mr
<span class="yiv4648084526moz-txt-citetags">> > </span>
<span class="yiv4648084526moz-txt-citetags">> > </span>
<span class="yiv4648084526moz-txt-citetags">> > </span>On 10 February 2016 at 09:08, Simon Brouwer <a rel="nofollow" shape="rect" class="yiv4648084526moz-txt-link-rfc2396E" ymailto="mailto:simon.o@brousant.nl" target="_blank" href="mailto:simon.o@brousant.nl"><simon.o@brousant.nl></a> wrote:
</pre>
<blockquote type="cite" style="color:#000000;">
<pre><span class="yiv4648084526moz-txt-citetags">> > > </span>Yes it was.
<span class="yiv4648084526moz-txt-citetags">> > ></span>
<span class="yiv4648084526moz-txt-citetags">> > > </span>However, this circuit still uses one opamp, a resistor and at least two
<span class="yiv4648084526moz-txt-citetags">> > > </span>diodes.
<span class="yiv4648084526moz-txt-citetags">> > > </span>The more straightforward approach adds two resistors, and replaces one diode
<span class="yiv4648084526moz-txt-citetags">> > > </span>by a
<span class="yiv4648084526moz-txt-citetags">> > > </span>transistor.
<span class="yiv4648084526moz-txt-citetags">> > > </span>So this doesn't add much in complexity and cost, and you can control both
<span class="yiv4648084526moz-txt-citetags">> > > </span>halves of an LM13700 independently.
<span class="yiv4648084526moz-txt-citetags">> > ></span>
<span class="yiv4648084526moz-txt-citetags">> > > </span>Best regards
<span class="yiv4648084526moz-txt-citetags">> > > </span>Simon
<span class="yiv4648084526moz-txt-citetags">> > ></span>
<span class="yiv4648084526moz-txt-citetags">> > ></span>
</pre>
<blockquote type="cite" style="color:#000000;">
<pre><span class="yiv4648084526moz-txt-citetags">> > >> </span>Op 9 februari 2016 om 20:20 schreef Mattias Rickardsson <a rel="nofollow" shape="rect" class="yiv4648084526moz-txt-link-rfc2396E" ymailto="mailto:mr@analogue.org" target="_blank" href="mailto:mr@analogue.org"><mr@analogue.org></a>:
</pre>
</blockquote>
<pre><span class="yiv4648084526moz-txt-citetags">> > ></span>
</pre>
<blockquote type="cite" style="color:#000000;">
<pre><span class="yiv4648084526moz-txt-citetags">> > >></span>
<span class="yiv4648084526moz-txt-citetags">> > >></span>
<span class="yiv4648084526moz-txt-citetags">> > >> </span>Aha!
<span class="yiv4648084526moz-txt-citetags">> > >> </span>It <b class="yiv4648084526moz-txt-star"><span class="yiv4648084526moz-txt-tag">*</span>was<span class="yiv4648084526moz-txt-tag">*</span></b> a beautiful trick. <span class="yiv4648084526moz-smiley-s1" title=":-)" title-off=""><span>:-)</span></span>
<span class="yiv4648084526moz-txt-citetags">> > >></span>
<span class="yiv4648084526moz-txt-citetags">> > >> </span><a rel="nofollow" shape="rect" class="yiv4648084526moz-txt-link-freetext" target="_blank" href="http://electronotes.netfirms.com/AN399.pdf">http://electronotes.netfirms.com/AN399.pdf</a>
<span class="yiv4648084526moz-txt-citetags">> > >></span>
<span class="yiv4648084526moz-txt-citetags">> > >> </span>/mr
<span class="yiv4648084526moz-txt-citetags">> > >></span>
<span class="yiv4648084526moz-txt-citetags">> > >></span>
<span class="yiv4648084526moz-txt-citetags">> > >> </span>On 8 February 2016 at 19:09, Ian Fritz <a rel="nofollow" shape="rect" class="yiv4648084526moz-txt-link-rfc2396E" ymailto="mailto:ijfritz@comcast.net" target="_blank" href="mailto:ijfritz@comcast.net"><ijfritz@comcast.net></a> wrote:
</pre>
<blockquote type="cite" style="color:#000000;">
<pre><span class="yiv4648084526moz-txt-citetags">> > >> > </span>The reference to the original Jung article is JAES, 23, 1975. This
<span class="yiv4648084526moz-txt-citetags">> > >> > </span>method
<span class="yiv4648084526moz-txt-citetags">> > >> > </span>was widely used in EN projects. I looked at using this method with the
<span class="yiv4648084526moz-txt-citetags">> > >> > </span>LM13700 to aid people who want to build off of these projects, but who
<span class="yiv4648084526moz-txt-citetags">> > >> > </span>can't
<span class="yiv4648084526moz-txt-citetags">> > >> > </span>obtain the CA3080. It's also an easy way to improve S/N by 3dB, as
<span class="yiv4648084526moz-txt-citetags">> > >> > </span>pointed
<span class="yiv4648084526moz-txt-citetags">> > >> > </span>out by Serge T. in his EN article from when the chip was new.
<span class="yiv4648084526moz-txt-citetags">> > >> ></span>
<span class="yiv4648084526moz-txt-citetags">> > >> > </span>I couldn't wade through Aaron's article either. It sounded like negating
<span class="yiv4648084526moz-txt-citetags">> > >> > </span>then subtracting? Isn't that the same as adding?
<span class="yiv4648084526moz-txt-citetags">> > >> ></span>
<span class="yiv4648084526moz-txt-citetags">> > >> > </span>Ian
<span class="yiv4648084526moz-txt-citetags">> > >> ></span>
<span class="yiv4648084526moz-txt-citetags">> > >> ></span>
<span class="yiv4648084526moz-txt-citetags">> > >> ></span>
<span class="yiv4648084526moz-txt-citetags">> > >> > </span>On 2/8/2016 2:41 AM, Mattias Rickardsson wrote:
</pre>
<blockquote type="cite" style="color:#000000;">
<pre><span class="yiv4648084526moz-txt-citetags">> > >> >></span>
<span class="yiv4648084526moz-txt-citetags">> > >> >> </span>On 4 February 2016 at 05:52, <a rel="nofollow" shape="rect" class="yiv4648084526moz-txt-link-rfc2396E" ymailto="mailto:ijfritz@comcast.net" target="_blank" href="mailto:ijfritz@comcast.net"><ijfritz@comcast.net></a> wrote:
</pre>
<blockquote type="cite" style="color:#000000;">
<pre><span class="yiv4648084526moz-txt-citetags">> > >> >>></span>
<span class="yiv4648084526moz-txt-citetags">> > >> >>> </span>Good grief! Just connect them directly in parallel. An example,
<span class="yiv4648084526moz-txt-citetags">> > >> >>> </span>complete
<span class="yiv4648084526moz-txt-citetags">> > >> >>> </span>with the W. Jung trick:
<span class="yiv4648084526moz-txt-citetags">> > >> >>></span>
<span class="yiv4648084526moz-txt-citetags">> > >> >>></span>
<span class="yiv4648084526moz-txt-citetags">> > >> >>> </span><a rel="nofollow" shape="rect" class="yiv4648084526moz-txt-link-freetext" target="_blank" href="http://electro-music.com/forum/viewtopic.php?highlight=jung+ota&t=50884">http://electro-music.com/forum/viewtopic.php?highlight=jung+ota&t=50884</a>
</pre>
</blockquote>
<pre><span class="yiv4648084526moz-txt-citetags">> > >> >></span>
<span class="yiv4648084526moz-txt-citetags">> > >> >></span>
<span class="yiv4648084526moz-txt-citetags">> > >> >> </span>What does it do? What is the "trick"?
<span class="yiv4648084526moz-txt-citetags">> > >> >> </span>I feel like one of the answers in that thread:
<span class="yiv4648084526moz-txt-citetags">> > >> >> </span>"I hadn't heard of this trick before, is there an article somewhere
<span class="yiv4648084526moz-txt-citetags">> > >> >> </span>that explains the benefit of drawing bias current from V-? I feel like
<span class="yiv4648084526moz-txt-citetags">> > >> >> </span>there's something obvious that I'm missing."
<span class="yiv4648084526moz-txt-citetags">> > >> >></span>
<span class="yiv4648084526moz-txt-citetags">> > >> >> </span>I spontaneously found Aaron's idea potentially better than nothing,
<span class="yiv4648084526moz-txt-citetags">> > >> >> </span>but I haven't plunged into it.
<span class="yiv4648084526moz-txt-citetags">> > >> >></span>
<span class="yiv4648084526moz-txt-citetags">> > >> >> </span>/mr
<span class="yiv4648084526moz-txt-citetags">> > >> >></span>
</pre>
</blockquote>
<pre><span class="yiv4648084526moz-txt-citetags">> > >> ></span>
</pre>
</blockquote>
<pre><span class="yiv4648084526moz-txt-citetags">> > >> </span>_______________________________________________
<span class="yiv4648084526moz-txt-citetags">> > >> </span>Synth-diy mailing list
<span class="yiv4648084526moz-txt-citetags">> > >> </span><a rel="nofollow" shape="rect" class="yiv4648084526moz-txt-link-abbreviated" ymailto="mailto:Synth-diy@dropmix.xs4all.nl" target="_blank" href="mailto:Synth-diy@dropmix.xs4all.nl">Synth-diy@dropmix.xs4all.nl</a>
<span class="yiv4648084526moz-txt-citetags">> > >> </span><a rel="nofollow" shape="rect" class="yiv4648084526moz-txt-link-freetext" target="_blank" href="http://dropmix.xs4all.nl/mailman/listinfo/synth-diy">http://dropmix.xs4all.nl/mailman/listinfo/synth-diy</a>
</pre>
</blockquote>
<pre><span class="yiv4648084526moz-txt-citetags">> > ></span>
<span class="yiv4648084526moz-txt-citetags">> > > </span>_______________________________________________
<span class="yiv4648084526moz-txt-citetags">> > > </span>Synth-diy mailing list
<span class="yiv4648084526moz-txt-citetags">> > > </span><a rel="nofollow" shape="rect" class="yiv4648084526moz-txt-link-abbreviated" ymailto="mailto:Synth-diy@dropmix.xs4all.nl" target="_blank" href="mailto:Synth-diy@dropmix.xs4all.nl">Synth-diy@dropmix.xs4all.nl</a>
<span class="yiv4648084526moz-txt-citetags">> > > </span><a rel="nofollow" shape="rect" class="yiv4648084526moz-txt-link-freetext" target="_blank" href="http://dropmix.xs4all.nl/mailman/listinfo/synth-diy">http://dropmix.xs4all.nl/mailman/listinfo/synth-diy</a>
<span class="yiv4648084526moz-txt-citetags">> > ></span>
</pre>
</blockquote>
</blockquote>
<pre><span class="yiv4648084526moz-txt-citetags">> </span>_______________________________________________
<span class="yiv4648084526moz-txt-citetags">> </span>Synth-diy mailing list
<span class="yiv4648084526moz-txt-citetags">> </span><a rel="nofollow" shape="rect" class="yiv4648084526moz-txt-link-abbreviated" ymailto="mailto:Synth-diy@dropmix.xs4all.nl" target="_blank" href="mailto:Synth-diy@dropmix.xs4all.nl">Synth-diy@dropmix.xs4all.nl</a>
<span class="yiv4648084526moz-txt-citetags">> </span><a rel="nofollow" shape="rect" class="yiv4648084526moz-txt-link-freetext" target="_blank" href="http://dropmix.xs4all.nl/mailman/listinfo/synth-diy">http://dropmix.xs4all.nl/mailman/listinfo/synth-diy</a>
</pre>
</blockquote>
<pre>_______________________________________________
Synth-diy mailing list
<a rel="nofollow" shape="rect" class="yiv4648084526moz-txt-link-abbreviated" ymailto="mailto:Synth-diy@dropmix.xs4all.nl" target="_blank" href="mailto:Synth-diy@dropmix.xs4all.nl">Synth-diy@dropmix.xs4all.nl</a>
<a rel="nofollow" shape="rect" class="yiv4648084526moz-txt-link-freetext" target="_blank" href="http://dropmix.xs4all.nl/mailman/listinfo/synth-diy">http://dropmix.xs4all.nl/mailman/listinfo/synth-diy</a>
</pre>
</div>
</blockquote></div>
<br clear="none">
</div></div><br><div class="yqt6725808257" id="yqt84181">_______________________________________________<br clear="none">Synth-diy mailing list<br clear="none"><a shape="rect" ymailto="mailto:Synth-diy@dropmix.xs4all.nl" href="mailto:Synth-diy@dropmix.xs4all.nl">Synth-diy@dropmix.xs4all.nl</a><br clear="none"><a shape="rect" href="http://dropmix.xs4all.nl/mailman/listinfo/synth-diy" target="_blank">http://dropmix.xs4all.nl/mailman/listinfo/synth-diy</a><br clear="none"></div><br><br></div> </div> </div> </div></div></body></html>