<div dir="auto">I am all for a UA726 sub.</div><div class="gmail_extra"><br><div class="gmail_quote">On 3 Nov 2017 19:46, "Ben Bradley" <<a href="mailto:ben.pi.bradley@gmail.com">ben.pi.bradley@gmail.com</a>> wrote:<br type="attribution"><blockquote class="quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">The talk of exponential converters on VCAs brings to mind the use of<br>
transistors for expo conversion, specifically on-chip transistor<br>
pairs. Was there any use of National's (and later TI until they<br>
stopped production) LM324 precision dual transistor in a synth expo<br>
converter? The only product I know of it being used in was the Jensen<br>
990 discrete op-amp. This tells Jensen's story of going through<br>
replacements for the LM324:<br>
<br>
<a href="http://www.technicalaudio.com/pdf/Jensen_Transformers/Jensen_OpAmps_990_and_related/Jensen_JE-990_opamp_JAES_reprint_1980.pdf" rel="noreferrer" target="_blank">http://www.technicalaudio.com/<wbr>pdf/Jensen_Transformers/<wbr>Jensen_OpAmps_990_and_related/<wbr>Jensen_JE-990_opamp_JAES_<wbr>reprint_1980.pdf</a><br>
<br>
On the first couple pages of text here is Deane Jensen's descriotion<br>
of the LM324, how it's made with many on-chip transistors wired<br>
together as two:<br>
<a href="http://www.johnhardyco.com/pdf/990.pdf" rel="noreferrer" target="_blank">http://www.johnhardyco.com/<wbr>pdf/990.pdf</a><br>
<br>
I noticed our friends from Latvia are now making an LM324 replacement:<br>
<a href="http://www.alfarzpp.lv/eng/sc/transistors.php" rel="noreferrer" target="_blank">http://www.alfarzpp.lv/eng/sc/<wbr>transistors.php</a><br>
<br>
There was also the ua726 self-heating temperature-regulated pair used<br>
in classic synths that is basically unobtainable now. It would be good<br>
to have that remade, or perhaps even an LM324 version with an on-chip<br>
heater/temp regulator.<br>
<br>
The newly-remade module-on-a-chip designs are wonderful in having<br>
everything built in, but I still want to make some "discrete" designs,<br>
and having these transistor-pair-on-a-chip products available helps a<br>
lot.<br>
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</blockquote></div><br></div>