<div dir="ltr"><div>Interesting to hear what everyone's favourites are. I also selected the OPA1679 recently for new designs (audio), but still wondering which opamp to use (or keep using) with respect to CV/DC stuff. I'd like to improve upon the offset and drift I've seen with the TL074, and rail-to-rail would be awesome as I've seen situations where Eurorack audio-rate-CVs at high frequencies really suffer. Any other suggestions for a good price-quality-ratio part for CV paths?</div><div><br></div><div>Rutger</div></div><div class="gmail_extra"><br><div class="gmail_quote">2018-04-19 19:28 GMT+02:00 Oren Leavitt <span dir="ltr"><<a href="mailto:obl64@ix.netcom.com" target="_blank">obl64@ix.netcom.com</a>></span>:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Thanks for the info on OPA1678/9! I do still find myself using the LT1013 a lot for CV/DC stuff (where the slow slew rate isn't an issue).<div class="HOEnZb"><div class="h5"><br>
<br>
<br>
On 4/19/18 11:16 AM, Tim Ressel wrote:<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;padding-left:1ex;border-left-color:rgb(204,204,204);border-left-width:1px;border-left-style:solid">
I pretty much use just 2 amps now; the 1678/9 any time I need performance, and the TL082/4 for generic stuff. My new filter module is a good example: 1678 for the audio processing and a TL082 for CV processing.<br>
<br>
In a way it feels funny to reduce the huge universe of op amps down to 2 parts. I know there are many applications where other amps are better. High power, high voltage, high accuracy, high frequency, etc. But for what I tend to do these two pretty much cover it. Many thanks for the dudes who came up with it!<br>
<br>
--Tim (parts nerd) Ressel<br>
<br>
<br>
On 4/19/2018 8:15 AM, Steve Lenham wrote:<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;padding-left:1ex;border-left-color:rgb(204,204,204);border-left-width:1px;border-left-style:solid">
I too designed the 1678 into a new product after Tim's original post drew it to my attention, and they work very nicely.<br>
<br>
The power of networking, eh - wonder if it will catch on?<br>
<br>
Cheers,<br>
<br>
Steve L.<br>
Benden Sound Technology<br>
<br>
<br>
On 19/04/2018 15:40, Matthias Herrmann wrote:<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;padding-left:1ex;border-left-color:rgb(204,204,204);border-left-width:1px;border-left-style:solid">
Nice.<br>
I use the OPA1678 as my new working horse for quite a while now.<br>
<br>
*From: *Synth-diy <<a href="mailto:synth-diy-bounces@synth-diy.org" target="_blank">synth-diy-bounces@synth-diy.o<wbr>rg</a><br>
<mailto:<a href="mailto:synth-diy-bounces@synth-diy.org" target="_blank">synth-diy-bounces@synt<wbr>h-diy.org</a>>> on behalf of Mattias<br>
Rickardsson <<a href="mailto:mr@analogue.org" target="_blank">mr@analogue.org</a> <mailto:<a href="mailto:mr@analogue.org" target="_blank">mr@analogue.org</a>>><br>
*Date: *Thursday, 19 April 2018 at 14:16<br>
*To: *Tim Ressel <<a href="mailto:timr@circuitabbey.com" target="_blank">timr@circuitabbey.com</a> <mailto:<a href="mailto:timr@circuitabbey.com" target="_blank">timr@circuitabbey.com</a>><wbr>><br>
*Cc: *Synth DIY <<a href="mailto:synth-diy@synth-diy.org" target="_blank">synth-diy@synth-diy.org</a><br>
<mailto:<a href="mailto:synth-diy@synth-diy.org" target="_blank">synth-diy@synth-diy.or<wbr>g</a>>><br>
*Subject: *Re: [sdiy] Happenin' new opamp<br>
<br>
I'm throwing in some news (for me at least) about the fairly new<br>
OPA1678/79 low-noise rail-to-railFET-input op-amps that I was trying<br>
as substitutes for the OPA1652/54, which has a price more than twice<br>
as high. The specifications are remarkably similar, and by accident<br>
I got in contact with TI's John Caldwell. He writes:<br>
<br>
"I’ll let you in a on a little secret, the silicon is identical<br>
between the two devices. OPA1652 was released by another engineer<br>
before me, and when I took over the portfolio of audio op amps I<br>
personally felt that OPA1652 was too expensive to address the bulk<br>
of audio opportunities. For that reason, we made some changes to the<br>
production testing (used new test hardware that let us test more<br>
units faster) to reduce the manufacturing cost and re-released the<br>
device at a lower price point.<br>
Fun fact: the OPA1652 / OPA1678 has the lowest broadband voltage<br>
noise of any FET-type input amplifier in TI’s portfolio. It even has<br>
lower broadband voltage noise than the much more expensive OPA827."<br>
<br>
I don't know if this was known before, but anyway great to have the<br>
same brilliant chip for a fraction of the price... and isn't it a<br>
great attitude about quality product sales? :-)<br>
<br>
Regarding the inputs, which they don't mention being FET in the<br>
OPA1678 datasheet:<br>
<br>
"We received your feedback on the OPA1678 datasheet. With regards to<br>
mentioning the input device type, the OPA1678 is fabricated on a<br>
CMOS process, so yes the device type is indeed a FET (MOSFET). This<br>
is also shown in the simplified diagram of the internal architecture<br>
on the first page.<br>
Calling it a “FET” input sometimes raises confusion between whether<br>
or not the devices is JFET or CMOS and I wanted to avoid that when I<br>
wrote the OPA1678 datasheet."<br>
<br>
/mr<br>
<br>
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