[sdiy] Latvian CEM Synth IC clones

[Mattias Rickardsson]

TL064 is too noisy and almost too slow in this application.

I've used it to save power in oscillators though, where the level is always
maximized and noise level less of an issue.

/mr


On 21 March 2018 at 10:57, Roman Sowa <modular at go2.pl> wrote:

> Why not use TL064, or TL034 if lower input offset voltage needed
>
> Roman
>
> W dniu 2018-03-21 o 10:41, Mattias Rickardsson pisze:
>
>> On 19 March 2018 at 23:48, Jay Schwichtenberg <jschwich53 at comcast.net
>> <mailto:jschwich53 at comcast.net>> wrote:
>>
>>     To me it seems like chips running at 50C-60C is way too hot and
>>     something is wrong. I'd expect to see something like a voltage
>>     regulator dropping a lot of voltage under a decent load doing that.
>>
>>
>> 55-60 degrees C was measured in the absolute middle of the top of the IC,
>> and the edges are a bit cooler. The PCB around it is 45 degrees, so it's
>> just 10-15 degrees above that.
>>
>>     ____
>>
>>     Are you driving low impedance loads or something?
>>
>>
>> Not extremely low, maybe 10k-20k on average - the quiescent currents are
>> still the majority of currents drawn by the ICs.
>>
>> But it adds up to some heat when having lots of TTSOP quad op-amps and
>> SOIC VCAs in a fairly small area, and all the passives on the bottom side
>> of the PCB.
>>
>> /mr
>>
>>
>>
>>     *From:*Synth-diy [mailto:synth-diy-bounces at synth-diy.org
>>     <mailto:synth-diy-bounces at synth-diy.org>] *On Behalf Of *Mattias
>>     Rickardsson
>>     *Sent:* Monday, March 19, 2018 7:10 AM
>>     *To:* mark verbos
>>     *Cc:* synth-diy at synth-diy.org <mailto:synth-diy at synth-diy.org>
>>     *Subject:* Re: [sdiy] Latvian CEM Synth IC clones____
>>
>>     __ __
>>
>>     On 14 March 2018 at 11:50, mark verbos <markverbos at gmail.com
>>     <mailto:markverbos at gmail.com>> wrote:____
>>
>>     Sorry if this is a stupid question, but when does it start to be an
>>     issue that the parts are too small. I mean in terms of current
>>     capacity and such. ____
>>
>>     __ __
>>
>>     One problem resulting from the tinyfication of everything is that
>>     the temperature gets higher when many ICs are packed into a small
>>     PCB area. My VCAs are running at over 50 degrees C here on the
>>     bench. The op-amps are approaching 60 degrees. When something
>>     reaches 180 degrees, we have an uncool audio fatality. ;-)____
>>
>>     __ __
>>
>>         I use 0603 resistors and they are only 100mW at some point it
>>         starts to be an issue for analog circuits, right? Not that I
>>         really want to use 01005 passives anyway, but my pick ’n' place
>>         is supposed to be able to. They look like salt and pepper.____
>>
>>     __ __
>>
>>     Surface-mount resistors with larger physical size typically have a
>>     bit lower excess noise and distortion. Size matters also among
>>     capacitors to some degrees. For some designs this can be
>> important.____
>>
>>     __ __
>>
>>     The ability to probe your ICs without shorting things is a good
>>     goal. With quad op-amps (outputs on the corner pins) TTSOP is fine,
>>     but otherwise I prefer the huge SOIC to reduce the risks.____
>>
>>     __ __
>>
>>     /mr____
>>
>>     __ __
>>
>>
>>
>>
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>>
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