[sdiy] Latvian CEM Synth IC clones

[Mattias Rickardsson]

On 19 March 2018 at 23:48, Jay Schwichtenberg <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] *On Behalf Of *Mattias
> Rickardsson
> *Sent:* Monday, March 19, 2018 7:10 AM
> *To:* mark verbos
> *Cc:* 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> 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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