[sdiy] What do people use for matched transistors these days?

Scott Bernardi scottbernardi55 at gmail.com
Mon Sep 11 15:18:56 CEST 2023


Like a CEM3340 or equivalent? I'm building one of those also, but not in
this design.
I've done CEM based , and Ian Fritz sawtooth VCO in the past, and triangle
- square LFO'sn I wanted to tackle a triangle-square VCO.

On Mon, Sep 11, 2023, 5:20 AM Mike Bryant <mbryant at futurehorizons.com>
wrote:

> Are you better off using one of the VCO ICs that include a temperature
> stabilised exponential convertor ?
>
>
>
> ------------------------------
> *From:* Synth-diy <synth-diy-bounces at synth-diy.org> on behalf of Spiros
> Makris via Synth-diy <synth-diy at synth-diy.org>
> *Sent:* 11 September 2023 12:37
> *To:* brianw <brianw at audiobanshee.com>
> *Cc:* synth-diy mailing list <synth-diy at synth-diy.org>
> *Subject:* Re: [sdiy] What do people use for matched transistors these
> days?
>
> The 4 transistor ICs offer the possibility of forming a thermal oven,
> which can be exceptionally stable if shielded from air breeze. I have built
> and evaluated a version using THAT-320 and it tracks very well regardless
> of season (indoor use). It's been a few years, but I remember that there's
> a tradeoff between Rbe and temperature; higher oven temperature offers more
> stability against ambient temperature changes (I picked 50C in my version),
> but increases Rbe, messing with high-frequency tracking.
> In any case, the stability of the expo pair essentially depends on the
> temperature matching of the transistors, and thus, having them on the same
> die is the optimal solution, even if you go with thermistor compensation
> instead.
>
> On Mon, 11 Sept 2023 at 07:47, brianw <brianw at audiobanshee.com> wrote:
>
> Does anyone here have access to a thermal chamber where the temperature
> drift of a given circuit can actually be assessed?
>
> My assumption is that things will probably work fine under "normal"
> conditions, but as soon as a musician brings gear in from a cold climate to
> a warm venue, or even starting from comfortable climes and then
> temperatures inside climb to sweaty, humid heat, there might be problems
> that didn't show up in the home studio.
>
> Brian
>
> On Sep 10, 2023, at 6:22 PM, crys <crystals at sonic.net> wrote:
> > I acquired a bunch of THAT 320 and 300 and used them for quite a few
> ircuits. Sometimes it was likely overkill, like when i built a ladder
> filter with them. I found them to be easy to work with and quite stable.
> They do cost but i think i either got a deal or bought a quantity. It was a
> decade ago. I did score about 20 LM394 cans but it was just as i packed up
> my lab to storage, I'm interested in what's what now.  I have made a tester
> and matched them myself, as already menioned quite easy these days. I
> started matching resistors, too, which was quite easy. I also built plenty
> of modules with just transistors from a new lot that sounded just fine.
> >
> > On 9/9/2023 6:21 PM, Paul Glass-Steel via Synth-diy wrote:
> >> I’ve had good results with those too.
> >>
> >> On Sat, Sep 9, 2023 at 4:20 AM Mike Bryant <mbryant at futurehorizons.com>
> wrote:
> >> Nxperia also do dual transistors without the base resistors e.g.
> BC856S.  They are on the same die so will be well matched.
> >>
> >> From: Synth-diy <synth-diy-bounces at synth-diy.org> on behalf of Scott
> Bernardi via Synth-diy <synth-diy at synth-diy.org>
> >> Sent: 09 September 2023 00:33
> >> To: SDIY List <synth-diy at synth-diy.org>
> >> Subject: [sdiy] What do people use for matched transistors these days?
> >>
> >> Right now I'm looking at matched pnp's, suitable for a VCO.  Something
> like the THAT-320 quad pnp would be ideal, but they are kind of pricey. The
> quad is nice because you have an extra matched transistor you can use for
> high frequency tracking adjustment.
> >>
> >> I ordered some BCM856's to see how they will pan out.  I think the VBE
> match will be good enough, I'm wondering about the base resistance that
> causes deviation from ideal log conformance.
> >>
> >> For npn's, THAT-300 or MAT14 are the best, also pricey.
>
>
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at synth-diy.org
> http://synth-diy.org/mailman/listinfo/synth-diy
> Selling or trading? Use marketplace at synth-diy.org
>
>
> ------------------------------
> *From:* Synth-diy <synth-diy-bounces at synth-diy.org> on behalf of Spiros
> Makris via Synth-diy <synth-diy at synth-diy.org>
> *Sent:* 11 September 2023 12:37
> *To:* brianw <brianw at audiobanshee.com>
> *Cc:* synth-diy mailing list <synth-diy at synth-diy.org>
> *Subject:* Re: [sdiy] What do people use for matched transistors these
> days?
>
> The 4 transistor ICs offer the possibility of forming a thermal oven,
> which can be exceptionally stable if shielded from air breeze. I have built
> and evaluated a version using THAT-320 and it tracks very well regardless
> of season (indoor use). It's been a few years, but I remember that there's
> a tradeoff between Rbe and temperature; higher oven temperature offers more
> stability against ambient temperature changes (I picked 50C in my version),
> but increases Rbe, messing with high-frequency tracking.
> In any case, the stability of the expo pair essentially depends on the
> temperature matching of the transistors, and thus, having them on the same
> die is the optimal solution, even if you go with thermistor compensation
> instead.
>
> On Mon, 11 Sept 2023 at 07:47, brianw <brianw at audiobanshee.com> wrote:
>
> Does anyone here have access to a thermal chamber where the temperature
> drift of a given circuit can actually be assessed?
>
> My assumption is that things will probably work fine under "normal"
> conditions, but as soon as a musician brings gear in from a cold climate to
> a warm venue, or even starting from comfortable climes and then
> temperatures inside climb to sweaty, humid heat, there might be problems
> that didn't show up in the home studio.
>
> Brian
>
> On Sep 10, 2023, at 6:22 PM, crys <crystals at sonic.net> wrote:
> > I acquired a bunch of THAT 320 and 300 and used them for quite a few
> ircuits. Sometimes it was likely overkill, like when i built a ladder
> filter with them. I found them to be easy to work with and quite stable.
> They do cost but i think i either got a deal or bought a quantity. It was a
> decade ago. I did score about 20 LM394 cans but it was just as i packed up
> my lab to storage, I'm interested in what's what now.  I have made a tester
> and matched them myself, as already menioned quite easy these days. I
> started matching resistors, too, which was quite easy. I also built plenty
> of modules with just transistors from a new lot that sounded just fine.
> >
> > On 9/9/2023 6:21 PM, Paul Glass-Steel via Synth-diy wrote:
> >> I’ve had good results with those too.
> >>
> >> On Sat, Sep 9, 2023 at 4:20 AM Mike Bryant <mbryant at futurehorizons.com>
> wrote:
> >> Nxperia also do dual transistors without the base resistors e.g.
> BC856S.  They are on the same die so will be well matched.
> >>
> >> From: Synth-diy <synth-diy-bounces at synth-diy.org> on behalf of Scott
> Bernardi via Synth-diy <synth-diy at synth-diy.org>
> >> Sent: 09 September 2023 00:33
> >> To: SDIY List <synth-diy at synth-diy.org>
> >> Subject: [sdiy] What do people use for matched transistors these days?
> >>
> >> Right now I'm looking at matched pnp's, suitable for a VCO.  Something
> like the THAT-320 quad pnp would be ideal, but they are kind of pricey. The
> quad is nice because you have an extra matched transistor you can use for
> high frequency tracking adjustment.
> >>
> >> I ordered some BCM856's to see how they will pan out.  I think the VBE
> match will be good enough, I'm wondering about the base resistance that
> causes deviation from ideal log conformance.
> >>
> >> For npn's, THAT-300 or MAT14 are the best, also pricey.
>
>
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at synth-diy.org
> http://synth-diy.org/mailman/listinfo/synth-diy
> Selling or trading? Use marketplace at synth-diy.org
>
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at synth-diy.org
> http://synth-diy.org/mailman/listinfo/synth-diy
> Selling or trading? Use marketplace at synth-diy.org
>
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