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

Mike Bryant mbryant at futurehorizons.com
Mon Sep 11 17:22:32 CEST 2023


I thought the SSI2130 was more or less the defacto standard nowadays ?   But I only design digital synths so maybe not aware of any shortcomings it has.

________________________________
From: Scott Bernardi <scottbernardi55 at gmail.com>
Sent: 11 September 2023 14:18
To: Mike Bryant <mbryant at futurehorizons.com>
Cc: brianw <brianw at audiobanshee.com>; Spiros Makris <spirosmakris92 at gmail.com>; synth-diy mailing list <synth-diy at synth-diy.org>
Subject: Re: [sdiy] What do people use for matched transistors these days?

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<mailto: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<mailto:synth-diy-bounces at synth-diy.org>> on behalf of Spiros Makris via Synth-diy <synth-diy at synth-diy.org<mailto:synth-diy at synth-diy.org>>
Sent: 11 September 2023 12:37
To: brianw <brianw at audiobanshee.com<mailto:brianw at audiobanshee.com>>
Cc: synth-diy mailing list <synth-diy at synth-diy.org<mailto: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<mailto: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<mailto: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<mailto: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<mailto:synth-diy-bounces at synth-diy.org>> on behalf of Scott Bernardi via Synth-diy <synth-diy at synth-diy.org<mailto:synth-diy at synth-diy.org>>
>> Sent: 09 September 2023 00:33
>> To: SDIY List <synth-diy at synth-diy.org<mailto: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.


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________________________________
From: Synth-diy <synth-diy-bounces at synth-diy.org<mailto:synth-diy-bounces at synth-diy.org>> on behalf of Spiros Makris via Synth-diy <synth-diy at synth-diy.org<mailto:synth-diy at synth-diy.org>>
Sent: 11 September 2023 12:37
To: brianw <brianw at audiobanshee.com<mailto:brianw at audiobanshee.com>>
Cc: synth-diy mailing list <synth-diy at synth-diy.org<mailto: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<mailto: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<mailto: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<mailto: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<mailto:synth-diy-bounces at synth-diy.org>> on behalf of Scott Bernardi via Synth-diy <synth-diy at synth-diy.org<mailto:synth-diy at synth-diy.org>>
>> Sent: 09 September 2023 00:33
>> To: SDIY List <synth-diy at synth-diy.org<mailto: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.


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