Discrete Synthesizers Question

classic Classic list List threaded Threaded
12 messages Options
Reply | Threaded
Open this post in threaded view
|

Discrete Synthesizers Question

Future_Sound _Of_Canada
Hey all,

I just got an e-mail from a friend who bought a small Technosaurus system. He tells me, despite the seemingly limited range of modules, the discrete design really lends itself to an enriching sound ("amazing", by his words). I'm just wondering if anyone can offer any views on synthesizers made with discrete components, and what makes them particularly interesting or pleasing. I heard Technosaurus systems are only available on the used market now, I've heard of CMS Discrete Synthesizers (but haven't heard any demos), and am familiar with the upcoming discrete Boomstar synths from Studio Electronics. Is there anything else available (new or used) that showcases the appeal of discrete designs specifically, and if so, what makes them so special, or is it all hype?

Cheers,

Andrew

Reply | Threaded
Open this post in threaded view
|

Re: Discrete Synthesizers Question

Nick Zampiello
It's inherently a more 'lively' sounding circuit in every application.

guitar amps, synths, pro audio gear.

discrete can seem somewhat less 'under control' in a good way.

CUE:   EE people please chime in!



z




 
NEW ALLIANCE EAST!!!!

--------------------------------------


New Alliance East - Facebook


X :::: B :::: S





From: Future_Sound _Of_Canada <[hidden email]>
To: [hidden email]
Sent: Thursday, January 10, 2013 12:45 PM
Subject: [AH] Discrete Synthesizers Question

Hey all,

I just got an e-mail from a friend who bought a small Technosaurus system. He tells me, despite the seemingly limited range of modules, the discrete design really lends itself to an enriching sound ("amazing", by his words). I'm just wondering if anyone can offer any views on synthesizers made with discrete components, and what makes them particularly interesting or pleasing. I heard Technosaurus systems are only available on the used market now, I've heard of CMS Discrete Synthesizers (but haven't heard any demos), and am familiar with the upcoming discrete Boomstar synths from Studio Electronics. Is there anything else available (new or used) that showcases the appeal of discrete designs specifically, and if so, what makes them so special, or is it all hype?

Cheers,

Andrew



Reply | Threaded
Open this post in threaded view
|

re: Discrete Synthesizers Question

Michael E Caloroso
In reply to this post by Future_Sound _Of_Canada
> I just got an e-mail from a friend who bought a small Technosaurus system. He
> tells me, despite the seemingly limited range of modules, the discrete design
> really lends itself to an enriching sound ("amazing", by his words). I'm just
> wondering if anyone can offer any views on synthesizers made with
> discrete components, and what makes them particularly interesting or
> pleasing. I heard Technosaurus systems are only available on the used
> market now, I've heard of CMS Discrete Synthesizers (but haven't heard
> any demos), and am familiar with the upcoming discrete Boomstar synths
> from Studio Electronics. Is there anything else available (new or used) that
> showcases the appeal of discrete designs specifically, and if so, what
> makes them so special, or is it all hype?

Not hype.  Two reasons: progression of active devices, and advancing
circuit design.

Modern ICs are linear devices.  Transistors are not linear.

The difference is distortion introduced by the non-linearity of transistors.

That couples in with advancing circuit design.  VCAs of the vintage
era were NOT high fidelity.  During the 60s and 70s there was no high
fidelity VCA available anywhere.  VCAs were designed using transistors
and their inherent distortion gave them a dirty edgy sound.  The same
was true for active filters, which are a form of VCAs.

If you study the schematics of the big Oberheim synths (OB-X, OB-Xa,
OB-8) as they progressed, you would see a direct correlation between
VCA technology and distortion.  Take the Voyager output before filter
(mixer insert) and route the Voyager audio to the external input of a
vintage Minimoog, and the Voyager has the high end sheen of the
Minimoog that had been missing from the Voyager signal chain.  The
Minimoog has not ONE but TWO dirty-sounding VCAs to mangle the sound.

Sent from smoke signals,
MC
Reply | Threaded
Open this post in threaded view
|

RE: Discrete Synthesizers Question

Future_Sound _Of_Canada
Wow. Thanks for the detailed explanation, it's appreciated.

Cheers,

Andrew

> Date: Fri, 11 Jan 2013 00:09:05 -0500

> From: [hidden email]
> To: [hidden email]
> Subject: re: [AH] Discrete Synthesizers Question
>
> > I just got an e-mail from a friend who bought a small Technosaurus system. He
> > tells me, despite the seemingly limited range of modules, the discrete design
> > really lends itself to an enriching sound ("amazing", by his words). I'm just
> > wondering if anyone can offer any views on synthesizers made with
> > discrete components, and what makes them particularly interesting or
> > pleasing. I heard Technosaurus systems are only available on the used
> > market now, I've heard of CMS Discrete Synthesizers (but haven't heard
> > any demos), and am familiar with the upcoming discrete Boomstar synths
> > from Studio Electronics. Is there anything else available (new or used) that
> > showcases the appeal of discrete designs specifically, and if so, what
> > makes them so special, or is it all hype?
>
> Not hype. Two reasons: progression of active devices, and advancing
> circuit design.
>
> Modern ICs are linear devices. Transistors are not linear.
>
> The difference is distortion introduced by the non-linearity of transistors.
>
> That couples in with advancing circuit design. VCAs of the vintage
> era were NOT high fidelity. During the 60s and 70s there was no high
> fidelity VCA available anywhere. VCAs were designed using transistors
> and their inherent distortion gave them a dirty edgy sound. The same
> was true for active filters, which are a form of VCAs.
>
> If you study the schematics of the big Oberheim synths (OB-X, OB-Xa,
> OB-8) as they progressed, you would see a direct correlation between
> VCA technology and distortion. Take the Voyager output before filter
> (mixer insert) and route the Voyager audio to the external input of a
> vintage Minimoog, and the Voyager has the high end sheen of the
> Minimoog that had been missing from the Voyager signal chain. The
> Minimoog has not ONE but TWO dirty-sounding VCAs to mangle the sound.
>
> Sent from smoke signals,
> MC
Reply | Threaded
Open this post in threaded view
|

Re: Discrete Synthesizers Question

rsdio-2
In reply to this post by Michael E Caloroso
> On Jan 10, 2013, at 21:09, Michael E Caloroso wrote:
>> I just got an e-mail from a friend who bought a small Technosaurus  
>> system. He
>> tells me, despite the seemingly limited range of modules, the  
>> discrete design
>> really lends itself to an enriching sound ("amazing", by his  
>> words). I'm just
>> wondering if anyone can offer any views on synthesizers made with
>> discrete components, and what makes them particularly interesting or
>> pleasing. I heard Technosaurus systems are only available on the used
>> market now, I've heard of CMS Discrete Synthesizers (but haven't  
>> heard
>> any demos), and am familiar with the upcoming discrete Boomstar  
>> synths
>> from Studio Electronics. Is there anything else available (new or  
>> used) that
>> showcases the appeal of discrete designs specifically, and if so,  
>> what
>> makes them so special, or is it all hype?
>
> Not hype.  Two reasons: progression of active devices, and advancing
> circuit design.
>
> Modern ICs are linear devices.  Transistors are not linear.
>
> The difference is distortion introduced by the non-linearity of  
> transistors.

That's a very misleading simplification. ICs are made with  
transistors inside. The difference is that ICs typically include more  
transistors than would fit on an affordable PCB, and also that there  
is usually some sort of crosstalk between the transistors because  
they're all on the same IC substrate. Another issue for high-powered  
devices is that ICs cannot generally handle the same level of current  
(and voltage) as discrete transistors.

Transistors have a linear range, just like tubes. ICs also have many  
nonlinearities, especially the zero-crossing of the signal, where  
there is plenty of distortion.


> That couples in with advancing circuit design.  VCAs of the vintage
> era were NOT high fidelity.  During the 60s and 70s there was no high
> fidelity VCA available anywhere.  VCAs were designed using transistors
> and their inherent distortion gave them a dirty edgy sound.  The same
> was true for active filters, which are a form of VCAs.
>
> If you study the schematics of the big Oberheim synths (OB-X, OB-Xa,
> OB-8) as they progressed, you would see a direct correlation between
> VCA technology and distortion.  Take the Voyager output before filter
> (mixer insert) and route the Voyager audio to the external input of a
> vintage Minimoog, and the Voyager has the high end sheen of the
> Minimoog that had been missing from the Voyager signal chain.  The
> Minimoog has not ONE but TWO dirty-sounding VCAs to mangle the sound.


You are correct here. VCAs are very dirty. They almost always have  
some amount of DC leakage from the CV to the audio signal. Where  
typical ICs have some nonlinear distortion, VCAs have a lot more.

To my knowledge, all VCAs are ICs. If anyone is aware of a discrete  
transistor VCA, please cite a reference - preferably with a schematic  
(I'd really like to see that). Now that I think about it, the early  
synths must have had discrete transistors VCAs, but I'm just not  
remembering ever seeing one in a schematic.

Anyone have a list of discrete synths? There's probably no point  
listed all the synths based on ICs, since that would include just  
about every one of them.

Brian Willoughby
Sound Consulting

Reply | Threaded
Open this post in threaded view
|

Re: Discrete Synthesizers Question

Andrew Dean-2
> To my knowledge, all VCAs are ICs. If anyone is aware of a discrete transistor VCA, please cite a reference - preferably
> with a schematic (I'd really like to see that). Now that I think about it, the early synths must have had discrete transistors
> VCAs, but I'm just not remembering ever seeing one in a schematic.

It's an optional upgrade for the SE Omega series

http://www.studioelectronics.com/products/synths/code/midiminiafy/


On 13 January 2013 18:51, <[hidden email]> wrote:
On Jan 10, 2013, at 21:09, Michael E Caloroso wrote:
I just got an e-mail from a friend who bought a small Technosaurus system. He
tells me, despite the seemingly limited range of modules, the discrete design
really lends itself to an enriching sound ("amazing", by his words). I'm just
wondering if anyone can offer any views on synthesizers made with
discrete components, and what makes them particularly interesting or
pleasing. I heard Technosaurus systems are only available on the used
market now, I've heard of CMS Discrete Synthesizers (but haven't heard
any demos), and am familiar with the upcoming discrete Boomstar synths
from Studio Electronics. Is there anything else available (new or used) that
showcases the appeal of discrete designs specifically, and if so, what
makes them so special, or is it all hype?

Not hype.  Two reasons: progression of active devices, and advancing
circuit design.

Modern ICs are linear devices.  Transistors are not linear.

The difference is distortion introduced by the non-linearity of transistors.

That's a very misleading simplification. ICs are made with transistors inside. The difference is that ICs typically include more transistors than would fit on an affordable PCB, and also that there is usually some sort of crosstalk between the transistors because they're all on the same IC substrate. Another issue for high-powered devices is that ICs cannot generally handle the same level of current (and voltage) as discrete transistors.

Transistors have a linear range, just like tubes. ICs also have many nonlinearities, especially the zero-crossing of the signal, where there is plenty of distortion.



That couples in with advancing circuit design.  VCAs of the vintage
era were NOT high fidelity.  During the 60s and 70s there was no high
fidelity VCA available anywhere.  VCAs were designed using transistors
and their inherent distortion gave them a dirty edgy sound.  The same
was true for active filters, which are a form of VCAs.

If you study the schematics of the big Oberheim synths (OB-X, OB-Xa,
OB-8) as they progressed, you would see a direct correlation between
VCA technology and distortion.  Take the Voyager output before filter
(mixer insert) and route the Voyager audio to the external input of a
vintage Minimoog, and the Voyager has the high end sheen of the
Minimoog that had been missing from the Voyager signal chain.  The
Minimoog has not ONE but TWO dirty-sounding VCAs to mangle the sound.


You are correct here. VCAs are very dirty. They almost always have some amount of DC leakage from the CV to the audio signal. Where typical ICs have some nonlinear distortion, VCAs have a lot more.

To my knowledge, all VCAs are ICs. If anyone is aware of a discrete transistor VCA, please cite a reference - preferably with a schematic (I'd really like to see that). Now that I think about it, the early synths must have had discrete transistors VCAs, but I'm just not remembering ever seeing one in a schematic.

Anyone have a list of discrete synths? There's probably no point listed all the synths based on ICs, since that would include just about every one of them.

Brian Willoughby
Sound Consulting


Reply | Threaded
Open this post in threaded view
|

Re: Discrete Synthesizers Question

Nick Zampiello
all early DBX products achieved gain control with potted transistor VCAs..

http://en.wikipedia.org/wiki/Dbx,_Inc.


zzzzz



 
NEW ALLIANCE EAST!!!!

--------------------------------------


New Alliance East - Facebook


X :::: B :::: S





From: Andrew Dean <[hidden email]>
To: [hidden email]
Cc: analogue <[hidden email]>; Future_Sound _Of_Canada <[hidden email]>
Sent: Sunday, January 13, 2013 12:56 AM
Subject: Re: [AH] Discrete Synthesizers Question

> To my knowledge, all VCAs are ICs. If anyone is aware of a discrete transistor VCA, please cite a reference - preferably
> with a schematic (I'd really like to see that). Now that I think about it, the early synths must have had discrete transistors
> VCAs, but I'm just not remembering ever seeing one in a schematic.

It's an optional upgrade for the SE Omega series

http://www.studioelectronics.com/products/synths/code/midiminiafy/


On 13 January 2013 18:51, <[hidden email]> wrote:
On Jan 10, 2013, at 21:09, Michael E Caloroso wrote:
I just got an e-mail from a friend who bought a small Technosaurus system. He
tells me, despite the seemingly limited range of modules, the discrete design
really lends itself to an enriching sound ("amazing", by his words). I'm just
wondering if anyone can offer any views on synthesizers made with
discrete components, and what makes them particularly interesting or
pleasing. I heard Technosaurus systems are only available on the used
market now, I've heard of CMS Discrete Synthesizers (but haven't heard
any demos), and am familiar with the upcoming discrete Boomstar synths
from Studio Electronics. Is there anything else available (new or used) that
showcases the appeal of discrete designs specifically, and if so, what
makes them so special, or is it all hype?

Not hype.  Two reasons: progression of active devices, and advancing
circuit design.

Modern ICs are linear devices.  Transistors are not linear.

The difference is distortion introduced by the non-linearity of transistors.

That's a very misleading simplification. ICs are made with transistors inside. The difference is that ICs typically include more transistors than would fit on an affordable PCB, and also that there is usually some sort of crosstalk between the transistors because they're all on the same IC substrate. Another issue for high-powered devices is that ICs cannot generally handle the same level of current (and voltage) as discrete transistors.

Transistors have a linear range, just like tubes. ICs also have many nonlinearities, especially the zero-crossing of the signal, where there is plenty of distortion.



That couples in with advancing circuit design.  VCAs of the vintage
era were NOT high fidelity.  During the 60s and 70s there was no high
fidelity VCA available anywhere.  VCAs were designed using transistors
and their inherent distortion gave them a dirty edgy sound.  The same
was true for active filters, which are a form of VCAs.

If you study the schematics of the big Oberheim synths (OB-X, OB-Xa,
OB-8) as they progressed, you would see a direct correlation between
VCA technology and distortion.  Take the Voyager output before filter
(mixer insert) and route the Voyager audio to the external input of a
vintage Minimoog, and the Voyager has the high end sheen of the
Minimoog that had been missing from the Voyager signal chain.  The
Minimoog has not ONE but TWO dirty-sounding VCAs to mangle the sound.


You are correct here. VCAs are very dirty. They almost always have some amount of DC leakage from the CV to the audio signal. Where typical ICs have some nonlinear distortion, VCAs have a lot more.

To my knowledge, all VCAs are ICs. If anyone is aware of a discrete transistor VCA, please cite a reference - preferably with a schematic (I'd really like to see that). Now that I think about it, the early synths must have had discrete transistors VCAs, but I'm just not remembering ever seeing one in a schematic.

Anyone have a list of discrete synths? There's probably no point listed all the synths based on ICs, since that would include just about every one of them.

Brian Willoughby
Sound Consulting




Reply | Threaded
Open this post in threaded view
|

Re: Discrete Synthesizers Question

K/Modeless Factory
MS-20?
 
Thank you.
Ko/Modeless Factory
 
----- Original Message -----
Sent: Sunday, January 13, 2013 3:01 PM
Subject: Re: [AH] Discrete Synthesizers Question

all early DBX products achieved gain control with potted transistor VCAs..



zzzzz



 
NEW ALLIANCE EAST!!!!

--------------------------------------


New Alliance East - Facebook


X :::: B :::: S





From: Andrew Dean <[hidden email]>
To: [hidden email]
Cc: analogue <[hidden email]>; Future_Sound _Of_Canada <[hidden email]>
Sent: Sunday, January 13, 2013 12:56 AM
Subject: Re: [AH] Discrete Synthesizers Question

> To my knowledge, all VCAs are ICs. If anyone is aware of a discrete transistor VCA, please cite a reference - preferably
> with a schematic (I'd really like to see that). Now that I think about it, the early synths must have had discrete transistors
> VCAs, but I'm just not remembering ever seeing one in a schematic.

It's an optional upgrade for the SE Omega series

http://www.studioelectronics.com/products/synths/code/midiminiafy/


On 13 January 2013 18:51, <[hidden email]> wrote:
On Jan 10, 2013, at 21:09, Michael E Caloroso wrote:
I just got an e-mail from a friend who bought a small Technosaurus system. He
tells me, despite the seemingly limited range of modules, the discrete design
really lends itself to an enriching sound ("amazing", by his words). I'm just
wondering if anyone can offer any views on synthesizers made with
discrete components, and what makes them particularly interesting or
pleasing. I heard Technosaurus systems are only available on the used
market now, I've heard of CMS Discrete Synthesizers (but haven't heard
any demos), and am familiar with the upcoming discrete Boomstar synths
from Studio Electronics. Is there anything else available (new or used) that
showcases the appeal of discrete designs specifically, and if so, what
makes them so special, or is it all hype?

Not hype.  Two reasons: progression of active devices, and advancing
circuit design.

Modern ICs are linear devices.  Transistors are not linear.

The difference is distortion introduced by the non-linearity of transistors.

That's a very misleading simplification. ICs are made with transistors inside. The difference is that ICs typically include more transistors than would fit on an affordable PCB, and also that there is usually some sort of crosstalk between the transistors because they're all on the same IC substrate. Another issue for high-powered devices is that ICs cannot generally handle the same level of current (and voltage) as discrete transistors.

Transistors have a linear range, just like tubes. ICs also have many nonlinearities, especially the zero-crossing of the signal, where there is plenty of distortion.



That couples in with advancing circuit design.  VCAs of the vintage
era were NOT high fidelity.  During the 60s and 70s there was no high
fidelity VCA available anywhere.  VCAs were designed using transistors
and their inherent distortion gave them a dirty edgy sound.  The same
was true for active filters, which are a form of VCAs.

If you study the schematics of the big Oberheim synths (OB-X, OB-Xa,
OB-8) as they progressed, you would see a direct correlation between
VCA technology and distortion.  Take the Voyager output before filter
(mixer insert) and route the Voyager audio to the external input of a
vintage Minimoog, and the Voyager has the high end sheen of the
Minimoog that had been missing from the Voyager signal chain.  The
Minimoog has not ONE but TWO dirty-sounding VCAs to mangle the sound.


You are correct here. VCAs are very dirty. They almost always have some amount of DC leakage from the CV to the audio signal. Where typical ICs have some nonlinear distortion, VCAs have a lot more.

To my knowledge, all VCAs are ICs. If anyone is aware of a discrete transistor VCA, please cite a reference - preferably with a schematic (I'd really like to see that). Now that I think about it, the early synths must have had discrete transistors VCAs, but I'm just not remembering ever seeing one in a schematic.

Anyone have a list of discrete synths? There's probably no point listed all the synths based on ICs, since that would include just about every one of them.

Brian Willoughby
Sound Consulting




Reply | Threaded
Open this post in threaded view
|

RE: Discrete Synthesizers Question

Future_Sound _Of_Canada
In reply to this post by Andrew Dean-2
Brian: Thank you for your informative post.

Regarding VCA's: Although I cannot provide schematics, the CMS 4088 drop-in VCA module for Arp 2600's is specifically described as discrete, and the 9017 VCA for their own Discrete Synthesizers range is presumably discrete because that is the basis of that product range's design philosophy.
 4088 (bottom of the page): http://www.discretesynthesizers.com/dsc/cmssubmods.htm
 9017: http://www.discretesynthesizers.com/dsc/9017.htm

I may be mistaken, but I thought the Roland System 100 was entirely discrete, VCA's and all.

There's a discussion about discrete VCA's here, with references to certain designs: http://www.gearslutz.com/board/geekslutz-forum/121538-discrete-vca.html

Here's a question for the list: are certain components in a synthesizer more likely to benefit from a discrete design than others, and what are the drawbacks of using discrete components in place of IC's for certain components of a synthesizer?

Cheers,

Andrew


Date: Sun, 13 Jan 2013 18:56:04 +1300
Subject: Re: [AH] Discrete Synthesizers Question
From: [hidden email]
To: [hidden email]
CC: [hidden email]; [hidden email]

> To my knowledge, all VCAs are ICs. If anyone is aware of a discrete transistor VCA, please cite a reference - preferably
> with a schematic (I'd really like to see that). Now that I think about it, the early synths must have had discrete transistors
> VCAs, but I'm just not remembering ever seeing one in a schematic.

It's an optional upgrade for the SE Omega series

http://www.studioelectronics.com/products/synths/code/midiminiafy/


On 13 January 2013 18:51, <[hidden email]> wrote:
On Jan 10, 2013, at 21:09, Michael E Caloroso wrote:
I just got an e-mail from a friend who bought a small Technosaurus system. He
tells me, despite the seemingly limited range of modules, the discrete design
really lends itself to an enriching sound ("amazing", by his words). I'm just
wondering if anyone can offer any views on synthesizers made with
discrete components, and what makes them particularly interesting or
pleasing. I heard Technosaurus systems are only available on the used
market now, I've heard of CMS Discrete Synthesizers (but haven't heard
any demos), and am familiar with the upcoming discrete Boomstar synths
from Studio Electronics. Is there anything else available (new or used) that
showcases the appeal of discrete designs specifically, and if so, what
makes them so special, or is it all hype?

Not hype.  Two reasons: progression of active devices, and advancing
circuit design.

Modern ICs are linear devices.  Transistors are not linear.

The difference is distortion introduced by the non-linearity of transistors.

That's a very misleading simplification. ICs are made with transistors inside. The difference is that ICs typically include more transistors than would fit on an affordable PCB, and also that there is usually some sort of crosstalk between the transistors because they're all on the same IC substrate. Another issue for high-powered devices is that ICs cannot generally handle the same level of current (and voltage) as discrete transistors.

Transistors have a linear range, just like tubes. ICs also have many nonlinearities, especially the zero-crossing of the signal, where there is plenty of distortion.



That couples in with advancing circuit design.  VCAs of the vintage
era were NOT high fidelity.  During the 60s and 70s there was no high
fidelity VCA available anywhere.  VCAs were designed using transistors
and their inherent distortion gave them a dirty edgy sound.  The same
was true for active filters, which are a form of VCAs.

If you study the schematics of the big Oberheim synths (OB-X, OB-Xa,
OB-8) as they progressed, you would see a direct correlation between
VCA technology and distortion.  Take the Voyager output before filter
(mixer insert) and route the Voyager audio to the external input of a
vintage Minimoog, and the Voyager has the high end sheen of the
Minimoog that had been missing from the Voyager signal chain.  The
Minimoog has not ONE but TWO dirty-sounding VCAs to mangle the sound.


You are correct here. VCAs are very dirty. They almost always have some amount of DC leakage from the CV to the audio signal. Where typical ICs have some nonlinear distortion, VCAs have a lot more.

To my knowledge, all VCAs are ICs. If anyone is aware of a discrete transistor VCA, please cite a reference - preferably with a schematic (I'd really like to see that). Now that I think about it, the early synths must have had discrete transistors VCAs, but I'm just not remembering ever seeing one in a schematic.

Anyone have a list of discrete synths? There's probably no point listed all the synths based on ICs, since that would include just about every one of them.

Brian Willoughby
Sound Consulting


Reply | Threaded
Open this post in threaded view
|

RE: Discrete Synthesizers Question

Paul Schreiber-3

Well, this debate has to be placed in historical (or hysterical, if on GearSlutz) perspective.

 

1)      In the ‘60s/early ‘70s, everything was discrete because you HAD to.

2)      Early op amps were *specifically designed* for DC performance. So, when early designers tried to use them in audio circuits, they sucked. And then here came the “all ICs suck” and “op amps suck” chorus.

3)      When op amps began not to suck for audio (NE5532, NJR4558 and TL072), many analog designers felt a bit threatened as the ‘secret sauce’ they had been developing for 15 years wasn’t so important.

4)      A lot of arguing about objective versus subjective started, because for a while there wasn’t any audio test equipment good enough to even measure the ICs. Then here came Audio Precision and that just added fuel to the fire.

5)      There are SOME benefits to discrete circuits in SOME functions, because you can really bias the operating points more into Class A versus Class AB (if you don’t know what I mean, Google is your friend). It is not uncommon for discrete line-stages (essentially unity gain or say gains around 20 or less) to have 10ma-30ma bias currents in the transistors where op amps are more like 1-3ma. You can swing more voltage over a larger linear operating point, and this means you can use larger supplies (+-24V is common as is +-36V). This means better SNR and more headroom.

6)      In some cases, you can get better matching parts for a “front end” than what comes ‘stock’ in op amps, although this is becoming less and less of an issue. There are now *specific audio* op amps that suck at DC (like a summing amp for CVs for a VCO design) but trade that off by burning more current, having REALLY BIG input bias currents and offset voltages but “sound really good” and in some cases cost more than a 32-bit DSP that runs at 250MHZ and has 4.5 million transistors. Like this one:

 

http://www.digikey.com/product-detail/en/OPA627AP/OPA627AP-ND/251165

 

Yes, there is a $28ea op amp. And if you Google it, many websites will pop up proclaiming it’s glory (or lack thereof, you pick).

 

7)      Sometimes, it’s just *more fun* to design all discrete (especially with bipolar transistors). SMT transistors are TINY and CHEAP (like $0.015ea) so even if you have something like my old MOTM-1800 Looping EG Frac that had 33 transistors, that’s like 50 cents, so big deal. Sometime, transistors are ALL you need.

8)      But, *just because* a particular circuit is “all discrete” does not mean the designer knows what the hell they are going, picked the right parts, calculated all the bias points correctly, etc. If you A/B an op amp version and a discrete version of the same function and the discrete is ‘better’, that more than likely means that DESIGN is BETTER.

Paul S.

 

Reply | Threaded
Open this post in threaded view
|

Re: Discrete Synthesizers Question

rsdio-2
I just remembered the LED+photoresistor in black shrink-wrap tubing,  
with the photoresistor setting gain, but I always thought of that as  
the poor man's VCA. My introduction was via Craig Anderton's  
"Electronic Projects for Musicians." Plus, those parts always seemed  
to be hard to obtain...

Thanks for the extra details, Paul. I'd guess you're off by a decade  
or two on 1), because SSI, MSI, and LSI were all available by the  
late '60s and op-amp ICs were available by the 60s. Maybe they were  
too expensive, but there's nothing saying that a synth HAD to be  
affordable.

Thanks to waveguide for the 902 VCA test procedure. That circuit  
looks quite like the internal transistor arrangement of the typical  
op amp.

Brian Willoughby
Sound Consulting


On Jan 12, 2013, at 22:54, Paul Schreiber wrote:

> Well, this debate has to be placed in historical (or hysterical, if  
> on GearSlutz) perspective.
>
> 1)      In the ‘60s/early ‘70s, everything was discrete because you  
> HAD to.
> 2)      Early op amps were *specifically designed* for DC  
> performance. So, when early designers tried to use them in audio  
> circuits, they sucked. And then here came the “all ICs suck” and  
> “op amps suck” chorus.
> 3)      When op amps began not to suck for audio (NE5532, NJR4558  
> and TL072), many analog designers felt a bit threatened as the  
> ‘secret sauce’ they had been developing for 15 years wasn’t so  
> important.
> 4)      A lot of arguing about objective versus subjective started,  
> because for a while there wasn’t any audio test equipment good  
> enough to even measure the ICs. Then here came Audio Precision and  
> that just added fuel to the fire.
> 5)      There are SOME benefits to discrete circuits in SOME  
> functions, because you can really bias the operating points more  
> into Class A versus Class AB (if you don’t know what I mean, Google  
> is your friend). It is not uncommon for discrete line-stages  
> (essentially unity gain or say gains around 20 or less) to have  
> 10ma-30ma bias currents in the transistors where op amps are more  
> like 1-3ma. You can swing more voltage over a larger linear  
> operating point, and this means you can use larger supplies (+-24V  
> is common as is +-36V). This means better SNR and more headroom.
> 6)      In some cases, you can get better matching parts for a  
> “front end” than what comes ‘stock’ in op amps, although this is  
> becoming less and less of an issue. There are now *specific audio*  
> op amps that suck at DC (like a summing amp for CVs for a VCO  
> design) but trade that off by burning more current, having REALLY  
> BIG input bias currents and offset voltages but “sound really good”  
> and in some cases cost more than a 32-bit DSP that runs at 250MHZ  
> and has 4.5 million transistors. Like this one:
>
> http://www.digikey.com/product-detail/en/OPA627AP/OPA627AP-ND/251165
>
> Yes, there is a $28ea op amp. And if you Google it, many websites  
> will pop up proclaiming it’s glory (or lack thereof, you pick).
>
> 7)      Sometimes, it’s just *more fun* to design all discrete  
> (especially with bipolar transistors). SMT transistors are TINY and  
> CHEAP (like $0.015ea) so even if you have something like my old  
> MOTM-1800 Looping EG Frac that had 33 transistors, that’s like 50  
> cents, so big deal. Sometime, transistors are ALL you need.
> 8)      But, *just because* a particular circuit is “all discrete”  
> does not mean the designer knows what the hell they are going,  
> picked the right parts, calculated all the bias points correctly,  
> etc. If you A/B an op amp version and a discrete version of the  
> same function and the discrete is ‘better’, that more than likely  
> means that DESIGN is BETTER.
> Paul S.
>
>
Reply | Threaded
Open this post in threaded view
|

Re: Discrete Synthesizers Question

K/Modeless Factory
In reply to this post by Future_Sound _Of_Canada
> Here's a question for the list: are certain components in a synthesizer more likely to benefit from a discrete design than others, and what are the drawbacks of using discrete components in place of IC's for certain components of a synthesizer?
 
You can select and match transistors and other parts as you want to.
As someone described IC is a package of transistors, some good, some not, but you can't arrange it.
It means if you build a discrete synth without selecting/matching good parts
it will be worse than mass-produced synths.
 
By the way, system-100 has 3080 OTA in VCA.
 
Thank you.
Ko/Modeless Factory
http://www.modelessfactory.com
 
 
Sent: Sunday, January 13, 2013 3:21 PM
Subject: RE: [AH] Discrete Synthesizers Question
 
Brian: Thank you for your informative post.
 
Regarding VCA's: Although I cannot provide schematics, the CMS 4088 drop-in VCA module for Arp 2600's is specifically described as discrete, and the 9017 VCA for their own Discrete Synthesizers range is presumably discrete because that is the basis of that product range's design philosophy.
4088 (bottom of the page): http://www.discretesynthesizers.com/dsc/cmssubmods.htm
9017: http://www.discretesynthesizers.com/dsc/9017.htm
 
I may be mistaken, but I thought the Roland System 100 was entirely discrete, VCA's and all.
 
There's a discussion about discrete VCA's here, with references to certain designs: http://www.gearslutz.com/board/geekslutz-forum/121538-discrete-vca.html
 
Here's a question for the list: are certain components in a synthesizer more likely to benefit from a discrete design than others, and what are the drawbacks of using discrete components in place of IC's for certain components of a synthesizer?
 
Cheers,
 
Andrew
 

Date: Sun, 13 Jan 2013 18:56:04 +1300
Subject: Re: [AH] Discrete Synthesizers Question
From: [hidden email]
To: [hidden email]
CC: [hidden email]; [hidden email]

> To my knowledge, all VCAs are ICs. If anyone is aware of a discrete transistor VCA, please cite a reference - preferably
> with a schematic (I'd really like to see that). Now that I think about it, the early synths must have had discrete transistors
> VCAs, but I'm just not remembering ever seeing one in a schematic.

It's an optional upgrade for the SE Omega series

http://www.studioelectronics.com/products/synths/code/midiminiafy/


On 13 January 2013 18:51, <[hidden email]> wrote:
On Jan 10, 2013, at 21:09, Michael E Caloroso wrote:
I just got an e-mail from a friend who bought a small Technosaurus system. He
tells me, despite the seemingly limited range of modules, the discrete design
really lends itself to an enriching sound ("amazing", by his words). I'm just
wondering if anyone can offer any views on synthesizers made with
discrete components, and what makes them particularly interesting or
pleasing. I heard Technosaurus systems are only available on the used
market now, I've heard of CMS Discrete Synthesizers (but haven't heard
any demos), and am familiar with the upcoming discrete Boomstar synths
from Studio Electronics. Is there anything else available (new or used) that
showcases the appeal of discrete designs specifically, and if so, what
makes them so special, or is it all hype?

Not hype.  Two reasons: progression of active devices, and advancing
circuit design.

Modern ICs are linear devices.  Transistors are not linear.

The difference is distortion introduced by the non-linearity of transistors.

That's a very misleading simplification. ICs are made with transistors inside. The difference is that ICs typically include more transistors than would fit on an affordable PCB, and also that there is usually some sort of crosstalk between the transistors because they're all on the same IC substrate. Another issue for high-powered devices is that ICs cannot generally handle the same level of current (and voltage) as discrete transistors.

Transistors have a linear range, just like tubes. ICs also have many nonlinearities, especially the zero-crossing of the signal, where there is plenty of distortion.



That couples in with advancing circuit design.  VCAs of the vintage
era were NOT high fidelity.  During the 60s and 70s there was no high
fidelity VCA available anywhere.  VCAs were designed using transistors
and their inherent distortion gave them a dirty edgy sound.  The same
was true for active filters, which are a form of VCAs.

If you study the schematics of the big Oberheim synths (OB-X, OB-Xa,
OB-8) as they progressed, you would see a direct correlation between
VCA technology and distortion.  Take the Voyager output before filter
(mixer insert) and route the Voyager audio to the external input of a
vintage Minimoog, and the Voyager has the high end sheen of the
Minimoog that had been missing from the Voyager signal chain.  The
Minimoog has not ONE but TWO dirty-sounding VCAs to mangle the sound.


You are correct here. VCAs are very dirty. They almost always have some amount of DC leakage from the CV to the audio signal. Where typical ICs have some nonlinear distortion, VCAs have a lot more.

To my knowledge, all VCAs are ICs. If anyone is aware of a discrete transistor VCA, please cite a reference - preferably with a schematic (I'd really like to see that). Now that I think about it, the early synths must have had discrete transistors VCAs, but I'm just not remembering ever seeing one in a schematic.

Anyone have a list of discrete synths? There's probably no point listed all the synths based on ICs, since that would include just about every one of them.

Brian Willoughby
Sound Consulting