[sdiy] Operating voltages questions about synthesizers

[brianw]

Yes. You will need the data sheets for every component, and you need to be sure you have the full part number off the part itself (e.g. 2N2222 is not the same as 2N2222A). Whichever component has the lowest voltage rating, that will be the limit for the input voltage. Components that are connected after the 6V regulator can be ignored, because their input voltage won't exceed 6V. Roman listed the components that are exposed to unregulated voltage, so you'll need to check the data sheets for all of those.

There's also the concept of engineering overhead. If you have a 6V supply, it's not really a good idea to use capacitors rated for 6V, because there's always a little bit of error in those voltages. Designing for a little extra is common. 5%, 10%, 20% - it depends. So, even if you find that the components exposed to 9V can handle a little extra, you would not necessarily increase the supply above 9V unless you still have some overhead left.

People have mentioned that "sounds better" might mean different things to different people. It's helpful to keep in mind the aspects of the human hearing system, such as the fact that we tend to think something sounds "better" just because it's louder ... even if the quality is identical. So, that extra 3V supply might just be making things sound a little louder, and not actually "better" - there are a lot of variables here.

Brian


On Sep 5, 2022, at 7:07 AM, Michael E Caloroso via Synth-diy <synth-diy at synth-diy.org> wrote:
> Not all discrete transistors will work at higher voltage so you need the datasheet for those transistors for those OEMs.  I found out the semi-hard way when using 2N2222 NPN in a circuit (there's a REASON why the 2N2222A was made available).
> 
> Same with any ICs.
> 
> Electrolytics and tantalums do not like their maximum voltage rating exceeded.
> 
> You really need to analyze the entire circuit AND the active devices used before changing the supply voltage.  Not at all trivial.
> 
> MC
> 
> On Mon, Sep 5, 2022 at 5:13 AM Roman Sowa <modular at go2.pl> wrote:
>> Depends what you call "sounds better".
>> 
>> AFAIK input voltage, 9V in original, and 12V in your case is only used 
>> for speaker amplifier, comparator, and pullup resistors for OTA outputs 
>> in the filter.
>> So the power amp may feel better, able to provide more power at lower 
>> distortion. For comparator it doesn't mean a thig. And for OTAs, well it 
>> changes the voltage of the output pullup resistor higher than OTA's 
>> power suply. That may affect how it works, introducing some nice 
>> distortion, increase levels, or whatever, but I'm only guessing here.
>> 
>> The thing is, most of the circuit is powered from internal 6V regulator 
>> made with TO92 transistor, so if you change input from 9 to 12V, it has 
>> to dissipate twice more heat than before. Probably not much anyway, but 
>> it's easy to check with your finger.
>> 
>> First thing I woudl do is to check current draw, how it changes when 
>> supply rises from 9 to 12. Next is to check how signal changes at OTA 
>> outputs.
>> 
>> Roman
>> 
>> 
>> W dniu 2022-09-05 o 09:33, Logan Mitchell Sr via Synth-diy pisze:
>> > I am finally working on completing modifying my Electro-Harmonix EH 0400 
>> > mini synthesizer that I purchased brand new around 1979/1980.
>> > 
>> > Its original factory power supply was two 9-volt batteries connected in 
>> > parallel with no external power supply adapter jack installed so I 
>> > installed one some years ago to use a 9 volt DC power supply.
>> > 
>> > Last night I connected a 12 volt DC power supply & noticed that the 
>> > synthesizer sounded a little better than when operating from the 9 volt 
>> > battery or from the 9 volt DC power supply.
>> > 
>> > I'm thinking about adding a 7812 or 7815 voltage regulator circuit to 
>> > connect to the power connection of this synthesizer since I have some 18 
>> > volts DC power supplies (wall warts) that I've used on some other 
>> > electronic music devices.
>> > 
>> > My question is this - does an electronic music circuit that works fine 
>> > from a 9 volt DC supply work even better at 12 or 15 volts DC & why is 
>> > that so ?
>> > 
>> > Logan
>> >