[sdiy] Operating voltages questions about synthesizers

[Logan Mitchell Sr]

Thanks Roman & Michael.

Logan

________________________________
From: Michael E Caloroso <mec.forumreader at gmail.com>
Sent: Monday, September 5, 2022 10:07
To: Roman Sowa <modular at go2.pl>
Cc: prowlerraven32 at hotmail.com <prowlerraven32 at hotmail.com>; Synth-diy at synth-diy.org <synth-diy at synth-diy.org>
Subject: Re: [sdiy] Operating voltages questions about synthesizers

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<mailto: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
>
>
>
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