[sdiy] 7815 / 7915, "vintage sound", and modern replacements

[crystal]

I did this many years ago. My plan was to make everything able to run 
off solar power without inverters. My memory is a bit hazy, but, i 
completely bypasses most of the power supplies and just fed DC into the 
equipment. I made a central power supply that just had multiple voltage 
output. I used different sized "molex" connectors and put different 
color zip ties and labeled everything clearly. I would not have wanted 
the average user to mess with the system. Admittedly is was a system 
suited to me but not everyone.

Back then i used LM317s with a lot of filtering both in the supply and 
in the equipment. I'd like to know the answer to better, more recent 
regulators.

c

On 7/9/2026 2:15 AM, cheater cheater via Synth-diy wrote:
> (this email seems to have been eaten by gmail... so I have to type it
> all out from memory)
>
>
>
> INTRO / BACKGROUND
>
> Hi all,
>
> I'm looking further into my project to modify rack devices to run on
> DC rather than AC. Looks like most of them use a 7815/7915 combo with
> a full-wave rectifier. Pretty much like the first circuit here:
>
> https://www.eleccircuit.com/power-supply-regulator-15v-15v-1a-by-ic-7815-7915/
>
>
>
> So the idea is to put a 4P2T switch (V, -V, phantom, 0V) or some
> jumpers, right after the rectifier but before the regulators, in order
> to either power the regulators from the internal power supply, or from
> the remote DC supply. I would feed DC in, and let the rack unit do its
> final volt or so regulation itself, to prevent sag and voltage rail
> based crosstalk from other rack devices (10-20 units) that live on the
> same DC distribution bus.
>
> It seems like most of those racks are below the 10W mark, meaning at
> 30V, we're talking about less than 0.5A being delivered by the
> regulators total.
>
>
>
> VOLTAGE REGULATOR QUESTIONS
>
> I've had a couple questions:
>
> 1. What is the best DC voltage to run to the 7815 / 7915 so they
> create the least dissipation, have the best regulation, and produce
> the least noise?
>
> 2. Are there any better modern replacement linear regulators for
> audio? (I'm assuming linear regulators are still what's recommended)
> Something with considerably better noise and regulation performance,
> no more than say $5 a pop, though that's not a fixed price. I'll be
> happy with something that's cents too if that's the go-to part. I
> don't need an exact pin for pin replacement, but being able to use
> something that doesn't require a massive amount of modification to the
> existing circuit would be nice. Although I might just bypass the
> existing internal power supplies completely, and build new ones, so
> feel free to suggest anything. Noise performance and ripple rejection
> are the most important thing here. I'm specifically not looking for
> any sort of "vintage sound".
>
>
> I would appreciate any info on the questions above. Thanks.
>
>
>
> P.S. "VINTAGE" SOUND
>
> I've also noticed something interesting when looking at 7815
> datasheets. Specifically the output impedance, which I found plotted
> in an older datasheet, on page 6 in the top left corner here:
>
> https://www.alldatasheet.com/datasheet-pdf/view/9046/NSC/7815.html
>
> The output impedance goes from 0.008 Ohm at 1 kHz to 0.03-0.04 Ohm at
> 20 kHz, even if bypassed with 1uF tantalum caps as the plot indicates.
>
> It's common to find that older synths sound darker and modern ones
> sound very bright (meaning older synths have lowered high frequency
> reproduction). I wonder if between this nature of the most popular
> linear regulators, and caps that were never good enough to bypass
> those frequencies when they were new (let alone after decades), that
> could explain some of that. Simply power supply sag in the higher
> registers, creating a compounding loss of gain. What do you guys
> think? I assume earlier voltage regulators were even worse than that
> plot.
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