Power Supply Voltage Out Mod - going from +-15V to +-18V

[Nen'O]

By the looks of the PW8 is an SMPS with linear regulators after , its probably very carefully designed to be noise free , your standard off the shelf switcher will have hundreds of mV of noise .

If you are looking at power supply from photo I posted earlier it's A&H stock SMPS I took out from Zed R16?
PW8 weighs over 10kg...it would be heaviest SMPS I've ever seen

 

[ccaudle]

If you are looking at power supply from photo I posted earlier it's A&H stock SMPS I took out from Zed R16?
PW8 weighs over 10kg...it would be heaviest SMPS I've ever seen

This appears to be the PW8, bigger than some power amps I have used.

Yamaha PW8

 

[radardoug]

Hey Khron,
Glad to see you here. Learned a lot from reading your blog.
Is your GTR amp coming out anytime soon?

Messing with circuits inside ADC is definitely no,no for me.
Good news is that this board has been very well calibrated, the analogue circuit will clip much sooner before ADC get overloaded.
Stock specs are actually not that bad at all... considering that A&H doesn't boost numbers for marketing purpose like some do...

Headroom

Analogue Headroom from nominal (0Vu) 21dB
Digital converter headroom from nominal analogue (0Vu) 16dB

Digital Performance

Analogue to Digital conversion 24bit 114dB dynamic range (A wtd)
Digital to Analogue conversion 24bit 118dB dynamic range (A wtd)

So your converters already have less input headroom than your mixer provides, so why are you doing the mod at all?
Desk output 21 dB, converter input 16 dB. From your description, but your figures look odd to me.

 

[Matt Syson]

There are a mixture of answers among the posts here . Many designs aimed at 'specmanship' so being able to boast an extra db of something claimed to be 'better' than other manufacturers whether true or not. With many A/D convertors only handling +20 or 21 dBu at their inputs before 'clipping' practically all audio gear can manage that with 15 Volt supplies. The usual design brief for audio mixers was 24dB headroom above 'line up' which was usually odBu in the UK (- 4 VU). Neve and Audix used 24 Volts supply so some of their gear could be used on a pair of 12 Volt vehicle batteries for 'portable use' To achieve +24dBu headroom input to output they used transformers with a 6dB step up ratio (or the single end class 'A' of the Neve design). Of course recording to tape where the tape itself presents a softer (and lower) limit was a factor.
Soundcraft and many other manufacturers used 17 Volts as a pragmatic compromise as the chips used (TL07X and 553X were 18 Volt rated) were suitable for long term use at this. Chip manufacturers quote their design specs as 15 Volts (bipolar) and then the 'maximum' ratings beyond which failures would increase. 5532 chips can run at 24 volt (bipolar so 48!) as I discovered in a mixer feeding live radio broadcasts for over a year can attest. Not recommended however! Of course the working temperature will be a big factor not just the supply voltage so chips in a 'cool' environment can survive longer than those crammed into a tiny space with no cooling.

 

[Nen'O]

So your converters already have less input headroom than your mixer provides, so why are you doing the mod at all?
Desk output 21 dB, converter input 16 dB. From your description, but your figures look odd to me.

Overall I don't have complains about performance of ZED R16 as it is, my studio is based around this mixer for over 10 years. Sound and workflow are top class. As i said mods I'm doing are more about exploring and learning about el. circuits and maybe improve things a bit.
Anyways, im recording mix bus with external Mytek converter and that thing has loads of headroom.
At the end it's all about gain staging.

Here are the words form designer himself.

It's true the signals are slightly hotter to & from the ADCs & DACs. I chose a slightly reduced headroom value for the digital interface mainly because nominal level 0dBu, which is say 21dB down from the analogue maximum level - or -21dBFS if matched in the digital domain seemed too low when recording to a DAW. The nominal level returning from the DAW is also matched to this and that's why it may appear quite a hot signal. Naturally you can tweak this at both ends if needs be, either with slightly less pre-amp gain or DAW output trim and the result is better signal to noise performance. Ultimately it's set to where I thought worked best, but it could be modified if you wanted to bring the digital nominal level down a bit.

Although headroom is stated as +21dB above nominal, the channel pan control and fader will have an effect on the headroom figure of the combined mix, effectively acting as trims. For example, a 0dBu signal pre-fade on a channel will be attenuated by 3dB when routed to the L&R buses with Pan in the centre, so the 21dB figure can be viewed as worst case if the pan controls are fully left (or right) and the fader is at unity. Obviously for lots of correlated, in phase signals you'd trim the faders down a tad, which goes for any multi-input device, in which case you would be setting the mix headroom to a higher figure manually depending on the nature of your mix.

HERE ARE ALL FIGURES

 

[abbey road d enfer]

Here are the words form designer himself.

It's true the signals are slightly hotter to & from the ADCs & DACs. I chose a slightly reduced headroom value for the digital interface mainly because nominal level 0dBu, which is say 21dB down from the analogue maximum level - or -21dBFS if matched in the digital domain seemed too low when recording to a DAW. The nominal level returning from the DAW is also matched to this and that's why it may appear quite a hot signal.

So, apparently the designer knows what he's talking about, but is not able to express it in a meanful way...