[GlorytheWiz825]

Hi guys,

What is the advantage of having the CMOY powered by two 9V battery in series (18V total) versus a single 9V battery? The only advantage I can think of is having power in the unit for a longer period of time. Are there any other differences?

 

[ruZZ.il]

yes, the op-amp is likely to function much better with much more head-room to begin with... you could also avoid the virtual ground circuitry but then the batteries may drain at different rates. I'd stick with a good rail splitter, but the extra voltage def. improves the op-amps functionality.. its also likely to last more than 2x the battery life of 1 battery, cause you'll stay above the minimal functional voltage for longer.

 

[vixr]

Tangent said THIS about it...

 

[balou]

Quote:

The only advantage I can think of is having power in the unit for a longer period of time.

The opamp will actually draw more power with more voltage. Yes, you don't reach the minimum working voltage of the opamp as fast as with just one 9v, but I don't think that's the reason why anybody uses two batteries.

As stated on tangents site, one reason is listening volume. 9v might not be enough for high impedance headphones. Another point which isn't stated on Tangents site is that some opamps won't even work with a single 9v battery. For example the OPA2107 - this chip is distorting like mad (I mean really distorting, obvious after 1sec of listening, not audiophile-just-a-bit distorting

) with a fresh 9v battery.
One thing to also consider is that some opamps have a voltage drop of several voltage - meaning the maximum output voltage is a lot lower than the supply voltage

 

[Arjisme]

Besides vixr's link, see also this at Tangent's site, which discusses 2 batteries as it relates to a CMoy. Be sure to read the section, Ways To Fix the Problem.

 

[GlorytheWiz825]

Thank you so much guys.