[Sir Nobax]

I am still figuring out how I will build my first CMoy, and as I dont know if the 20-40mA current will be enough to please my Aurvana's. (42 Ohm, sensitivity of 115dB / mW)

Should i create the virtual ground by a TLE2426 or should i use the usual 4.7KΩ Resistors?

And I am curious if using Paper 0.47µF cap's will be noticable over Polyester 0.47µF cap's.

(CMoy will be powered from a single 9V battery or 4 AA NiMh's)

 

[Joshatdot]

TLE or resistors, depends on what opamp you are using. A TLE would be more stable, but you are also only using one 9v batt. Four AA NiMh's would not supply enuff power for the opamp, 4.8v / 2 = +2.4v & -2.4

 

[balou]

Joshatdot, why should it be opamp depending? Instantaneous current spikes should be handled by the opamps, and I don't think that there are any dual opamps you'd normally use in a cmoy which have a higher quiescent current than 20mA

 

[jcx]

easy calc

2 channels, 1.4x pk-to-rms factor gives ~ 10 mArms/side from TLE2426's ~ 30 mA current breakaway on the data sheet

(10mA)^2 * 42 Ohm = 4.2 mW

10 * log10(4.2) = 6.2 dB re 1 mW

115 + 6.2 = 121 dB spl from your cans before the active ground begins to add distortion from current limiting

I don't like the TLE2426 because this ground current limit math is way wrong for most common cans but you're fine with these sensitive iem

4 cell operation is also practical with these sensitive iem, you can then just use the battery string midpoint as gnd

Op amp selection does become limited, AD823 would be one option available in DIP package and able to run at the low V

 

[Sir Nobax]

Ahh, thank you for the calculation JCX, i'm pretty glad that it will work, TLE's makes the CMoy even easier to create!

However are there any other decent low-voltage Op-amp's other then the AD823, which will work on a TLE2426 powered CMoy?

The AD823's arent stocked at the shop where I will buy all my components, and paying 25 Euro's for the shipping of a single AD823 is a bit too much.

[edit] Will the 8-pin TLE make a lot of difference compared to the casual 3-pin (without the Noise reduction) ?

 

[balou]

The AD8066 works also with low voltages. It is only spec'd down to 5v, but I once used it down to 2.6v, when I started noticing that the noise floor got higher. Oh, and this was with a 7.2v rechargeable...

Xin/Fixup also has found some decent low voltage opamps. Look here or at headwize or at his site for more information