Which OPAMP

I'd use an OP275 instead of a NE5532, it's better sounding (sweeter) and has no dc offset to contend with 1to5mv, so can be direct coupled, unlike the NE5532 which i've seen sometimes at 400mv, and the OP275 can be cheaper, sometimes.
Or if you want what I consider to be the ants pants the AD825 but it's single and smd you have to get a dual Browndog adatper board and put 2 on it if you want 8 pin dil normal size, and they are tripple the price, but very very good, and still virtualy zero dc offset.

Cheers George
 

djk

R.I.P
2001-02-04 4:23 am
USA
"The maximum input differential voltage that can be applied to the OP275 is determined by a pair of internal Zener diodes connected across its inputs. They limit the maximum differential input voltage to ±7.5 V. This is to prevent emitter-base junction breakdown from occurring in the input stage of the OP275 when very large differential voltages are applied. However, to preserve the OP275’s low input noise voltage,"
 

djk

R.I.P
2001-02-04 4:23 am
USA
"Read, It has Jfet's as it's input."

"BTW the max input v on the OP275 is +- 22v "

My quote was a cut-and-paste from the 12 page pdf on the AD275.

The input bias spec screams 'BJT', and the Spice model shows a BJT diff pair.

Try all of them (OPA2134/2604, OP275, AD823/dual 825) in the P88 and see what you like.

The dual AD825 /adaptor modules sell for about $20 each, the AD823 will go for about $5 in one lot quantity. Keep in mind that a stereo three-way P09 crossover and P88 preamp will require over $200 worth of AD825 modules.

I would build up the preamp first and try one AD825 module out vs the others, and see what you like before dropping the hammer on the whole project. The AD825 module is a bit tougher for bypass requirements too.
 
Mike (kestrel200) if you want to go the best the AD825 can be got here for $22, a duals already on Browndog boards, if your doing the ESP P88 you need 2 of these for stereo, grand total $44.

http://www.soundodyssey.com/AudioParts/AD825.html

In the bottom photo next to the price, there is one ad825 on top and one underneath, this is the setup i favour.

If you want to do the ESP P09 stereo, you will need 5 of them at $110.

Also read the absolute max input ratings yourself on the OP275 running at +22v -22v rails, page3 of the Annalog Devices pdf spec sheet.

Cheers George
 

djk

R.I.P
2001-02-04 4:23 am
USA
Page 2 of the data sheet clearly states:

"Input Voltage Range (Vcm) ±10.5V"

and on page 3:

"Differential Input Voltage ±7.5V"

page 8 is where

"The maximum input differential voltage that can be applied to the OP275 is determined by a pair of internal Zener diodes connected across its inputs. They limit the maximum differential input voltage to ±7.5 V. This is to prevent emitter-base junction breakdown from occurring in the input stage of the OP275 when very large differential voltages are applied. However, to preserve the OP275’s low input noise voltage,"

came from. Voltages above this will cause current to flow in the protection diodes, this current must be limited by external circuit design to 8mA or destruction of the device will occur.

I will add:

When using this opamp in a current-to-voltage circuit (DAC or any inverting summing circuits, ie: a mixer) it's a good idea to add a Schottky diode between ground and the negative supply. This goes for opamps like the NE5532 as well.

The NE5532 gets a bad rap from improper use in said circuits. The input pair is permanently degraded in terms of noise performance without adequate design oversight.