LM4562 (dual op-amp) simple preamplifier

[veteran]

This is my LM4562 based preamplifier. Noise free and transparent sound - this is what I can say after first tests. Output offset voltage (even without DC blocking caps) - about 1-3mV. This PCB can be used for every dual op-amp.

I used R3,R9: 2k, R4,R10: 680R.

schematic

[lineup]

.

The circuit looks good and I see no problems.
Not even if somebody would like to use higher gain.
(change R3/R9 to higher value)

Data:
Input impedance: 47 kohm
Output impedance: 47 ohm
HF Noise, high freq filter at input: 1 kohm + 47pF
Voltage gain: x 3.0 ( ~ +10dB )
Power supply: +/- 15V regulated

As you told, veteran,
this circuit would suit most any other audio op-amp.
The chosen input 47kohm is a good value.
And the gain, x3, is also often all we would need in an audio preamp.


One question, because I haven't studied LM4562 closely, yet.
How much Supply Current is drawn by one LM4562 chip (two channels)?


Thanks for sharing your schematic.
lineup
Lineup Audio Lab > for topclass Discrete Operational Amplifiers, Op-Amps

[veteran]

Exactly 10mA (Rl = 300R - 10k, supply = +-15V) for both channels.

[zhopudey]

Hi,

I'm looking for a simple design for the LM4562. Can you describe how this design sounds?

[veteran]

Neutral, with lots of air. You can also bias this op-amp to work in a ~class A - this will give you a little bit wormer sound.

I have to say that my signal path is a typical DC in this application - without capacitors and there is only minimal offset.

[tino96]

good work,
You have the PCB layout to share?
many tnx in advance

[theAnonymous1]

Can someone explain the purpose of C6 and C7?

Just a noob trying to learn.

[Tolu]

Originally posted by veteran
Neutral, with lots of air. You can also bias this op-amp to work in a ~class A - this will give you a little bit wormer sound.

I have to say that my signal path is a typical DC in this application - without capacitors and there is only minimal offset.

do you have a circuit for bias in class A? Which values do you recommend?

[veteran]

Originally posted by tino96
good work,
You have the PCB layout to share?
many tnx in advance

Why not I'm working on another version of this board so here you are:

Schematic:
http://unisonus.com/pdf/DIY/LM4562_schematic.pdf

PCB top layer (description):
http://unisonus.com/pdf/DIY/LM4562_PCB_top.pdf

PCB bottom layer (tracks):
http://unisonus.com/pdf/DIY/LM4562_PCB_bottom.pdf

[ashok]

Are you using a buffer with unity gain in the second implementation for any special reason ?

Do you expect any difference in sound ?

Veteran :

You can also bias this op-amp to work in a ~class A - this will give you a little bit wormer sound.

Warmer sound generally means added even order harmonics.
So does class A bias increase the distortion figures here ?

Cheers.