LM4562 (dual op-amp) simple preamplifier

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veteran

veteran

Member
Joined 2004
unisonus.com
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

An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.
 
lineup

lineup

Member
Joined 2005
veteran pre amplifier circuit for op-amps

.

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
 
Tolu

Tolu

Member
Joined 2007
veteran said:
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.
Click to expand...


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

ashok

Member
Joined 2002
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.
Click to expand...

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

Cheers.
 
veteran

veteran

Member
Joined 2004
unisonus.com
Tolu said:
Hi Veteran

where are your price and order informations on your site?

Tolu
Click to expand...

There is no pricelist on my site because only few boards for my project are available - I always order about 20-30.


wim said:
Nice design Veteran. What's the price a board?

Do i understand that it will work with a OPA2134 too?
What VA (W) toroid do you recomment?
Click to expand...

Thank you Wim. It will word with every pinout compatible op-amp (two of them inside like OPA2134, OPA2640, ...). Price for one - about 5$. I have to check if I still have them.
 
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