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rıdvan

Well-known member
Joined
Jan 1, 2013
Messages
50
Hi,

I'm really inexperienced! I have an mic preamp with 3 band eq.And there is an TL072.But i want to improve this preamp.It has really simple design.

So, can i use any discrete opamp in this? I want to remove TL072 and add any other good opamp.Something like 990,2520 etc.. Is this possible?

Please help me about it.

Thanks!
 
It depends whereabouts in the circuit that the TL072 is that determines if there will be any real improvement by replacing it. Can you post a schematic??

Cheers

Ian
 
Note that the 2520/990 opamp is a different footprint and is much larger in size. Also, the tl072 is a DUAL opamp, where the 2520/990 is a single opamp.
 
ruffrecords said:
It depends whereabouts in the circuit that the TL072 is that determines if there will be any real improvement by replacing it. Can you post a schematic??

I have no schematic  :-\ Just i have hardware.

gemini86 said:
Note that the 2520/990 opamp is a different footprint and is much larger in size. Also, the tl072 is a DUAL opamp, where the 2520/990 is a single opamp.

Is there any way fit 2520/990 to TL072? Or is this question idiotic?

 
If you google search it first , you'll likely find more grps & forums where someone has asked or tried
[ to make an adaptor perhaps ] besides size and configuration if you think you're preamp is that average
it may be time to build a new preamp !  I believe the answer is Not practical to adapt two 2520 types into
one tlo72 type
 
rıdvan said:
ruffrecords said:
It depends whereabouts in the circuit that the TL072 is that determines if there will be any real improvement by replacing it. Can you post a schematic??

I have no schematic  :-\ Just i have hardware.

If you don't have the schematic can you post a picture of the PCB?


gemini86 said:
Note that the 2520/990 opamp is a different footprint and is much larger in size. Also, the tl072 is a DUAL opamp, where the 2520/990 is a single opamp.

Is there any way fit 2520/990 to TL072? Or is this question idiotic?

Short answer is no.

I am anticipating that TL072s are also on the EQ in which case it is highly likely that you will have oscillation problem. Changing opamps in EQs will require a bit more attention than the mic-pre stage.
 
Abechap's discrete DIP8 opamp would get you in the ball park with a 2520 style Opamp in a dip-8 package... but you still have the issue of dual vs. monolithic.
 
Most microphone preamps use a couple of transistors in front of the OpAmp.
In this case, the transistors determine the signal to noise ratio.
The OpAmp used is then not very critical and does not contribute much to the quality or "sound"

I can't imagine that the input is only constructed around a TL072. (Or it must be a very bad design...)
 
Travis1000 said:
Abechap's discrete DIP8 opamp would get you in the ball park with a 2520 style Opamp in a dip-8 package... but you still have the issue of dual vs. monolithic.

Do you mean it?  http://www.groupdiy.com/index.php?topic=44169.0

pucho812 said:
You could try texas instruments OP2134. They will drop right in. Scope for any oscillations and  give a listen. 

There is no in my country. :-\

So i think i can't change  TL072.Ok..I want to improve sound but how?


 
A TLE2072 will drop right in. I wouldn't necessarily recommend trying to replace the chip that's in there with 2 discrete opamps. Probably would be a pretty involved job with minimal sonic changes. If i were you looking for a better sound out of the pre amp i would DIY a new one.
 
rıdvan said:
http://www.ebay.com/itm/Dual-channels-Audio-Discrete-HDAM-Discrete-Opamp-Module-/280670457694

Is there any circuit something like this? I think i can use something like this.Right?
Maybe, maybe not. (probably not).
The DOA data given from your linked page says nearly nothing about this devices parameters and performance (a LM741 might do better) and I'd not trust a claim for a 'Direct Replacement for the following Opamps' listing IE a JRC5534. Coming with outer dimension H 40mm, you'd need a >1HE case as well to make it fit.
just my 2ct
 
Replacing the op amp in the middle of a mic preamp is not the same as using a different vegetable in a stew recipe.

As an old school circuit designer, I would sure love for you to dissect how the particular circuit works, to understand why the TL072 was used by the original designer in the first place, then make an intelligent decision about how to improve it.

Yes, you should be able to get it to work with a DOA, whether it is worth the trouble, depends on why you are drawn to those older DOAs. If your real intention is to improve the circuit performance, a more logical path is to use a modern bifet op amp that could probably drop in the same socket. I would only expect marginal improvement if at all. Noise floor and some basic performance characteristics will be dominated by the circuitry around the op amp. 

JR
 
As an old school circuit designer, I would sure love for you to dissect how the particular circuit works, to understand why the TL072 was used by the original designer in the first place, then make an intelligent decision about how to improve it.

Yes,you are right! First i have to understand that why TL072.

So,i decided to build 2 Channel preamp without any modifications.Thanks for all answers.

Now i need help about power supply. I need two phantom power and two +/- 15V. So,dual power supply.

For now it's working with this circuit but without phantom power. 
p43-fig1.gif


And i have transformer.It has four AC outs. 8V,12V,12V and 24V.Can i feed preamp with this trafo?


 
This will work as long as the current consumption is low, and the current for the positive side is more or less the same as the current for the negative side. There is no compensation for current differences, so if the positive current is higher than the negative current, you will get an unbalance, resulting in for example +10 V and - 20 V, instead of +15 and - 15 V.
I would suggest that you build a simple regulated power supply, based on the 7815/7915 regulators.
Circuit diagrams are easy to find on the Internet.
 
I would select the voltage of the zeners D1-D4 much lower. A reverse voltage of 6 volts or more could destroy a base-emitter junction.
I would go for 4.7 or 5.6 V. (A microphone doesn't produce 'volts' anyway.)
 
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