Need advice replacing RC4156 equalizer op amp

bluquartz · 10th June 2011, 12:51 PM

I would like to replace the original 4156 14 PIN quad op amp in a parametric equalizer (SAE 180) and would like to improve the performance, i.e. signal to noise ratio. I was thinking about using an Analog Device OPA470GPZ. It would need to be used at unity gain.

Arty · 10th June 2011, 06:05 PM

should be okay.
i do check the pinout, even when i em 100% sure it is identical but it never hurts

Mooly · 06:25 PM

I'm not sure on the pinouts on this too.

The 4156... if its the one I'm thinking of then it has non standard pinouts and it appeared in the late 1970's. I believe there are some DIL to SMD adapters available to fit 2 dual opamps to make an upgrade for this device.

The OPA470... do you mean a OPA4704 which is a quad device. If so that has the "normal" pinouts of most quads... and I suspect different to the 4156.

Can't just find a data sheet for the 4156.

Edit... can't find it because it is the 4136 I am thinking of.
Replacement for 4136CP

bluquartz · 11th June 2011, 03:00 AM

Quote from the Analog Device OP470 data sheet:
The OP470 conforms to the industry standard 14-lead DIP
pinout. It is pin compatible with the LM148/149, HA4741,
HA5104, and RM4156 quad op amps and can be used to upgrade

systems using these devices.
Also the OP470 conforms to industry standard 14 lead DIP pinout.
I am just a little unsure what affect the different quad op amp will have, i.e. is it a direct swap or do I need to change resistor values to compensate for different gain or characteristics?

Mooly · 11th June 2011, 06:25 AM

I have found the data sheet for the OP470, still can't find one for your original 4156.
I can see its the standard pinout. Now tbh the OP470 looks pretty lousy for audio... its slow with a slew rate of only 2volts/uS. Thats only marginally better than a 741 opamp.

Anyway, having looked at this and seeing that the pin outs are standard I wouldn't hesitate, I would use something like the TL074 quad opamp which is a FET device. The TL074 offers excellent audio performance. The LF347 is similar. Even better something like the OPA4134.

With all these devices no changes are needed to any components in the equaliser however if using something like the OPA4134 then its sensible to check with a scope that the device is stable. For the TLO74/LF347 there should be no such issues.

bluquartz · 11th June 2011, 06:44 AM

Thanks for the tips on audio op amps Mooly. I will check them out.

RJM1 · 08:53 AM

RC4156 data sheet
http://www.meditronik.com.pl/doc/plus/rc4156.pdf

Supply Voltage ±20V

RJM1 · 09:02 AM

The LME49740 would also fit.
http://www.national.com/ds/LM/LME49740.pdf

As long as the supply voltage is ±17V or less.

bluquartz · 12th June 2011, 10:03 AM

Wow, thanks RJM1 for the LME49740 substitute suggestion. I have +/-15 Vdc power supply and the specs are outstanding for audio applications. The data sheet also had a very interesting circuit for a phono stage which I may give a trial as well. I have a few really good opamp chip options. Thanks everyone for your advice!!

10th June 2011, 12:51 PM	#1
bluquartz diyAudio Member Join Date: Jun 2010 Location: Adelaide, South Australia	Need advice replacing RC4156 equalizer op amp I would like to replace the original 4156 14 PIN quad op amp in a parametric equalizer (SAE 180) and would like to improve the performance, i.e. signal to noise ratio. I was thinking about using an Analog Device OPA470GPZ. It would need to be used at unity gain.

10th June 2011, 06:23 PM	#3
Mooly diyAudio Member Join Date: Sep 2007	I'm not sure on the pinouts on this too. The 4156... if its the one I'm thinking of then it has non standard pinouts and it appeared in the late 1970's. I believe there are some DIL to SMD adapters available to fit 2 dual opamps to make an upgrade for this device. The OPA470... do you mean a OPA4704 which is a quad device. If so that has the "normal" pinouts of most quads... and I suspect different to the 4156. Can't just find a data sheet for the 4156. Edit... can't find it because it is the 4136 I am thinking of. Replacement for 4136CP __________________ ------------------------------------------------------- *A simulation free zone.* *Design it, build it, test it.* Last edited by Mooly; 10th June 2011 at 06:25 PM.

11th June 2011, 06:25 AM	#5
Mooly diyAudio Member Join Date: Sep 2007	I have found the data sheet for the OP470, still can't find one for your original 4156. I can see its the standard pinout. Now tbh the OP470 looks pretty lousy for audio... its slow with a slew rate of only 2volts/uS. Thats only marginally better than a 741 opamp. Anyway, having looked at this and seeing that the pin outs are standard I wouldn't hesitate, I would use something like the TL074 quad opamp which is a FET device. The TL074 offers excellent audio performance. The LF347 is similar. Even better something like the OPA4134. With all these devices no changes are needed to any components in the equaliser *however* if using something like the OPA4134 then its sensible to check with a scope that the device is stable. For the TLO74/LF347 there should be no such issues. __________________ ------------------------------------------------------- *A simulation free zone.* *Design it, build it, test it.*

11th June 2011, 06:44 AM	#6
bluquartz diyAudio Member Join Date: Jun 2010 Location: Adelaide, South Australia	Thanks for op amp suggestions. Thanks for the tips on audio op amps Mooly. I will check them out.

11th June 2011, 08:43 AM	#7
RJM1 diyAudio Member Join Date: Jan 2010 Location: Titusville, Fl.	RC4156 data sheet http://www.meditronik.com.pl/doc/plus/rc4156.pdf Supply Voltage ±20V Last edited by RJM1; 11th June 2011 at 08:53 AM.


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10th June 2011, 06:05 PM	#2
Arty diyAudio Member Join Date: Feb 2011	should be okay. i do check the pinout, even when i em 100% sure it is identical but it never hurts

11th June 2011, 03:00 AM	#4
bluquartz diyAudio Member Join Date: Jun 2010 Location: Adelaide, South Australia	Quote from the Analog Device OP470 data sheet: The OP470 conforms to the industry standard 14-lead DIP pinout. It is pin compatible with the LM148/149, HA4741, HA5104, and RM4156 quad op amps and can be used to upgrade systems using these devices. Also the OP470 conforms to industry standard 14 lead DIP pinout. I am just a little unsure what affect the different quad op amp will have, i.e. is it a direct swap or do I need to change resistor values to compensate for different gain or characteristics?

11th June 2011, 08:50 AM	#8
RJM1 diyAudio Member Join Date: Jan 2010 Location: Titusville, Fl.	The LME49740 would also fit. http://www.national.com/ds/LM/LME49740.pdf As long as the supply voltage is ±17V or less. Last edited by RJM1; 11th June 2011 at 09:02 AM.

12th June 2011, 10:03 AM	#9
bluquartz diyAudio Member Join Date: Jun 2010 Location: Adelaide, South Australia	Wow, thanks RJM1 for the LME49740 substitute suggestion. I have +/-15 Vdc power supply and the specs are outstanding for audio applications. The data sheet also had a very interesting circuit for a phono stage which I may give a trial as well. I have a few really good opamp chip options. Thanks everyone for your advice!!

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