Looking for Opamp numbers...

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Maybe you can mention the resources you have already consulted and the searches you have already tried? To prevent duplicate and wasted effort from helpful diyAudio responders?

Hello Mark

Yes I went on NJM and tried for to find an Opamp that is the single equivalent of these two dual Opamps...spent some time on this.
Also I forgot to say I made research in this forum.
So I guess you don't have time to waste on a "lazy" guy like me and you seem to speak for other members at the same time.
But I find the time to answer your question to justify myself.
Another thing I have to conclude is that you don't have the answer for a relatively simple question for a competent person, which I am not.
I don't want to say you're not competent but I always wonder what someone think by replying a message like you do.
Thanks anyway.

Luke
 
Last edited:
Member
Joined 2011
Paid Member
I used a resource called "Linear Technology Product Selection Guide" to find out that
  • LT1128 appears to be a single opamp substitution for the NJM4580
  • LT1028 appears to be a single opamp substitution for the NJM2114

This was not one of the resources you mentioned when you talked about the data you studied and the cross-references you checked.
 
Try NJM5534D. It a through hole, single op-amp. Are you building new or modifying?


Hello Mike

Thanks for replying.
I'm actually thinking of modifying a design of mine, an electronic crossover using GIC all-around, LPF,HPF,BPEQ,APF2 and all shelving types.
The buffers used for these are OPA604 and LME49710.
The reason why i'd like to make tests with single equivalent of these two Opamps.
NJM5534...Gain 3 or higher... A thing I forgot to mention....all these buffers are user as non-inverting mode at unity-gain.

Luke

PS. I prefer an more equivalent sounding one than technically equivalent.
 
Last edited:
I used a resource called "Linear Technology Product Selection Guide" to find out that
  • LT1128 appears to be a single opamp substitution for the NJM4580
  • LT1028 appears to be a single opamp substitution for the NJM2114


I am sorry to say this, but LT1028 is far from a single opamp substitution for NJM2114. LT1028 is rated 0.85 nv/sqrt(HZ)@1k whereas the NJM2114 is 3.3 nv/sqrt(HZ)@1k. The later is almost 4 times noisier!
 
Hello

A thing I forgot to mention....all these buffers are to be used in non-inverting mode and unity-gain.
LT1028 is ultra-low noise and not stable in unity gain non-inverted..bad choice.
Good for Mic or RIAA preamp, advantahe of ULN is useless for gain+1 at line level.

Luke
 
Last edited:
Given that these NJR chips are so cheap, one could take one of the dual opamps that you're asking about and disable one side so that it could be ignored, resulting in a "single" opamp.

I'm not sure what the best way to do this is, but one approach could be to connect the unused channel's inputs to either V- or V+ to disable the input stage. This might work well, but it might annoy the disabled channel, operating it out of its linear region, which may or may not do good things.

Another possibility is to connect the unused channel's output to its inverting input and then ground the non inverting input. In this way, the unused channel will idle in its linear region, but with no variations that could disturb the 'desired' channel. This seems to be the safest approach, since the entire chip will be operating in the way that it was designed for, but the unused channel will not be able to affect the other channel.

IMHO, this is the most simple way to solve your problem. While there are 'equivalent' amplifiers, they're obviously different circuits. If you want to make an NJM2114 dual into a single, why not just "handcuff" one channel and use the other channel as you like? It'll now be a single channel NJM2114… by definition.
 
^^^^^^^ Basic idea is perfect, but way to disable an Op Amp is to short OUT to -IN and connect +IN to some bias point (not +Vcc or -Vcc which are too extreme) , usually same as what's used for the active half.

That said, all we can answer with any precision is "technically equivalent one" ; because "same sounding one" is a subjective asessment where no two people agree.
 
Member
Joined 2011
Paid Member
If you want to make an NJM2114 dual into a single, why not just "handcuff" one channel and use the other channel as you like? It'll now be a single channel NJM2114… by definition.
One possible implementation is to solder an SMD dual opamp chip onto an adapter PCB like the one shown below. On this board you disconnect one opamp in your preferred manner, AND you perform the required pin scrambling that gives you the standard single-opamp-pinout. (For example, Vsupply+ moves from pin8 to pin7)

But I suspect this may not be enough. I suspect that the Original Poster may want a single opamp because singles have offset-adjust pins and/or external frequency compensation pins.

edit: BTW my preferred way to render the 2nd opamp harmless, is to connect it as a unity gain follower driven by the first opamp's output. The 2nd opamp presents negligible load to the 1st, and the number of required PCB traces is only two.

_
 

Attachments

  • adapter_concept.png
    adapter_concept.png
    118.7 KB · Views: 69
Last edited:
Given that these NJR chips are so cheap, one could take one of the dual opamps that you're asking about and disable one side so that it could be ignored, resulting in a "single" opamp.

I'm not sure what the best way to do this is, but one approach could be to connect the unused channel's inputs to either V- or V+ to disable the input stage. This might work well, but it might annoy the disabled channel, operating it out of its linear region, which may or may not do good things.

Another possibility is to connect the unused channel's output to its inverting input and then ground the non inverting input. In this way, the unused channel will idle in its linear region, but with no variations that could disturb the 'desired' channel. This seems to be the safest approach, since the entire chip will be operating in the way that it was designed for, but the unused channel will not be able to affect the other channel.

IMHO, this is the most simple way to solve your problem. While there are 'equivalent' amplifiers, they're obviously different circuits. If you want to make an NJM2114 dual into a single, why not just "handcuff" one channel and use the other channel as you like? It'll now be a single channel NJM2114… by definition.

Hello Monte

You did not read the first posts(s) I've written..
Needed to replace for experiments OPA604 or LME49710 in actual sockets of actual circuits.
Note that the actual sockets are configured for single opamps.
I guess...unfortunately...that this discussion is going anywhere.
Anywhere but the main question...a single equivalent (and equivalent sounding...) of duals 4580 or 2114.
Thanks...
Luke
 
Last edited:
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.