Opamp replacements for Yamaha MLA7?

[dickiefunk]

Hi,

I've just been given 4 Yamaha MLA7's!!

I notice that they use through the hole soldering so I thinking of upgrading the OpAmps in it.

Has anyone done this with one of these?

I have a schemo if it's any help.

Thanks

[dementedchord]

have you popped them open yet??? wonder what they used in there... post the schemo and a list of parts if you can that'll give us some idea what might help....

[dickiefunk]

Originally Posted by dementedchord

have you popped them open yet??? wonder what they used in there... post the schemo and a list of parts if you can that'll give us some idea what might help....

Thanks for the reply, here's the schemo!

It lists the original opamps in it.

[Minion]

Though the schematic is hard to read it look like the preamp uses a NJM4556 (same as the JRC4556) which is a jelly bean BJT dual opamp which is a quite old model but still used in a lot of consumer products, probably because they are extremely cheap...

There are a number of Opamps which would be a better choice that should be drop in replacements....

Like the LM4562 - a very low noise ,high performance ,audo grade ,dual opamp....

OPA2132/2134 -a very good dual fet input opamp....

OPA2604- a good Dual opamp , used in many higher end Mic preamps....


Cheers

[dickiefunk]

Originally Posted by Minion

Though the schematic is hard to read it look like the preamp uses a NJM4556 (same as the JRC4556) which is a jelly bean BJT dual opamp which is a quite old model but still used in a lot of consumer products, probably because they are extremely cheap...

There are a number of Opamps which would be a better choice that should be drop in replacements....

Like the LM4562 - a very low noise ,high performance ,audo grade ,dual opamp....

OPA2132/2134 -a very good dual fet input opamp....

OPA2604- a good Dual opamp , used in many higher end Mic preamps....


Cheers

Hi,

Thanks for the reply! Which is the best Opamp out of the ones you mentioned?

I'm also considering the THAT 1510 / 1512. How would this fare as an alternative?

[Minion]

Sonicly the best sounding one is probably the LM4562 ,I use a pair in a Headphone amp I built and it sounds great...

When useing the LM4562 you might have to put a couple of 0.1uf caps from each supply pin to ground because these chips can be a bit tempermental...
The OPA2134 is very stable and sounds good and would also be a good replacement...

The THAT 1510 & 1512 would "NOT" be suitable because they aren"t opamps they are Instrumentation amplifiers (they are usually built with 3 or more opamps in a differential configuration on the same chip) and are used differently than a regular opamp ,Pluss they have different pin outs....
They are great if you want to build your own Mic preamp from scratch because allmost everything is allready on the chip so you can build a very high quality mic pre with very few parts...



Cheers

[dementedchord]

Originally Posted by dickiefunk

Hi,

Thanks for the reply! Which is the best Opamp out of the ones you mentioned?

I'm also considering the THAT 1510 / 1512. How would this fare as an alternative?

the that's will work fine... the point is that the 4556's are pretty much generic types and all of the manufacturers have improved models... go to any of the manuf sites and data sheets for their chips should be easy to find... since the use here is pretty general too almost anything can be used... try burr-brown/national/linear technology...

[dickiefunk]

Thanks for the replies again! I won't be able to replace 0.1uf caps at this stage so the OPA 2134 looks like it might be a good option.

[dickiefunk]

I've also had the LM6172 recommended but am unsure if this would be a simple swap? I would like to avoid having to do any other work apart from the opamp swap right now.
Would the LM6172 and LM4562 require me swapping some caps?

[Minion]

With Fast opamps (Ones with a High slew rate) they are somewhat more tempermental than slower ones ,especially Bipolar opamps, they like some local decoupleing to retain PSSR....

It also depends on the board layout, if the board is properly layed out there might not be any need for extra capacitance, Pluss the board might allready have some caps close to the IC Power pins.....

I would suggest that you get some IC Sockets so you can swap in a few different types of opamps ,Maybe have a couple channels with different opamps for some variety.....

Also if these Boards are somewhat old (over 10 years) then the opamps might not be the weakest link, You might gain more of a Increase in sound quality by upgradeing some of the Passive components like the Electrolytic caps ,and swap out any ceramics for Poly or silver mica ,maybe swap out any 5% carbon resistors for 1% metal film....You could even mod the board so you have a ballanced output.....


Cheers