Neotek Elite EQ, Room for improvements?

Hi guys,
I recently bought a late eighties Neotek Elite console. I got a nice deal on it and so far I'm really enjoying it!
The EQ is actually quite good. I like it up to about 4-5k, ish, but above that it has a tendency to sound a bit harsh. I love the sound of my Sontec clones but the Neotek is pretty much the opposite.
I'm not looking to do a total rebuild but any input on mods, large or small, is very appreciated.

I have been thinking about replacing the TL074 for the high and high mid band to something more "sexy" that might do something, and also maybe try to replace the capacitors for styrflex. What do you think?

Sounds like a good plan. You may want to try mica or FKP (foil/foil polopropylen) caps as filter caps as well. Use whatever your ears like better. I´ve used OPA2132/4 or in very similar circuits with good results. In your case you´d need OPA4134 on adaptors since those chips are SMD only, unfortunately. Make sure that you add 0,1uF ceramic caps from B+ and B- pins of the new chips to ground. These are important to avoid oscillation.

Thanks for your advise Jens! And also thanks for contributing to the Harrison Ford filters, I have made a small PCB prototype without the balancing ICs for my Neotek. Not sure it will work out cos of panel space but I'll see what i can do.


Alright I'll try those caps and see if i can find an easy upgradeable IC for  the TL074. I know that Texas instruments makes a "HIFI" version of the TLX series that is a common replacement on the Neoteks as they are prone to occilate with modern OPs. And ill se if i can find an OPA4134 and adapters to.
Thanks!

jensenmann said:

Sounds like a good plan. You may want to try mica or FKP (foil/foil polopropylen) caps as filter caps as well. Use whatever your ears like better. I´ve used OPA2132/4 or in very similar circuits with good results. In your case you´d need OPA4134 on adaptors since those chips are SMD only, unfortunately. Make sure that you add 0,1uF ceramic caps from B+ and B- pins of the new chips to ground. These are important to avoid oscillation.

Click to expand...

The Texas Istruments TL074 upgrade is called TLE2074

jensenmann said:

Sounds like a good plan. You may want to try mica or FKP (foil/foil polopropylen) caps as filter caps as well. Use whatever your ears like better. I´ve used OPA2132/4 or in very similar circuits with good results. In your case you´d need OPA4134 on adaptors since those chips are SMD only, unfortunately. Make sure that you add 0,1uF ceramic caps from B+ and B- pins of the new chips to ground. These are important to avoid oscillation.

Click to expand...

That´s another good chip for that purpose. They have lower power consumption than TL07Xs which occasionally is very handy. I´ve used them in circuits when the increased current draw of OPAx134s is a no-go.

Ok then! Thanks again!

jensenmann said:

That´s another good chip for that purpose. They have lower power consumption than TL07Xs which occasionally is very handy. I´ve used them in circuits when the increased current draw of OPAx134s is a no-go.

Click to expand...

Do you think i will need the 0,1uf ceramics for the TLE2074 as well?

jensenmann said:

That´s another good chip for that purpose. They have lower power consumption than TL07Xs which occasionally is very handy. I´ve used them in circuits when the increased current draw of OPAx134s is a no-go.

Click to expand...

It´d be risky not to use them. The TLE has a higher gainbandwidthproduct which means (simplified) that it´s more prone to oscillations than the TL072. These TLEs have not been tested in this particular circuit, so the ceramics are your safety net.

Alright. Thank you, i will make sure to add them if/when i start to experiment.

jensenmann said:

It´d be risky not to use them. The TLE has a higher gainbandwidthproduct which means (simplified) that it´s more prone to oscillations than the TL072. These TLEs have not been tested in this particular circuit, so the ceramics are your safety net.

Click to expand...

Should be able to get theOPA2132/4 pre soldered on DIP8 boards here: https://www.cimarrontechnology.com/browndog-970601-so8-to-dip8-adapter

Super cheap too and lots of other modern options you could try too.

I got tons of new brown dog dip8 adapters for sale if you want to do a whole console