UREI 529: Choosing newer/cleaner replacement ICs for input & output

[Mammals]

Hello,

I have a UREI 529 EQ I've asked a person with competence to modify on my behalf; I'm hoping to have its ICs swapped out at the input and output of its path to (1) be much cleaner, and (2) be fixed-gain at these stages, at higher than net unity gain so this will function as a preamp/eq. Since there are a couple points where it can already be switched (-20dB I think?) or slid (subtractive -15dB) to change its total dB +/- by the time it's at output, I don't feel super concerned about the idea to aim for the +35-40dB range or thereabouts for fixed gain on the ICs.
My hope is that this forum may have recommendations for appropriate preamp ICs that will match well for pin configuration, will be low noise, and will be low-enough power to avoid extra work in that department.
Apologies if I am missing (or unnecessarily including) obvious information; I am moderately ignorant but the tech I'm hiring is not. I would like to minimize extra time he needs to spend researching this by asking, myself.
Attaching 529 documentation. Thank you very much for your time and expertise fielding this question.

 

[Mammals]

Hello. Thought I'd duck back in to see if anyone can recommend proper IC replacements to bring the noise down, as above. Thanks in advance for sharing your knowledge.

 

[TheJames]

I don't think I'd fuss with it honestly. Use and love it for what it is.

If you insist on making changes, note that the output quad opamp is a 4136. There aren't any pin-compatible replacements. Joe Malone at JLM audio made an adapter, and maybe BrownDog or other adapter makers have one that will stick a modern SMT quad or pair of SMT duals on an adapter board for replacing the 4136.

The LM301's are still available today and aren't that bad. Sure there are technically better opamps out there, but I don't think there's much juice to squeeze out of this thing with fancy opamps. Maybe some better noise could be had, but you could probably achieve better noise performance by running the EQ sections in parallel rather than series and sum the sections together.

I wouldn't really mess with the gain staging either. The EQ was meant to run at line level in front of a power amp to assist in "tuning" a room to achieve better speaker performance in a given room.

This is a high quality piece of gear. Go through it, replace the electrolytics, fix whatever is bad, restore it to it's natural state and enjoy it.

 

[Bo Deadly]

The noisiest part is probably going to be the low-cut / high-cut filter section and that op amp which apparently is difficult to replace.

But before you get too into that, are the sliders ok? The sliders on these old UREI inductor EQs usually get really gummed up to the point of being useless. I actually made replacement slide assemblies for my pair of 527A.

If for some reason you still want to proceed, the second noisiest part is probably the supply. Making an external SMPS supply would probably drop the hum to nothing (whereas new amps would drop the hiss).

I like graphic EQs and I think EQ in general is overrated. The LC ones are very elegant circuits. But three completely different and formidable problems might be too much effort for something that most people will not see the value in.

 

[Mammals]

Thank you both. Good info. I'll aim for some rehab instead and see how it turns out.

 

[CFB4]

The sliders on these old UREI inductor EQs usually get really gummed up to the point of being useless. I actually made replacement slide assemblies for my pair of 527A.

Hi Bo, curious abut these replacement assemblies, how did you do this please?