ProTech (Protech) Audio Model 1000 Discrete Op Amp

[bxt403]

I acquired two of them with a bulk purchase of some other DOAs. They have gold labels with black text and have a PT logo on them and the pins are labelled like a Melcor 1731 or API 2520 (+IN ,-IN, OUT, +V, -V, COM, and TRIM).

Looking at Protech Audio's current used units on eBay that have frames with the new text only logo (where the company's spelled Protech) that are filled with a mix of modules that have the ProTech spelling with a PT Logo exactly like the Model 1000)- I've been able to confirm that Protech and ProTech are the same. Since the company started around the time the JE-990 paper was published- my inference is that it's based on the JE-990 (given the model number). Otherwise- it could be some other relabelled op amp.

I've contacted them (at the end of September) but haven't heard back.

At this point- I'm guessing they run on +/- 15 or 16 Volts (given that's the voltage used on their current frames) but could be wrong.

Knowing the original JE-990 was designed to operate at +/- 24 Volts, I'm curious to find out what voltage the Model 1000 would get on a ProTech/Protech module, along with the feedback RC values that would be used.

 

[mjrippe]

I am familiar with ProTech and some of their products. I was aware they made a 2520 compatible opamp but have never seen one in person. However, I think that your inference is based on coincidence. Without evidence to the contrary I would stick to +/-15V.

 

[bxt403]

Given Protech chose 1000 for the model number (and the JE-918 operated at +/-16V)- perhaps it's a 990 that operates at a lower voltage. The fact that the model number isn't 1800 or 2600 implies it might be based on the JE-990.

 

[mjrippe]

No, it really does not imply any such thing. Model numbers can be completely arbitrary. I am not trying to be a jerk, but your reasoning is not sound.

 

[bxt403]

I'm certain there must've been a deeper meaning to the model number (w.r.t. marketing). The fact the JE-990 was published around the time ProTech was formed would imply the 990 might've been the easiest basis for an "original" discrete op amp design without having to worry about any additional monetary cost or legal ramification. For a young company like ProTech- the JE-990 being public domain would've allowed them to implement their own version efficiently. Given the way their current modules are designed- making a DOA based off of the JE-990 would seem consistent with the design philosophy they evoke.

In any case- I'm hoping to test them by building the microphone preamp circuit from the JE-990 paper (rather than risk damaging or destroying one of them by removing the plastic casing and epoxy) but am still inclined to think the Model 1000 is based on the JE-918 or the JE-990.

With that in mind- I'm assuming the feedback RC values I'll have to use will be the ones from JE-990 paper schematic.

 

[bxt403]

My educated guess (after some more research) is if it's based on the JE-990: I'll need 91pF and 10kOhm. If it's based on the 918, I'll need 75pF and 27.4kOhm.