So you've narrowed it down some, which is good.
Just to try to be clear, there is no actual historical '1081 mic preamp' as a stand alone product - the 1081 product was a mic/line pre with 4 band eq, using a ba338/438 'discrete amp' module front end and a b340/440 'discrete class ab line amp' module backend (it also uses several filter gain modules in between)
So whichever way you put it together, a stand alone mic-pre only will be a somewhat different animal from the venerated classic.
Now the reason I point that out is the product 1081 gain switch is a complicated affair, more so because it does switching between mic & line input transformers as well as providing attenuation of both the ba338 and b340 modules together.
IF you only have a mic input, you can simplify down to a 2 deck rotary or even 1 deck, as done in the JLM by sacrificing the line amp altogther.
ie. the JLM '1081 mic pre' circuit takes the '1081 pre+eq' front end ba338 module and utilises it in a modern, 1 deck gain switch configuration - a simple inverting amplifier with attenuation being in the -ve leg .... 'api style'
However, it's current drive capacity is not really up to the job of a line amp - the one I'm playing with now is not as strong an output as even an api doa. And it does require heatsinking if it's trying to drive heavy (low Z) loads.
The '1081 mic-pre+eq' and others have the b340 for that reason.
Just to be clear !
So the design question now is 'do you want to keep the historic gain switch attenuation OR simplify and use the 'non inverting op amp' configuration (jlm and api style).
The answer dictates how 'close' to the historical you will be. If you want closer to original, then you need a 3 decker.
If you can stand to deviate, then a 2 deck or even 1 deck can be used, bringing you closer to a pretty generic config.
If you can leave out the line amp as well, then you are in jlm's circuit territory, where a 1 decker is all that's needed.
What that means to the sound is another question.
I think I would be hard pressed to tell the difference between an 'old school' ba338/b340 config or a 'modern' ba338/b340' config, if they were using the same parts.
Still further, I doubt I could tell apart a 'modern' 'ba338/b340' config from say an 'api style mic pre' made from same parts.
However, it is all good - quality in will surely give quality out whichever way you go.
SO - did you get all that?
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Also, you mention an output level control - the original product of course used the channel strip fader for that.
So, to add that has some considerations.
In the historic way, the output fader is connected between the the ba338 and the b340 (just before the b340).
SO, if you are going historic, meaning you will have a b340 amp section, that's no problem and a simple affair.
If you are not planning on using a b340 line amp module, and go for the 'jlm 1081' then you need to make other arrangements.
The decision therefore is 'do I want a proper mic pre with a good drive capability that the use of a line amp+traffo brings'.
If so, then the output fader is simple to implement.
NOTE - it's been a while since I looked at the original 1081 gain switch detail and fader arrangement. I could be a little mixed up between models, so please fact check
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My own 'mongrel 1081 pre+eq' uses the b338 amp module in the modern api inverting amp config, with a single deck rotary attenuator (ie. like the jlm 1081) and unipolar +24V rail.
The line amp is a 2520 doa with bipolar +/- 18V rails, driving a 1:1.73 step up transformer which can drive 600ohm loads and higher to
a very respectable voltage
The output fader is a 10K reverse audio log pot attenuator on the -ve leg of the 2520, again 'api style' or 'modern inverting opamp config' .
Luckily the hard yards of pcb design/fab/test were done by others ... members here over the years
Mine uses a 'bauman simple 1081' pcb implementation of the 'jlm 1081 mic pre' and Pier Paulo's APP Studio 'I/O board'.
The APP Studio pcb is possibly the best preamp board design I've come across - beautifully implemented with di, twin 2520 blocks and transformer options etc. All round class act and worthy of high praise
Perfect for a preamp with eq courtesy of the 2nd 2520 used as eq-gain-make-up.
Add some 'poormans eq' blocks from Ruffrecords in the 'between' and you have a fab '1081 micpre+eq' mongrel build.
Actually -> 1081 mic/line/DI preamp + pultec-ish eq + fixed api makeup + variable api makeup/line amp + traffo
Ok then. Coolio!