AML ez1073 modification: Can a knob be built in the kit in place of the "Trim" dial?

[Troisi]

I just completed the new DIYRE 1073 clone and I really enjoyed the build.

I really want to try one of Colin's kits, and obviously the 1073 makes the most sense.

Compared to the ez1081, I like to have two "gain stages" for lack of a better term, which is somewhat universal and the absence of one on the 1081 seems odd.

MY QUESTION:

Has anyone successfully implemented a KNOB in place of the "Trim" screwdriver slot on the AML EZ1073PRE?

Like, literally just did whatever it took to have a potentiometer sticking out the front panel, presumably the exact size to fit the smaller grey marconi knob?

Would this be a futile effort? Or a nightmare?

Should I try a 1081 instead and see what it's like to only have a gain switch?

Thank you very much for any information.

 

[TwentyTrees]

Yep, both my ez1073pre units have pots with longer shafts in the output trim position, which is R73 (dual 10k linear) in the version of the build manual I have. Unfortunately I don't have a note of which pots I used, but apart from the shaft length they will need to have exactly the same dimensions as the originals (Sfernice P9A) in order to fit - it's a very full and mechanically relatively complex module, so it's not going to be possible to just shove any old pot in. I may have had to ream the holes slightly for the shaft as well, I can't remember.

In my view it's definitely worth doing. The gain switches are well matched regardless, but it does allow for "pushing" the preamp more easily. You can also reduce the value of R71 to allow a greater range of attenuation from this trim pot. 0 ohms = full attenuation counterclockwise.

 

[Troisi]

Thank you for your reply.

I will definitely do some research with the colourbook and what exactly goes in and around that trim knob. While I do have quite a large amount of those sweet 70's - 80's precision scientific pots (inherited from my late father), I know I can't just pull one out of the pile and shove it in.

But if I'm reading you right, and what my research will probably tell me - is that I need a Dual Gang 10kohm Linear Taper pot with a shaft (and bushel) thin/narrow enough to fit.

If this is all there is to it then that's wonderful news.

Thanks again.

 

[TwentyTrees]

If this is all there is to it then that's wonderful news.

Pretty much, yes. You could also use a single gang 5k (or 4k7) pot, as the two gangs of the 10k are paralleled, though if you can find a two gang 10k then it will be marginally stronger and more stable, mechanically speaking. Though if you use one with a long enough bushing to secure to the front panel with a nut, you'll be fine with a single gang.

On the pot itself, I think the Sfernice P9A range has been discontinued but the datasheet is still out there so you should be able to get the key dimensions from that.