8 Channel, Jensen 990 Completed

Finally finished this up. A great utility preamp in a 2U case.
The transformers are Jensen (JT16, JT11BM), the pcb is by Mitsos, the gain switch boards are from ClassicAPI, and the case is from Dan at Collective.
Based on the Deane Jensen / John Hardy design.

another pic

And the insides.

Looks great. Tight squeeze in there!

Are they illuminated switches (the pushbuttons)? Where did you get them from?

Yes, they are illuminated pushbuttons. I still might have to file the holes a bit to get them all working smoothly.
They originally came with the boards I think.

Great work! How to you calculated resistances to gain switch?

nice work man!

ramshackles said:

Are they illuminated switches (the pushbuttons)? Where did you get them from?

Click to expand...

We did a group buy direct from the manufacturer back when the PCBs were done.  Rapid UK sells them, also hairball and grove audio.
http://www.rapidonline.com/Electronic-Components/Illuminated-Push-Button-Switches-70729

How to you calculated resistances to gain switch?

Click to expand...

I made a spreadsheet to calculate the R values since I was using 12 position switches.
The opamp gain is 10k/Rgain, where Rgain is the resistance from the switch.
The transformer gain is 2.
So the overall gain is dB = 20*log(2*10000/Rgain)
 

Hi DMP.
I was reading another thread where you said you got your M1 style pre to output 70dBs? how did you manage so?
im working on a similar style pre but my overall output starts distorting a bit.
Let me know!

Thank you.

I just tried it and never noticed any distortion or other problems. I haven't measured distortion though, so it could be you are hearing something I haven't noticed.
I don't typically record with that high a level, but I find it handy to have it available for quiet sources.
I suppose you could either have distortion through coupling from the inputs/outputs or from the DOA crapping out.
Maybe try a different 990 and check shielding / transformer orientation?

well the question was maybe your idea was better than mine but thanks.
Ill try something else.