Posted: Thu Oct 16, 2014 1:06 am
Also, won't I have to attenuate the signal at some point so the converter doesn't clip?
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You imagine correctly We are using the JLM14 backwards in this case so there will be a 12dB loss of gain which works well as most A/D IC's only want a 1 or 2v peak to peak to hit 0dBFS. So you should at least need +12dBu or more to get 0dBFS.Thanks Joe! Is there a drawing of the JLM14 windings so I can understand the wiring? From your description I would imagine that yellow and blue are the primaries in a single winding, and red and green are two secondary windings with black the center tap?
Yes balanced in or unbalanced in doesn't matter as it is a floating transformer input so does not care. You should never have DC on the input as almost everything is capacitive coupled output and any DC servo outs will not have more than a few mV so will not matter.living sounds wrote:Thank you Joe, sounds great. Just two more question: Will this configuration work well with balanced as well as unbalanced sources? Also, how much DC on the input can the transformer handle?
A row of caps were removed to allow the input transformer to feed direct into the A/D chip. A2D PCB is no longer available unfortunatelycraigmorris74 wrote:I was always fascinated with this project, and hated to see that it wasn't issued as a kit. Were any components removed from the A/D board, or did the signal go through all the input circuitry before the A/D chip?
If you can take a large clear in focus photo of the top and bottom of the SM Pro PCB I am sure I can draw the mod on there for you to try.craigmorris74 wrote:Thanks for the reply Joe. Interesting stuff!
I have an old SM Pro Audio ADAT board, and would love try hooking up a couple of JLM14's to it and see what it sounded like.
EDITcraigmorris74 wrote:Hey Joe,
Thanks again for your reply. I've attached photos of the top and the bottom of the board, as clear as I could get of the analog sections, and the schematic.