You guys are always kind to teach me... So, here goes nothing. Per schematic attached, the relays are in the open position for a normally open relay, correct? So, wouldn't all the input GNDs be shorted together when powered off per the schematic? Do I have it backwards or just plain wrong? It looks like the positive input leg connects when the relay closes for a normally open relay.
Under power, if they were all normally closed, wouldn't all the relays, except the input selected, be closed when in normal use? If the input selected switched from closed to open, it would not send a signal through the pre-amp when powered on, right?
I looked at the schematic and my brain melted (again).
View attachment Iron Pre SE Twister input select sch (1).pdf
Under power, if they were all normally closed, wouldn't all the relays, except the input selected, be closed when in normal use? If the input selected switched from closed to open, it would not send a signal through the pre-amp when powered on, right?
I looked at the schematic and my brain melted (again).
View attachment Iron Pre SE Twister input select sch (1).pdf
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In post #215 you mentioned:
"mains xformer - secondary 36Vac CT 10VA is minimum , either one per channel of common for both"
Does it matter 2x15VAC or 2x18VAC?
well, what's few volts between friends ? 
both will work, if you set reg to +/-12Vdc, though 18Vac secondaries will give greater margin for mains fluctuations
due to logically poor regulation factor of small Donuts ( difference of unloaded vs. loaded Vac) most of them are having higher Vac than declared ( usually declared/constructed for full load), so more often than not we can practically use smaller voltage than Funny Constructor said in first place
Good Gemini reg is good in one thing (besides some other ones) - not excessive load - each rail is drawing "just" 90mA .......... set by Vbe/(15R // 15R) - in input CCS of reg
ref. to first pic in post #1149 - What's wrong with the kiss,boy ?
both will work, if you set reg to +/-12Vdc, though 18Vac secondaries will give greater margin for mains fluctuations
due to logically poor regulation factor of small Donuts ( difference of unloaded vs. loaded Vac) most of them are having higher Vac than declared ( usually declared/constructed for full load), so more often than not we can practically use smaller voltage than Funny Constructor said in first place
Good Gemini reg is good in one thing (besides some other ones) - not excessive load - each rail is drawing "just" 90mA .......... set by Vbe/(15R // 15R) - in input CCS of reg
ref. to first pic in post #1149 - What's wrong with the kiss,boy ?
Thanks to the generosity of Jim, I have received one of the Iron Pre boards (2020 version). I also got meldano's Muses Volume Kit, which conveniently needs a +/-15V power supply. Should be a good project!
The case, transformers and Jfets already arrived, so now I just need to collect all the remaining parts.
The case, transformers and Jfets already arrived, so now I just need to collect all the remaining parts.
Attachments
I did the "surgery" and the boards are stuffed sans iron. Then, a leg of one of the Edcor transformers snapped off as soon as I touched it...
I tried to solder in a new leg, which was unsuccessful to say the least. So, this won't be finished this side of the holidays unfortunately.
I tried to solder in a new leg, which was unsuccessful to say the least. So, this won't be finished this side of the holidays unfortunately.
