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Did some verification on the next upgrade. I took apart the um70 again to check if the figure 8 pattern switch in the head basket would be disconnecting the ring and the rear diaphragm. To my delight it did disconnect the two parts. This means I can simply use dc blocking cap between the diaphragms and everything else happens inside the headbasket.
[ATTACH=full]118626[/ATTACH][ATTACH=full]118629[/ATTACH]

Gave the above schematic a go this afternoon.

[ATTACH=full]118628[/ATTACH]

Fired it up and it worked fine in omni and Cardioid... as expected. However the figure 8 was still off and noisy.
Looked back at the m49c schematic and realized I had transposed some junctions. Glad to learn more about that today... Its all a learning experience. So now, below... behold the working schematic and the high z work. I grounded the capacitor on one of the mechanical mounting lugs on the circuit board. I drew B+ from the top of the 100k resistor. Worked out great...Much cleaner and it sounds great in all patterns.
[ATTACH=full]118625[/ATTACH]

[ATTACH=full]118627[/ATTACH][ATTACH=full]118630[/ATTACH]

LOVE IT!

[ATTACH=full]118631[/ATTACH]

Now to mod the other one

<blockquote data-quote="SparkleBear" data-source="post: 1122549" data-attributes="member: 61490">Did some verification on the next upgrade. I took apart the um70 again to check if the figure 8 pattern switch in the head basket would be disconnecting the ring and the rear diaphragm. To my delight it did disconnect the two parts. This means I can simply use dc blocking cap between the diaphragms and everything else happens inside the headbasket.[ATTACH=full]118626[/ATTACH][ATTACH=full]118629[/ATTACH]Gave the above schematic a go this afternoon.[ATTACH=full]118628[/ATTACH]Fired it up and it worked fine in omni and Cardioid... as expected. However the figure 8 was still off and noisy.Looked back at the m49c schematic and realized I had transposed some junctions. Glad to learn more about that today... Its all a learning experience. So now, below... behold the working schematic and the high z work. I grounded the capacitor on one of the mechanical mounting lugs on the circuit board. I drew B+ from the top of the 100k resistor. Worked out great...Much cleaner and it sounds great in all patterns.[ATTACH=full]118625[/ATTACH][ATTACH=full]118627[/ATTACH][ATTACH=full]118630[/ATTACH]LOVE IT! <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile&nbsp; &nbsp; :)" loading="lazy" data-shortname=":)" />[ATTACH=full]118631[/ATTACH]Now to mod the other one <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile&nbsp; &nbsp; :)" loading="lazy" data-shortname=":)" /></blockquote>

[QUOTE="SparkleBear, post: 1122549, member: 61490"] Did some verification on the next upgrade. I took apart the um70 again to check if the figure 8 pattern switch in the head basket would be disconnecting the ring and the rear diaphragm. To my delight it did disconnect the two parts. This means I can simply use dc blocking cap between the diaphragms and everything else happens inside the headbasket. [ATTACH type="full" width="215px" alt="1702513526344.png"]118626[/ATTACH][ATTACH type="full" width="262px" alt="1702513860301.png"]118629[/ATTACH] Gave the above schematic a go this afternoon. [ATTACH type="full" width="363px" alt="1702513604063.png"]118628[/ATTACH] Fired it up and it worked fine in omni and Cardioid... as expected. However the figure 8 was still off and noisy. Looked back at the m49c schematic and realized I had transposed some junctions. Glad to learn more about that today... Its all a learning experience. So now, below... behold the working schematic and the high z work. I grounded the capacitor on one of the mechanical mounting lugs on the circuit board. I drew B+ from the top of the 100k resistor. Worked out great...Much cleaner and it sounds great in all patterns. [ATTACH type="full" width="465px" alt="1702512661239.png"]118625[/ATTACH] [ATTACH type="full" width="446px" alt="IMG_0712.JPG"]118627[/ATTACH][ATTACH type="full" width="391px" alt="1702514070876.png"]118630[/ATTACH] LOVE IT! :) [ATTACH type="full" width="435px" alt="IMG_0720.JPG"]118631[/ATTACH] Now to mod the other one :) [/QUOTE]

Verification