Re: Switchable patterns in Dual OPA Alice with dual capsule #°Õ¸é±«·¡°ä°¿±·¶Ù·¡±·³§·¡¸é¡±²Ñ±õ°ä¸é°¿±Ê±á°¿±··¡³§ dualopaalice
#°Õ¸é±«·¡°ä°¿±·¶Ù·¡±·³§·¡¸é¡±²Ñ±õ°ä¸é°¿±Ê±á°¿±··¡³§
(off topic) We built one of those recently ¡ª invaluable for sanity-checking mics for output polarity. It¡¯s also red. :) ¡ª matt.
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recordinghacks
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#33886
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Re: Switchable patterns in Dual OPA Alice with dual capsule
#°Õ¸é±«·¡°ä°¿±·¶Ù·¡±·³§·¡¸é¡±²Ñ±õ°ä¸é°¿±Ê±á°¿±··¡³§
#dualopaalice
Mix the signals at the output. Connect XLR pin 2 to pin 2 output from front side. XLR pin 3 is switched between front side pin 3 for cardioid, rear side pin 2 for fig-8, and rear side pin 3 for omni.
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Henry Spragens
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#33885
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Re: Hex inverter issue. Alice OPA
Hello The internal resistance of my meter appears to be 955kOhm so about 1MOhm. Best regards Wiktor Molak
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LonDek
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#33884
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Re: Hex inverter issue. Alice OPA
If you have a 1M resistor, try this: measure a known voltage source 12V supply is good, even a 9V battery. Then put the 1M in series with the meter and measure again. You can calculate the internal
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Jules Ryckebusch
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#33883
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Re: Switchable patterns in Dual OPA Alice with dual capsule
#°Õ¸é±«·¡°ä°¿±·¶Ù·¡±·³§·¡¸é¡±²Ñ±õ°ä¸é°¿±Ê±á°¿±··¡³§
#dualopaalice
Full balanced signal is soooo overated... Balanced impedance is what matters. But why not?
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Jerry Lee Marcel
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#33882
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Re: Switchable patterns in Dual OPA Alice with dual capsule
#°Õ¸é±«·¡°ä°¿±·¶Ù·¡±·³§·¡¸é¡±²Ñ±õ°ä¸é°¿±Ê±á°¿±··¡³§
#dualopaalice
Instinct tells me that trying to add switches around that kind of high impedance circuitry is asking for trouble! .. I may be proved wrong of course! :) I'm not sure why you're not keen on the single
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Arjay1949
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#33881
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Re: Switchable patterns in Dual OPA Alice with dual capsule
#°Õ¸é±«·¡°ä°¿±·¶Ù·¡±·³§·¡¸é¡±²Ñ±õ°ä¸é°¿±Ê±á°¿±··¡³§
#dualopaalice
You can't. Capsules need to see very high impedance, typically 1G (1 000 Megohm). You cannot operate a diff amp with such high values, noise would be enormous.
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Jerry Lee Marcel
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#33880
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Re: Switchable patterns in Dual OPA Alice with dual capsule
#°Õ¸é±«·¡°ä°¿±·¶Ù·¡±·³§·¡¸é¡±²Ñ±õ°ä¸é°¿±Ê±á°¿±··¡³§
#dualopaalice
Actually, that's it! Removing U3 by making U4 a full differential means we can use that spare OpAmp after the U4 mixing stage as an inverting amplifier to produce the cold signal, thus giving us a
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michaeljtbrooks@...
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#33879
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Re: Switchable patterns in Dual OPA Alice with dual capsule
#°Õ¸é±«·¡°ä°¿±·¶Ù·¡±·³§·¡¸é¡±²Ñ±õ°ä¸é°¿±Ê±á°¿±··¡³§
#dualopaalice
I did think about that Jerry, but decided that as the existing project PCB already has 2 x dual amps - each with one amp configured as a non inverting buffer and the other as an inverter - it might
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Arjay1949
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#33878
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Re: Switchable patterns in Dual OPA Alice with dual capsule
#°Õ¸é±«·¡°ä°¿±·¶Ù·¡±·³§·¡¸é¡±²Ñ±õ°ä¸é°¿±Ê±á°¿±··¡³§
#dualopaalice
Hi Arjay, Looks interesting! Thanks for the idea. I'm still quite keen on a balanced signal output though. How feasible is it to put switches on the high impedance side? If so, how about this... Still
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michaeljtbrooks@...
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#33877
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Re: Switchable patterns in Dual OPA Alice with dual capsule
#°Õ¸é±«·¡°ä°¿±·¶Ù·¡±·³§·¡¸é¡±²Ñ±õ°ä¸é°¿±Ê±á°¿±··¡³§
#dualopaalice
There is also a possibility of using one less opamp, by omitting U3 and making U4 a full differential amp.
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Jerry Lee Marcel
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#33876
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Re: Hex inverter issue. Alice OPA
Hello, just a simple meter, it has few years now and I think I bought it for like 10 bucks. Best regards Wiktor Molak sob., 9 kwi 2022 o 18:35 Jules Ryckebusch <ryckebusch@...> napisa?(a):
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LonDek
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#33875
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Re: Hex inverter issue. Alice OPA
I would ask the same. The first asset of voltages all seem good. The higher the stages the less current available thus the Meter can load it down. I have fluke 87 that has a 20M input impedance.
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Jules Ryckebusch
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#33874
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Re: Switchable patterns in Dual OPA Alice with dual capsule
#°Õ¸é±«·¡°ä°¿±·¶Ù·¡±·³§·¡¸é¡±²Ñ±õ°ä¸é°¿±Ê±á°¿±··¡³§
#dualopaalice
I live in the UK, so the shipping costs for Jules' PCBs are way too expensive for me!...... So I tried out my own experiments with the OPA1642 and OPA 1641 amps that Jules recommended.... Some project
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Arjay1949
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#33873
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Re: Hex inverter issue. Alice OPA
What are you using to measure the voltage? It is essential to use a high impedance meter (at least 10 Megohms)
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Jerry Lee Marcel
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#33872
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Hex inverter issue. Alice OPA
Hello, I am currently going through mental breakdown because of this circuit! I have no idea why it's not working, I'm beginner with electric circuits, simply following guides out there, schematics,
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LonDek
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#33871
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Switchable patterns in Dual OPA Alice with dual capsule
#°Õ¸é±«·¡°ä°¿±·¶Ù·¡±·³§·¡¸é¡±²Ñ±õ°ä¸é°¿±Ê±á°¿±··¡³§
#dualopaalice
Hi All, (Mainly FAO Jules, but I thought this discussion would be useful to a others) What would be the best way of introducing a pattern switch to the Dual OPA Alice circuit (
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michaeljtbrooks@...
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#33870
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Re: Foam rot in AT3528
In this particular case, the foam does not seem to play any acoustic role: it's in the path of no soundwave. It appears to me to just beign a soft intermediary (damping?) layer between the backplate
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Pierre Olivier
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#33869
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Re: Foam rot in AT3528
I HAVE HAD GOOD RESLTS CUTING FOME WITH ELECTRIK CARVING KNIFE and stitching to gether the end¡¯s with fine sowing thread and then turning the fome tube incideout This teck-neek is good to make a
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STEPHEN MUIR-FIELD
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#33868
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REVEIL 9 - dawn chorus radio broadcast over 30/4 to 1/5 2022
Dear MicBuilders Each year on Dawn Chorus Day, we organise a 24+1 hour radio broadcast that circles the earth on live audio ?streams at daybreak. Many of the microphones used by streamers as the sun
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Grant Smith
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#33867
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