I don't think the tin is your issue. Try grounding the inputs, one at a time, to see if you can trace the problem to a specific channel.
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Double Bass Homebuilt EUB build thread
- Thread starter Videojunkie
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I don't think the tin is your issue. Try grounding the inputs, one at a time, to see if you can trace the problem to a specific channel.
On the mic, it's a single channel. On the piezo, I was just testing a single channel as well. But that was soldered into the 'blend circuit'...
Are all the preamps you aren't using still wired up, just disconnected from the pickups? If so I would disconnect all but a single preamp to narrow the source of the noise.
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You may need to shorten the inputs on the unused channels. Also check if there is a input resistor installed for the piezos. An open, non-terminated FET-input can act like a radio receiver.
And check your grounding. If a grounded metal case does not help, it‘s either a missing input resistor or a fault in the grounding.
And check your grounding. If a grounded metal case does not help, it‘s either a missing input resistor or a fault in the grounding.
I agree with DoubleMIDI's advice...
subtle English distinction - shorten vs short.
ps no criticism - I wish I had 1% of DoubleMIDIs command of English in my knowledge of German!
i.e. 'short' the inputs electrically = connect signal side directly to ground.
subtle English distinction - shorten vs short. ps no criticism - I wish I had 1% of DoubleMIDIs command of English in my knowledge of German!
So I am trying to get the mic system working as it is the simplest.
Mic -> 3.5mm jack -> preamp-> 1/4" jack-> amplifier.
Preamp-> battery.
On the good news side, the mic works fine. Picks up the bass well (a bit of feedback, but that's expected with no processing).
Unfortunately it is also picking up the local radio. This is after swapping out all of the wiring for shielded wire. Shield connects through to the jack. Preamp has signal and ground connections that are separated from the shield. All of this is inside the mint tin.
Mic -> 3.5mm jack -> preamp-> 1/4" jack-> amplifier.
Preamp-> battery.
On the good news side, the mic works fine. Picks up the bass well (a bit of feedback, but that's expected with no processing).
Unfortunately it is also picking up the local radio. This is after swapping out all of the wiring for shielded wire. Shield connects through to the jack. Preamp has signal and ground connections that are separated from the shield. All of this is inside the mint tin.
Thanks for the little lesson.
Is the mic meant to be used with the mic preamp?
It looks like you have an electret mic that needs power on the hot connector. If there is no power, it should not work at all and you might think that you need a lot of amplification and mostly amplify noise and RF.
Is the mic meant to be used with the mic preamp?
It looks like you have an electret mic that needs power on the hot connector. If there is no power, it should not work at all and you might think that you need a lot of amplification and mostly amplify noise and RF.
Ah-ha! So you're suggesting that instead of an RFI issue, I'm having a gain and signal to noise ratio issue!
Fortunately, the preamp board has a volume potentiometer that I haven't played with yet. Let me fiddle with that and see what I come up with.
The board description says it's for condenser microphones, but you are correct that there doesn't seem to be a 3rd pin connection for phantom power.
Fortunately, the preamp board has a volume potentiometer that I haven't played with yet. Let me fiddle with that and see what I come up with.
The board description says it's for condenser microphones, but you are correct that there doesn't seem to be a 3rd pin connection for phantom power.
Won’t be another pin for the phantom power, should be between the differential signal pins
https://en.m.wikipedia.org/wiki/Phantom_power
(Edit) note zener diodes. Cold solder joints might make them good antennas.
. And unless you have enough voltage on your rails, they’ll need a step-up power supply for which can be a significant source of noise including RF. Check DC between the signal pins if nothing look for errors in Phantom power connections. this is two 9V back to back for power for everything ?
https://en.m.wikipedia.org/wiki/Phantom_power
(Edit) note zener diodes. Cold solder joints might make them good antennas.
. And unless you have enough voltage on your rails, they’ll need a step-up power supply for which can be a significant source of noise including RF. Check DC between the signal pins if nothing look for errors in Phantom power connections. this is two 9V back to back for power for everything ?
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Electrets are powered over the single (unbalanced) hot signal line, so a two line connection, not phantom power. (In german it is called „Tonaderspeisung“. It can damage dynamic mics, phantom power does not when the dynamic mic is balanced.
The receiving side decouples dc (injected power) and ac (mic signal with a bit bigger capacitor.
The preamp/power adapter might deliver a balanced signal, but typically there is the unbalanced powered connection to the electret.
More expensive electrets might not have an FET in the capsule. Then it won‘t work with a cheap electret mic preamp and needs to be handled like a non-precharged condenser capsule with an external FET close to the capsule. This is for mic builders/modifiers with electronic knowledge, not for the cable connectors.
But I‘m rather sure yours don‘t fall into that category.
Do you have the power enabled? Since dynamic mic capsule can be destroyed by the power, there might be a jumperor switch for that.
I just thought it might come from an overly large amplification factor and no input signal. Need to think a bit more about it, but no time for that now.
The receiving side decouples dc (injected power) and ac (mic signal with a bit bigger capacitor.
The preamp/power adapter might deliver a balanced signal, but typically there is the unbalanced powered connection to the electret.
More expensive electrets might not have an FET in the capsule. Then it won‘t work with a cheap electret mic preamp and needs to be handled like a non-precharged condenser capsule with an external FET close to the capsule. This is for mic builders/modifiers with electronic knowledge, not for the cable connectors.
But I‘m rather sure yours don‘t fall into that category.
Do you have the power enabled? Since dynamic mic capsule can be destroyed by the power, there might be a jumperor switch for that.
I just thought it might come from an overly large amplification factor and no input signal. Need to think a bit more about it, but no time for that now.
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Update, so I rewired the mic using the tip/ring from the preamp (good grief, a wiring schematic for this would be nice.). And I turned the preamp volume down. This seems to have largely solved the issue, but touching the metal sleeve of thi mic will induce the radio noise, so I still have a ground issue.
Do you have a wiring diagram for your mic? If not, how many segments are there on the jack (i.e.: how many metal parts separated by plastic spacers)?
If it was intended for a typical mobile phone it is probably a "TRRS" (4 pole) jack, in which case the mic + is the sleeve, and the ground is the ring nearest the sleeve. That's the CTIA way. Of course, there are other standards that reverse those two so nothing is as simple as it should be.
Normally mobile phones power the mic with a couple of volt source connected in series with a 2.2k ohm resistor. You can measure the voltage on the input of your preamp to see what it is supplying to be sure.
If it was intended for a typical mobile phone it is probably a "TRRS" (4 pole) jack, in which case the mic + is the sleeve, and the ground is the ring nearest the sleeve. That's the CTIA way. Of course, there are other standards that reverse those two so nothing is as simple as it should be.
Normally mobile phones power the mic with a couple of volt source connected in series with a 2.2k ohm resistor. You can measure the voltage on the input of your preamp to see what it is supplying to be sure.
You need to check how the mic is connected and where the power needs to go (my guess is in the ring on a TRS connector). It might have an extra line, not coupled with the signal on one like I said before but the preamp might expect that. Also check how and where the preamp does the powering.
It might be that the preamp and mic won‘t fit together well.
Another thing is that you better cut the shield from the battery and also the mic so that the only connection of the shield to ground is at the output connector. Otherwise you have a ground loop that can receive RF.
It might be that the preamp and mic won‘t fit together well.
Another thing is that you better cut the shield from the battery and also the mic so that the only connection of the shield to ground is at the output connector. Otherwise you have a ground loop that can receive RF.
+1 @DoubleMIDI pointing towards looking at what-it-might-be not what-should , and the endless saga of ground loops.
OK, you have a single supply preamp. That means that the board makes its own "virtual ground" between the 9 V (+) and (-). Depending on the wiring of the preamp, the virtual ground may be what you see at the input/output (-) terminals. If you have a multimeter it would be helpful to know the voltage between the input (+) and input (-) and also between the output (-) and 9 V (-) with the inputs and outputs entirely disconnected -- both + and - connections. Alternatively, a picture of the front and back of the preamp might also help to see how it is wired.
Regarding the wiring, it is good that you have the shield of the cables (labeled drain) connected to the virtual ground at the jack sleeve. What is not good is that you also have the shield of the cable connected to the 9 V power supply (-) because, as a general rule, you want your grounds connected to a single point only. A simple change would be to remove the connection between the shield and the 9 V (-) terminal and see if it affects anything.
My previous question was asking about the internal wiring of the microphone itself. If you have no data on it then it might take some testing to see what is going on. Sometimes PC electret mics (which it looks like you may have based on the 3.5 mm TRS connector) are wired such that both the tip and the ring are connected together. Others may treat the ring as a bias supply with a possible internal biasing resistor and output capacitor. It makes a difference to how you wire the mic. If you have a multimeter, can you test the resistance between the tip and ring? If it measures near zero ohms then you need to connect the T and R terminals to the input (+) and the sleeve to input (-). Otherwise it would likely be better to connect the ring to the 9 V (+) terminal. Either way the sleeve should be connected to the input (-) terminal, and the shield left disconnected from the mic jack.
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Ok, I measured the following:
Tip to sleeve (black at sleeve) .939Kohm
Sleeve to tip (black at tip) .793Kohm
Ring doesn't appear to have any connections to either tip or sleeve (OL).
Here are some pictures of the circuit board. For reference, those are 24AWG wires.
I really appreciate the help on this.
I have to ask, am I better off grabbing something like this:
In Ear Back Electric Microphone - Portable Omnidirectional Wired Headset Pro Voice Audio Condenser Mic with 4 Pin Mini XLR Cable Wire and Windscreen - For Shure System - Pyle Pro PMEMS10 (Skin Tone) https://www.amazon.com/dp/B003D2YRLA/ref=cm_sw_r_apan_glt_fabc_VBBVKSS0F95CFWCCV8MF
And wiring up a ta4m for the preamp?
Tip to sleeve (black at sleeve) .939Kohm
Sleeve to tip (black at tip) .793Kohm
Ring doesn't appear to have any connections to either tip or sleeve (OL).
Here are some pictures of the circuit board. For reference, those are 24AWG wires.
I really appreciate the help on this.
I have to ask, am I better off grabbing something like this:
In Ear Back Electric Microphone - Portable Omnidirectional Wired Headset Pro Voice Audio Condenser Mic with 4 Pin Mini XLR Cable Wire and Windscreen - For Shure System - Pyle Pro PMEMS10 (Skin Tone) https://www.amazon.com/dp/B003D2YRLA/ref=cm_sw_r_apan_glt_fabc_VBBVKSS0F95CFWCCV8MF
And wiring up a ta4m for the preamp?
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Other things that I realized need attention, is that I have 5 knobs for the pots that need making.
So I glued up this test board and I plan on cutting out the knobs with my drill press and hole saw drill bits, and then 'turning' them on my drill press for sanding and finishing. My plan is to cut a table saw kerf in each of the knobs and insert a vertical fillet of purpleheart as an indicator.
Never made knobs before. This should be fun!
So I glued up this test board and I plan on cutting out the knobs with my drill press and hole saw drill bits, and then 'turning' them on my drill press for sanding and finishing. My plan is to cut a table saw kerf in each of the knobs and insert a vertical fillet of purpleheart as an indicator.
Never made knobs before. This should be fun!
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OP, how about taking your electronics problem to the electronics forum? Not to talk down the knowledgeable folks in this thread, but there might be someone who has just the solution for you. Not everyone frequents the EUB section, you know.
