Keyboard Shortcuts
ctrl + shift + ? :
Show all keyboard shortcuts
ctrl + g :
Navigate to a group
ctrl + shift + f :
Find
ctrl + / :
Quick actions
esc to dismiss
Likes
- MicBuilders
- Messages
Search
|
Re: Switchable patterns in Dual OPA Alice with dual capsule
#°Õ¸é±«·¡°ä°¿±·¶Ù·¡±·³§·¡¸é¡±²Ñ±õ°ä¸é°¿±Ê±á°¿±··¡³§
#dualopaalice
toggle quoted message
Show quoted text
On May 15, 2022, at 11:02, Arjay 1949 <info@...> wrote:
|
|
Re: Switchable patterns in Dual OPA Alice with dual capsule
#°Õ¸é±«·¡°ä°¿±·¶Ù·¡±·³§·¡¸é¡±²Ñ±õ°ä¸é°¿±Ê±á°¿±··¡³§
#dualopaalice
Using Jerry's idea in post #3 of using 3 op-amps, I've added a 'multi pattern' version to my collection of OPIC project mics here:
Seems to perform really quite well for such a simple variation..... |
|
Re: How to test if dual condenser capsule is working?
toggle quoted message
Show quoted text
On May 11, 2022, at 09:58, tedsorvino via groups.io <tedsorvino@...> wrote:
|
|
Re: How to test if dual condenser capsule is working?
All good. As I said before no issue with the voltage (constant 64v occasionally -50mv). Mainly housing issue. I mean very tight space for all components and interconnections. I reflowed some solder around the 1gohm and the Opa legs and all good. I put things back while I was auditioning? it loudly through headphones (I know it can be dangerous for a lot of reasons - but I 've done it before with other builds). The issue was mainly the interconnection cable of bias that was touching somewhere, and something around the xlr base (I guess all the trial - error with heat on the cheapo components of BM 800 mic body don't help a lot). Covered the exposed things, put things back carefully while listening. No external noise. Really really quiet built. Good signal to noise ratio for my liking. A bit darker sounding mic, compared to my usual ADK Vienna and also compared to the OPA based electret build.
I think it will be an ongoing project, since I have some more boards and there is another capsule side that asks to be used (and a personal ambition for a 3 mode DIY mic). But I guess I will allow myself some time with the cardioid part just to familiarize myself with the characteristics and the potential issues that may arise on these 2 newly built mics. Thanks Jules for the excellent design and Jerry Lee for the advice and help while things were not clear. |
|
Re: How to test if dual condenser capsule is working?
¿ªÔÆÌåÓýAlso ensure you clean the PCB well especially around the 1gig?Best Regards, Jules Ryckebusch? On May 11, 2022, at 08:10, tedsorvino via groups.io <tedsorvino@...> wrote:
|
|
Re: How to test if dual condenser capsule is working?
I assume that you are constantly measuring it? Hi Jules. I mean I was measuring the supply on its own for quite a long time several times before using it on the mic. Because it was built last (after an accident on the previous one). I will follow your guidelines carefully (most of my voltage are correct - haven't? measured around the 1gohm yet), And the SMDs can be a little bit frastruting on what is considered a good or bad solder without microscopic inspection....It's good to know that such problems have sn easy(???) fix. ? |
|
Re: How to test if dual condenser capsule is working?
Please look at this. You have something?touching possibly. I write this based on my own feedback (I have misconnected almost anything that can be hahaha) And from users I have helped to get this going. When you say the sound squeaks and then starts to come and go AND that you have a constant 65V I assume that you are constantly measuring it? The symptoms you describe sound like the voltage supply at the OPA dropping and then returning. Typically that is when something?touches intermittently. Jules? On Wed, May 11, 2022 at 2:16 AM tedsorvino via <tedsorvino=[email protected]> wrote: As I said I would get back with updates. I insulated both pcbs (bias- high impedance) using tape around them and I cover all the inside of the mic body with copper tape. Good signal and healthy signal? initially with phantom. No noise.??All my testing setup is good with any other mic.? --
Best Regards, Jules Ryckebusch 214 399 0931 |
|
Re: How to test if dual condenser capsule is working?
As I said I would get back with updates. I insulated both pcbs (bias- high impedance) using tape around them and I cover all the inside of the mic body with copper tape. Good signal and healthy signal? initially with phantom. No noise.??All my testing setup is good with any other mic.?
But.... after a couple of minutes (on a shockmount) a "squeeking" pitch raising sound starts and then the sound starts coming and going. Can't blame the OPA IC? since with the simple electret it works really well - same pcb . And the capsule seems like it's working, since initially is functioning absolutelly properly. Maybe a problem with any of the larger electrolytic caps on the high impedance pcb or the 2 small 20nf around the xlr pin 2-3?(for noise reduction)? or maybe the 1gohm resistor (which could be sensitive since its value is huge)? I can't blame the bias pcb since it's providing constant 65V. |
|
Re: How to test if dual condenser capsule is working?
¿ªÔÆÌåÓý
Le 10/05/2022 ¨¤ 10:51, tedsorvino via
groups.io a ¨¦crit?:
It should be OK as long as the unconnected wire is properly dressed as not to pick up interference.As I suspected from the start, I believe your capsules are good and the problems you had are elsewhere. Does it matter if I connect the center of the capsule on the bias pcb and the backplate on the high impedance one or vice versa? Does it affect the microphone output?Well, it does matter, since the stray capacitance of the backplate is higher than that of the center termination, so the output level and distortion may suffer a little. In addition, applying bias to the backplate makes it attract dust instead of the diaphragm. |
|
Re: How to test if dual condenser capsule is working?
As I suspected from the start, I believe your capsules are good and the problems you had are elsewhere. Thanks Jerry. To start with while I was reducing cabling length I shorted either the bias IC or a cap - diode around it. When I sort that out I will try all the meters you suggested. Just a couple of quick questions Is it ok to leave one side of the dual capsule disconnected with it's lead on? Is it a possible cause of interference and lack of signal sensitivity? Does it matter if I connect the center of the capsule on the bias pcb and the backplate on the high impedance one or vice versa? Does it affect the microphone output? |
|
Re: How to test if dual condenser capsule is working?
¿ªÔÆÌåÓý
Le 10/05/2022 ¨¤ 10:02, tedsorvino via
groups.io a ¨¦crit?:
As I suspected from the start, I believe your capsules are good and the problems you had are elsewhere.You can start with checking with the mulimeter that the capsules are not shortedWithout being sure I just used the continuity mode on my DMM. No continuity between capsules and between capsules and backplate (common backplate cable). |
|
Re: How to test if dual condenser capsule is working?
¿ªÔÆÌåÓý
Le 10/05/2022 ¨¤ 09:54, tedsorvino via
groups.io a ¨¦crit?:
No. It can be separate.I would try to make a PCB that holds all the high impedance circuits for two capsules, and put the rest, included the bias generators on a separate PCB.Thanks Jerry. Is it necessary the bias PCBs being in the same enclosure with the high impedance circuits? Copper foil is OK. |
|
Re: How to test if dual condenser capsule is working?
I would try to make a PCB that holds all the high impedance circuits for two capsules, and put the rest, included the bias generators on a separate PCB.Thanks Jerry. Is it necessary the bias PCBs being in the same enclosure with the high impedance circuits?? As I wrote earlier, using shielded wire is not adequate. You have to make sure that all the high impedance circuitry is in a shielded enclosure, which must also be acoustically transparent, such as mesh.True. Sorry for that. I read it later. The capsule is in a mesh - the normal faraday BM 800 microphone top . Can I use copper foil around? the mic enclosure on the inside - like I'm using on my guitars- to reduce EMI noise, or does it affect sensitivity? |
|
Re: How to test if dual condenser capsule is working?
Le 09/05/2022 ¨¤ 19:51, tedsorvino via groups.io a ¨¦crit?: Thanks Jerrt Lee Marcel. Head is the circuitry that receives the capsule and transforms the very high impedance into a more manageable impedance. Is there shielded wire of such small gauge (or could I create one by "knitting" 2 wires)? As I wrote earlier, using shielded wire is not adequate. You have to make sure that all the high impedance circuitry is in a shielded enclosure, which must also be acoustically transparent, such as mesh. In my case what would you do to achieve my goal?I would try to make a PCB that holds all the high impedance circuits for two capsules, and put the rest, included the bias generators on a separate PCB. |
|
Re: How to test...
¿ªÔÆÌåÓý
Thanks Jerrt Lee Marcel. Head is the circuitry that receives the capsule and transforms the very high impedance into a more manageable impedance. Is there shielded wire of such small gauge (or could I create one by "knitting" 2 wires)? As I wrote earlier, using shielded wire is not adequate. You have to make sure that all the high impedance circuitry is in a shielded enclosure, which must also be acoustically transparent, such as mesh. In my case what would you do to achieve my goal?I would try to make a PCB that holds all the high impedance circuits for two capsules, and put the rest, included the bias generators on a separate PCB. |
|
Re: How to test if dual condenser capsule is working?
¿ªÔÆÌåÓý
Le 09/05/2022 ¨¤ 19:52, tedsorvino via
groups.io a ¨¦crit?:
Could you please be more specific? How can I do that with a simple multimeter and a small variable DC supply up to 50V? Thanks.You can start with checking with the mulimeter that the capsules are not shorted. |
|
Re: How to test if dual condenser capsule is working?
Thanks Jerrt Lee Marcel.
That's a really good advice. By head I guess you mean the pcb outs (signal and voltage polarity). Am I correct? Is there shielded wire of such small gauge (or could I create one by "knitting" 2 wires)? In my case what would you do to achieve my goal? I mean it's highly improbable to find a donor body capable to host all 4 pcbs. Even 3 of them (and forget about fig. 8. |
|
Re: Pat's Mic (Fetzer Valve Mic)
¿ªÔÆÌåÓýHi Homero,The signal level into the FET is one of the things that will need to be tuned, depending on the capsule output, the use of the mic, what acoustic levels it operates at, and how much distortion and compression you want out of it. Think of a guitar amplifier or sustain pedal. The harder you hit the FET, the more color it will introduce, and that is a matter of personal taste. Old tube mics were not intended to distort. They were designed as linear and clean as possible, but engineers found that a rock singer screaming into a mic at 3 inches sounded much louder than the actual level on disk, as the tube was pushed slightly into clipping. 400mV is a reasonable level for 0.5% 2nd harmonic with a LDC. It should sound like a good tube mic. If it is too clean, then you can experiment. Large capsules I have measured are more than 56pF, around 80pF out of circuit, and just over 100pF in circuit with 60V bias. As for sensitivity, feeding a transformer-less charge amp with a 100pF dummy capsule: Gain vs feedback cap, no cap = 0dB;? 10pF = -3.4dB; 25pF = -5.9dB; 48pF = -8.7dB; 68pF = -10.7dB; 115pF = -13.4dB. @100mV RMS (280mV p/p) out w/10pF, 2nd harmonic = 0.5%; @ 10mV out, 2nd = 0.05% It will be interesting to see if P@t¡¯s mic measures similarly to mine, which is like a KM-84 with a Schoeps PNP output stage instead of a transformer. I have no idea how much of the distortion in my mic is due to the charge amp and how much is FET since the FET is also the charge amp. Your mic has the two circuits separate, so you can experiment if you want. Bypass the FET and see how different ratios of feedback work. Try different bias points and load resistors on the FET while keeping the input stage fixed. Try different FETs.? Or just find something which sounds good and go with it. I¡¯d build one if I didn¡¯t have 3 or 4 circuits ahead of it to try out. Regards, Henry
|
to navigate to use esc to dismiss