Le 09/05/2022 à 14:37, tedsorvino via groups.io a écrit?:

For "real estate purposes" I'm using an external box for the pcbs and then leads to the mic and leads to the xlr of the pre amp.

Wires between capsule and head must be kept as short as possible and must be shielded for proper operation.

However shielded cable is improper since it adds parasitic capacitance that reduces sensitivity.

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As a simple first test, measure its capacitance?

-Scott

Hi.
My question is this simple one.
Is there any easy test to make sure that a dual side true condencer capsule is not burnt or shorted or faulty without using it on a mic. No data available. Cheaper- about 30 euros- Ali Express capsule.
Thank you in advance.

Here's my longer story .After experimenting a bit on electret with success using the OPA alice design (all OPA 1642 bought from Ali Express because of the know shortage from known retailers - good results). Used larger Electret capsule bought from Ali Express for 15euros, All good so far with that simple built.
Then I experimented a bit with the Hex Inverter DC - DC CMOS design and I managed to build 2 boards, One providing 65VDC and another one - 65VDC.
So now I 've decided to use a dual side true condenser capsule I've also bought from Ali Express for 30 euros for a more ambitious built,
I'm using 4 pcbs. 2 different single OPA ones for the signal (didn't have dual OPA pcbs around), and two Voltage ones for + and - polarity. For "real estate purposes" I'm using an external box for the pcbs and then leads to the mic and leads to the xlr of the pre amp.
My initial testing with it?(just cardioid, then just omni, then just fig. 8),? was quite all right. All out of the box, really noisy there is signal and appropriate behaviour in accordance to each mode, but it seems to have really low signal and after trying to change the lead and positions and using the box, with some grounding issues, I lost signal alltogether.
Firstly I'm afraid of having burnt or shorted something on the capsule and then I would like to know if this capsule is all right and whatever problem occurs hasn't got to do with it.

That's all.

-- 
---- Scott Helmke ---- scott@... ---- (734) 604-9340 ----
"I have ceased distinguishing between the religious and the secular,
for everything is holy"  - Joe Henry

Hi.
My question is this simple one.
Is there any easy test to make sure that a dual side true condencer capsule is not burnt or shorted or faulty without using it on a mic. No data available. Cheaper- about 30 euros- Ali Express capsule.
Thank you in advance.

Here's my longer story .After experimenting a bit on electret with success using the OPA alice design (all OPA 1642 bought from Ali Express because of the know shortage from known retailers - good results). Used larger Electret capsule bought from Ali Express for 15euros, All good so far with that simple built.
Then I experimented a bit with the Hex Inverter DC - DC CMOS design and I managed to build 2 boards, One providing 65VDC and another one - 65VDC.
So now I 've decided to use a dual side true condenser capsule I've also bought from Ali Express for 30 euros for a more ambitious built,
I'm using 4 pcbs. 2 different single OPA ones for the signal (didn't have dual OPA pcbs around), and two Voltage ones for + and - polarity. For "real estate purposes" I'm using an external box for the pcbs and then leads to the mic and leads to the xlr of the pre amp.
My initial testing with it?(just cardioid, then just omni, then just fig. 8),? was quite all right. All out of the box, really noisy there is signal and appropriate behaviour in accordance to each mode, but it seems to have really low signal and after trying to change the lead and positions and using the box, with some grounding issues, I lost signal alltogether.
Firstly I'm afraid of having burnt or shorted something on the capsule and then I would like to know if this capsule is all right and whatever problem occurs hasn't got to do with it.

That's all.

Triton Audio (Fethead etc) and also based in the Netherlands have been marketing a True Phantom phantom power supply for some time:

https://www.tritonaudio.com/true-phantom

Jerry Lee Marcel,

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I agree with all that's been written before.
It's a very interesting intellectual challenge though. Brilliant piece of design.
The claimed benefits are at least of second order.

The test circuit they use to demonstrate performance is typical of the first transformerless preamps of the early 70's.
The typical circuits used today, even in cheap products are way better than this crude one.
Mating their chip with this outdated circuit does not make any sense.

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In the light of chip shortages I would be really hesitant to add to the BOM of a product for marginal benefits. ?They are optimizing something that is really in the weeds here. ?

--

What is the signal level (either input or output)? Distortion in a common-source JFET or triode is normally very sensitive to level. The 2nd harmonic at 46dB roughly (0.5%) below the 1KHz signal and 3rd harmonic roughly 30dB lower looks like a pretty good tube or JFET as it approaches saturation. This should sound pleasant. I would expect distortion to drop significantly at lower levels, and 3rd harmonic to rise rapidly above this level.

The OPA Alice is remarkably clean, as expected. (Yay Jules!)

A K596 or other JFET with diode input has additional distortion mechanisms which make it unsuited for this circuit. It will have too much 3rd harmonic. It is possible to get similar percentages of distortion using different circuitry, though. Whether it sounds like a triode is a matter of opinion. Some will maintain you need a real vacuum state amplifier and transformer for a true triode sound. Which triode? Any tube guy will tell you they sound different. Others will say as long as the harmonic structure is the same, it makes no difference what's inside the mic. Build 'em and see if you can hear the difference. If I take 2 of my mics with the same capsules and transistors, one with a clean Schoeps circuit, and one with a Transformer-Less Charge amp which has around 0.5% 2nd harmonic, they sound ALMOST identical. The Schoeps will have more fine inner detail. The TL/C will have more "body" or "richness" or "warmth". Without doing an A-B comparison though, I wouldn't hear enough difference to choose one over the other.

Hi!

Just uploaded two THD Graphs, one for a Pat's Mic build and the other one for an OPA Alice build.

I tried to use the same Input levels on both tests.

Here are the graphs:
?
Pat's Mic Build :?/g/MicBuilders/files/Homero%20Leal%27s%20Files/Pat%27s%20Mic/PatsMicTHD.png

OPAAlice Build:?/g/MicBuilders/files/Homero%20Leal%27s%20Files/Pat%27s%20Mic/OpaAliceTHD.png

By the way, THD for the OPA Alice build is amazingly low.? :O

On the Pat's Mic Build you can see some 2nd and 3rd harmonics.

What do you think?

Regards!

HL

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Jerry - Thank you for the input.? My train of thought was that a Jfet Op Amps may be used to replace the discrete Jfet in the triode mode.? My understanding is that Jfet Op Amps essentially have multiple Jfets?structures on one IC.? Is it not possible to use them in this way???

It is quite possible, but, as I wrote earlier, it wouldn't result in the "tube sound" the dicrete JFET is supposed to bring.

An additional RC filter would work, or simply adding a resistor between the BC549 and C14, and increasing C14 to push the RC time constant below audibility. The op-amps have good power supply noise rejection, but the FET has none. It needs pure DC.

The advantage of the zener plus transistor style VR in China mics is operation at low voltage, like 3V PIP for use with PC sound cards. The disadvantage is it's noisy.

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Could the JFET and/or the transistor be replaced by using a Quad JFET Opa?? An example would be the?OPA1644 (quad).

In terms of functionalities, it would certainly work.

However, the subject here is getting the circuit to sound like a vacuum tube. An opamp could not do that.

? Not sure if there are?triple Op Amps but could that be something too?

No. only singles, duals and quads.

However a combination of a dual with a single? or three singles could be functional.

A quad would probably exceed the available current.

I like minimizing parts when I can.

(Almost) Everybody does.
But minimalism is not a proper design endeavour. It takes what it takes to make the thing work.

On Friday, April 29, 2022, 06:25:18 AM PDT, goldenhours_71 <davidstalling@...> wrote:

Here is a great implementation of Wurcer's chargeamp by forum member Zapnspark: /g/MicBuilders/files/Zapnspark/Occam-3b.pdf