Turnstile Audio TAC700 schematic

[DFischer]

I've previously posted a schematic on the Turnstile Audio TAC1100 mic in THIS thread. Out of curiosity, I also bought a pair of Turnstile TAC700 mics and decided to do the same. Being a cheap transformerless mic, I was expecting it might use a Schoeps circuit, but it appears to be an impedance balanced output instead. Here's what I have so far. Any comments are welcome. I'm learning a lot by doing this, and hopefully the schematics are useful to somebody.

 

[DFischer]

A couple of questions:

1. The circuit looks flat to my inexperienced eyes. Am I correct?
2. I tried to figure out what kind of oscillator was used so that I could draw Q1 more accurately. The two inductors made me think it might be a Hartley oscillator, but that doesn't seem to fit. I noticed it was almost identical to the one used in Studio Projects C1. However, the output to the voltage quadrupler is taken at a different node. Would this still be correct? What is this oscillator circuit called?

C1 Oscillator


TAC700 oscillator???

 

[Khron]

The circuit looks flat to my inexperienced eyes. Am I correct?

If by "flat" you mean "with no high-frequency attenuation", then yeah, it's flat.

I'm still not 1000000% convinced about the accuracy of that schematic, though...

 

[micolas]

@DFischer
Check carefully if you have drawn the diagram correctly.

 

[DFischer]

@DFischer
Check carefully if you have drawn the diagram correctly.

Will do, thanks!

 

[micolas]

@DFischer
About DC/DC converter:
You can collect and rectify/multiply the high frequency voltage produced by the oscillator, either against GND or against U+.

 

[RuudNL]

I suppose in the C1 schematic C12 is connected to the 'left' side of L2, not to the base of the transistor.

 

[Voyager10]

The circuit around R9/R10/R11 would be easier to read if it were redrawn to show 'pin 4' as the positive supply rail (at the top, therefore). R10/R11 are then a simple voltage divider which biases the JFET gate to half the supply voltage via R9. Q2 is a simple source follower, with the drain going straight to the +ve supply.

It might also help to redraw the pattern-select switch, to use ground instead of 'pin 1' (the same thing, just confusing).

The unusual thing about this circuit is putting the pad after the JFET stage, so if that stage is overloading, the pad won't do anything to help.

 

[micolas]

The circuit around R9/R10/R11 would be easier to read if it were redrawn to show 'pin 4' as the positive supply rail (at the top, therefore). R10/R11 are then a simple voltage divider which biases the JFET gate to half the supply voltage via R9. Q2 is a simple source follower, with the drain going straight to the +ve supply.

It might also help to redraw the pattern-select switch, to use ground instead of 'pin 1' (the same thing, just confusing).

The unusual thing about this circuit is putting the pad after the JFET stage, so if that stage is overloading, the pad won't do anything to help.

A scheme must be drawn in such a way that it has an electronic, functional logic, as simple as possible.

 

[pderbidge]

Does anyone know what governs the low end in this type of circuit/schematic?

 

[Khron]

Does anyone know what governs the low end in this type of circuit/schematic?

C12 & C13

 

[pderbidge]

C12 & C13

Thanks!

Here is a pic of the capsule. Is this another 797??? For $40, seems like a cheap way to get one of these capsules.

 

[pderbidge]

Here's the top circuit board front and back

and Bottom board front and back

 

[pderbidge]

Thanks!

Here is a pic of the capsule. Is this another 797??? For $40, seems like a cheap way to get one of these capsules.

View attachment 144796

Actually, it looks like these capsules have come down in price recently.
https://www.alibaba.com/product-det...Centering-Single-Condenser_1600960691375.html

Edit: Looking online, most are still selling this capsule for $50 to $70

 

[micolas]

Thanks!

Here is a pic of the capsule. Is this another 797??? For $40, seems like a cheap way to get one of these capsules.

View attachment 144796

Yes it looks like 797

 

[micolas]

Hi @157audio !
You personally purchased Turnstile TAC microphones from the Adorama store in NYC.
Did you also notice the Turnstile TAC300 microphone, do you know if it has a small, electret capsule?
https://www.adorama.com/tac300.html

 

[micolas]

@pderbidge
It seems that it is also sold at:
https://www.walmart.com/ip/Concourse-Series-TAC700-Multi-Pattern-Condenser-Microphone/1517985613

 

[157audio]

Hi @157audio !
You personally purchased Turnstile TAC microphones from the Adorama store in NYC.
Did you also notice the Turnstile TAC300 microphone, do you know if it has a small, electret capsule?
https://www.adorama.com/tac300.html

Sorry for the late reply, I just saw your question. I havent looked at the 300, but I just looked at the site and when I zoomed in, you can see the holes that you’d see on an electret.

The tac700 is back at $40 last I checked. My neighbor who did the voiceover tests has my second tac700 right now, so I may need to get another!

I put the flat k47 in the other 700 I have but I’m going to put it in the unmodded 1100 this week so I have a matching pair. I just got asked to record a piano trio next week (hoping it gets confirmed because they are amazing!) and I would like to use the 1100’s on piano.

 

[micolas]

Sorry for the late reply, I just saw your question. I havent looked at the 300, but I just looked at the site and when I zoomed in, you can see the holes that you’d see on an electret.

The tac700 is back at $40 last I checked. My neighbor who did the voiceover tests has my second tac700 right now, so I may need to geThnakt another!

I put the flat k47 in the other 700 I have but I’m going to put it in the unmodded 1100 this week so I have a matching pair. I just got asked to record a piano trio next week (hoping it gets confirmed because they are amazing!) and I would like to use the 1100’s on piano.

Excellent! Good luck with DIY and music!
Thanks for infos