THAT line & mic output stage

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carlmart
Posts: 169
Joined: Mon May 19, 2014 6:11 am

THAT line & mic output stage

Post by carlmart »

I am trying to implement a line and mic option we had used, with success, on an SSM2142 based output, but this time using a THAT 1606.

Has anyone tried anything similar to this on the THAT output balanced chips? I've already asked THAT support, but your comments are very welcome.

As you can see, I'm going into the 1606 through In-, instead of In+. That is because the previous stage is a 10x inverting one, so phase should be corrected by doing this.

The output 47uF bipolar caps were recommended to me by THAT, even if I would like to lower them down to 22uF.

What I'm not sure is if C1 is necessary, as the previous stage should have an output capacitor before entering the pot.

The pot value is also something I asked THAT about, even if for the 1606's 5K impedance a 10K log type should do.
Attachments
THAT line-mic output.png
THAT line-mic output.png (169.19 KiB) Viewed 16274 times
Speedskater
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Joined: Mon Jun 02, 2014 8:14 am
Location: Cleveland, Ohio, USA
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Re: THAT line & mic output stage

Post by Speedskater »

That must be an old drawing, as it has the XLR pin1 connected to the audio circuit common (ground) rather than the correct connection to the chassis (shield).
Kevin
ricardo
Posts: 262
Joined: Sun Apr 10, 2011 7:24 am

Re: THAT line & mic output stage

Post by ricardo »

If you want 1606's good performance, you can't feed it from a pot. See datasheet.

You can't have C2/3 where they are. They (and the switch) have to be on the other side of the diode bridge. Presently, they shove loadsa DC onto whatever you feed. There are probably other caveats.
carlmart
Posts: 169
Joined: Mon May 19, 2014 6:11 am

Re: THAT line & mic output stage

Post by carlmart »

The "Black" ground is the battery/chassis ground, the "orange" ground is the Vcc/2 ground. I don;t know if that's what you mean. There should be one place where battery ground and chassis ground will meet, as a star type ground.

You're right about the pot, Ricardo, and THAT warned me about that too. I will be feeding the 1606 from an inverting 10x gain stage right after the limiter.

The pot will be before the limiter or maybe inside the limiter itself, as THAT is suggesting me to do. There should be just one pot to handle the preamp levels.

THAT's support has seen this output, and they did warn me about the input pot and advised me to change the 49K9 resistors for 10K ones, which I already did on my schematic. No comment about C2 and C3 or switch being a problem before the diode bridge, but I will ask them. In any case thanks for warning.

In fact that is how they are used at the 1510 input.
ricardo
Posts: 262
Joined: Sun Apr 10, 2011 7:24 am

Re: THAT line & mic output stage

Post by ricardo »

carlmart wrote:THAT's support has seen this output, and they did warn me about the input pot and advised me to change the 49K9 resistors for 10K ones, which I already did on my schematic. No comment about C2 and C3 or switch being a problem before the diode bridge, but I will ask them. In any case thanks for warning.

In fact that is how they are used at the 1510 input.
One is an INPUT, the other an OUTPUT.

Why don't you knock up a simple 12V amplifier with diodes to 12V & GND and see for yourself? Put some signal through & measure DC on the output with the diodes in the 2 different positions.
carlmart
Posts: 169
Joined: Mon May 19, 2014 6:11 am

Re: THAT line & mic output stage

Post by carlmart »

What is the difference between my diode arrangement and the one in the 1606 data sheet? Let's forget about the caps and switch.
Attachments
1606 output.jpg
1606 output.jpg (88.04 KiB) Viewed 16238 times
ricardo
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Joined: Sun Apr 10, 2011 7:24 am

Re: THAT line & mic output stage

Post by ricardo »

carlmart wrote:What is the difference between my diode arrangement and the one in the 1606 data sheet? Let's forget about the caps and switch.
Yours is a single 12V supply circuit with caps in the wrong place.

The DC is introduced by your caps in the wrong place so we can't forget them. The diodes protect the 1606/1510 from, among other stuff, the effects of the capacitors. That's why they need to be on the 1606/1510 side.

Study "The Phantom Menace" and subsequent papers by THAT & others.

Why don't you build your circuit and see for yourself?
carlmart
Posts: 169
Joined: Mon May 19, 2014 6:11 am

Re: THAT line & mic output stage

Post by carlmart »

But I already said I WILL move the diodes right after the 1606, closer to the chip output pins and before the caps and switch.

That's why I had said it was similar to the 1510, where the protection diodes are after input caps and series diodes, closer to the input pins.

But I think you imply that even so it will not work, and I would like to know why BEFORE I build anything. Neither do I have the parts yet to do so.

So again, if I move the diodes before th capacitors will things be fine or not, with the 1606 protected as it should, or not? If not, why?
ricardo
Posts: 262
Joined: Sun Apr 10, 2011 7:24 am

Re: THAT line & mic output stage

Post by ricardo »

I'm not implying anything. Read my posts carefully and also the datasheets.

If you want good advice on circuit changes, show EXACT circuits .. instead of implying changes to circuits you may or may not have modified.

I also recommend you build stuff as early as possible. You'll learn a lot more than mincing words.
carlmart
Posts: 169
Joined: Mon May 19, 2014 6:11 am

Re: THAT line & mic output stage

Post by carlmart »

Point taken. This is the circuit with mods applied: diodes moved back before the caps and pot taken away.
Attachments
THAT line-mic output.jpg
THAT line-mic output.jpg (99.74 KiB) Viewed 16225 times
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