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THAT Driver :: A minimalistic differential driver / preamp with 0.000021 % THD

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#41
tomchr said:
Sure. I released the THAT Receiver circuits yesterday. 🙂
More information available here: THAT Receiver – Rev. 1.0.

THAT Receiver -> Volume Control -> THAT Driver would be a complete differential in, differential out preamp.

Tom
Click to expand...


Thanks.

I have been reading up a lot more and I am really impressed with your PCB design and layout of parts.

Just an aside-the documentation of the 1606 indicates that pin #6 can be used as a separate -In since the ground pin #5 is not internally shorted like in the 1646; so would that not permit the use of the 1606 in a driver that would also allow a differential input which could be fed from a volume control after suitable buffering?

Nash
 
#43
Do the pcb-mount XLR outputs on the THAT Line driver need to be connected to PE through the chassis, or can they be isolated?

Here's a picture of my build www.diyaudio.com/forums/digital-line-level/283319-dac-preamp.html#post4535959. It sounds really good I think, but I wonder if I don't even know what I may be missing. My uneducated guess is that the THAT Driver gets its ground from the Power86 board the way I have this set up.
 
#45
Hi Tom,

These boards look like a very nice implementation of the THAT ICs. I have used them on several commercial projects for years and they always perform very well. And the photos of your boards are very good looking.

However I do need to point out that the way you specify output noise floor (-152dBV) is completely meaningless. When taking the FFT of a noise signal which is predominantly white, a doubling of the FFT size will lower the spectrum by 3dB. So you can essentially get the spectrum of any white-noise signal as low as you want by just increasing the FFT size to something very large.

Since you have an APx you have a much better way of measuring noise (and/or SNR) in your circuit, either by measuring the amplitude of the output with inputs shorted to ground, or use APx SNR measurement directly. Could you post those measurements as well? We might learn something from it.

Br,
OJG
 
#46
tomchr said:
For safety the (metal) chassis and all exposed metal bits that protrude through the chassis should be grounded to protective earth. That's the case with any circuit that connects to the mains.

Tom
Click to expand...

Oh duh,.. I guess I knew that, silly me.

I do have all the metal parts inside the box connected to protective earth. I guess for some reason I thought that things like audio connections protruding through to the outside of the box were the exception. I see so many panel mount RCA jacks come with an isolating plastic ring for example.

Anywho, this probably isn't the right thread for such discussion, and I know it's talked about to nausia in other threads. I'll go ahead and simply earth them for safety. 🙂. There's a little metal strip on the neutrik connector, and it looks like it could be clipped to isolate the housing of the corrector from the board. It sounds like this isn't necessary, or you would have mentioned it in instructions.

As always Tom, thanks for your undying support. It's among the best in the world! (I should know, I teach Support and Service among other topics at an accredited college)

AlexQS
 
#52
CBS240 said:
Volume can easily be controlled by a THAT_2162 using only a single pot......or any other way to control a DC signal such as a PWM + low pass filter or something like that. No need for ganged pots.🙂
Click to expand...

The THAT2181 would be my choice, actually. I'd probably control the gain with a motorized pot, just because I like being old-fashioned. A DAC would be another option.

Tom
 
#54
ojg said:
However I do need to point out that the way you specify output noise floor (-152dBV) is completely meaningless. When taking the FFT of a noise signal which is predominantly white, a doubling of the FFT size will lower the spectrum by 3dB. So you can essentially get the spectrum of any white-noise signal as low as you want by just increasing the FFT size to something very large.

Since you have an APx you have a much better way of measuring noise (and/or SNR) in your circuit, either by measuring the amplitude of the output with inputs shorted to ground, or use APx SNR measurement directly. Could you post those measurements as well? We might learn something from it.
Click to expand...

No comment on this, Tom?
 
#57
The fact that SE connections used in consumer equipment are there just because it is cheeper than balanced, tells you enough. Balanced is a way to go, although for sure is pain that everything is doubled. When multi channeled than one really feels the pain 🙂 Great project.

Tom, I just discovered your web site and downloaded your math scripts to control HP instruments. There are not that many users of HP3562, and even less of software for it. It is a real treasure find, thank you. I see you are now on AP, I am as well (only Sys 1), but that HP3562 is still awesome for audio. I really love it. I use NI HPIB to USB controller. I hope it will be not to hard to adjust from scripts you made for Pro Logic controller. My AP 2322 supports only FFT measurements up to 22KHz, where HP goes up to 100KHz.
 
#60
Try taking the top off the case and hitting the reset button sticking up on the CPU board after getting the message. It might perk up; then again, maybe not. All parts are DIP packages so you might be able to find some RAM to replace.
 
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