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THAT Driver :: A minimalistic differential driver / preamp with 0.000021 % THD
THAT Driver :: A minimalistic differential driver / preamp with 0.000021 % THD
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Old 5th November 2015, 04:58 AM   #21
tomchr is offline tomchr  Canada
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Quote:
Originally Posted by hazard500 View Post
So, if you are balanced at the source and balanced at the output, why would you want to go single-ended in between?
Many (most?) commercially available sources have a single-ended output. Some high-end units offer differential out. The advantages of differential signalling are pretty clear. The THAT Driver makes it possible to retrofit a differential output to an existing source - or add a differential output to your circuit.

The only reason I can think of for using single-ended signalling is within preamp or cross-over filtering unit. You can design differential filters, volume control, etc. but it's much easier with single-ended. Within the enclosure, you have full control over ground and signal routes, hence, can design for high signal integrity.

Tom
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Old 5th November 2015, 06:54 AM   #22
Pano is offline Pano  United States
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THAT Driver :: A minimalistic differential driver / preamp with 0.000021 % THD
Quote:
Originally Posted by hazard500 View Post
Well just about every cartridge is a balanced device.
How many balanced phono preamps do you own?
Quote:
And most DACs are balanced output.
Yes, and mine has 1/4" balanced outputs. That's nice. Also RCA.
Quote:
And most solid state power amps are push pull output, which functionally is the same as a valve balanced push pull output, except that complementary s-s devices let you do single ended push pull.
OK, but how many home amps have balanced inputs? The only one I have at home with balanced inputs is an old Crest pro amp.

Quote:
So, if you are balanced at the source and balanced at the output, why would you want to go single-ended in between?
You wouldn't, but that's not the point. Very few consumer devices have balanced ins and outs. Not many DIY, either, looking around here.
Don't get me wrong, I like balanced signal runs. I'm just curious how many home systems can actually use them. What is the target audience for a driver like this?
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Old 6th November 2015, 02:28 AM   #23
tomchr is offline tomchr  Canada
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Quote:
Originally Posted by Pano View Post
What is the target audience for a driver like this?
People who want to use differential signalling between their preamp and power amp, for example. If their preamp doesn't have differential out, they can add the THAT Driver.

I had customer requests for such a circuit so I figured I'd address the market need.

Tom
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Old 14th November 2015, 09:21 PM   #24
AlexQS is offline AlexQS  United States
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My Power86 board went together perfectly. Excellent instructions.

I'm going to be populating the THAT Line Driver boards, but I won't have amplifier with XLR input until I build the Mod86 next month.

Is there any problem with temporarily running the THAT Driver with a Pseudo-Differential Cable to an amp with a single-ended input? I just want to make sure that shorting pin 1 & 3 won't harm the THAT Driver.

I ask because I think the intent of the cable was to go from a single ended source to an amplifier with XLR inputs. In my case I'd be running the cable backwards, putting the RCA on the male end of the cable.
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Old 14th November 2015, 10:18 PM   #25
cbdb is offline cbdb  Canada
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Originally Posted by hazard500 View Post
So, if you are balanced at the source and balanced at the output, why would you want to go single-ended in between?
Because inside every device the signal is unbalanced. So balancing adds complexity and extra components which means you're adding noise and distortion.
And pro interfaces are not only ballanced but also 14db hotter. The latter makes more difference than the earlier in short cables for noise rejection. Why do very few people know this.
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Old 14th November 2015, 11:03 PM   #26
buzzforb is offline buzzforb  United States
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I have Tom's circuit and think it is extremely well done. I am sending it to a friend who will be using it in a live recording to really put it through a thorough examination in terms of transparency. Thus far, I see no reason not to recommend it for the task it is made for. Every audio device I have ever heard has a nature or character. This one is no difference. Audio is less about what is right or wrong and more about whether a particular circuit fits your needs and tastes.
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Old 14th November 2015, 11:37 PM   #27
tomchr is offline tomchr  Canada
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Quote:
Originally Posted by AlexQS View Post
My Power86 board went together perfectly. Excellent instructions.
Cool! Glad you liked it.

Quote:
Originally Posted by AlexQS View Post
Is there any problem with temporarily running the THAT Driver with a Pseudo-Differential Cable to an amp with a single-ended input? I just want to make sure that shorting pin 1 & 3 won't harm the THAT Driver.
That'll be fine. In fact, one of the selling points of the THAT1646 is that it will provide high-end performance even if one of the output pins is shorted to ground. The designers at THAT apparently figured that someone would do exactly what you want to do so they made the chip so it'd support that mode of operation. For many differential drivers, that's not the case.

Tom
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Old 14th November 2015, 11:48 PM   #28
billshurv is offline billshurv  United Kingdom
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THAT Driver :: A minimalistic differential driver / preamp with 0.000021 % THD
Quote:
Originally Posted by Pano View Post
How many balanced phono preamps do you own?
I have the parts for two now! Just have to build them.


Quote:
OK, but how many home amps have balanced inputs? The only one I have at home with balanced inputs is an old Crest pro amp.
The mod-86 is balanced in, which I am building, so for me it's a no brainer to go to balanced interconnects as well, even if the THAT1200 Tom uses still performs well on single ended sources for CMRR.

DIY needs more balanced options IMO
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Old 14th November 2015, 11:59 PM   #29
buzzforb is offline buzzforb  United States
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I love balanced interconnection and feel the same. Yes SE is perfectly fine, but balanced offers protections that bring nothing but positives, IMO.
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Old 15th November 2015, 12:08 AM   #30
AlexQS is offline AlexQS  United States
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Originally Posted by tomchr View Post
Cool! Glad you liked it.



That'll be fine. In fact, one of the selling points of the THAT1646 is that it will provide high-end performance even if one of the output pins is shorted to ground. The designers at THAT apparently figured that someone would do exactly what you want to do so they made the chip so it'd support that mode of operation. For many differential drivers, that's not the case.

Tom
Thanks Tom. I'm getting excited. I've listened to and been able to A/B compare Single Ended RCA against Balanced XLR. My first impression was blind, because I didn't know. I just remember going to visit Dad. He had an Anthem or Sonic Frontiers CD Player with a tube in it's output. It sounded so good when I came home, and I asked him if he rolled the tube. Nope, he said, I finally got the XLR Cables.
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