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
How many balanced phono preamps do you own?
Yes, and mine has 1/4" balanced outputs. That's nice. Also RCA.
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.
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?
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
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.
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.
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.
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.
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
I have the parts for two now! Just have to build them.
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 🙂
I love balanced interconnection and feel the same. Yes SE is perfectly fine, but balanced offers protections that bring nothing but positives, IMO.
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.😀
Be careful selling pcb's with components missing.
I have had stuff sent back on ebay because of that despite my protests that it was deliberate !
I have had stuff sent back on ebay because of that despite my protests that it was deliberate !
Still confused. What has that got to do with this thread? No one here is selling populated PCBs.
There was a picture of a partly populated pcb I thought was what he was selling.
Sorry I should have the thread completely.
I don't recall posting a picture of a partially assembled THAT Driver board and I have no plans for selling any partially assembled boards. It'll be either bare boards or assembled boards. No in-between.
I do agree that you need to be careful when selling on eBay, but that's a topic for a lounge thread - and probably a lengthy one at that. 🙂
Tom
I do agree that you need to be careful when selling on eBay, but that's a topic for a lounge thread - and probably a lengthy one at that. 🙂
Tom
I like your idea of using this as a preamp with volume controls. You have suggested a 10k pot. Does a 10k pot have a low enough output impedance for driving the THAT 1646? I ask because a quick glance thru the literature under Applications says "2. Both devices must be driven from a
low-impedance source, preferably directly from
opamp outputs, to maintain the specified performance."
Good to see that one can use a pseudobalance output without compromising performance.
However can one somehow use balanced inputs too? Meaning a balanced input and balanced output preamp? That would make it really versatile.
Thanks.
Nash
low-impedance source, preferably directly from
opamp outputs, to maintain the specified performance."
Good to see that one can use a pseudobalance output without compromising performance.
However can one somehow use balanced inputs too? Meaning a balanced input and balanced output preamp? That would make it really versatile.
Thanks.
Nash
No, not directly. That's why I have a buffer (with gain option) at the input. The input impedance of the THAT Driver board is 100 kΩ set by a resistor. You can crank this up a bit if 100 kΩ doesn't suit your fancy. 🙂
Tom
Thanks Tom for the explanation.
Regarding my second query is there a way to use balanced inputs too?
Nash
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
