True. In my case, it's just a differential amplifier taking a balanced signal from an upstream source. Maybe the upstream source injects DC, maybe it doesn't.
If DC is the problem, can the buffer stage be eliminated if I put DC blocking caps on both legs of the balanced input, taking care to impedance-match the two legs?
The INA is just the #451 circuit in a small box, but the THAT Ingenious diff line receiver maintains all required specs.
I dont know what it costs, and you may want to check if a simple buffer works well enough for you, do some listening tests and/or measurements if you can.
Otherwise, the THAT Ingenious is failsafe.
BTW Why do you want to go to se, can't you maintain it bal all the way?
Jan
I dont know what it costs, and you may want to check if a simple buffer works well enough for you, do some listening tests and/or measurements if you can.
Otherwise, the THAT Ingenious is failsafe.
BTW Why do you want to go to se, can't you maintain it bal all the way?
Jan
Yes, I revisited the INA134 datasheet, and its internal circuit is basically the same as the output buffer stage which XRK is using in the BTSB.
Why do I want to go SE? Look, I'm not very smart, electronics-wise, and I just want to accept a balanced input into an active speaker, and then feed the signal to a normal active xo, which will then feed a set of normal Class B amps. What else am I supposed to do? If I didn't have a few friends and diyaudio.com, I wouldn't even attempt what I'm trying to do.
The THAT 1206 seems affordable at least for my low-volume hobby usage. The INA 1651 is one-third the price.
Interestingly, the INA 165x has exactly the same single-opamp based output buffer which the BTSB is using.
Why do I want to go SE? Look, I'm not very smart, electronics-wise, and I just want to accept a balanced input into an active speaker, and then feed the signal to a normal active xo, which will then feed a set of normal Class B amps. What else am I supposed to do? If I didn't have a few friends and diyaudio.com, I wouldn't even attempt what I'm trying to do.
The THAT 1206 seems affordable at least for my low-volume hobby usage. The INA 1651 is one-third the price.
Interestingly, the INA 165x has exactly the same single-opamp based output buffer which the BTSB is using.
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Just curious. Lots of active speakers and other stuff these days have bal inputs.
Sometimes you just need a se signal, and then the best of the best is the superbal, but you often can get good results with simpler circuits also.
If you are aware of the issues and you find the resuklt less than you would want, you know there are better solutions.
But, as Nelson used to say: "it's all entertainment, not dialysis"!
Jan
Sometimes you just need a se signal, and then the best of the best is the superbal, but you often can get good results with simpler circuits also.
If you are aware of the issues and you find the resuklt less than you would want, you know there are better solutions.
But, as Nelson used to say: "it's all entertainment, not dialysis"!
Jan
Oh, I am not insisting that the bufffer be dropped, as I sort-of clarified at the end of #451. I am trying to understand the rationale, because some designs seem to have something like this, and others do not. I want to have some scientific basis for deciding whether to retain or drop it, in my design, that's all.
That's sort of what I'm trying to do. I'm aiming for a "pretty good" level of performance and avoiding total bloopers, but I'm not under any illusion that this is "endgame" (a word I see some people using in the audiophile world). The way I see it is:
- I do some draft design, to the best of my limited abilities, and post here.
- For the remaining questions, I ask here. Maybe some veteran dudes like you will answer, maybe I'll get the royal ignore. I've received both, so it's a matter of luck if I get guidance.
- I build what I've arrived at.
- I try to measure the performance (HD, IMD, noise) of the thingie with my Scarlett 2i2. It's not an AP, but it's more than good enough to tell me whether something is seriously screwed. I can live with 95dB THD+N when others are doing 120+, but I don't want to accept 70.
- I post queries again here, ask for help, be a bit of a pest, and see what I can learn. I then build a v2. And the story goes on.
So I think I'm doing exactly what you suggested.
Is this copyrighted? I'd like to tattoo this on my forehead when I meet my "special" friends, you know --- those who use risers to raise their power cables off their floors.
Yes it could work - but as Jan said, it’s only half the signal and you need a GND reference. Best thing is to stick with circuit as designed - why omit a $3 opamp and lose that extra functionality and introduce sub optimal performance?
Thanks X.
Since I have the luxury of a fresh designs, should I put in two opamps then and make a Superbal block?
Since I have the luxury of a fresh designs, should I put in two opamps then and make a Superbal block?
Hey @xrk971 and other clever people in here. I have recently started my own jurney into audio electronics, mostly for the fun of it, but also to make som killer sound projects for myself 😛
I have bought one of your BTSB boards and love it. Now next step for me is to actually understand it so I can implement something similar directly in my own designs. Since you share the full schematic and BOM here I hope you dont mind me asking such questions.. If its crossing the line then feel free to ignore me 🙂
I will be using the design to interface to amplifiers such as the Icepower modules and hypex modules which prefer balanced inputs. The 1200AS2 also needs quite a large input signal. The sources will for a start be SE but later maybe Balanced, so this design seems perfect for that (I will ommit the last SE buffer).
I understand the basic idea of how it works, with the two opa1656 acting as input buffers, then the selectable gain and the LME49724/opa1632 to create the balanced signal. However I do not understand the nuances of these resistors and capacitors and the reverse buffer(marked in red). Can anyone elighten me on the purpose of these components?
I would guess that the resistors and capacitors between the inputs are some sort of pull down resistors/filters to stabalise the input when ther is no signal?
The reverse buffer I would assume is something to do with stability, but not sure how it works?
Maybe this will answer itself when I understand it better, but JLC does not seem to have any thin film SMT resistors between 20k and 100k. would it be okay to use 100k(instead of 24k9) and 200k(instead of 49k9)? or 10k and 20k? I assume the ratio must be preserved?
Thanks in advance for any help understanding this circuit. I am really impressed how it performs and will like to get smarter 🙂
I have bought one of your BTSB boards and love it. Now next step for me is to actually understand it so I can implement something similar directly in my own designs. Since you share the full schematic and BOM here I hope you dont mind me asking such questions.. If its crossing the line then feel free to ignore me 🙂
I will be using the design to interface to amplifiers such as the Icepower modules and hypex modules which prefer balanced inputs. The 1200AS2 also needs quite a large input signal. The sources will for a start be SE but later maybe Balanced, so this design seems perfect for that (I will ommit the last SE buffer).
I understand the basic idea of how it works, with the two opa1656 acting as input buffers, then the selectable gain and the LME49724/opa1632 to create the balanced signal. However I do not understand the nuances of these resistors and capacitors and the reverse buffer(marked in red). Can anyone elighten me on the purpose of these components?
I would guess that the resistors and capacitors between the inputs are some sort of pull down resistors/filters to stabalise the input when ther is no signal?
The reverse buffer I would assume is something to do with stability, but not sure how it works?
Maybe this will answer itself when I understand it better, but JLC does not seem to have any thin film SMT resistors between 20k and 100k. would it be okay to use 100k(instead of 24k9) and 200k(instead of 49k9)? or 10k and 20k? I assume the ratio must be preserved?
Thanks in advance for any help understanding this circuit. I am really impressed how it performs and will like to get smarter 🙂
Hi DannerD3H,
@jhofland designed the circuit so he would best know the nuances. I think the capacitor and resistor network on the inputs are basically filters to reduce EMI from external sources and to provide an input impedance. As far as U4B backward facing voltage buffer, I’ll let Jhofland answer that.
@jhofland designed the circuit so he would best know the nuances. I think the capacitor and resistor network on the inputs are basically filters to reduce EMI from external sources and to provide an input impedance. As far as U4B backward facing voltage buffer, I’ll let Jhofland answer that.
The SuperBalanced circuit using two opamps seems like a good way to do it. It’s simpler to use an OPA1637 which will handle balanced drive output natively with one chip. It works really well as I have demonstrated that in balanced mode it can drive 40Vpp easily with low distortion.
Jhofland said this was the purpose of the circuit - it’s not his original idea but a common implementation in opamp circuits: