Balanced B1 Buffer

[generg]

I think you have to make two stereo sets of the buffer and keep the psu ....

Warning there maybe newer versions in the diyaudio forum from Salas and other users!

[aston45]

Gentlemen,
what has ever come out of this approach.
I´ve been reading through a bunch of threads covering the B1 in various versions with various alterations and got lost in the meantime.
It´s just not possible to grasp the substance of a thread running a couple of years.
But right now I´m in the process of buying some PCBs and starting with building the B1.
But since I´m mainly using equipment with balanced in- and outputs (Professional active speakers for example and a Wadia as DAC, also with balanced in/out) I would not like falling back to RCA connectors again.

From what I am understanding (and I actually understand little in regard to the technical side) the main problem here is the matching of the resistors of the input side of the B1.
This actually would not be a real problem for me since I will continue using the Wadia for volume control and the B1 just as a way for matching in- and output capacities/impedance between the Wadia and the speakers.
That´s at least my plan.
So I would probably be fine with 5 steps or something like that and therefore it would be not really onerous to match 4x5 resistors to the last 0,01% or something like that.
So what does the esteemed audience think about that?

Cheers,
Kai

[palmito]

+1 to aston45's request...

[qusp]

aston45: is the output impedance of the wadia really that high? or the power so weak? seems rather pricey to be a faulty product. the b1 doesnt add any gain and its output impedance isnt really that low; probably higher than your dac. it does sound very good and is a good fun project, but no buffer is better than any buffer no matter how good imo. i would advise you think about whether you really need it, i'm just finishing off a dual mono dcb1 for driving the long cables to my active monitors in the workshop, but its not in the signal path for the main rig which is nearby.

yes if you dont need a pot, then just pick a set value thats easy for your dac to drive and use some well matched resistors. personally though, i would go without it if i were you; if your dac has low output impedance and you arent driving long capacitive cables, then it serves no purpose and just adds components in the signal path that need not be there. no need to match impedances, you just need to make sure the output impedance is low and the input impedance of the next stage is high. i would be flabbergasted to find that the wadia iv was not lowz and your monitors are definitely going to have a high inputz

[ruudjoo]

What about going to Ground in the balanced B1 ?
Should I really go to ground twice as in the schematic in post 1 above?
So pin 1 of the XLR and between C1 and D2?
My technical knowledge is not very high but my gut feeling says no, maybe only the XLR pin1. In my idea it would make the amp unbalanced?
Ruudjoo

[ruudjoo]

It's actually 6 times to ground in a balanced setup, isn't it?
4 XLR pins and 2 power supply Grounds.
Ruudjoo

[Arick]

Originally Posted by ruudjoo

It's actually 6 times to ground in a balanced setup, isn't it?
4 XLR pins and 2 power supply Grounds.
Ruudjoo

Hi,
What do you mean by 2 power supply grounds? In my case I used 1 ground for each # 1 XLR pin, one for the ground pin of the power cord and one for each PCB. All of them were bolted together with the same bolt at one point on the case. The idea was to do a star ground to prevent any hum's.
Cheers,
Eric

[ruudjoo]

I'm beginning to see that it will work with all "grounds" together.
I'm not very technical, I was afraid of hum and found it strange that the minus of the power supply is connected to the other grounds in the scheme.
I count 4 #1 XLR pins and 2 minus/grounds (for a balanced setup of twice the stereo setup) but indeed I am testing my first print now and it all works fine, whatever I do with the Grounds.
A star ground is more or less what I try to do; it has many fans but I also read an article against it which was beyond my understanding; I think it was about tube amps.

[AndrewT]

I thought the PIN1 problem required the XLR PIN1 to be connected to chassis right next to the XLR socket.

[ruudjoo]

That seems the best solution.
And the rest as a star also to chassis (at the bottom somewhere?)
Ruudjoo