What's a Balance Preamplifier Should Be Like?

[KSTR]

It should be balanced input to balanced output

@SSS,
The whole idea of a balanced input is that it extracts the difference and re-references it to the local GND. Making the internal circuits after this re-referencing point balanced just adds complexity and gains nothing.
Fully balanced (without re-referencing) is doomed because common-mode noise will pass through and any slight imbalance in CMRR here or further downstream will be converted directly into signal, meh.

 

[antcollinet]

@SSS,
The whole idea of a balanced input is that it extracts the difference and re-references it to the local GND. Making the internal circuits after this re-referencing point balanced just adds complexity and gains nothing.
Fully balanced (without re-referencing) is doomed because common-mode noise will pass through and any slight imbalance in CMRR here or further downstream will be converted directly into signal, meh.

Bruno would disagree. Have a look at the article I linked earlier.

 

[KSTR]

Bruno would disagree. Have a look at the article I linked earlier.

Looks like you cannot ready a schematic nor follow the description.
U1/6 are input buffers to achieve high impedance and U2/7a is the mentioned core subtractor/re-referencing stage, followed by the unbalanced variable gain stage U2/7b, and finally an impedance-only balanced output.
So, no disagreement here.

 

[KSTR]

And btw, the volume control is a disaster unless there is a mechanical end stop to prevent the infinite gain... where the output will run into the rails and will output full DC.
I have a lot of respect for Bruno but this preamp is not road-ready.

 

[Mart68]

View attachment 308755

Ultracurve

Behringer Ultracurve DEQ2496 Lampizator

lampizator.eu

This looks like the thing Mr Sulu uses to work out how many Klingon Warbirds are attacking.

My pre-amp requirements are like a lot of other people here it seems - every possible feature is required (except an on board DAC as that should be a separate toy).

No menus, a button for everything, and please as someone mentioned earlier, no blue LEDs. Power should be indicated by red, orange or yellow, input selection should be green or red (if you didn't use red for power). These are the correct LED colours for hi-fi equipment.

Grab handles and optional rack mount ears. The case to be black with white legends or white/silver with black legends. All in the same font. No italics. Manufacturer name to be top left.

Anyone can knock up a pre-amp with a couple of inputs and a volume control. Usually looking like it cost five bob to make. No-one is making a pre-amp with all the features and which looks like proper equipment. Not even Benchmark. The market gap is there.

 

[antcollinet]

Looks like you cannot ready a schematic nor follow the description.
U1/6 are input buffers to achieve high impedance and U2/7a is the mentioned core subtractor/re-referencing stage, followed by the unbalanced variable gain stage U2/7b, and finally an impedance-only balanced output.
So, no disagreement here.

OK - I was mainly referring to the philosophy of the whole article rather than the specific pre-amp example. But even here the point is to keep signal and reference separate from ground - in that neither the signal, nor the signal return share the ground with any other signal, hence the separate signal and return tracks, yes referenced to ground but (due to the link tie arrangement) not sharing a current path with ground. As stated:

PCB lay-out.
Differential circuit design treats every signal as a pair of wires. Usually though, only one of them is actively driven. The other is tied to the ground plane at some point by means of which the two processing stages at either end agree to call this particular potential “reference potential”.

And yes - perhaps an additional resistor between R3 and R5 would be advisable to avoid that infinite gain scenario.


EDIT - PS, I may have misunderstood your "re-referencing" as meaning "conversion to unbalanced/single signal connection through device". If so, I apologise for my contradiction.

 

[Prana Ferox]

I don't think the output switch makes sense. I'm confused what the light on the input button is for since there are discrete lights for the inputs. Those discrete lights and inputs are absurdly small, especially with white text on silver. Don't use serif'ed fonts.

Personally if I needed EQ and bass management with a miniature, presumably affordable box like this, I would prefer to insert a discrete device between the preamp and power amp, than clutter up this specific box. It's not like the room curve changes based on my input. It would be nice to have a digital 'tape loop' to do that at line level for max resolution, but that wouldn't help for splitting out a sub.

 

[Fosi Audio]

Hello audio lovers! Thanks for your attention again. Recently we have adjusted some features of this balanced preamp. We've canceled the DAC function. Now we need to discuss with you some more details.

1. Is it a must to make it balanced input to balanced output and single-ended input to single-ended output, or allow it to have the function to transfer balanced/single-ended to single-ended/balanced?

2. We have two industrial designs shown as follows for this preamp. Pls tell me which you prefer.

3. Is it necessary to add tone controls (bass, mid-range, and treble) to this balanced preamp?

 

[Talisman]

Hello audio lovers! Thanks for your attention again. Recently we have adjusted some features of this balanced preamp. We've canceled the DAC function. Now we need to discuss with you some more details.

1. Is it a must to make it balanced input to balanced output and single-ended input to single-ended output, or allow it to have the function to transfer balanced/single-ended to single-ended/balanced?

2. We have two industrial designs shown as follows for this preamp. Pls tell me which you prefer.

3. Is it necessary to add tone controls (bass, mid-range, and treble) to this balanced preamp?

1
A

important to make possible the possibility of active RCA XLR conversion, it would be fantastic as a function.
Tone controls are welcome only if it is possible to bypass them completely with the appropriate "direct" button

Personal note. I love the center volume knob

 

[TonyJZX]

this thing have subwoofer out??

the preamp HAS to mix single ended and balanced inputs, otherwise its useless

i dont really care what it looks like to be honest

tone controls i dont care

 

[pmichael]

1
B

 

[JeremyFife]

1, A

 

[sergeauckland]

Hello audio lovers! Thanks for your attention again. Recently we have adjusted some features of this balanced preamp. We've canceled the DAC function. Now we need to discuss with you some more details.

1. Is it a must to make it balanced input to balanced output and single-ended input to single-ended output, or allow it to have the function to transfer balanced/single-ended to single-ended/balanced?

2. We have two industrial designs shown as follows for this preamp. Pls tell me which you prefer.

3. Is it necessary to add tone controls (bass, mid-range, and treble) to this balanced preamp?

For me there's so much wrong!

1) No on-off switch on the front panel - Why would I want to grovel around the back to switch it off?
2) No tone controls
3) No phono input
4) Not enough inputs
5) No tape loop or external processor loop.
6) Wrong size. Either 19" rack mounting or at least 17" width with optional rack mounts.

S.

 

[TonyJZX]

my understanding is that there should be a master hard power at back but a soft resume standby power on the remote

tone or loud controls are neither here nor there to me

also if they removed digital input then they should also not bother with phono...like if you truly want that buy an external box

i'm probably going to agree there's not enough inputs... like 1 x xlr and 2 x rca is bare bare minimum

i would prefer 1ru half width but this makes it hard for the xlr so the size is sort of ok with me.

i'm ok with no tape loops.... this isnt a 'thing' in 2023

we are talking about a low cost preamp here

ironically the Schitt Kara comes at a good time for Fosi because its comparo with what they reckon consumers want

Schiit KARA Preamp and Headphone Amp Review

This is a review, listening tests and detailed measurements of the Schiit KARA balanced preamplifier and headphone amp with stepped relay control. It was sent to me by the company and costs US $699. Oh wait... that is the picture of our dog, Kara! :D Here is the Schiit version: As I have...

www.audiosciencereview.com

one thing i am slightly fussy on is that it looks like they have a taper vol. like the V3 but its not the same shit where you turn it for vol. but you push it down to change the input

i notice there's no input button... that's kind of awful as far as tactility, utility goes?

 

[Jeromeof]

1. allow it to have the function to transfer balanced/single-ended to single-ended/balanced !
2. (design A - maybe give it a similar colour volume as the V3?? )
3. Optional Tone controls (they need to be "defeatable") and I would probably not use them but I imagine some people would.

 

[radix]

I like A more than B. A looks balanced (in a design sense).

In a preamp separate, in order of importance

• Drive both XLR and RCA outputs (or have a switch on the back for which you drive), but everything has to go to the same outputs. This is your option #1.
• Should have power control on front and 12V trigger out (if not also in). It's the heart of the system.
• Sub out with crossover, even if it's a fairly limited set of choices (e.g. none, 80, 100, 120) to go with typical bookshelf or modest floor.
• tone controls

For me, it's really a question of basic functionality (drive both outputs and 12V trigger), then what will make the best improvement to sound (sub, then tone).

How does one select inputs? Press the volume control?

I think dropping the DAC is OK. If someone is buying a separate preamp, having separates is their thing.

 

[surroundman]

I like A more than B. A looks balanced (in a design sense).

In a preamp separate, in order of importance

• Drive both XLR and RCA outputs (or have a switch on the back for which you drive), but everything has to go to the same outputs. This is your option #1.
• Should have power control on front and 12V trigger out (if not also in). It's the heart of the system.
• Sub out with crossover, even if it's a fairly limited set of choices (e.g. none, 80, 100, 120) to go with typical bookshelf or modest floor.
• tone controls

For me, it's really a question of basic functionality (drive both outputs and 12V trigger), then what will make the best improvement to sound (sub, then tone).

How does one select inputs? Press the volume control?

I think dropping the DAC is OK. If someone is buying a separate preamp, having separates is their thing.

I'll just quote your post - pretty much exactly what I too would have said.

 

[Salt]

For my needs 2 XLR inputs with 2 (preferred) XLR outputs that can be switched passthrough or attenuated.
Nothing in the market like this.

 

[Mart68]

Appreciate it's low cost but does it have to look so bland?

'B' at least has the volume control and the name in the right place so I'd veer to that - but as suggested, power button on the front, with an LED indicator, gradations around the volume control and some buttons for selecting inputs. None of this 'press and hold the one control to work through the selections'. Nobody wants that.*

*May not be true, audiophiles can be weird.

 

[TonyJZX]

yeah there looks to be a major downgrade in aesthetics but also i assume, cost.

I'm ok with this.

Like if you want a sub $200 type preamp w/ xlr and int. psu. then this is what its going to look like

it actually reminds me of the douk '3 little bears' whatever type switch box things