Line preamps using battery power supply _ any experience ?

[gino1961]

One thing you need to keep in mind is that pre-amp circuits are going to use a +/- 12 or +/- 15 volt supply. This is not as straight fotward as you may think.

Hi thanks a lot I guess that a single 12VDC supply could be enough for a line preamp circuit I saw even a small integrated working with 12VDC
This choice would make things much easier

The easiest way is to use 2-12 volt batteries in series and take the power from + from - and from the middle connection. The two issues are batteries are usually not exactly the same voltage and you want the split rails to be identical. The other is the internal resistance of the battery is relatively high.

yes this would be very good with opmaps expecially The internal resistance of the battery can be reduced with some uF at the output
Like it is often done in car audio systems They have a big cap close to the amp Even a 1F cap

My solution was to use 2- 12 volt batteries in series and a voltage splitter circuit design I found online which used some regulators to split the voltage and some decent size caps to lower the internal resistance. You can use resistors to accomplish this as well but they waste a lot of power. If you are interested I can dig up the link or if the link is dead I have the schematic somewhere.

Yes please the link would be very welcome I am trying to make up my mind in this phase

 

[antcollinet]

Hi ! yes you are clearly very right
speaking of practicality, nothing beats a switching power supply and in fact they are everywhere
perhaps a weird solution to isolate the equipment from the mains could be a step-up DC DC converter that takes the 12 VDC from the battery and raises it to the voltage level necessary for the circuit
like it is done in car audio for instance
Unfortunately I don't have the slightest possibility of measuring small noises and I regret it immensely
I'm not saying measure the distortion but at least the noise carpet
When the noise is very low even the self-noise of cheap measuring instruments can be deceiving
Such a shame. I have to find out about the best and cheapest way to measure noise levels of mV
Noise has absolutely nothing to do with music
When the noise is low the listening experience can become exciting. You can hear everything
I am captured

you are wasting your time. If you can't hear noise at your normal listening level, you don't have a noise problem.

 

[levimax]

Yes please the link would be very welcome I am trying to make up my mind in this phase

See link for the circuit I used. I can confirm this works, looks like they have PCB's available now. https://www.goldpt.com/virtual_ground_circuit.html

A few notes:

1. There appears to be a bunch of other choices I didn't have when I built this years ago. The "good thing" about this design is that it is efficient and "analog" (no switching) if you believe in that sort of thing. I used to, I don't any more.

2. I used to run my DAC, pre-amp, phono preamp, and Analog Active Crossovers off of battery power. I don't anymore as I don't think it makes any difference.

3. While some devices can take a single voltage supply "externally", internally they all use split rail supplies if op-amp based.

4. I think the whole subject is interesting. One thing I found is that many objectively oriented audio people really don't like battery supplies, not sure why as objectively they actually do measure better (almost no noise) even if they don't make a difference (The CMR of the pre-amp is going to be more important for noise in most cases). I think it is like transformers, while objectively they are often the best performing solution the cost and size and weight and complexity make them seem silly when there are much easier and cheaper ways to accomplish the same thing.

Have fun.

 

[gino1961]

See link for the circuit I used. I can confirm this works, looks like they have PCB's available now. https://www.goldpt.com/virtual_ground_circuit.html
A few notes:
1. There appears to be a bunch of other choices I didn't have when I built this years ago. The "good thing" about this design is that it is efficient and "analog" (no switching) if you believe in that sort of thing. I used to, I don't any more.
2. I used to run my DAC, pre-amp, phono preamp, and Analog Active Crossovers off of battery power. I don't anymore as I don't think it makes any difference.
3. While some devices can take a single voltage supply "externally", internally they all use split rail supplies if op-amp based.
4. I think the whole subject is interesting.

thank you sincerely for the very interesting link
i understand better now that batteries are not essential to get very low noise

One thing I found is that many objectively oriented audio people really don't like battery supplies, not sure why as objectively they actually do measure better (almost no noise) even if they don't make a difference (The CMR of the pre-amp is going to be more important for noise in most cases). I think it is like transformers, while objectively they are often the best performing solution the cost and size weight and complexity make them seem silly when there are much easier and cheaper ways to accomplish the same thing.
Have fun.

here i disagree I wonder which kind of equipment they actually listened to Maybe power amps

 

[levimax]

Looks to me the answer is highlighted in your comment already. I bet most of them would consider it as "useless" and move on to other area to make a difference.

Yes I think that is right. I have moved on to the speaker, crossover, room, DSP rabbit hole as these no doubt make a difference (for better or worse).

 

[TonyJZX]

i'm surprised people have not heard of the Technics battery operated preamp line from the 80s 90s?

this was before my time but i remember reading articles about it

they had a whole slew from upper consumer grade to their 'reference grade'

i assume in this age its all crummy lead acid batteries but how it worked made sense

when the unit was on standby it charged the battery - when in operation you can get it to run in battery mode where it would then power down all the A/C circuitry

i think the entire industry treated it as a giant wank and put money into... A/C isolation

but I mean i like the concept... but to me arent all modern line stage preamps basically very very low voltage devices???

surely you could make a standard line stage that just runs off say 5v 2a type usb power??? what's it doing that requires all the much power???

or hell... just use a laptop 19v 3.5a 45w psu???

 

[levimax]

i'm surprised people have not heard of the Technics battery operated preamp line from the 80s 90s?

this was before my time but i remember reading articles about it

they had a whole slew from upper consumer grade to their 'referenc

surely you could make a standard line stage that just runs off say 5v 2a type usb power??? what's it doing that requires all the much power??

Regardless of external voltage internally op amps perform best with +/- 12 to +/- 15 volt rails. If external voltage is less they use a switching supply to increase the voltage and split the rails . If you were trying to eliminate all noise on the rails by using a battery then going through a switching stage would add a bunch of HF noise. Not that it would matter with a well designed device but to be "pure battery" you need to create the +/- rails with a fairly high voltage battery.

 

[Leeken]

i'm surprised people have not heard of the Technics battery operated preamp line from the 80s 90s?

this was before my time but i remember reading articles about it

they had a whole slew from upper consumer grade to their 'reference grade'

i assume in this age its all crummy lead acid batteries but how it worked made sense

when the unit was on standby it charged the battery - when in operation you can get it to run in battery mode where it would then power down all the A/C circuitry

i think the entire industry treated it as a giant wank and put money into... A/C isolation

but I mean i like the concept... but to me arent all modern line stage preamps basically very very low voltage devices???

surely you could make a standard line stage that just runs off say 5v 2a type usb power??? what's it doing that requires all the much power???

or hell... just use a laptop 19v 3.5a 45w psu???

Grattan catalogue material from the 80s,spent many a while perusing the audio pages,and certain other page’s which would interest teenage lads

Still want one now all these years later.

 

[Cbdb2]

Regardless of external voltage internally op amps perform best with +/- 12 to +/- 15 volt rails. If external voltage is less they use a switching supply to increase the voltage and split the rails . If you were trying to eliminate all noise on the rails by using a battery then going through a switching stage would add a bunch of HF noise. Not that it would matter with a well designed device but to be "pure battery" you need to create the +/- rails with a fairly high voltage battery.

Theres lots of opamps that work fine with one supply and get close to rail to rail output. If you use an opamp to supply the Vcc/2 voltage it doesn't burn much power.

 

[levimax]

Theres lots of opamps that work fine with one supply and get close to rail to rail output. If you use an opamp to supply the Vcc/2 voltage it doesn't burn much power.

Ok learned something. Can you give me some examples of these op amps and a schematic of how they are used with a single supply. I am only familiar with the old standby audio op amps like NE5532, OPA 2134, LM4562 and these all recommend 12 to 15 volt rails for optimum performance although they work OK at lower voltages. Thanks

 

[antcollinet]

Ok learned something. Can you give me some examples of these op amps and a schematic of how they are used with a single supply. I am only familiar with the old standby audio op amps like NE5532, OPA 2134, LM4562 and these all recommend 12 to 15 volt rails for optimum performance although they work OK at lower voltages. Thanks

An op amp only has two power connections. It has no idea if that is +/- 10V or 0V/20V.

Obviously if you don't have a negative rail you can't use 0V as. your reference for many circuits - in which case you need to bias that at (normally) half the supply voltage.

 

[gino1961]

i'm surprised people have not heard of the Technics battery operated preamp line from the 80s 90s?
this was before my time but i remember reading articles about it
they had a whole slew from upper consumer grade to their 'reference grade'
i assume in this age its all crummy lead acid batteries but how it worked made sense
when the unit was on standby it charged the battery - when in operation you can get it to run in battery mode where it would then power down all the A/C circuitry
i think the entire industry treated it as a giant wank and put money into... A/C isolation

hi thank you for the interesting information I have been advised above against using SLA batteries
Li Ion batteries seem more usable Any element provide 3.7V I guess they can be recharged in parallel and used in series to get higher voltage
i never seen application by the way This should mean something

but I mean i like the concept... but to me arent all modern line stage preamps basically very very low voltage devices???
surely you could make a standard line stage that just runs off say 5v 2a type usb power??? what's it doing that requires all the much power???

it depends on the circuit but i guess that 100mA for both channels would be a maximum
opamps usually draw like 20mA each ?

or hell... just use a laptop 19v 3.5a 45w psu???

yes their are almost everywhere and cost nothing Maybe it could be just to add some active/passive filtering downstream the power supply
These things are all around literally
I will ask better for a usb oscilloscope I understand that an entry level could be the Picoscope and a semi pro level at about 600USD the QA403

QA403 Audio Analyzer

29-Mar-2024: The QA403 is back in stock and orders can be placed, but fulfilling orders may take up to 5-10 days. Elektor and Saelig should have stock next week. 26-Feb-2024: The QA403 is sold out until the end of March. We'll resume orders in the middle middle of March once the delivery date...

quantasylum.com

on 1st August i will retire I will have to do something I could start lower with the Picoscope
I have a goal To beat the very expensive tube line preamp of my friend With a DIY humble thing
I am optimist

 

[gino1961]

Regardless of external voltage internally op amps perform best with +/- 12 to +/- 15 volt rails. If external voltage is less they use a switching supply to increase the voltage and split the rails . If you were trying to eliminate all noise on the rails by using a battery then going through a switching stage would add a bunch of HF noise. Not that it would matter with a well designed device but to be "pure battery" you need to create the +/- rails with a fairly high voltage battery.

i used two 12V batteries connected in this way (withouth any regulation)

they worked of with an ad797

 

[gino1961]

Theres lots of opamps that work fine with one supply and get close to rail to rail output. If you use an opamp to supply the Vcc/2 voltage it doesn't burn much power.

for sure a single supply is more convenient But i read something about noise in the negative rail that is not regulated ? i did not understand well but dual power supplies have some intrinsic advantage because both rails are regulated ? if true this could be an important advantage

 

[naviivan]

Hi to Everyone
When low noise is a much wanted requirement batteries can help for sure
Do you have any experience of line preamps powered by batteries ? in the high end sector i know of some Jeff Ropwland Design Group units Very very nice but also expensive
I live in a place where the grid voltage is quite dirty The batteries can provide a very nice plus with a complete separation from the grid
Then my fantasy was pumped up by this old paper i found in the web
https://tf.nist.gov/general/pdf/1133.pdf
Impressive indeed
Anyone who has experience of battery powered preamps ?

You can build a Nelson Pass B1 buffered pre/volume control - which is a buffer and run it from 2x 9VDC batteries.
I've used it with a 15V Power supply and it's pretty neutral. Stepped attenuator + Buffer. Doesn't mess with the sound too much.

 

[gino1961]

Hi thank you for the very kind and valuable advice
I am quite set on the schematic I have attached above
1 npn 1 PNP
5 resistors 3 of which same value 3 caps and
I will have a buffer with gain of 2 times
It's just a matter of select the parts given the supply voltage
It's a low distortion circuit called Sziklai pair
I see it used in some good totl preamps of 70s
Simple and elegant Genial
I like the approach of extracting the best from very few parts
I am not convinced that to be good a circuit must be necessarily complex
I read some comments like the schematics is pretty basic with some design flaws
Nevertheless the unit performs impeccably at the lab bench
And this for me would be more than enough
I had a good experience with the Nelson Pass Bride of Zen
Only complain slightly high Zout and 2nd harmonic
The pair should have lower of both
And higher rejection of Power supply noise because there's feedback

 

[antcollinet]

But i read something about noise in the negative rail that is not regulated ?

I don't know where you read that, but it is nonsense.

You don't regulate the +ve and 0V rail, because the 0V rail is the reference (just as you don't "regulate" the 0V when you have dual rail supply).

The regulator doesn't regulate the +ve rail standalone (Which makes no sense because in that case what are you regulating it to?), it regulates the voltage between the positive rail and the 0V rail.

 

[SSS]

Many years ago I built for a friend a Hiraga MC pre amp with self set turret boards. External power supply with line filter and + an - regulators. On the pre amp board additoinally caps for further noise reduction. Result was no hum and no additional noise from the power chain. Therefore my opinion is that battery power is not really necessary. But it may help to avoid ground loop.

 

[gino1961]

I don't know where you read that, but it is nonsense.

You don't regulate the +ve and 0V rail, because the 0V rail is the reference (just as you don't "regulate" the 0V when you have dual rail supply).

The regulator doesn't regulate the +ve rail standalone (Which makes no sense because in that case what are you regulating it to?), it regulates the voltage between the positive rail and the 0V rail.

Hi thank you for the very helpful advice
Then I miss the reason for dual power supply
I can understand if they want to avoid the output cap
But many circuits with dual voltage have still the output cap
Why not using a single voltage?

 

[SSS]

Hi thank you for the very helpful advice
Then I miss the reason for dual power supply
I can understand if they want to avoid the output cap
But many circuits with dual voltage have still the output cap
Why not using a single voltage?

Depends on the amplifier circuit and specifically on the op-amp used. There exist ones which need a + - dual supply. And there are also ones built for single rail supply. Output cap, thats a philosophical thing. But needed when single rail supply.