Batteries powered line preamps. - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 5th March 2006, 07:05 PM   #1
beppe61 is offline beppe61  Italy
diyAudio Member
 
Join Date: Feb 2005
Location: torino
Default Batteries powered line preamps.

Dear Sirs,

I understand that in a preamp the power supply quality makes or breaks the sound of the preamp.
I am gathering information on line preamp with battery power supply (DIY of course).
I have already got opinion like: very low noise but also a lack of dynamics.
I would like to hear from people that have listen to line preamp powered by batteries.

Thank you very much indeed.
Kind regards,

bg
  Reply With Quote
Old 6th March 2006, 05:53 AM   #2
m@ is offline m@  Thailand
diyAudio Member
 
Join Date: Nov 2004
Location: bangkok
Default DC

From what i understand, a properly sized DC power supply is just that. To a certain extent, it should make no difference where the DC is coming from - filter caps or batteries. Although batteries and rectified supplies do operate in very different ways, of course, mainly to do with the capacitance used and current. Ripple on the supply is the major difference, with batteries being superior by design. Of course, at line level you're looking at a regulated supply anyway...

On the other hand, a common theme in audio is that people consistently (and inconsistently) here differences where there technically shouldn't be any. Does a few microvolts of 60hz ripple reach your ears? Does it add something?

I approach it from a different angle - I prefer battery supplies because i live in an electically noisy environment. Using batteries is a simple way to isolate my (line-level) gear from the mains. It saves me from having to over-enginner a power supply and deal too much with grounding. At line-level current requirements are small enough that batteries don't have to be costly. The opposite is true for power amps so i use rectified AC. YMMV =)
  Reply With Quote
Old 6th March 2006, 06:58 AM   #3
beppe61 is offline beppe61  Italy
diyAudio Member
 
Join Date: Feb 2005
Location: torino
Default Re: DC

Quote:
Originally posted by m@
From what i understand, a properly sized DC power supply is just that. To a certain extent, it should make no difference where the DC is coming from - filter caps or batteries.
...
I approach it from a different angle - I prefer battery supplies because i live in an electically noisy environment. Using batteries is a simple way to isolate my (line-level) gear from the mains.
...
At line-level current requirements are small enough that batteries don't have to be costly. The opposite is true for power amps so i use rectified AC. YMMV =)
Dear Sir,
thank you very much for your kind and valuable reply.
Could you tell me something more about your use of batteries for powering line-level units, in particular the line preamp?
Am I very interested in simple application.

Kind regards,

bg
  Reply With Quote
Old 6th March 2006, 07:57 AM   #4
m@ is offline m@  Thailand
diyAudio Member
 
Join Date: Nov 2004
Location: bangkok
Default dc

If you want really simple, use 4 9V batteries in series with the middle of the two pairs tied to ground. That gives you +/-18v which is suitable for most opamp circuits. Keep the rail caps on the opamps (ceramic usually). The rest of the psu can be replaced by the batteries. In my experience this works but you do get voltage drop as the batteries discharge (means you lower the clipping threshold in a unity gain setup or lower the volume in a postive gain setup). You might want to reg the supply down to 12v or 15v to give you a steady supply.

Maybe someone can correct me on this. I'm not 100% if regulation is necessary all the time with batt supplies. I regulate - but maybe all i'm doing is turning juice into heat.

If you want sth more permanent, use SLA batteries and design a charger for it that turns on when you shut the unit off. The setup will disconnect from the mains when it's on, just running off the batteries, and will disconnect power to the unit while it's charging (or a variation thereof). check out www.sound.au.com for ideas about this. also, build any of Rod's projects and you're in the clear.

Whether or not there is any real performance advantage over a properly designed psu is debateable - but it does feel good to do it this way. I'll take SLABs and a charger any day - it's fun to do things manufacturers can't b/c of cost.
  Reply With Quote
Old 6th March 2006, 08:53 AM   #5
beppe61 is offline beppe61  Italy
diyAudio Member
 
Join Date: Feb 2005
Location: torino
Default Re: dc

Quote:
Originally posted by m@

1) If you want really simple, use 4 9V batteries in series with the middle of the two pairs tied to ground.
That gives you +/-18v which is suitable for most opamp circuits. Keep the rail caps on the opamps (ceramic usually).
The rest of the psu can be replaced by the batteries.
In my experience this works but you do get voltage drop as the batteries discharge (means you lower the clipping threshold in a unity gain setup or lower the volume in a postive gain setup).
You might want to reg the supply down to 12v or 15v to give you a steady supply.
Maybe someone can correct me on this.
2) I'm not 100% if regulation is necessary all the time with batt supplies. I regulate - but maybe all i'm doing is turning juice into heat.
3) If you want sth more permanent, use SLA batteries and design a charger for it that turns on when you shut the unit off. The setup will disconnect from the mains when it's on, just running off the batteries, and will disconnect power to the unit while it's charging (or a variation thereof).
check out www.sound.au.com for ideas about this.
also, build any of Rod's projects and you're in the clear.
4) Whether or not there is any real performance advantage over a properly designed psu is debateable - but it does feel good to do it this way.
I'll take SLABs and a charger any day - it's fun to do things manufacturers can't b/c of cost.
Dear Sir,
thank you so much for your really kind and valuable reply.
1) I want even simpler than that.
I would like to explain my idea.
A really simple (maybe 2 bjts) circuit with a 12V supply.
I am gathering schematic of such a circuit and it is my intention to ask for help from DIYaudio friends.
I would like to use just a single 6-7Ah SLABattery and check for its duration with a tester.
I strongly think that 12V should be enough. I noticed that the well regarded T-Amp works out of 12V power supply.
If 12V are enough for an amp more than so for a preamp.
2) No regulation here.
Just a really nice electrolytic cap to low down the impedance of the battery, even if I will search for a full class A circuit, so that the current draw is constant.
3) Very very nice idea. I like very much the idea of a switch to change from operating to charging.
4) I think that you have pointed-out an important point in the isolation from the AC mains.
It is always very beneficial.
I have already read about the great performances expecially of digital units (DAC for instance) when powered with batteries.
I am convinced that this kind of PS have indeed a great potential.
The Silbatone C-102, one of the very best preamps on the planet, has a battery power supply.

In the end, if you know any really simple circuit (I would not like to use op-amps) that works with a 12V PS I am all ears.

Thank you very much indeed.
Kind regards,

bg
  Reply With Quote
Old 6th March 2006, 09:33 AM   #6
lineup is offline lineup  Sweden
diyAudio Member
 
lineup's Avatar
 
Join Date: Dec 2005
Location: the north
Dear Sirs.
Thank for most kindly reading this post.
.................................................. .................................


There are a few situations,
where battery supply can be an easy and good alternative:
- Portable equipement
- Very high voltage gain circuits

When making very high gain preamplifiers,
they will also amplify noise, hum and ripple from power supply.
They can have a voltage gain of 100-1000 ....

Such amplifiers.
- Microphone amplifiers
- RIAA phono amplifier
For these applications, it is not unusual we can see battery supply.

Such high gain amplifiers needs very clean supply and also be careful
not have Transformer close to circuit.
Because will pickup hum from trafo.


If using transformer you often see these amplifiers have a separate box for transformer
and power supply and circuit have very good filters to take way all noise.

When using 230 VAC, you have to use:
- transformer
- rectifier diodes
- eletrolytic mains filter capacitors
- (eventually voltage regulators)

If you compare to this, using batteries is much more easy.
Problem with batteries is they are better for low current circuits.

==================

For normal preamplifiers, line amplifiers, there is no obvious better performance using battery supply.
These amplifiers have a gain of something like 4-10,
There is a practical benefit using battery.
It is simple and easy to get clean DC voltage using batteries.
But drawback is you need new battery or use re-chargeable cells.


This Article was written by lineup. All rights reserved.
__________________
lineup
  Reply With Quote
Old 6th March 2006, 09:53 AM   #7
diyAudio Member
 
Join Date: Aug 2003
Location: Prague,Czech Republic
Best microphone preamps are in studio equipments ( mixing consoles, external mic preamps ) ... Have you seen these machines battery powered ? All hifi DIY is, how I see, full of good washed brains...
  Reply With Quote
Old 6th March 2006, 10:03 AM   #8
lineup is offline lineup  Sweden
diyAudio Member
 
lineup's Avatar
 
Join Date: Dec 2005
Location: the north
Quote:
Originally posted by Upupa Epops
Best microphone preamps are in studio equipments ( mixing consoles, external mic preamps ) ...
Have you seen these machines battery powered ?
All hifi DIY is, how I see, full of good washed brains...
Upupa Epops uses studio equipments
( He is probably owner of professional recording studio in his hometown )
A much higher division of audio, than we discuss here




Here we are talking good home diy audio stuff.
And in microphone amplifiers, portable or stationary,
surely battery power is a good and usual alternative.
I know this from many good DIY audio websites and projects.

__________________
lineup
  Reply With Quote
Old 6th March 2006, 10:05 AM   #9
m@ is offline m@  Thailand
diyAudio Member
 
Join Date: Nov 2004
Location: bangkok
Default DC

yeah, i agree with that. there is very little advantage to using batteries in most line level apps - but then again, i just like the idea of it. for me, it's a hobby, so i do whatever lights my lamps.

beppe61, are you building a buffer or a gain stage? a couple of jfets will require, if memory serves, a resistor network for biasing and coupling caps - so you're actually over your parts count from a standard opamp. opamps have better noise figures as well. If you're building a gain stage - desinging with bjt's isn't trivial, but it's not going to kill you either.

If you are building a buffer, i've seen a few slick schematics for dual jfet buffers that run with no DC offset - hence no coupling caps - just a few reistors to set bias and all the other goodies. google it.

i wouldn't worry about the life of a battery at all. you're probably looking at days or weeks between charges with an SLA and a single gain stage. voltage is different however - voltage determines your maximum swing before clipping - if you need lots of gain, you need lots of Vs (someone feel free to correct me on that). yes, you can run it on 12v - but you either have to design for a single supply (again, coupling caps and extra goodies) or you have to split it +/-6v, which is quite low.

If you want simplicity, you don't get much simpler (with acceptable performance) than running an opamp off a split battery supply. setting gain is trivial and hard to mess up. i know your pain - there's something very attractive about those one or two transistor circuits.

if you see a commercial offering with a battery supply it's a whim or pure marketing - anyone who can design at that level can almost certainly design a blameless rectifier circuit.

if you really want to go nuts - there's an EDN article out there about running a low V opamp (2-3v) off of a couple of supercapacitors - takes a few seconds to recharge and runs for hours. again, there's little to no advantage over plugging in a transformer - but it sounds neat, doesn't it?
  Reply With Quote
Old 6th March 2006, 10:12 AM   #10
diyAudio Member
 
Join Date: Aug 2003
Location: Prague,Czech Republic
My job is design of professional equipment for audio...
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Battery powered tube preamps/effects (guitar) pbholmen Tubes / Valves 11 11th August 2009 06:56 PM
ABX Switching Box for Phono + Line Preamps thermionic Solid State 0 11th February 2008 07:39 PM
A discussion about batteries on preamps... robselina Chip Amps 16 14th September 2005 03:21 PM
Line-powered SMPS for Power Amp? marcus66 Class D 47 8th October 2004 12:49 PM
Battery powered Balance Line Stage icceman Pass Labs 10 26th December 2003 01:35 AM


New To Site? Need Help?

All times are GMT. The time now is 10:04 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2