Hello Peter
Welcome to the club. I use batteries in preamplifiers and amplifiers for ages and today I never ever would return to any other power supply for audio applications.
I use a very simple charger design with great success. This design may fit your requirements.
Charger Schematic Diagram: http://home.tiscalinet.ch/cooltune/Projects/MCLP-BSU1aS.pdf
Power Supply/Amplifier Block Diagram : http://home.tiscalinet.ch/cooltune/Projects/MegalithBlockDiagram.pdf
The complete amplifer article: http://home.tiscalinet.ch/cooltune/Projects/Megalith01.htm
advance
Welcome to the club. I use batteries in preamplifiers and amplifiers for ages and today I never ever would return to any other power supply for audio applications.
I use a very simple charger design with great success. This design may fit your requirements.
Charger Schematic Diagram: http://home.tiscalinet.ch/cooltune/Projects/MCLP-BSU1aS.pdf
Power Supply/Amplifier Block Diagram : http://home.tiscalinet.ch/cooltune/Projects/MegalithBlockDiagram.pdf
The complete amplifer article: http://home.tiscalinet.ch/cooltune/Projects/Megalith01.htm
advance
This is totally unfair. 
I am just lurking around, planing to use all the good tested ideas and only doing a minimum work and testing myself 😎
First it was the AX clone. (never really got started with the project (got the prints), don't understand it enough). Then it was the IGC in all the shape and colors it went through and the resistor war.
When you just thought everything was worked out, Peter destroys it all be using different materials in the chasing which caused changes to the sound.
Then all of the sudden the non inverting GC was a hit (yes it is a lot easier to integrate into systems) and now I had just build my prototype IGC's.
Then a few days later my BUF634 preamp got absolute, due to some rather expensive trafo's.
And just for the fun of it you add batteries
But anyway thank you for all that testing and sharing your finds, you make it so simple for us (me anyway) that one just have to build it.
/Flemming
To do list:
Rebuild my 4 mono IGC's to GC's.
Design and build an active XO (currently using a non DIY... yak)
Build new boxes for my speakers (jbl2225 sealed + fe206e OB)
Redesign IV and output stange on my non os 2x1541S1 dac.
Build the powersupply for the CD-PRO2.
Rob somebody so that I can get those trafo's for a new preamp.
I am just lurking around, planing to use all the good tested ideas and only doing a minimum work and testing myself 😎
First it was the AX clone. (never really got started with the project (got the prints), don't understand it enough). Then it was the IGC in all the shape and colors it went through and the resistor war.
When you just thought everything was worked out, Peter destroys it all be using different materials in the chasing which caused changes to the sound.
Then all of the sudden the non inverting GC was a hit (yes it is a lot easier to integrate into systems) and now I had just build my prototype IGC's.
Then a few days later my BUF634 preamp got absolute, due to some rather expensive trafo's.
And just for the fun of it you add batteries
But anyway thank you for all that testing and sharing your finds, you make it so simple for us (me anyway) that one just have to build it.
/Flemming
To do list:
Rebuild my 4 mono IGC's to GC's.
Design and build an active XO (currently using a non DIY... yak)
Build new boxes for my speakers (jbl2225 sealed + fe206e OB)
Redesign IV and output stange on my non os 2x1541S1 dac.
Build the powersupply for the CD-PRO2.
Rob somebody so that I can get those trafo's for a new preamp.
Peter Daniel said:
You won't get much offset if the rails are 1 or 2 volts out.I had a bigger problem when I attached a battery voltmeter to one just to one battery to check the state but the meter was drawing apparently more than 70ma and drained the battery.However I didn't have problems with the speaker.
A battery charger can be as simple as one lm 317 current regulated only for about a tenth or a fifth of the Ah of your batteries.It is not absolutely necessary to add a voltage regulator as well unless you plan to leave the charger on continually as a trickle charger because you don't want the batteries to draw too much current all the time.
I guess you could use a generic 12v charger off the shelf for all the batteries.I was thinking off the top of my head that this could be possible if you add diodes at the connections between the batteries so that you wouldn't short the charger when connected in parallel.
Rail splitter?
Hi Peter, compliments for your new masterwork!
I'm not an expert on that, but I think that If the current flowing thru the ground line is little, you could use a rail splitter (precision voltage divider) to balance the voltages:
http://headwize2.powerpill.org/images2/opamp20.gif
This technique is used in several diy portable headphone amplifiers. Please note the TLE2426 has a maximum rating of 40V, so not useful here. Not sure, but I think a power opamp with a couple of precision resistors could be used for the same purpose.
Hope it helps,
Massimo
Hi Peter, compliments for your new masterwork!
I'm not an expert on that, but I think that If the current flowing thru the ground line is little, you could use a rail splitter (precision voltage divider) to balance the voltages:
http://headwize2.powerpill.org/images2/opamp20.gif
This technique is used in several diy portable headphone amplifiers. Please note the TLE2426 has a maximum rating of 40V, so not useful here. Not sure, but I think a power opamp with a couple of precision resistors could be used for the same purpose.
Hope it helps,
Massimo
Re: Rail splitter?
Yes, a (unity-gain stable) power op-amp does it.
Like the Burr-Brown ones.
Divide the voltage with two resistors and buffer the virtual ground.
And connect all the batteries in series.
Say goodbye to differences between rails.😉
Nice jod, Peter, as usual.
NASA will contact you.😀
antomas said:
Yes, a (unity-gain stable) power op-amp does it.
Like the Burr-Brown ones.
Divide the voltage with two resistors and buffer the virtual ground.
And connect all the batteries in series.
Say goodbye to differences between rails.😉
Nice jod, Peter, as usual.
NASA will contact you.😀
Peter ,what is the purpose of this resistor?
I have noticed on my GC (the same layout accept this resistor) that when there is no source and no cable connected to the amp the DC offset is 200mV (speakers connected to amp are cracking and humming).When I plug the preamp in it is about 30mV and speakers are dead silent.I think DC offset in both cases should be the same.
Any one has idea ,why it is so?
Bartek
zygibajt said:
With my limited expertise the possibilities are:
1. Noise in the input. Without cable connected the input is not shunted by the low output impedance of your source/preamp and more susceptive to noise.
2. There is a change of the DC component at the input of the GC. It would happen if you don't have input cap and your source/preamp has low DC impedance.
This is just a speculation because I don't know your exact sch.
DC offset will not cause hum or static of any kind.It will move the cone to a given position and the incoming sine wave will have to exceed the DC offset voltage for the cone to move from that position.
ron
ron
FWIW ..... An op-amp with assymetrical supplies (as long as they're within proper operating range) still centers on 0volts (assuming the inputs are there) The output does not reflect offset in the rails.........mike
Thanks guys,
Then what can be wrong???
My setup is:
2*19VAC power transformer
double MUR860 bridges
2*1000uF Panasonic FC caps (directly on the chips)
22K feedback resistor
- input connected with 680R to ground (no cap here)
+input connected through 22K resistor to ground.
I tried to put 220R resistor in series with + input,nothing changes.
When I put 4uF coupling cup the DC offset got to -200mV ,but speakers are silent.
It looks like this:
The speakers and preamp connected:about 30mV offset and dead quiet.
I disconnect the cables from preamp to GC:
There is -200mV offset (how come minus?)
and there is a big humm in the speakers.
Bartek
Then what can be wrong???
My setup is:
2*19VAC power transformer
double MUR860 bridges
2*1000uF Panasonic FC caps (directly on the chips)
22K feedback resistor
- input connected with 680R to ground (no cap here)
+input connected through 22K resistor to ground.
I tried to put 220R resistor in series with + input,nothing changes.
When I put 4uF coupling cup the DC offset got to -200mV ,but speakers are silent.
It looks like this:
The speakers and preamp connected:about 30mV offset and dead quiet.
I disconnect the cables from preamp to GC:
There is -200mV offset (how come minus?)
and there is a big humm in the speakers.
Bartek
My Dac is AC coupled. If I don't have the resistor at the input, and the potentiometer is at the max volume (effectively no series resistance) the oofset jumps from 30mV to 200mV and there is a noise in speakers. I'm using 244 ohm resistor to take care of that particular situation.
Also, the Caddock in FB might be a bit hrash sounding. Vishay S102 brings better tonal balance, as they always sounded very soft.
Also, the Caddock in FB might be a bit hrash sounding. Vishay S102 brings better tonal balance, as they always sounded very soft.
zygibajt said:
With interconnect connected I have 10mV and 20 mV in ea channel respectively.
When I disonnect it I got 50mV and 80mV (I didn't check for polarity). Your 200mV seems normal and I noticed before that some chips present more offset than others. I once had a chip which in particualr NI setup produced 400mV (no 22k to ground) and when I replaced it with the other one, I got 170mV of offset. So don't worry, just keep the cables connected all the time😉
Thanks a lot for that informations
Just half an hour ago I checked everything once again.
I put that 220ohm resistor in series with + input and I think I leave it there becouse it seems not to change the sound (opposite than with putting input coupling cap).
It's not the offset that I'm worring about but the noise in speakers when I unplug the input cables.
I remember from Aleph expirences that DC offset stayed the same either input cables were connected or not ,and there was no noise in the speakers either.
Do you have any noise in the speakers when You plug the amp in without input cables connected?
My GC is an open design (no enclosure) for now so that may be the couse.
Just half an hour ago I checked everything once again.
I put that 220ohm resistor in series with + input and I think I leave it there becouse it seems not to change the sound (opposite than with putting input coupling cap).
It's not the offset that I'm worring about but the noise in speakers when I unplug the input cables.
I remember from Aleph expirences that DC offset stayed the same either input cables were connected or not ,and there was no noise in the speakers either.
Do you have any noise in the speakers when You plug the amp in without input cables connected?
My GC is an open design (no enclosure) for now so that may be the couse.
When I disconnect the cables at amp's side, no noise. When the cables are disconnected from the preamp (and connected to amp) I get noise in the speakers. It was the same for inverted amp and I think it's normal.
Mmmmm....
zygibajt, it seams that you have a ground loop there...
Can you test only one channel?
Do you have one or two PSUs/transformers?
If only one, you have to put the two channels (chips) very close one from the other, and join the two star grounds with a very small piece of wire.
zygibajt, it seams that you have a ground loop there...
Can you test only one channel?
Do you have one or two PSUs/transformers?
If only one, you have to put the two channels (chips) very close one from the other, and join the two star grounds with a very small piece of wire.
Thanks again Peter
There is always noise when one disconnects cable at preamp side,but I have a noise when I disconnect the cables at amp side leaving only amp and speakers connected.
Something must be wrong,but it seems my schem. is identical to yours ,now.
Hmm..
There is always noise when one disconnects cable at preamp side,but I have a noise when I disconnect the cables at amp side leaving only amp and speakers connected.
Something must be wrong,but it seems my schem. is identical to yours ,now.
Hmm..
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