Trying to improve on a GainCard concept

[ronc]

No danger to the speakers, it just starts to distort like crazy.
ron

[advance]

Hello Peter

I switched to batteries now, and although I said in the other thread that I wasn't impressed that much, after listening again for a while, I have to admit that there is something to the sound of the amp running on batteries. It sounds like nothing else and the music seems to be very effortless. The detail is improved and everything seems to be harmonically right and coherent. The effect similar to using an air suspention platform. Nothing really to complain about. Also, the bass is deeper.

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.

Since I'm using 2 of them in series, I have to figure out a convenient way to charge. I think they could be charged in series as well, by 24V charger?

I use a very simple charger design with great success. This design may fit your requirements.

Charger Schematic Diagram: http://home.tiscalinet.ch/cooltune/P...CLP-BSU1aS.pdf
Power Supply/Amplifier Block Diagram : http://home.tiscalinet.ch/cooltune/P...ockDiagram.pdf
The complete amplifer article: http://home.tiscalinet.ch/cooltune/P...Megalith01.htm


advance

[advance]

... and by the way Peter,

Your gainclone design looks very impressive. Congratulations.

advance

[Flemming J P]

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.

[tbla]

Rob somebody so that I can get those trafo's for a new preamp.

i have some trafos - but they are very expensive.....

[protos]

Originally posted by Peter Daniel
But I still don't feel that comfortable with batteries. What happens after they run out of voltage (unevenly)? Any DC offset danger?

Since I'm using 2 of them in series, I have to figure out a convenient way to charge. I think they could be charged in series as well, by 24V charger?

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.

[antomas]

Hi Peter, compliments for your new masterwork!

But I still don't feel that comfortable with batteries. What happens after they run out of voltage (unevenly)? Any DC offset danger?

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

[carlosfm]

Originally posted by antomas
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

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.

[zygibajt]

Signal goes directly through 244 ohm Vishay to + input

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

[GregGC]

Originally posted by zygibajt

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

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.