- 133 Posts. Joined 8/2012
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My new 3x9V CMoy - Page 2
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One board are ready and working. Everything work perfect - LED switched color at 21.8V as expected, charger charge.
With Lm4562 and gain 2 sound is really powerful and clean, like with my external regulated 24V PS, maybe little cleaner and more controlled bass (probably just placebo :)
Edited by Zigis - 12/16/12 at 1:29pm
This looks really awesome , i would like to know how its performing .
Whats the battery life ?
DC offset ?
Output current ?
Is it able to power those really demanding headphones like 68ohm ?
I had a look at the prototype schematic , have a few questions about it if your printed boards are not available yet .
Good luck , keep up the good work
Amp perform good, like any CMoy, depending chip used:)
DC offset is very low, with FET input opamp like OPA2134 - less than 1 mV, with bipolar input like LM4562 - 2-4 mV
Main improvement over simpler CMoy is increased headroom, because of high power voltage. This is especially good for higher impedance phones.
PCB are available, if someone are interested, 20 Euro including shipping.
That's pretty decent 20 euros .
I'm a total novice so forgive me if i say something stupid which is likely if we were to talk about electronics for any length of time.
Any way looking at the schematic i worked out that the bottom bit is the charger . ( not the voltage splitter)
And that the LM4562 is a single op-amp .
So have you piggy backed the op-amps on each other ?
Do you use the same virtual ground for both op-amps or do they need seperate one ?
Yes, bottom part is voltage multiplier and charger, voltage splitter is TLE2426, LM4562 is dual opamp for both channels, on schematic one channel shown, second channel is similar. Virtual ground/rail splitter is one for whole amp, as always.
Edited by Zigis - 12/26/12 at 7:42am
Finally first amp on PCB is ready
Here is inside with PCB
Batteries are very tight in place
And here you can see most important difference from first prototype - battery voltage indicator in action
Upper image - battery voltage in good condition.
Lower image - battery voltage too low, requires charging. Actually LED's color is red here, just bad camera.
Thanks JohnnyCrash8 !
I make small change in schematic. 75 ohm resistor near LM317 is changed to 50 ohm or even 46 ohm, for increasing charging current from 16mA to 25-27mA.
In the beginning I just copy/paste 75 ohm resistor from some older well known designs like amb's m3 or Tangent's PIMETA. In real world 16mA is too slow for today's 250-280mAh batteryes, overnight charging not charging battery at max.
So, I increase current closer to C/10.
This information will be usable for anyone who use amp with 9V batteries and built in charger, not depend - one battery, 2 or 3 in series.