[Goobley]

What sort of cost are we talking about to get it off the ground? (I'm sure that you want your pcbs too) I might be able to convince a friend of mine to chip in too.

 

[Zigis]

Complete amp with Hammond al. enclosure, panels, everything will be 130 Euro. 
PCB, I have not experience with this size, somewhere 15-20 Euro, I think.

 

[Zigis]

PCBs are ready.
 

 
 
 
I am going to build one amp to test everything.

 

[Zigis]

[size=small]One board are ready and working. Everything work perfect - LED switched color at 21.8V as expected, charger charge.[/size][size=small][/size]
[size=small]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 [/size]
 
 
[size=small]o[/size]

 

[Glovebox]

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
 
Glovebox .
 

 

[Zigis]

Hi Glowebox,
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.

 

[Glovebox]

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 ?
 
Glove .
 

 

[Zigis]

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.

 

[Zigis]

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
 

 
[size=small]Upper image - battery voltage in good condition.[/size][size=small][/size]
[size=small]Lower image - battery voltage too low, requires charging. Actually LED's color is red here, just bad camera.[/size]
 
 
[size=small]Zigis[/size]

 

[JohnnyCrash8]

Nice, very clean & well implemented build.  Very unique as well!

 

[Zigis]

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.

 

[chispa02]

Great build... Thanks for the amp's schematic, I will try to build one in my next vacations...