[peranders]

What do you think of my ultra universal Gainclone project?
I have made partslists for common 6 different models.

1 Non-inverting buffer, Non-inverting LM3886, DC-servo
2 Non-inverting buffer, Inverting LM3886, DC-servo
3 Inverting buffer, Non-inverting LM3886, DC-servo
4 Inverting buffer, Inverting LM3886, DC-servo
5 No buffer, Non-inverting LM3886, No DC-servo
6 No buffer, Inverting LM3886, No DC-servo

*  Inverting or non-inverting LM3886, can be chosen
* Inverting or non-inverting input buffer, with or without gain, can be chosen
* Feedback network which can satisfy everyone, full gain at DC or gain of 1 using a capacitor in the feedback
* With or without DC-servo for both inverting or non-inverting LM3886, can be chosen
* Output filter, L//R, small handwound inductor plus a resistor.
* Inputfilter, lowpass and also highpass to block incoming DC-signals. You could also skip the filters if you want to. I recommend though to use a high frequency lowpass filter.
* Mute, the LM3886 is "dead" for a short time at power up, can be chosen.
* Bridge connection and the LM3886 can operate in inverting or non-inverting mode, can be chosen.
* Pcb for 2 separate channels, stereo, or one channel in bridge connection. It's possible to change mode easily with help from a jumper.
* Power supply be on the pcb with sufficient amount of smoothing capacitance.
* Stabilized power supply for the buffers. +-12 V is chosen (can easily be changed) so the amazing AD8620 can be used.

http://home8.swipnet.se/~w-80046/hifi_files/qrp/qrp01r0schema_p1.pdf
http://home8.swipnet.se/~w-80046/hifi_files/qrp/qrp01r0schema_p2.pdf
http://home8.swipnet.se/~w-80046/hifi_files/qrp/qrp01r0schema_p3.pdf

http://home.swipnet.se/~w-50719/hifi/gainclone


....  but there is a small problem! The amp doesn't exist in the real world, not yet. But there is a way to get hold of pcb's. This project is a t hobby level for me and it costs money, but it takes also time, which I have not much of. 3-5 people is needed to help me in building and debugging the pcb. When I write this I have two persons which is interested. Those who help me get also rewarded.

[JohnR]

Hi peranders, I'm kinda curious, why do you want to have so many different configurations?

BTW, what is the DC offset without the servo? Can't be very high surely - ?

[peranders]

I wanted to make the pcb super universal, that's the reason.

The DC offset can be rather high in some circumstances but if you want the lowest noise possible it's a good thing to use a servo. I have read rather much about offset problems so I made the DC-servo option just to eliminate the offset completely and also make more room for a wider choice of component values.

[peranders]

I have ordered pcb's today.

[peranders]

What do you think?

[Ferdi]

Looks great!

I am really keen to hear your experiences. I seem to remember from most discussions I have read that physical proximity of parts is a main reason for the good performance of Gainclones. Using a PCB goes against that to an extent.

Good luck!

[peranders]

Have you checked how far away many parts are? It's always a good thing to keep amplifier compact.

Please notice that the picture is changed, took the wrong one...

[peranders]

I have changed the picture above. What do you think now?

[JohnR]

Looks good!

How does it sound?

[peranders]

Thanks!

I don't know really, good I hope. I have very little spare time at the moment so I'll have to wait a while.

[peranders]

My QRP-01 is alive!!!! Seems to work very nicely so far without heatsink. Output offset 115 uV, Left channel, 10 uV!! Right channel.