Incredible quality amplifier by Graham, prepare your ears for it

[destroyer X]

I hope things goes fine...as when something goes bad...we feel more and more hot

nd a hard time to adjust the whole thing.

Those resistors are a little bit critical...i hope you can find them...or install a lot of them in parallell and go measuring till you reach 39 ohms.

To make them pretty>..well.... after debugging...will have time to make up.

Please...make images for us while you construct.....it is nice to see.

regards,

Carlos

 

[Nordic]

OK... will see what I can do... will probably need to get one or two things from the shop first...

PCB is etched...

 

[Nordic]

and tinned

 

[Nordic]

And now for the ghetto silkscreen.

Makes you just want to jump in there and get it done.

 

[destroyer X]

Ahahaha!...lovely work Nordic...thank you by the images.

Please..continue to keep us informed.

I finish the supply to the Dx amplifier...the 3601

Very clever to cover the board with the schematic to have references...easy and good.

regards,

Carlos

 

[Nordic]

Haha I posted in the wrong thread....

as I was saying I don't have a 2p2 cap...

 

[destroyer X]

I have noticed...hehe..i was there and i found.

Now i am here to see the schematic....i wanna know were is that 2,2 picofads small capacitor.

Yessss!...it is in the feedback line...to adjust the high frequency cut off...you can increase this capacitor till 12 picofarads without too much problem...because this capacitor value choice was really small.

Only instruments will perceive differences if you use 3,3p...or 8pF...or 10pF

regards,

Carlos

 

[Nordic]

Cool, I have some 5 or 6 pf ceramics (yeah, I know they are nasty) but I can't wait till Monday now can I.... Tommorrow we test!

 

[Nordic]

Ok I have not tested, as I got the J-fet buffer to work, and its awesome... except for some small things I can hear, but they are 100% because of the power supply I think, very crappy capacitors etc... minimal filetering etc... although there is no noise in the background... its absolutely pitch black on my speakers.

Also the LEDs failed to arrive today...

BUT I got this message from Graham (I feel quite honoured), so I don't expect it to beat the J-fet. I Will test it, as I need to open the other preamp to modify the relay to also softstart, as the fets puts out serious DC for the first minute.

When Andy Collinson first started his construction website he asked if I could come up with a circuit to demonstrate Tina.
I forwarded that gain stage.

It is not suitable for audio -
Not quiet enough input.
It has way too high gain.
No stabilisation components are shown, they must be determined from gain and usage.
It does not have a low output impedance or large swing driving capability.

It is there to show how Tina works and to fire imagination.

Yes it can be made to work, and has done so, but for hi-fi ?
I wouldn't.

Cheers ...... Graham.

Have a great day

 

[pgbhat]

Hi Carlos,

I am suprised that the 25Watt class A amp circuit did not work for you. The circuit is same as the one posted here http://www.diyaudio.com/forums/showthread.php?s=&threadid=40355

Can you explain more about your experince because i am on the way of building one.

Thanks
Prasanna

 

[Graham Maynard]

For Hajame In Carlos' Dx Thread

Hi Hahame,

Carlos is so fast with his constructions he became the first person to build a GEM after me.

He had some genuine bias and stability problems causing output device destruction which were not down to the 'Destroyer' himself; now cured.
Also the first circuit had a fractional mix of class-A and class-AB bias currents at the output stage which were audible; now separated.

Before anyone builds they should read this long page first.

http://gmweb2.net/Documentation/GEM document authored by Graham Stephen Maynard.htm

In;-

http://gmweb2.net

The matching Mar07 buffer/pre-amp circuit has also been fully tested.

Cheers ........ Graham.