ExtremA, class-A strikes back?

[Pan]

Out of 25 about half the lot was within a couple of % so there was no problem at all to find Hfe matched inputs with a tolerance better than +/-1%.

Good enough!


/Peter

[Pan]

About heatsinks, I have no idea what rating these have but I do have four pieces of them.

Size is 30cm x 20cm x 4cm which should be about 12" x 8" x 1.6". The "baseplate" is 1cm thick and there are 30 or so grooves/fins where 1/3 of the material is left.

Any chance that one sink is enough for one channel or should I play safe and use two sinks from start?

I have tried to add a pic but I seem to be retarded when it comes to computors and intenet.


/Peter

[SSassen]

Peter,

You can easily find out what rating they are. Simply attach a case style 20 or 50W resistor, for example 10-ohm, if possible via a copper plate to spread out the heat better. Then apply a known current and voltage and calculate the dissipation of the resistor. By simply measuring the temperature of the heatsink after 30-mins or so and determining the deltaT vs. the ambient temperature you can make a good guess of the heatsink's K/W rating.

Best regards,

Sander Sassen
http://www.hardwareanalysis.com

[Pan]

Sander,

thanks for your quick reply. Actually I was thinking along those lines and I'll try it to see what it will give. I have a couple of Arcol HS100 6.8ohm which will be just about perfect for the job.


/Peter

[Vadim]

Peter,
Have you completed your project? How did it turn out?

[madrigal]

I am still surprised that nobody, i mean really nobody, can give us any details about the sounding of this amp.

Thats why i am going to build one myself.

I have now for 11 years the LFA-50 OA running in my hifiset, also an DIY amp published in the Elektor. It sounds like a angel (till today). Compared with commercial amps it was then times its value to the cost to built it. I am really surprised to read so many bad comment on this forum about this amp. Must be a taste question.
However, not to much discussion about his.
I just want to make everybody aware of the fact that i have trust
in the amp projects from Elektor. Even without hearing them. Because i vote for class A (not a tube fan) I have been waiting long for a new Class a project from Elektor like this ExtremA amp.

Now having more time off with my new job, i think it is time for a replacement amp for my hifiset. (updating my complete set)

So, who can provide me with a stereo set of PCB's for the ExtremA, or can tell me where to order.

[GK]

Originally posted by madrigal
So, who can provide me with a stereo set of PCB's for the ExtremA, or can tell me where to order.

Right here:
http://www.hardwareanalysis.com

[peranders]

Originally posted by madrigal
I am still surprised that nobody, i mean really nobody, can give us any details about the sounding of this amp.

Thats why i am going to build one myself.

This is a rather advanced and also expensive amp, not common DIY stuff. I think it will take a while but surely it will be built.

[jacco vermeulen]

Originally posted by madrigal
a taste question.

It takes some time to build a suitable low thd+n pre-amplifier for the E-A if there's no feel to drive the power amps with an LM4562 based balanced pre.

The thing with the LFA50/150 is related to the CFP output in general, not aimed at criticising Andre Schmeets (or Elektruca salsa, those guys used to have admirable hearing)
Maybe one day someone will stick some A1360/C3423 in the front end of the LFA50 and load it with a triple darlington output stage.

[madrigal]

I don't think this amp is more difficult to built then the LFA-50.
Almost everything is provided on the PCB. Of course you must work accurate with building an Amp and not to rush.
A small mistake is made easily. I remember that i also made one miner one building the LFA, one wrong transistor type solderd in.
Took me 2 days to solve. Building amps can be frustrating