L'Amp: A simple SIT Amp

[Michael Rothacher]

I just use a big dumb generic 30A 400V from Digikey.

[serengetiplains]

Michael, have you compared the sound using the switchers vs. a simple CRC passive supply?

I don't know if Vicors sound better, but you often can pick up an appropriate model from eBay without too much waiting or searching.

[generg]

Juanitox! Excuse me not asking for the heat problems, but.....

For the sound, did you here the same big jump forward in precision and clarity I meant to here after changing to thick film resistors.....?

[stefanobilliani]

Originally Posted by generg

Juanitox! Excuse me not asking for the heat problems, but.....

For the sound, did you here the same big jump forward in precision and clarity I meant to here after changing to thick film resistors.....?

What I have found with the resistors as light bulbs ( incandescent or halogen ) that they are slightly sensitive to vibrations . In other words they can "sound" better dependin where and how they are mounted .

Regarding the dissipation , I am approaching 2 Amps with 2 little fans , the heat sinks and then the Sit transistors cool down to a comfortable temperature with little effort . The fans are not noisy at all .

[Michael Rothacher]

Originally Posted by serengetiplains

Michael, have you compared the sound using the switchers vs. a simple CRC passive supply?

I don't know about that particular supply, but I have an adjustable heavy duty switching power supply in my lab and it's terrible for audio work.

[juanitox]

michael , you are the man!! i put the heatsink of the 10ohm resistor outside the case, it is very hot but the case , transfo and Caps stay warm for the sound no change for me with the wirewound resistor , but i have lost my hexfred bridge for a 3 cents one .. this afternoon if my wife set me free i will put a old good motorola bridge and tell you..

[generg]

finally it looks like a heavy machine......driving something very dangerous.....


glad you fixed the problem.....

and I am astonished that you do not have the sound difference with the thick film resistors I found astonishing..................................that´ s life!

[Michael Rothacher]

That's great! And, it looks great too.

Now you can focus on dialing-in the sweet spot for your speakers/taste. It may take a little time, but you'll have fun.

Well done

[juanitox]

Originally Posted by generg

finally it looks like a heavy machine......driving something very dangerous.....


glad you fixed the problem.....

and I am astonished that you do not have the sound difference with the thick film resistors I found astonishing..................................that´ s life!

bow with the motorola bridge it sounds superb! , even better than before with the hexfred and the wirewound resistor , so it think the upgrade came from the Thick film res ..

this week / Rcore transfo test and CLC with Rifa PeH200 and hammond 10mh choke ...

this amp 's got so few part , very funny to tweak

[Roscoe Primrose]

Originally Posted by nicoch58

well the lamps are beautiful but not simple here in EU , the alogen stick have hi price and not so clear resistence ...plus the philips mbtf only 200hr ,the GE 2000hr but I see only 500w .....

with 39v bias 2A ,speakers 5,5ohm I'm near of Stefano working amp ie 16 to 20ohm needed resistence...

Suggestion?

What's the voltage/current rating of the Philips pieces? If you're running them at significantly less than rated power, MTBF will increase dramatically...

Roscoe