L'Amp: A simple SIT Amp

[nicoch58]

with so big caps at fist position we have a big current pulse,rfi, better put a small resistor for more conduction angle.....

[juanitox]

like a 0,5 ohm ?

[nicoch58]

yes 0.1 to 0.5,try test on PSUD software...

[Michael Rothacher]

More cowbell, maybe.

[generg]

Originally Posted by Tea-Bag

Gerd,
What brand, how many of what wattage thick film resistors. I have thought about parralleling a few 100W thick film types.

Hi tea-bag,

they are Vishay, I cannot get them here in 100W so I took 50W and 4x10 Ohm in series and parallel gives 10 Ohm and one 2,2 Ohm and one 1 Ohm and I get the chain of 13,2 Ohm I need with the 45-48V DC an 2x18V AC xformer from my FW PSU can make......

the sound its really a big change now I can understand the BTW was speaking of "tube rolling" ; I made resistor rolling........

my battle between resistor solution and Mufollower is still not decided ...

not to speak of the Salas CCS..

RTO 50F 47 - Dickschichtwiderstand 50W TO220 47 Ohm, 5 - Dickschichtwiderstände TO220 bei reichelt elektronik

[generg]

juanitox,

I am sorry to hear about your hum, after I got away from the + -24V arrangement from the First Watt PSUs, and built it like Mike suggested with 48V I have no hum, only going to the speaker very close I can hear a little bit....

unfortunately i have no good idea what you should do,

when the hum is induced by the bias voltage you could try a nine Volt block instead for a moment, may be the hum is over.....
you will be happy about your thick film resistors....

and there must be a simple solution for your hum.....

[juanitox]

for this week my Sit is dead , cause i killed the bridge rectifier with a bad live action ... so waiting for the new ones , i hve time to re-thinking my Amp Config.. it's better when it"s not working to fast

[Michael Rothacher]

Take your time. It's a journey. We'll all still be here.

[generg]

Yes, I can send you two from Germany maybe faster....

I have an idea, I would build only one channel with no extras, only main function to isolate the guilty part.


Oh rereading your posting you did not kill the SIT, but the bridge rectifier.... So no need to send you a part I suppose...

[Michael Rothacher]

I pulled up my notes:

The resistor / lightbulb version measured 70 nanowatts noise + hum. With 101 dB speakers @ 2 meters distance that would be around 23 dB, or somewhere between a really quiet room and a faint whisper.

Forgive me for quoting the wrong units earlier (uV). I was away from my underground lair.