Two days ago I finished my ExtremA poweramplifier. This is a 100watt pure class A fully balanced power amplifier by Sander Sassen and Bruno Putzeys. The project started 1,5 years ago when I bought the pcb's, ring-emitters and (relatively hard to find) crd's from some-one who could not find the time to start the project. When I look back the hardest part was to find a case that is able to handle the heat generated by 100watt class A.
Finally I found a case made by an Italian company (modushop.biz / hifi2000). They also made the custom frontplate. Case is full anodized aluminium with large heatsinks which are bearly able to handle the heat (heatsinks up to 65-70 degree celcius). Then the next presented itself; the bottom plate (3mm alu) was bending under the wait of the huge 650va shielded transformers. So I constructed a frame from 2mm alu squares. Now the bottom bends less then 1mm. Problem solved.
I know another builder had some trouble while buidling the amplifier. I am not a novice builder but also defenetely not an expert. Buidling this amp is very do-able. The partlist supplied by Sander is very straight forward. Mechanical construction is the hardest part. And off course, I had some help from my brother who is an electronics designer/engineer, especially during final testing. Just one problem I need to look into; when a input signal with high volume is send to the amp and then the amp is turned on, the amp sometimes latches up. When the source is muted and then the amp is turned on, the problem does not seem to occur. Hmmmm......maybe the value of the powerresitor on the softstart pcb is a bit too high. And maybe I will replace the emitter resistors with higher values. This way a bit of output power is sacrifised but the amp will remain a bit cooler.
Sound? I always have to laugh about comments like "a lot of air", "very black" etc. First impression: "wire with gain", just as the designers intended.
Below some pictures of the project.
Finally I found a case made by an Italian company (modushop.biz / hifi2000). They also made the custom frontplate. Case is full anodized aluminium with large heatsinks which are bearly able to handle the heat (heatsinks up to 65-70 degree celcius). Then the next presented itself; the bottom plate (3mm alu) was bending under the wait of the huge 650va shielded transformers. So I constructed a frame from 2mm alu squares. Now the bottom bends less then 1mm. Problem solved.
I know another builder had some trouble while buidling the amplifier. I am not a novice builder but also defenetely not an expert. Buidling this amp is very do-able. The partlist supplied by Sander is very straight forward. Mechanical construction is the hardest part. And off course, I had some help from my brother who is an electronics designer/engineer, especially during final testing. Just one problem I need to look into; when a input signal with high volume is send to the amp and then the amp is turned on, the amp sometimes latches up. When the source is muted and then the amp is turned on, the problem does not seem to occur. Hmmmm......maybe the value of the powerresitor on the softstart pcb is a bit too high. And maybe I will replace the emitter resistors with higher values. This way a bit of output power is sacrifised but the amp will remain a bit cooler.
Sound? I always have to laugh about comments like "a lot of air", "very black" etc. First impression: "wire with gain", just as the designers intended.
Below some pictures of the project.
Attachments
Last edited:
Hi Jacco,
It is not exactly a preamp; it is a twistedpear audio buffalo32s dac with volume control. So...sort of preamp. It's the only source I have with balanced out so I connected it directly to the ExtremA. Works perfect!
Scanspeakman
What an absolute monster...
I love it!!!
I'm often bitching about modern 7x150Wrms amps weighing a lot less than my 2x100Wrms amp.
I think you can beat my 18kg
hmmm. my tiny 25W amp beats that 18KG
hmmm. my tiny 25W amp beats that 18KG
I do not have a scale here but I guess this one weights about 35kg. The case alone is almost 18kg and the big 650va tranformers are also around 8 kg's each.
Scanspeakman
At first I had the ExtremA hooked up to a pair of old Jamo speakers. Sound is crap and I couldnt care less if these were damaged of blown up, so that makes them perfect for testing. After some further testing everything seemed ok so I hooked the amp up to my diy Scanspeak speakers. Wow! My 18 year old Elektor LFA50 25watt class A amp I have used until today has beaten a lot of much more expensive amps but it is no match for the ExtremA. Better imaging, better bass control, some small details I have never heard before. A worthy upgrade!
Scanspeakman
Scanspeakman
I believe the person I bought them from had them custom made by Tauscher in Germany. If I am correct the transformers were made for a diy pass labs project that never happened.
Scanspeakman
I have not measured the temp of the transformers but when I accidently touched them two days ago to adjust the dc offset, they felt pretty cool. No problem there in my opinion.
Scanspeakman
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.