Amp Camp Amp - ACA

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2 picoDumbs

2 picoDumbs

Member
Joined 2013
Variac said:
It seems that one of you full range drivers should be rolled off lower than the other to avoid comb filtering etc. Probably you are- to counteract the rising response they tend to have..
Click to expand...
Correct. The funny thing is, even with the rising response, they don't sound very detailed. That's why I added the horn.
I'm going to do measurents on the following.
1 x Seas driver FR
2 x Seas drivers FR
2 x Seas drivers 1 FR the other with low pass filter
Horn with high pass filter (around 9 to 10kHz) + 2 x Seas Drivers FR
Horn with high pass filter (around 9 to 10kHz) + 1 × Seas Driver low pass around 9kHz the other with low pass around 160Hz
Horn with high pass + 1 x Seas with low pass + 1 x 12" with low pass.

There are few more variations I can think of but I'll let the measurements and ears dictate what changes I will make to crossover and driver combo etc.

I just threw it all together quickly. I don't like to let textbooks get in the way of having fun.
Once I'm happy I'll rebuild.
 
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mc297

Member
Joined 2011
I tryed to change the IRFP240 when I built my ACA with the 044 to have better bottom end and maybe lower distorsion but the result was good on it but higher frequencies where attenuated too much so I replaced again with IRFP240.



Eric said:
Mark: Here are some notes I tucked away about different IRFP devices - I think these came from the huge Aleph-X thread long ago...

IRFP044 vs IRFP240 vs IRFP244 vs IRFP250 : A number of amps have been built using each of these transistors. Nelson has characterized the differences among the three latter transistors as follows: The 250's have greater current capacity, but twice the capacitance of the 240's and 244's. They will give a better bottom end, and will sound a bit different, for better or worse, depending on your situation and taste. There is very little practical difference between the 240's and 244's. Some have reported that the IRFP044 sounds a little "darker" (more narrow frequency bandwidth and greater high-frequency roll off) than the 240, though this is not really surprising as the 044 has greater capacitance than the 240 series. Essentially, greater capacitance provides slightly better bass, but at the cost of slightly reduced treble. The practical difference, though, is their current capacity. The maximum current and operating temperature ratings have lead many to use the IRFP240/244 for rail voltages of 20v or higher, while using the IRFP044 for 15-20v rails. The lower voltage versions of the amp tend to feature higher current, and the 044's can handle significantly more heat.


Device (Max Voltage, Max Current, Max Temp)

IRFP044 (60v, 57A, 175c)
IRFP240 (200v, 20A, 150c)
IRFP244 (250v, 15A, 150c)
Click to expand...
 
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bonz91

Member
Joined 2015
Hi everybody, I'm from Italy and I'm trying to build my own ACA but I've came across some issues.
I've got everything I need from digikey, and I've built myself the PCB.
First of all, when I measure the voltage from the input connector (3,5 Jack), I see at least 1V, that in a couple of seconds turn down to zero. Is that correct? Could this Voltage possibly damage any external hardware connected ?
 
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bonz91

Member
Joined 2015
Yes, I've Made 2 pcb and change all the components to be really shure, but the problems remains! Speaker connected everything Seems to be right!
Don't look at those little dissipators, they are just hooked for testing.

Already check for any short circuit, but everything Seems to be right in place.
 
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bonz91

Member
Joined 2015
sorry, can't upload from the phone. Here they are!
 

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2 picoDumbs

2 picoDumbs

Member
Joined 2013
After finding both supplies and powering up both channels for first time, one amp starts buzzing through the loudspeaker and progressively becomes louder.
Mosfets are drawing 1A and getting 10V between middle pin of Q1 and Ground.
All I can think of is bad Output cap?
Bad Jfet?

It's 2am got to go to sleep
 
Last edited:
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mikegranger

Member
Joined 2010
2 picoDumbs said:
After finding both supplies and powering up both channels for first time, one amp starts buzzing through the loudspeaker and progressively becomes louder.
Mosfets are drawing 1A and getting 10V between middle pin of Q1 and Ground.
All I can think of is bad Output cap?
Bad Jfet?

It's 2am got to go to sleep
Click to expand...

Have you tried swapping the power supplies side to side? You may have a bad smps . A wise man once told me to try the easy things first. I'm still trying to remember that (but usually forget).
 
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