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β24 on the move

beta24

Re: β24 on the move

Postby cobretti » August 3rd, 2015, 4:50 am

Second channel adjustment = done!
Once again, no issues besides VR4 trimpot and output DC offset that is really sensitive to adjust.
As described in manual, the initial setting of VR4 trimpot is to balance the current between R11 and R13 resistors to reach approximately 130mV on each resistor. But the real target here is to bring the output DC offset to 0V, right? I completely forgot about the DC offset on the first channel and I kept thinking how come I have 150mV DC offset on the output looking at the schematic, it didn't make any sense.I knew something was wrong. Then, of course, reading the manual again I found out I skipped point #9.
OK, When DC offset on output pads is adjusted to 0V, then, mV reading on R11 and R13 is no longer equal. One resistor reads like 68mV and other one reads lets say 170mV. So, I am assuming this is how all component differences are compensated to make bot sides symmetrical-balanced.
I am ready to do some mechanical finish on my rear panel......
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Re: β24 on the move

Postby amb » August 3rd, 2015, 5:43 am

cobretti wrote:Second channel adjustment = done!

Great!

...
So, I am assuming this is how all component differences are compensated to make bot sides symmetrical-balanced.

Correct.
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Re: β24 on the move

Postby cobretti » August 3rd, 2015, 6:12 pm

Almost done. I am pretty close to the finish line. All in box power tested. All I have to do is to bring the wire to the input connectors.
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Re: β24 on the move

Postby cobretti » August 4th, 2015, 1:01 pm

Done! I just finished it.
I was expecting that something might go wrong with this project because all the peripherals are my own design but it didn't happen. Time will tell. Everything, besides the b24 boards and sigma22 power supplies is my design so I am happy that I didn't have to look for extinguisher :mrgreen:

It is up and running.
What a :shock: f****n sound! Unbelievable! I am very pleasantly surprised about the sound, and believe me, if it's not good, I would let you know.
This amp has incredible sound control on the bottom range. My speakers are crap floor standing Focal( but are they?) with two bass drivers on each of them. There was nothing surprising coming out of these Focal speakers when plugged in to my old integrated amp. Maybe they were too complex load for my integrated to drive. They had no balls, no punch. Kind of OK-ish sounding from mid range to higher frequencies. My old integrated amplifier has fantastic THD, crosstalk, noise floor and dumping factor parameters, but there was something missing.
I had a Benchmarkmedia sales rep here once in my house and he also said that it's been long time since he heard anything good sounding like my old integrated and my old Shan E530 speakers.
But b24 is way above that! I don't know why, but it is. It could be because I took the power supply seriously, I used separate toroids, fast switching diodes and storage caps those have ripple current 23Amps.
So everything is hunky dory. I am very happy with this built. The only small issue I have is that I put a potentiometer on the input for debugging reasons when I first time plug it in so that I don't blow up my speakers up. But I can hear some very very negligible noise when I press my ear on the tweeter. When I switch to XLRs, the problem is gone. I used some good quality HVAC shielded wire (with foil shield) that I had handy but I will definitely rewire it and go straight from XLR connectors to the amp input. I am using RCA connection right now. What a sound! :!:
DC offset it 0.5mV one right channel and 2mV on left channel. Fantastic!
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Re: β24 on the move

Postby amb » August 4th, 2015, 1:12 pm

That's fabulous, and a very neat and tidy build! Welcome to the β24 club.
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Re: β24 on the move

Postby cobretti » August 4th, 2015, 3:51 pm

Thanks. All I have to do is to finish that speaker protection I was talking about earlier. But it is not a must have emergency right now.....
I just ordered Canare L-4E6S wire and Neutrik connectors to make myself XLR interconnects. I wonder how many B24 are out there....
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Re: β24 on the move

Postby amb » August 4th, 2015, 4:26 pm

cobretti wrote:I wonder how many B24 are out there....

I don't know how many are actually built, but I've shipped enough boards for over 100 stereo β24s.
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Re: β24 on the move

Postby cobretti » August 4th, 2015, 5:12 pm

Nice. BTW, I didn't install Zobel network. And I am not sure if it is needed.
If I can give an advice to other potential builders, I recommend to let the amp warm up for like 1 hour for final setting adjustments. It may be overkill but I had my Fluke meter hooked up on the R7 resistor and the voltage was still slightly climbing after 30 min, even though it seemed that heat sinks reached its max temperature. Later, the amp will undergo some serious listening torture test :lol: I have overheat protection installed, I want to see if I can warm it up enough to shut it down.
I noticed there is no much heat sink temperature difference between if I let the amp just sit on idle, or playing a music through it.
Well done. :geek:
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Re: β24 on the move

Postby particleman14 » August 4th, 2015, 5:36 pm

Great looking build! I like the organization and layout. Very utilitarian. I like the black and red color scheme as well.
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Re: β24 on the move

Postby bk_856er » August 4th, 2015, 7:54 pm

Nicely done! Seemed to come together rather quickly for you, but certainly very carefully planned and executed.

I'm planning my build for this winter - all parts already on hand.

BK
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