DIY ACA mini

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#2,141
So,
all just fine with my parts but I reach not expended values for VB / VO (20V powered) .
1k for these pot seams not working for me i will test tomorrow more and will a 1k or 1k5 and we will see (or go to 2k lettered on the bag).

For today I can only say to Nelson .... more of the simple toys!
 
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#2,142
Yea, well for what it is worth. I have amped up one mini. The mini in the first picture as a cool summer amp.

One ampere bias per channel, 24 volts. Not really super cool. But still far under 50C.

I was hoping it would be ”good enough” in the summer as a substitute to the twin Aleph J amplifiers.

Well? Not even far from close 🙂

But the magic is absolutely there. Just. Do not over crank it 🙂
 
#2,143
Well, and what would be the actual difference in sound? Speakers and room may turn all that i am describing exactly up side down. So…

The pure muscular power advantage between twin Aleph J:s and one ACA mini is not even remotely fair:

Yeah. Correctly, but that is what i am compairing here.

So: ACA mini has a clear purity, with a backoff in the high bass, low midrange that makes it sound clear and lean.

Beutiful.

But the twin Aleph J’s holds the clarity, adds more midrange fullness, adds more bass muscularity, stronger dynamic and control.

Well?
Say.
No more. 🙂👍
 
#2,144
Following up on my experience with my just-completed ACA mini. I connected this great little powerhouse to my main speakers this morning. The speakers are a Malcolm Jones design known as the "Tabor" that was popular in the 1970s. That's when I built mine. I was in high school and saw a pair at the swanky modern home of one of my classmates. They looked cool. And even more badass was the massive, gleaming power amp attached to them. Must be good, I thought. I tucked the brand name into memory: Threshold. The more I learned about audio, the more I was curious about these amps. That led me to Nelson Pass. First Watt. Pass Labs and finally the ACA mini - something I could build and afford. So, really, today has seen the culmination of a 40+-year quest to match my Tabors with a Pass class A design.

Thanks @Nelson Pass for making such lovely sound possible, DIY-able and wonderfully affordable! There is so much rich detail and instrument separation. Just really, really delicious sound. And it is obviously also very pleasing to the furry ears that are far more sensitive than mine.

Thanks also to the forum for keeping me on track and the good multimeter tip.

Al
 

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#2,150
Dennis Hui said:
@ALNY:

I picked up a UNI-T UT61 meter 7 or 8 years ago. It was pretty inexpensive and has served me well. I'm surprised your two meters threw you off so much. Do they behave better with fresh batteries?
And congratulations on solving bias problem. :cheers:
Click to expand...
@Dennis Hui

Thanks for the meter tip. Both of the bad meters are more than 10 years old and were in the $15 range of cheap-o, a Velleman DVM850BL and a GB Instruments GDT-11. The Velleman goes to "1." after getting to 199.9 mV on VB. It just couldn't do 300 mV. Weird. I am an adult. Time for a decent meter. The one that worked reliably is a Commercial Electric MS8301B, also quite old at this point.
 
#2,151
^ My WAG is that the Velleman needed to be set to the proper range. Perhaps the same with the GB. The CE may have worked well for you b/c the lowest range goes up to 400mV. I am speculating re: where you had them set, but I'm going by your mention of the Velleman reading "1".

Now that you've verified the voltages with the CE, maybe check them using the 2V (2000mV) range on the other meters. If they show good values, then you can keep them around. Having multiple meters is a nice thing.

With that said, a new auto-ranging meter may be a nice thing too. 🙂

Edited to add - the CE version of the MS8301B seems to be autoranging, while the Mastech is not. The lower range seems to be the same between the two...
 
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#2,152
Agreed. Looking at this photo https://www.diyaudio.com/community/attachments/img_4878-jpg.1183799/ the Velleman looks is manual ranging.

@ALNY: Please try measuring the same voltage source with your three meters as IAIMH suggested to see how well they match. If you don't want to measure on the amp, just use a regular 1.5V battery (AA or AAA) and measure the voltage with all three meters. With the manual ranging ones, set the DC range to 2V (or whatever the lowest one that is higher than the expected value).
 
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#2,153
^ Yep. I checked the operating manuals for the Velleman and the GB prior to the previous post. Both manual ranging with lowest range up to 200mV. The MS8301B seems to have been sold by both CE and Mastech. The CE version is advertised as autoranging, and the Mastech is advertised as manual. Both show the 'lowest' range for DC as up to 400mV. That's why I think it worked vs. the others which may have been set to the 200mV range. Guess, but... why not check it vs. tossing out what may be perfectly good meters.
 
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