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Joined 2002
I got a pile of irfbc40, would they work?
Oops, which one's J? (I did read like 20 pages but didn't find it.)
zen mod-
A personal note of thanks for always taking the time to help others with expert advice and assistance.
Got to ask, ZM.
There are 2 approaches to raise the bias, increase R11, decrease source resistor, or both. My question is, which one is better and why? R11 seems to be much simpler than changing all the source and series resistors. BTW, I used the later to bump the bias.
There are 2 approaches to raise the bias, increase R11, decrease source resistor, or both. My question is, which one is better and why? R11 seems to be much simpler than changing all the source and series resistors. BTW, I used the later to bump the bias.
Just decrease the source resistors. Changing r11 will have almost no effect on the dc bias and changing it will mess up the active behavior of the current source. It would
probably be ok to just decrease R18 and leave the other source resistor alone.
probably be ok to just decrease R18 and leave the other source resistor alone.
I lowered the source resistors by placing a 2.2R across them resulting in a ~0.39R. Bias current now is ~1.05 amps. That's better. DC offset is ~56 mV.
Gonna let it idle for an hour and then repeat measurements and check heatsink temp.
Gonna let it idle for an hour and then repeat measurements and check heatsink temp.
I've been lurking on this thread for a little while, and am wondering how the Mini Aleph sounds. I heard a big Aleph X pair once (belonging to Hugo/Netlist the moderator on this forum) and it made such smooth and detailed music I was hooked. Does the Mini do they same thing to any great degree??
Sorry if this has all been said before.
Thanks,
Simon
Sorry if this has all been said before.
Thanks,
Simon
Stop lurking, go on and make your own. It's fun! 😀
BTW, I have only listened to mine just this morning and really like what I was hearing. Still final verdict is pending as it was only the left channel at a low bias level. I'm still busy tweaking the bias ATM.
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I'm looking forward to your final impressions.
Logistically it will be hard to fit the amp into my system as it will mean bi-amping, unless it can drive a very tough load (3 way open baffle with transformer bass boost). I have very little space on the rack, but I keep thinking class A thoughts. One solution could be tiny digital amps on the bass and Mini Aleph on mids and tweeter....
Logistically it will be hard to fit the amp into my system as it will mean bi-amping, unless it can drive a very tough load (3 way open baffle with transformer bass boost). I have very little space on the rack, but I keep thinking class A thoughts. One solution could be tiny digital amps on the bass and Mini Aleph on mids and tweeter....
OK, so I got excited there for bit until I saw the j109!
I suppose the answer is "go and match some j74" 😀
You know Spencer? He still has very few matched quad j74 left. Go get them before they are gone, while you are at it, get a couple hundred of K170 as well 😀
I went out to get some 1R / 3W resistors. Source resistors are now ~0.32R. I now have the mini-A idling @ 1.25 amps with a heatsink temp of 40°C (104°F) at 20°C ambient. A nice stopping point IMO.
The mini A is a (sort of) single ended ClassA design.
Does that limit it's transient output to 1.25Apk?
If so then that is just 6W into 8ohms or 3W into 4ohm.
Does that limit it's transient output to 1.25Apk?
If so then that is just 6W into 8ohms or 3W into 4ohm.
say that goal is to have around 500-600mV across source resistor ;
source resistor is for coarse biasing , "R11" ( in that schmtc) is for fine bias adjusting
every Aleph ( implementing active CCS , so called Aleph CCS ) will have max current peak in range of twice Iq
Using Ohm's Law I was able to get the bias current I wanted by lowering the (combined) source resistor. Fine tuning with the source resistor is also possible, wether it's an elegant solution is another matter.
I now have both channels idling at ~1.25 A, heatsink is ~41°C (~21°C above ambient). Since it's only about 12 Watts per channel it's not a very powerful amp but the sound is phenomenal. Think quality rather than quantity. Tremendous clarity and depth, even at low listening levels. I'm very pleased with the results. And with autumn and winter coming it serves a dual purpose because it also is a wonderful heater. 😀