it was when Vale, in his Ducati stint, took Casey along with him outa race
if not, Casey would got that one, while Vale was desperate
anyway, fun ......
if not, Casey would got that one, while Vale was desperate
anyway, fun ......
Interesting... the better DF clearly can help bass in your hard to drive case, but more details in the mids and HF are intringuing
The VFET has also negative H2. Of course the neg H2 effect varies with its level as can be heard in the B1K for example. More airiness comes usualy at the cost of precision, but all that wouldn't explain the better details indeed.
Need probably to build an ACA Mini to find out 🙂
Claude
The VFET has also negative H2. Of course the neg H2 effect varies with its level as can be heard in the B1K for example. More airiness comes usualy at the cost of precision, but all that wouldn't explain the better details indeed.
Need probably to build an ACA Mini to find out 🙂
Claude
I shouldn't be by now, but I am always surprised by how Papa manages to create something so gorgeous from small, simple elements.
I finished my Mini ACA today and it's singing with a B1R2 and some inefficient, '70s, 3 way speakers, the size of a small refrigerator. Not an easy combo to play nicely with, but again, I shouldn't be surprised by the sound it produces.
Thanks to Papa for his skill and generosity. And thanks to Kevinheem for organizing the GB. I know how much fun they are.....
For the record- jumpers out.
I finished my Mini ACA today and it's singing with a B1R2 and some inefficient, '70s, 3 way speakers, the size of a small refrigerator. Not an easy combo to play nicely with, but again, I shouldn't be surprised by the sound it produces.
Thanks to Papa for his skill and generosity. And thanks to Kevinheem for organizing the GB. I know how much fun they are.....
For the record- jumpers out.
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I completely missed that detail! 😁 Thank you for pointing that out. Now I know it's not the negative H2 that plays tricks with me.
The Mini-ACA is just a seriously good amp! 😮
Can we use alternative JFETs other than sk170/sj74 for this ACA mini amplifier?
My build with Fairchild 2N5458/2N5461 (easier to find and much lower price) and results are good! But beware for different JFET pin assignments.
Did you have to buy multiples and match them? I used the matched pairs from diyAudio. Not cheap. But are they even necessary considering the separate adjustments for each FET?
Yes, buy 20 for each and only match pairs with same polar (match 2N5458 to 2N5458, 2N5461 to 2N5461, as I remembered PaPa told in some message posts. Correct me if wrong). FETs with Idss from 6mA to 8mA is better?
I have both the ACA and the VFET follower and with my speakers 104 dB speakers the mini ACA wins. I have not used the vfet since building the aca. Much better bass, lower distortion, dynamic and detailed w/o any fatigue. The amp is super energy efficient, too. IMO The best 1W of music per unit of wasted power.
Hmm, that's exactly the opposite of how I understand it. With the input JFFETs, N channel to P channel matching is important, while matching between left and right amplifier channels is unimportant.
Thanks Grataku
Do you have the impedance curve(s) of your speakers perhaps?
Thanls again
Claude
Do you have the impedance curve(s) of your speakers perhaps?
Thanls again
Claude
First of all thanks again to Nelson and Mark for the design and boards!!! I finished installing my almost clone of ACA Mini in a chassis. I bought a reproduction Dynaco ST-120 chassis from Dalaudio and it worked well. I was a little worried about noise by having the power supply located so close but it’s dead silent. I glued down the power supply and threw on a big zip tie for extra security. I had to drill holes to mount the board but it was not a problem using a cheap step bit from harbor freight.
A cheaper route would be a find a non-working ST-120 (most are no longer working), strip the internals and repaint the chassis.
A cheaper route would be a find a non-working ST-120 (most are no longer working), strip the internals and repaint the chassis.
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My mistake. It should be matched all of them as close as possible. For my case, it is sad that not many JFETs I have to have exact match. 🙁
One question: What is the output impedance (or the damping factor for 8 Ohm speakers) from the ACA mini?