I have used paralleled thousand mi roFarad silmic II caps as output coupling caps and to my ears it sounded very good. I am amazed at the quality of these parts.
Ok added to digikey basket. It would be nice if a future revision of the board could possibly allow for it.
I'll probably put them on a separare board on stand offs
Last edited:
Shouldn't make any audible difference having four or three, frequency response is already below 10Hz
Edit: I'll rephrase that, unless you have 2 Ohm speakers there shouldn't be any audible difference between 3000uF and 4000uF, and even then, the speakers would need to be capable of 20Hz which is mostly noise (not music notes)
Edit: I'll rephrase that, unless you have 2 Ohm speakers there shouldn't be any audible difference between 3000uF and 4000uF, and even then, the speakers would need to be capable of 20Hz which is mostly noise (not music notes)
Last edited:
Thank you for the information. I have built the ACA using the IRFP240's and the IRFP 140's. They both work great to my ears. I am supposed to receive my tube of Cree SiC power mosfets today. They will go on my curve tracer for matching and to finally see the much sought after (at least by me) triode like curves. I have been thinking of building another pair of ACA's for my daughter and just might throw a few of the Crees in to give it a try.
The amp sounds great already, in fact I love it, It sounds like real live music.
Knowledge is evil, it gets in the way of enjoying what is already an absolutely excellent amp, but tweaking is fun too. 😉
Which curve tracer do you have? I've been thinking of getting one for a while.
Will be great if you can post a picture of the curves when complete.
Knowledge is evil, it gets in the way of enjoying what is already an absolutely excellent amp, but tweaking is fun too. 😉
Which curve tracer do you have? I've been thinking of getting one for a while.
Will be great if you can post a picture of the curves when complete.
I will be happy to snap some photos and upload them to the group for whoever is interested. My curve tracer is a Heathkit model 1121 (I think) and I built it in 1975. It still works perfectly! I built an add-on that allows me to test enhancement devices. The tracer was designed to test depletion mode FET's with its built-in stair-step bias generator. I made a simple opamp unity gain inverter to allow it to output proper voltage bias to the mosfet under test. It has a cool a/b switch that is useful to compare curves when searching for exact component matches.
The Silmics are something I've considered. In fact I bought some for that! Since they are a part Papa likes, why not? It's good to know that 3 should do it as it is a lot easier and cheaper to package and cheaper to use 3 instead of 4. I'm sure a wire tie can make it work!
Frankly I expected more mods to this amp. It's inexpensive, simple and safe. Also has useful stuff like the CCS and the JFET on the front end. I think the problem is that it's just fine as it is!
Frankly I expected more mods to this amp. It's inexpensive, simple and safe. Also has useful stuff like the CCS and the JFET on the front end. I think the problem is that it's just fine as it is!
crank the PSU voltage , use IRFP150 , halve all 3W resistor values (that will double Iq) and there is ACA on steroids
well , that what I wrote - keep it in usual FW amp dissipation bracket , and it will last ,without being too hot
avoid Crikey Hot 😉
Actually I have direct experience with the ACA on a closed back shelf with another shelf about a foot (30cm) above it, so it was only open to the front, (but the shelf was about 3' wide so seemed pretty open) vs. it just sitting on an open desk. On the shelf was MUCH hotter!
Actually I have direct experience with the ACA on a closed back shelf with another shelf about a foot (30cm) above it, so it was only open to the front, (but the shelf was about 3' wide so seemed pretty open) vs. it just sitting on an open desk. On the shelf was MUCH hotter!
Last edited:
I always feel sorry for those little MOSFETs working their hearts out in terrible conditions, but perhaps I'm wrong to anthropomorphise them. Looks like Crickey Hot isn't close to a problem!
Those are great suggestions for implementing in a bigger case.
What about a better mosfet to use within the limitations of the existing design/heatsink/psu? Any ideas?
I've never used irfp150, what do you like about it? More transconductance/More feedback?
Zennie, what's the arithmetic for an IRFP250? I have a small cache of them. Papa says they're just like a 240 but on a bigger die, which sounds similar.. I assume I could just pop them in too?
My ACA and F5 runs close to 58C (measured on top of mid point heatsink).
Should I be worried? 😕