You can also change R15 from 2K2 to 1K5. Increases bias from about 1,5A to about 1,7A. Have tested it and I thought it sounded "smoother". I had big chassis and linear PSU.
Can I say that from a hundred IRFP240s, you wont get closely matched pairs as one IRFP150?
I say "Go for it!" You probably will notice a little better sound. With the stock pcb, you can run twisted pair wire to the total of three 1000uF Silmic II caps mounted or glued to bottom or far side of chassis. And while you are at it, try the suggestions ZenMod made in post #2317. If you use stock heatsink then you can get extra cooling by using one of the ultra quiet, low speed computer fans from NewEgg, ect. I hear nothing from a meter away, even at 12V (on a couple of brands). The ACA is designed to be an easy build in one day, but I am sure a lot of us are curious what they can do if a fearless amp builder mods away on them, especially low cost and low labor mods with a fan. I have built a CLC power supply (post #1301) for my ACA's and did notice a cleaner, more detailed sound (lower noise floor), but that cost more and took more time than the actual ACA's did.
I'll give those ideas a shot. I have a lab power supply, which I could use to compare against switch mode.
One thing I discovered is the power jack doesn't give me a great connection with my Asus laptop power supply, not sure if it might also be an issue with the supplied switch mode supplies or it's just my supply. I hate bad connections. I might look for something that meets aerospace requirements
I think several of us might have had a problem with that 2.5 mm connector jack that comes with the ACA kit. I have one bad one now on one of my amps. The solution is to buy a pair of heavy duty ones from either Parts Express, or Mouser, ect
The new batch of ACAs has a very nice DC Jack. It also only has 2 connections so is less likely to confuse people. Not sure if 2 picoDumbs has the old or new kit but his PSU is just what he had around, so might not fit the jack specs. The downside is that the new jack might require that the mounting hole be enlarged a small amount with a round file or abrasive paper around a dowel. However the RCA jacks should fit just fine now with no mods..
I think I bought the kit when it was first released so almost certainly have the old jack.
Do you sell any of the parts separately?
I love those washers for the to247 mosfets. I'd buy 50 if you sold thrm separately.
I'd also buy the chassis too if you sold it separately. Great for headphone amps. You've done a great job with the case. Absolutely first class.
Do you sell any of the parts separately?
I love those washers for the to247 mosfets. I'd buy 50 if you sold thrm separately.
I'd also buy the chassis too if you sold it separately. Great for headphone amps. You've done a great job with the case. Absolutely first class.
Hi,
Normally I use the original 1994 Nelson's Zen Amp. But I admit it gets hot so I wanted to explore somewhat cooler options.
This little amp was just begging to be made one day. I was worried about lowish output (but my speakers - Troels Gravesen C17 should be of efficiency wise; less impedance wise - they are 4Ohm)
Today was a rainy bank holiday. In the afternoon I had assebled pcbs with some heatsinks hooked up.
Even with the small heatsinks it does not get alarmingly hot. I power it with two 19-20V Dell bricks each capable of 3.5A. No thump on power on or off.
The sound is very nice. It plays loud enough for all my practical purposes.
I didn't go beyond 11o'clock on my B1 buffer!
At this stage after 1hr listening and no optimizing I find the Zen somewhat more relaxed.
Attached some pictures.
Normally I use the original 1994 Nelson's Zen Amp. But I admit it gets hot so I wanted to explore somewhat cooler options.
This little amp was just begging to be made one day. I was worried about lowish output (but my speakers - Troels Gravesen C17 should be of efficiency wise; less impedance wise - they are 4Ohm)
Today was a rainy bank holiday. In the afternoon I had assebled pcbs with some heatsinks hooked up.
Even with the small heatsinks it does not get alarmingly hot. I power it with two 19-20V Dell bricks each capable of 3.5A. No thump on power on or off.
The sound is very nice. It plays loud enough for all my practical purposes.
I didn't go beyond 11o'clock on my B1 buffer!
At this stage after 1hr listening and no optimizing I find the Zen somewhat more relaxed.
Attached some pictures.
Attachments
No I do not have Zen 4, but I have some Zen 4 pcbs in making;-)
I have to admit Zen 4 is very tempting. I have read so many good opinions. I thing it would suit my bill very well (except for heat...)
Having said that, I also have Aleph Mini (hopefully J fet input) and Juma's Cubie 2 in the pipeline. So little time and so many exciting projects.
I have to admit Zen 4 is very tempting. I have read so many good opinions. I thing it would suit my bill very well (except for heat...)
Having said that, I also have Aleph Mini (hopefully J fet input) and Juma's Cubie 2 in the pipeline. So little time and so many exciting projects.
I am using this two pin xlr type of connector
Regards
Sachin
Where can I get this chassis in Europe?
Thanks.
Pass DIY Addict
Joined 2000
Paid Member
Mark: Here are some notes I tucked away about different IRFP devices - I think these came from the huge Aleph-X thread long ago...
IRFP044 vs IRFP240 vs IRFP244 vs IRFP250 : A number of amps have been built using each of these transistors. Nelson has characterized the differences among the three latter transistors as follows: The 250's have greater current capacity, but twice the capacitance of the 240's and 244's. They will give a better bottom end, and will sound a bit different, for better or worse, depending on your situation and taste. There is very little practical difference between the 240's and 244's. Some have reported that the IRFP044 sounds a little "darker" (more narrow frequency bandwidth and greater high-frequency roll off) than the 240, though this is not really surprising as the 044 has greater capacitance than the 240 series. Essentially, greater capacitance provides slightly better bass, but at the cost of slightly reduced treble. The practical difference, though, is their current capacity. The maximum current and operating temperature ratings have lead many to use the IRFP240/244 for rail voltages of 20v or higher, while using the IRFP044 for 15-20v rails. The lower voltage versions of the amp tend to feature higher current, and the 044's can handle significantly more heat.
Device (Max Voltage, Max Current, Max Temp)
IRFP044 (60v, 57A, 175c)
IRFP240 (200v, 20A, 150c)
IRFP244 (250v, 15A, 150c)
