Yup. Work, kids, dishes, amp building in between. That is why it is on the living room table and not the workshop. Easier to toggle tasks that way. I almost forgot how much work it was building an amp from scratch… haha! The P2P PSU doesn’t save me time, that’s for sure. It is a kinda baptism into PSU’s for me. The same as matching MOSFETs and making a pimped up 6-8 deep BA-2 board one day will be. Starting with PSU, then we’ll see. Choky got me thinking of the XA-252 as a possible next project. Luckily, life is long.
On the living room table… lucky you!
My family claim they hear the cello suites equally good on either a smartphone and a ATC scm7, so no building at home 4 me.[emoji849]
My family claim they hear the cello suites equally good on either a smartphone and a ATC scm7, so no building at home 4 me.[emoji849]
Aleph J noisy channel and offset fluctuations is now SOLVED!
My problem was exactly yours, thank you so much.
I exchanged the JFETs with a new pair and everything is back to normal, at least for now. This time I used a grounding wristband, so my conscience is at peace in this respect: if it goes sour again, I know gave my best 😉
Amp now cooking along with lid on, to readjust bias and offset on working conditions in 1h.
Attached photo without the lid.
The chassis is a 4U pre-drilled and the PSU is the UPSU from diyaudio store. It's the same I used for the F5 build, so the PSU has red LEDs but the boards blue LEDs. I'll probably try to make the blue ones less bright: even through the lid slots, they illuminate my room with a lot of blue in the night... 🙂
Transformer is 500VA (Toroidy was Covid-late with my 300VA, so I sourced a 500VA from another place) and it's too big:
1) Had to attach it to the front panel, so it's front heavy
2) Inrush current is higher, so I had to change the fuse
So, one of these days I'll man up (or down?) and change the transformer to the 300VA, it will make it easier to move around.
Other than that, it's just another plain boring build, based on the wonderful guides 6L6 keeps on rolling out (a special thanks to him!).
Again, it's great to be able to rely on all your experience, I wouldn't dare doing all this stuff without the knowledge you people share everyday.
Thanks!!!
My problem was exactly yours, thank you so much.
I exchanged the JFETs with a new pair and everything is back to normal, at least for now. This time I used a grounding wristband, so my conscience is at peace in this respect: if it goes sour again, I know gave my best 😉
Amp now cooking along with lid on, to readjust bias and offset on working conditions in 1h.
Attached photo without the lid.
The chassis is a 4U pre-drilled and the PSU is the UPSU from diyaudio store. It's the same I used for the F5 build, so the PSU has red LEDs but the boards blue LEDs. I'll probably try to make the blue ones less bright: even through the lid slots, they illuminate my room with a lot of blue in the night... 🙂
Transformer is 500VA (Toroidy was Covid-late with my 300VA, so I sourced a 500VA from another place) and it's too big:
1) Had to attach it to the front panel, so it's front heavy
2) Inrush current is higher, so I had to change the fuse
So, one of these days I'll man up (or down?) and change the transformer to the 300VA, it will make it easier to move around.
Other than that, it's just another plain boring build, based on the wonderful guides 6L6 keeps on rolling out (a special thanks to him!).
Again, it's great to be able to rely on all your experience, I wouldn't dare doing all this stuff without the knowledge you people share everyday.
Thanks!!!
Attachments
Good to know, @joaoranito, that your problem is solved 🙂
Please let us know it the new Jfets keep being fine in a few weeks or so.
Nice build overall 🙂
Concerning the blue LEDs, with those that I use extended on the wires to the front pannel, I use 100K resistors to tame them to the brigthness that is fine with me.
Also a note just in case if you also decide to extend some LEDs to the front pannel: when you switch it off, not all LEDs fades at the same time, some of them keep shining longer in this schematic. So, you cannot take the 2 that are closest to the front pannel 🙂
All the best! Have a nice music!
-Alvis
Please let us know it the new Jfets keep being fine in a few weeks or so.
Nice build overall 🙂
Concerning the blue LEDs, with those that I use extended on the wires to the front pannel, I use 100K resistors to tame them to the brigthness that is fine with me.
Also a note just in case if you also decide to extend some LEDs to the front pannel: when you switch it off, not all LEDs fades at the same time, some of them keep shining longer in this schematic. So, you cannot take the 2 that are closest to the front pannel 🙂
All the best! Have a nice music!
-Alvis
Hi folks! I'm getting prepared to build at least one, maybe two Aleph J amplifiers. I have a question about which MOSFETS to use for the best performance. I built several ACAs and made a few subsitutions. I am just wondering if the specific MOSFET device used for the output has as big of an impact on sound quality as it does with the ACA. I have several different part numbers I collected since starting down this DIY path. Here are my choices:
IRFP040
IRFP044
IRFP044N
IRFP048
IRFP048N
IRFP140
IRFP140N
IRFP240
FHQ44N10
Also a chassis question. Based on what I have read on this site, I assume the best "pre-fab" case for these are the 4U Dissapante case, correct? Thanks!
IRFP040
IRFP044
IRFP044N
IRFP048
IRFP048N
IRFP140
IRFP140N
IRFP240
FHQ44N10
Also a chassis question. Based on what I have read on this site, I assume the best "pre-fab" case for these are the 4U Dissapante case, correct? Thanks!
I don't have any MOSFET advice, but I will plug the build guide that I made, which was aimed exactly at someone who has built the ACA and is interested in moving to the Aleph J:
DIY Aleph J: A Build Guide
The Deluxe 4U Aluminum is perfect for the Aleph J, and opting for the pre-drilled silver front panel makes the build even easier to lay out.
The Mosfets for the Aleph J need to be matched. The diyAudio store carries matched sets of IRFP240. This is the easiest way to get the amp to sound the way it is supposed to.
If you want to change something, build a dual-mono power supply. For that, you will need a 400mm deep chassis.
If you want to change something, build a dual-mono power supply. For that, you will need a 400mm deep chassis.
Thanks for the reply. I noticed the store will send either IRFP140 or IRFP240 based on availability. This is in part what started me thinking about different MOSFETS. The other reason is reading through Nelson's Zen amplifier progression, there are several instances of IRFP040 and IRFP044 preferences noted with the IRFP240 being used mostly because of availability. Just wondered if anyone had tried an Aleph J with something other than IRFP240. I can match MOSFETS myself if I need to.
I just rebuilt new Aleph J boards.and switched to the 140s because that was what was sent to me.. The amp boards sound similar to the 240s. The boards were just a lot easier to build the second time around.
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only Sissies are using 2 pairs of IRFP240 in their Alephs
Real Men are using just one pair of IRFP150
no matching involved, use that time for Beer
Real Men are using just one pair of IRFP150
no matching involved, use that time for Beer
only Sissies are using 2 pairs of IRFP240 in their Alephs
Real Men are using just one pair of IRFP150
no matching involved, use that time for Beer
No Sissies here! And I am not standing by...😀 ; Direct Coupled*, offset is +/- 5mV. -3dB @ 110Khz; phase is nearly flat up to 20khz.
* = only for brave souls, not sissies 😉
Best,
Anand.
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Here are some comments that Nelson shared way back when the Aleph-X amps were all the rage here (nearly 20 years ago...)
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
Ian posted some of his impressions of using IRFP044 vs IRFP244s in his Aleph-X amps:
After using the IRFP044s, I then changed over one channel to the IRFP240's with the same power supply conditions (Grey's original schematic). Nelson's comments about gain devices effecting the sound were borne out here. In comparisons, the IRFP240 appears to have a somewhat thinner presentation and more brilliant high frequency response. The IRFP044 is richer sounding with more body in the midrange but otherwise less linear .....The jury is still out but I tend to think that while using only one pair per side of each, neither is better than the other and the IRF240 perhaps offers more latitude to use in various numbers for the right tonal balance. I doubt if I would use the IFRP044 for a tweeter amp in a bi amp setup and more likely the midrange.
The entire thread can be found here.