Question about the BOM. For R121 they are listed at 1K but the product descriptions say 1.4Kohms. Typo?
Also, what's the consensus on PSU right now? I'm leaning towards a 400VA, 18V toroid with a CRC of 60uF per channel, a la the F6 PSU build. Do I need to be worried about in-rush or pop at turn-on/off? Any other issues with the ALPHA and this setup?
Also, what's the consensus on PSU right now? I'm leaning towards a 400VA, 18V toroid with a CRC of 60uF per channel, a la the F6 PSU build. Do I need to be worried about in-rush or pop at turn-on/off? Any other issues with the ALPHA and this setup?
R121 is definitely 1k 1% metal thin film. Sorry about the typo.
I am now using F6 PSU with 400VA 18V Antek toroid and 33mF x 8 and 0.235R (paralleled 0.47R) for all resistors. Use the CL60 NTC's per schematic to avoid in-rush. The amp has a mild slow thump (negative going) upon turn on. Nothing my speakers can't handle. The turn on thump makes no noise as it is slow maybe over 1/4 to 1/2 second. Other than that, no turn off thump.
The one issue I have is if I connect a mains powered preamp I have mild hum. If I connect my battery powered DAP, no hum. Of course, disconnect amp from any mains powered preamp or source, no noise of any sort.
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No worries X. Thanks for confirming R121. Same thing on R127 if using the resistor ILO the pot? Listed as 1K and described as 1.4K again.
You have a lot of capacitance on your PSU! I'm questioning whether 15uF x 8 is enough. What do you think?
That sounds bearable regarding the turn on "thump".
Interesting about the hum using the mains connected preamp. I wonder if it's noise from the DC/DC step up in AKSA Lender pre? A topic for the preamp thread, I can't remember, but did you ever try a linear PSU on the pre?
You have a lot of capacitance on your PSU! I'm questioning whether 15uF x 8 is enough. What do you think?
That sounds bearable regarding the turn on "thump".
Interesting about the hum using the mains connected preamp. I wonder if it's noise from the DC/DC step up in AKSA Lender pre? A topic for the preamp thread, I can't remember, but did you ever try a linear PSU on the pre?
Like Vunce said, “no replacement for displacement!” 
In other words, nothing beats boatloads of Farads. I think the CDE 33mF 25v caps were only $4ea so was not too bad.
SLPX333M025E9P3 Cornell Dubilier - CDE | Mouser
In other words, nothing beats boatloads of Farads. I think the CDE 33mF 25v caps were only $4ea so was not too bad.
SLPX333M025E9P3 Cornell Dubilier - CDE | Mouser
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But I usually listen orchestral music and others very good records with high dynamic range: DR: 12...15
With modern and commercial music with DR < 9 dB you need much less power.
An example, this 24/192 great vinyl rip.
Mahler* - Leonard Slatkin, Saint Louis Symphony Orchestra - Symphony No. 1 "Titan" In D Major (Vinyl, LP) at Discogs
DR Peak RMS Filename
----------------------------------------------------------------------------------------------
DR17 -0.36 dB -23.96 dB A1 I. Langsam, Schleppend - Im Anfang Sehr Gemaechlich.aif
DR15 -1.19 dB -21.98 dB A2 II. Kraeftig Bewegt, Doch Nicht Zu Schnell.aif
DR15 -13.59 dB -33.33 dB A3 III. Feierlich Und Gemessen, Ohne Zu Schleppen.aif
DR14 -9.52 dB -28.39 dB B1 III. Wieder etwas bewegter, Wie Im Anfang (Conclusion).aif
DR16 -0.30 dB -21.65 dB B2 IV. Stuermisch Bewegt.aif
----------------------------------------------------------------------------------------------
Number of files: 5
Official DR value: DR15
====================================================
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What is your average (non peak SPL) loudness? I typically listen at 80dB (not dance floor 89 dB). So 15dB peak for DR is 95dB. For 82dB speakers to get 95dB is about 16w I think so well within range of this amp. If you like THX 115dB top end then that’s another matter. Only pro audio speakers or big multiways can do that.
Hi Hugh,
So I am preparing parts for the B.B. I think going with a linear trafo will be required here given the 3amps standing current at 70v. For a monoblock would a 400VA 25v toroidal trafo work? I will need two of those and Antek AS-4225 is going for $51ea. 50v caps for the CRC will not be $4ea ($10ea) unfortunately. So is a 400VA trafo suitable for 200w dissipation amp?
380LX333M050A082 Cornell Dubilier - CDE | Mouser
So I am preparing parts for the B.B. I think going with a linear trafo will be required here given the 3amps standing current at 70v. For a monoblock would a 400VA 25v toroidal trafo work? I will need two of those and Antek AS-4225 is going for $51ea. 50v caps for the CRC will not be $4ea ($10ea) unfortunately. So is a 400VA trafo suitable for 200w dissipation amp?
380LX333M050A082 Cornell Dubilier - CDE | Mouser
There is a AMEC THERMASOL ultra flat heatpipe available at Farnell, Amazon or eB that can be used for heat transfer if the case should act as radiator. Not extra cheap but DIY viable.
Attachments
Hi X,
I retire to sleep and look what happens when I'm away!! WOW, this is big news!
Now, let's look at the drive. I calculate 216W dissipation from 3A with two 36V, pos and neg, rails. Looking at a monobloc, one channel, a 300VA toroid would be more economical and just supply enough power at 72% full rating. Two of the Antek 300VA at 25Vac secondaries would do it very nicely. 50VW is around the optimum; no higher than 40Vdc on these devices, so 35V would be fine. Of course, if the 400VA trafo is the same price as the 300VA, it would be even better, but not necessary.
HD
I retire to sleep and look what happens when I'm away!! WOW, this is big news!
Now, let's look at the drive. I calculate 216W dissipation from 3A with two 36V, pos and neg, rails. Looking at a monobloc, one channel, a 300VA toroid would be more economical and just supply enough power at 72% full rating. Two of the Antek 300VA at 25Vac secondaries would do it very nicely. 50VW is around the optimum; no higher than 40Vdc on these devices, so 35V would be fine. Of course, if the 400VA trafo is the same price as the 300VA, it would be even better, but not necessary.
HD
X, when you say, "off main supply" do you mean at the 18V DC of one of the rectifiers, before the CRC? Or are you talking about a totally separate transformer to supply power to the LM7812?
I would spend that fund on more heatsink and hard wire all the mosfets like the DIY Aleph X or Aleph 4. One main board with two daughter board solution etc.
Daughter board like the attachment.
I have 15" tall (long) heatsink the best option for me.
I wait until someone builds the BB. I want to replace the Aleph X with the BB. Aleh X just too much (at the hydro bill) with the 7A bias per channel.
An AS-3225 is $41 so a little less and more compact. That might be good $20 well spent to ensure it is not stressed and less mechanical hum.