300 VA will be sufficient, but per channel. At least get 250 VA per channel or 500 VA stereo.
I went for 500 VA each.
Even more important: Get enough capacitance. Lots of it. This is class A and class A draws
lots of current and lots of current means high ripple. Even when you listen to 'silent' music.
So buy the biggest lytics you can afford and consider to build it CLC, CRCLC or at least CRC.
I went for 500 VA each.
Even more important: Get enough capacitance. Lots of it. This is class A and class A draws
lots of current and lots of current means high ripple. Even when you listen to 'silent' music.
So buy the biggest lytics you can afford and consider to build it CLC, CRCLC or at least CRC.
300VA is quite sufficient for a stereo amp.
The Aleph is single-ended. You can't have more output than your bias, but SE (in)efficiencies play into output power as well... Reducing it.
The big transistors are biased at approximately 20W each. There are (8) in an stereo amp. 8 x 20 = 160W
VA is roughly equal to Watts. So how can a 300W transformer be too small for a circuit that draws just a bit more than 160W?
That said, bigger transformers are nice. (Make them too big,however, and they start buzzing if you have traces of DC on your AC line...)
Your comments about PSU capacitance and filtering are right on.
300VA is quite sufficient for a stereo amp.
The Aleph is single-ended. You can't have more output than your bias, but SE (in)efficiencies play into output power as well... Reducing it.
The big transistors are biased at approximately 20W each. There are (8) in an stereo amp. 8 x 20 = 160W
VA is roughly equal to Watts. So how can a 300W transformer be too small for a circuit that draws just a bit more than 160W?
First, I should mention, the Aleph CCS design is capable of outputing more than the bias!
And, you can never read enough Pass I guess. From the BA1 article, which is not an Aleph CCS design but, is SE: "As the typical Burning Amp will dissipate more than 300 watts, the transformer wants to be rated at least twice that."
Having read that, I would say you would want at least 320VA, if not more?
Both you're right, mates.
It all depends on the money one is able to spend, but let us agree in that on an Aleph J,
PSU capacitance and filtering is much more important than the transformer's VA rating.
BTW, I'd rate two 200 VA transformers over one single 500 VA. It wil, measure better and
it will sound better.
Nevertheless I went for two 500 VA toroidals (as this will make the PSU more universal
for future projects). The only downside besides cost is the inrush current, which makes
the need for a soft start or at least for an NTC, of course the first one being better.
I'd greatly recommend to go for a set of four decent inductors and some, say 0.5 R resis-
tors and go the CRCLC route or similar. Some of you may find some old speaker crossover
inductors in your spare box. Of course you need 4 identicals ones for a stereo amp if you
want two seperate PSUs (which I would prefer).
It all depends on the money one is able to spend, but let us agree in that on an Aleph J,
PSU capacitance and filtering is much more important than the transformer's VA rating.
BTW, I'd rate two 200 VA transformers over one single 500 VA. It wil, measure better and
it will sound better.
Nevertheless I went for two 500 VA toroidals (as this will make the PSU more universal
for future projects). The only downside besides cost is the inrush current, which makes
the need for a soft start or at least for an NTC, of course the first one being better.
I'd greatly recommend to go for a set of four decent inductors and some, say 0.5 R resis-
tors and go the CRCLC route or similar. Some of you may find some old speaker crossover
inductors in your spare box. Of course you need 4 identicals ones for a stereo amp if you
want two seperate PSUs (which I would prefer).
Excellent News - Boards Arrived!
And boy are they pretty!
So now a few questions.
1. Are we going to use this thread for build discussion?
2. How's the build guide coming along? (hint, hint);-)
3. Would anyone like to discuss their preferred component choices as compared to the basic BOM? I would love to learn more and get some ideas.
4. I'm thinking about building mine BLAT style (liquid cooling). Are there others on that path, or am I the usual outlier?
Finally, I just ordered 2SJ74BL's from Spencer at FET Audio. He still has more available. With shipping for 4 to the US and Paypal fees, they cost $8.71 each. I'll let you make the cost/benefit decision.
And boy are they pretty!
So now a few questions.
1. Are we going to use this thread for build discussion?
2. How's the build guide coming along? (hint, hint);-)
3. Would anyone like to discuss their preferred component choices as compared to the basic BOM? I would love to learn more and get some ideas.
4. I'm thinking about building mine BLAT style (liquid cooling). Are there others on that path, or am I the usual outlier?
Finally, I just ordered 2SJ74BL's from Spencer at FET Audio. He still has more available. With shipping for 4 to the US and Paypal fees, they cost $8.71 each. I'll let you make the cost/benefit decision.
Hey, spare a thought for us living out here in the sticks! I might only get mine in another 3 weeks.
Hey, spare a thought for us living out here in the sticks! I might only get mine in another 3 weeks.
Sorry. I didn't mean to rub it in. I just got excited.
I got my boards as well and started immediately stuffing the first one.
I ran into a clearance issue between C2 and C7 because I picked a 5mm width polyprop cap for C7. It's very snug but otherwise looks ok. 4mm width for C7 seems to be the max for a proper fit. Also, the BOM calls for a 10mm lead spaced part for C7 but the holes are spaced 5mm on the board. No big deal except it makes my OCD itch.
I ran into a clearance issue between C2 and C7 because I picked a 5mm width polyprop cap for C7. It's very snug but otherwise looks ok. 4mm width for C7 seems to be the max for a proper fit. Also, the BOM calls for a 10mm lead spaced part for C7 but the holes are spaced 5mm on the board. No big deal except it makes my OCD itch.
I got my boards as well and started immediately stuffing the first one.
I ran into a clearance issue between C2 and C7 because I picked a 5mm width polyprop cap for C7. It's very snug but otherwise looks ok. 4mm width for C7 seems to be the max for a proper fit. Also, the BOM calls for a 10mm lead spaced part for C7 but the holes are spaced 5mm on the board. No big deal except it makes my OCD itch.
Are you using the Revision C BOM? As far as I know the Revision C BOM specified MKP2D031001F00JSSD for C6 and C7 which has a lead spacing of 5mm.
I attach it in any case.
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Nice catch. Thank you.
I was planning on using my usual V-R MKP1837 bypass cap out of existing stock for C6 and C7. Thanks to you, I measured them and found that they are 7.5 mm wide and probably wouldn't fit even with a small diameter in C2 or C3. Looks like I have a good start to my purchase BOM.
Ugh, the next two posts after the other Rev C BOM you posted in #265 talk about this change. I just missed it the first time through.
Don't expect any real sig changes in sound due to cap selection in this amp. You can leave off the cap on the neg input. Drive it with balanced signal or with negative leg and you got something wonderful. The topology defined 80% of the sound. Better PSU defines last 15%. Your blood alcohol level determines 3.5% of the sound, and the last 1.5% is passive parts choice
Sorry, my mistake. I should have bumped the revision to D then. No help I have revisions if I don't maintain it religiously.