Speakers are a nice design! And the efficiency is outstanding at 96dB. Black would be nicer than the orange. The idea of a full isolation for no cross-channel coupling has merit.
I'm sure I will be looking to sell my B&W 803D, they don't have the efficiency (91dB) for the power of the AJ. But, I'll be building a pair and running them in bi-amp, but it's an speaker internal crossover bi-amp, which may help a bit. At the crossover points most of the drive power is already sent to the LF speakers so the boost will be nominal. But until I get it all connected up, I will see then!
I'm sure I will be looking to sell my B&W 803D, they don't have the efficiency (91dB) for the power of the AJ. But, I'll be building a pair and running them in bi-amp, but it's an speaker internal crossover bi-amp, which may help a bit. At the crossover points most of the drive power is already sent to the LF speakers so the boost will be nominal. But until I get it all connected up, I will see then!
Agreed. I love mine too, and Eric was great to work with. I have been eyeballing those perfect SETs... Post if you pull the trigger.
I sorta like what I see ..... even if I'm not exactly keen of zillion drivers replacing one
OK, from my amateurish stance I have one objection - their decibels are somewhat as Klipsch decibels (those cheap decibels, they having for small boxes) - that must be one helluva physics-breaking 12" transducer, when speaker declared as 96db/2.83V (8 Ohms? eeek!!) , supposedly 30Hz-30KHz
it doesn't matter - what matters is that you like them
aha - you like AJ; AJ is good ........ but SissySIT is Pleasure Factory ....... Machine that goes PING!
I have found a few posts that indicate the steady-state current of one Aleph-J is about 2A maximum. What is the efficiency? Cannot find anything on that. If the amp is perhaps 25%, that means the transformer has to supply 8A on one channel, that makes 16A on two. Does this seem about right? Not asking because I care about efficiency, I'm doing some back calculations from the soft-start. Thanks!
who cares about efficiency, when simple calculus of dissipation, thus current consumption from wall - is enough for soft start design?
That is the consumption of the amplifier, not the wall consumption? Look, on 117VAC, a 4A slow blow translates to about 600W or more. So, given the amplifier consumption of 200W, that's perhaps 30% efficient. Which is what I was getting at in the post. If he specifies a 4A SB, then that's what I was after. Question answered. Thanks. And thanks for the link, helpful. 😉
proper A Class amp consumption is exactly what is sourced from the wall
how clearly you asked, you that clearly got your answer
if you were asking for peak current during powering on cycle, that's different thing and you needed to ask that
anyhow, you have fuse value, so done
The quiescent current per each PCB is 2A (with the voltage drop across each 0.47ohm/5W resistor = 440mV, so let's call it 1A per each MOSFET pair). The total current draw from the transformer secondary is 4 A at 48V DC (the rails are +24 and -24V DC). The power drawn from the toroidal secondary is 192W... let's call it 200W (which is exactly what the FW Alep J product brochure states, by the way...)
If we ignore the toroidal transformer losses (which are actually quite high... the best case is 5%; the average is 10%), we could say that at the primary side (at the mains/grid /wall outlet), our Aleph J draws 200W at all times. This draw is constant.
The usable speaker output at 8 ohms is around 20-25W (it depends on what distortion level is acceptable for you, to state the output power). Let's say that the usable power at tolerable distortion & at 8-ohm load is 20W.
So, for 200W burnt from the mains supply, you get 20W of speaker (usable) power. And that's... a whopping 10% efficient. Nevertheless, it sounds superb, so it's a price well spent for the musical enjoyment the amp provides. I, however, have a great many difficulties explaining/justifying/selling this to my kids... both are involved in environmental studies... BUT, they both love the sound of this particular amp compared to anything else we tried, so things are reasonably okay still.
Of course, my calculations might be wrong... hence, I'd like someone else to glance over'em and correct them if need be...
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I then think the 4A SB is to handle the big inrush. Yes, all sounds reasonable, and 4 amps per side at each 24V sounds right according to your numbers. thanks for the clarification. 10% for class A seems in the ballpark. BTW - tell your kids it's solar powered. (it did come from there a long time ago, how it got to your amp isn't so important right now, the music is)
😏
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That’s a great template! Print at size to make the measurements match the UMS found here - https://cdn.shopify.com/s/files/1/1006/5046/files/universal-mounting-specification-v2.1.pdf
I am getting un-equal temperature between the channels with no signal, inputs not shorted - one side is about 48 C, other around 53 C. Bias is set at 350MV for now. Supply rails are +/- 25V.
No big change while playing at moderate volumes.
Any one else has faced this? It would be great to receive some insights and implications if any.
No big change while playing at moderate volumes.
Any one else has faced this? It would be great to receive some insights and implications if any.
Following up on ZM's suggestion, perhaps also try measuring the voltage drops across all the source resistors to test for the possibility your original measurements were affected by mismatched parts.
Thanks let me try these with specific conditions you mention.
What pics would be appropriate please? It is still in very 'disintegrated' stage! For record, I am using the standard PCB from the DIY audio store and their 'matched' active components. The passive ones are all from elements 14 with resistors at 1% tolerance where available. I was not able to measure the ohms for 0.47R with my DMM, but Dennis' suggestion of measuring V drop is good. Let me try that as well.
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Hi, I'm hoping to tap on the experience of a builder who knows the design of the AJ and the LS74 J-Fets to provide some feedback. I've read some of the info from NP on FET ranges, where he mentioned a upper limit of 8mA Idss, with a recommended set point of 4mA for the AJ. Still some questions. Here they are.
1 - If I have a pair on the left channel that I have measure at Idss 5.4,5.6 and then a pair on the right channel that's 7.9, 8.1, what difference if any will there be? Does this difference manifest in a different biasing of L,R and hence more/less current to the output drive?
2 - I see a few posts about the maximum difference, typically 1mA. Will distortion result if this is any higher? At what value will it become audibly detectable?
Here's a list of (mixed Toshiba, LS) JFets I have. Which ones should be rejected, which ones are usable in the AJ? (tested at 12V, current measured on Fluke 87) x2 = 2 pieces.
3.8, 3.9x2, 4.0 x2, 4.6 x2, 4.7, 5.0, 5.2, 5.4, 5.4, 5.6, 6.0, 6.7, 7.0, 7.5, 9.3, 9.5, 9.9, 10.0, 11.0, 15.0 x2
Thanks for your responses in advance.
1 - If I have a pair on the left channel that I have measure at Idss 5.4,5.6 and then a pair on the right channel that's 7.9, 8.1, what difference if any will there be? Does this difference manifest in a different biasing of L,R and hence more/less current to the output drive?
2 - I see a few posts about the maximum difference, typically 1mA. Will distortion result if this is any higher? At what value will it become audibly detectable?
Here's a list of (mixed Toshiba, LS) JFets I have. Which ones should be rejected, which ones are usable in the AJ? (tested at 12V, current measured on Fluke 87) x2 = 2 pieces.
3.8, 3.9x2, 4.0 x2, 4.6 x2, 4.7, 5.0, 5.2, 5.4, 5.4, 5.6, 6.0, 6.7, 7.0, 7.5, 9.3, 9.5, 9.9, 10.0, 11.0, 15.0 x2
Thanks for your responses in advance.
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