Nelson Pass (being wise regarding the sound of any one component needing to be considered within the the context of the system it is in to be properly evaluated) made some qualifying statements about his choice of Aleph J as "best of the Alephs" one of which was something like: "...if you had speakers like mine..."
So all you Aleph J builders/owners (designer, Papa?): what speakers are you liking with the Aleph J?
So all you Aleph J builders/owners (designer, Papa?): what speakers are you liking with the Aleph J?
You can see mine following the link below:
http://www.diyaudio.com/forums/multi-way/235768-building-basszilla-platinum-edition-fall-2012-a.html
Other amplifiers to which I listened connected to the same speakers:
F5 (DIY clone)
Aleph 5 (DIY clone)
Krell KSA-50 (DIY clone)
The Aleph J has been used almost daily with them since early May.
http://www.diyaudio.com/forums/multi-way/235768-building-basszilla-platinum-edition-fall-2012-a.html
Other amplifiers to which I listened connected to the same speakers:
F5 (DIY clone)
Aleph 5 (DIY clone)
Krell KSA-50 (DIY clone)
The Aleph J has been used almost daily with them since early May.
A beautiful build!
What sort of load do they present to the bevy of amps you have had and why do you think the Aleph J has stayed "top of the list" for so long?
What sort of load do they present to the bevy of amps you have had and why do you think the Aleph J has stayed "top of the list" for so long?
This is the impedance response plot provided by Dick Olsher, the designer, in the BassZilla construction manual.
Larger amplifiers, like the Aleph 2 and the Krell KSA-100, do raise the room temperature during long listening sessions. The Aleph J has lower heat rejection, which is one reason why I am favoring it and the F5. But the main reason is how the Aleph J enhances textures and the sense of presence in the room.
Larger amplifiers, like the Aleph 2 and the Krell KSA-100, do raise the room temperature during long listening sessions. The Aleph J has lower heat rejection, which is one reason why I am favoring it and the F5. But the main reason is how the Aleph J enhances textures and the sense of presence in the room.
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My vote on speakers is such ones that play sound nicely when a voltage is applied on them =)
Any 8 ohm+ speaker should work as long as it is reasonably efficient.
Any 8 ohm+ speaker should work as long as it is reasonably efficient.
I have two reasons to be concerned, one is already stated and "amplified" if you will by the 6 Moons review of the Aleph J...it is a matter of matching the voice and load of each speaker to the amp that is key. (I'm sure the Aleph J is a stellar design...)
And the second is that it seems like the Aleph J does not play well with 4 ohm loads, at least, no one has talked about how it sounds with a 4 ohm speaker...
I only have one set of speakers rated at 8 ohm, two at (nominal) 6 and my best pair represents a 4 ohm load (Kef 104/2s). I may have to go out in search of a proper mate for the Aleph J once I have it built, so I am putting out feelers as to what that mate might be. Folks here on the Pass forum would be the place to start 🙂
Cheers!
And the second is that it seems like the Aleph J does not play well with 4 ohm loads, at least, no one has talked about how it sounds with a 4 ohm speaker...
I only have one set of speakers rated at 8 ohm, two at (nominal) 6 and my best pair represents a 4 ohm load (Kef 104/2s). I may have to go out in search of a proper mate for the Aleph J once I have it built, so I am putting out feelers as to what that mate might be. Folks here on the Pass forum would be the place to start 🙂
Cheers!
The Aleph J should sound about the same in any load, you just have much less output power into lower loads with slightly higher distortion but if I remember correctly there is no massive increase.
I remember Nelson mentioning that the Aleph (30 I think in that case) was stable into 2 ohm, and the J is similar to the 30.
But with such loads then you could look to the F6, which if I remember correctly handles low loads very good and you can tailor the sound to be 2nd dominant like the Aleph J.
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Well that's cool, if the J will drive a four ohm speaker...the KEF 104/2 is a fairly uniform load and fairly efficient at 90dB/ W 🙂
It is strange though that the J should put less power into a four ohm load. I'm not versed in the ways of the Aleph but most SS amps (good ones) will increase the power into a four from an eight ohm load?
It is strange though that the J should put less power into a four ohm load. I'm not versed in the ways of the Aleph but most SS amps (good ones) will increase the power into a four from an eight ohm load?
Depends on topology, most push-pull amps like the F5, F6, F1 and so on eat 4 ohms for breakfast. The single ended ones, however, are generally more picky about load and often prefer 8-16 =)
You can add extra pairs of output devices and increase the current capability so your A-J will be more happy with lower impedance loads. Takes a bit of work, but do-able.
NP's caveat means fairly sensitive benign impedance speakers - no dips too low, no wild reactance. If your speakers will give you 90 db/W and your Aleph J will make 30W you can get 105 dB peaks cleanly. OTOH, your speakers are more like 80 dB/W you will be limited to 95 dB peaks. This may be enough for you, or may not.
NP's caveat means fairly sensitive benign impedance speakers - no dips too low, no wild reactance. If your speakers will give you 90 db/W and your Aleph J will make 30W you can get 105 dB peaks cleanly. OTOH, your speakers are more like 80 dB/W you will be limited to 95 dB peaks. This may be enough for you, or may not.
On the FirstWatt website the Aleph J is rated 25W into 8 and 13W into 8 ohms. My question is at which impedance does the amp start running out of current ? A speaker with 6 ohms minimum will already lead to limited power output or not ?
What the first Watt site is saying is that the Aleph J can produce 3.125A of output current.
The simplified equation is P = I^2 x R So, at 6 ohms you can expect 18.75W.
The reason that is simplified is that 1. Speaker impedances are not constant and 2. Speaker loads are not purely resistive. So, a "6 ohm speaker" could have an impedance ranging from say 4 to 20 ohms over the audio band. The power delivered depends on the magnitude and phase angle of the load and the voltage available at a particular frequency. Look for a review of your speaker to see what the load actually is.
The good thing about DIY is that you can change things to suit the load, within reason. Output power is determined by output voltage and current. The A-J is a single ended amp and can deliver roughly rail voltage and bias current times AC gain (typically set at around 50%). This differs from typical push pull circuits that can provide increased current into lower impedance loads.
Have a low impedance load to drive with your Aleph J? Increase the bias, add more output devices, change the active current source gain or all three. I'd tend to leave the current source gain alone just because that has more of an impact on the character of the sound than the others. Need more power? Increase the rail voltage, up to say 30V. This will put a bit more stress on your 2SJ74s but NP seems to think they can handle it in the F5 Turbo article. You can add another pair of output devices (one ACS and one OP) or maybe 2 without impacting the sound character. Need to drive lots more output devices? Parallel multiple pairs of 2SJ74s.
These options allow you to make your A-J YOUR A-J This is a lot of the fun of DIY, at least to me. Read through the various Aleph threads. You'll see a lot of discussion about increasing bias, number of outputs and AC current gain. All applies to the A-J, with a rail voltage limitation due to the JFETs.
Of course, you can also build the A-J exactly as specified and build a pair of super efficient, preferably Lowther based speakers to get to hear what it sounds like on speakers like Nelson Pass'. 😉
The simplified equation is P = I^2 x R So, at 6 ohms you can expect 18.75W.
The reason that is simplified is that 1. Speaker impedances are not constant and 2. Speaker loads are not purely resistive. So, a "6 ohm speaker" could have an impedance ranging from say 4 to 20 ohms over the audio band. The power delivered depends on the magnitude and phase angle of the load and the voltage available at a particular frequency. Look for a review of your speaker to see what the load actually is.
The good thing about DIY is that you can change things to suit the load, within reason. Output power is determined by output voltage and current. The A-J is a single ended amp and can deliver roughly rail voltage and bias current times AC gain (typically set at around 50%). This differs from typical push pull circuits that can provide increased current into lower impedance loads.
Have a low impedance load to drive with your Aleph J? Increase the bias, add more output devices, change the active current source gain or all three. I'd tend to leave the current source gain alone just because that has more of an impact on the character of the sound than the others. Need more power? Increase the rail voltage, up to say 30V. This will put a bit more stress on your 2SJ74s but NP seems to think they can handle it in the F5 Turbo article. You can add another pair of output devices (one ACS and one OP) or maybe 2 without impacting the sound character. Need to drive lots more output devices? Parallel multiple pairs of 2SJ74s.
These options allow you to make your A-J YOUR A-J This is a lot of the fun of DIY, at least to me. Read through the various Aleph threads. You'll see a lot of discussion about increasing bias, number of outputs and AC current gain. All applies to the A-J, with a rail voltage limitation due to the JFETs.
Of course, you can also build the A-J exactly as specified and build a pair of super efficient, preferably Lowther based speakers to get to hear what it sounds like on speakers like Nelson Pass'. 😉
In the Aleph J manual it states that some of the changes are "Reduced gain on the active current source, giving better overall performance into 8-16 ohm loads". It also states that maximum output current is +and- 2.5A.
Just sayin 😉
Just sayin 😉
Hey FLG, no fair reading the manual! I wonder if that means that it sounds better into 8-16 ohm loads than higher AC current gain or if with these settings it simply prefers higher impedance loads.
As for current, I just went back to Georg's stated power ratings. NP rate things conservatively? Horrors!
As for current, I just went back to Georg's stated power ratings. NP rate things conservatively? Horrors!
The new store boards allows for higher bias, as it has two output pairs. It will give the extra current needed for low Z loads. It gets moer complicated after that. THat being said, it sounded great drving a pair of 88dB 8ohm(more like 6) multiways I have. I tihnk the Aleph J is one of the best amps I have heard when it comes to mids and highs, bar none.
Once again it is the mating game...
Amps and speakers ought to be sold soldered together with a select speaker cable! Arrg!
And if thats true then they ought to be built for each other 🙂
Maybe that is what I was hoping for in the back of my mind and it was kind-of supplied by my first responder with his basszilla speakers... That build is a bit rich for myself at this time.
If I like this Aleph J enough (and I'm guessing I will) I just have to build it a bride! I don't think I can swing the Lowther build (I'm using junkyard parts for the chassis as it is) but maybe I can build a mule...
Wild Burro Audio Labs - DIY Full Range Speakers
Seems like a place to start without too much fuss; any comments?
Oh and thanks BobEllis for the insight and good suggestions. I may try to modify the Aleph J as you have pointed to given a successful build of a standard "J" in the first place and no satisfaction with the speakers I own and/or the wildburro build shot down...
Amps and speakers ought to be sold soldered together with a select speaker cable! Arrg!
And if thats true then they ought to be built for each other 🙂
Maybe that is what I was hoping for in the back of my mind and it was kind-of supplied by my first responder with his basszilla speakers... That build is a bit rich for myself at this time.
If I like this Aleph J enough (and I'm guessing I will) I just have to build it a bride! I don't think I can swing the Lowther build (I'm using junkyard parts for the chassis as it is) but maybe I can build a mule...
Wild Burro Audio Labs - DIY Full Range Speakers
Seems like a place to start without too much fuss; any comments?
Oh and thanks BobEllis for the insight and good suggestions. I may try to modify the Aleph J as you have pointed to given a successful build of a standard "J" in the first place and no satisfaction with the speakers I own and/or the wildburro build shot down...
The new store boards cost almost the same as the needed boards to diy a set. I can assure yuo that it will handle most speakers just fine. This is Class A. It is different.
I remain optimistic. I have four sets of speakers to try...
I just like asking questions that might have surprising answers and lead me to more questions and more insights/knowledge and finally to...better listening 🙂
You guys are great! All we who cannot afford tuition applaud your tutelage!!!
I just like asking questions that might have surprising answers and lead me to more questions and more insights/knowledge and finally to...better listening 🙂
You guys are great! All we who cannot afford tuition applaud your tutelage!!!
I assembled one of the prototype boards and it only has one pair of output devices and another for the current source, exactly like the schematic Nelson Pass published. The final version now being offered in the store has the same configuration. Which board are you talking about?
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