> 300 VA ?? Will 500 VA be harmful ??
Refer to the First Watt schematics. Supply is +/-24V. Total bias is about 2A. That would make about 100W continuous draw. So 300VA would be sufficient.
However, should you wish to upgrade later to an AJ-X, then 500VA (or 600VA) would fit the bill perfectly.
The price difference between the two is less than 1.5x.
Patrick
Refer to the First Watt schematics. Supply is +/-24V. Total bias is about 2A. That would make about 100W continuous draw. So 300VA would be sufficient.
However, should you wish to upgrade later to an AJ-X, then 500VA (or 600VA) would fit the bill perfectly.
The price difference between the two is less than 1.5x.
Patrick
Not quite sure how this could happen, but it seems I somehow managed to screw up the transistor pinouts on the biploar parts and the 2SJ. Here's the corrected board:
Bottom layer pdf: http://www.hb001.de/alephjpcbbottom_rc9.pdf
An externally hosted image should be here but it was not working when we last tested it.
Bottom layer pdf: http://www.hb001.de/alephjpcbbottom_rc9.pdf
You're not alone Holger. That even happens in the industry, when you give the final OK for a 1000pcs. batch of PCBs to the boardhouse only to discover you mangled some part's, or more typically, some connector's pinout (happend to me). That's why we need so many "soldering students", at timesHBarske said:
Hiticktock said:
I would tend to build the bigger supply, as an X-version surely is an option... Only consider that the voltage output would be a little hihger, but given the allowed (>=2008) 195V...265V mains AC span, this is another can of worms...
- Klaus
Hello Klaus,
nett, daß Du auch hier bist
I know You prefer the XA and Aleph X, maybe I will build one sometime.
But not sure at all.
Are You sure of the voltage span? Never heard of something like that.
Actually we have exactly 230 V.
For this (195V...265V mains AC span) You'd need a smps . . . .
nett, daß Du auch hier bist
I know You prefer the XA and Aleph X, maybe I will build one sometime.
But not sure at all.
Are You sure of the voltage span? Never heard of something like that.
Actually we have exactly 230 V.
For this (195V...265V mains AC span) You'd need a smps . . . .
> Are You sure of the voltage span? Never heard of something like that. Actually we have exactly 230 V.
The AC Voltage from the wall is allowed to vary to a certain tolerance to regulate load on the network, but I would not expect more than 10% in most cases. In the U.K., the electricity suppliers deliberately put it on the high side (220V nom, ~240V actual) so that they can sell more electricity (most equipment consumes more as the input voltage is increased).
> a larger trannie could cause higher ripple to the DC voltage.
Can you offer a scientific explanation ?
Patrick
The AC Voltage from the wall is allowed to vary to a certain tolerance to regulate load on the network, but I would not expect more than 10% in most cases. In the U.K., the electricity suppliers deliberately put it on the high side (220V nom, ~240V actual) so that they can sell more electricity (most equipment consumes more as the input voltage is increased).
> a larger trannie could cause higher ripple to the DC voltage.
Can you offer a scientific explanation ?
Patrick
I have to correct myself... EU mains voltage is 230V+-10% from 2008, not 230V+-15% (but I remember this value to be used as a design goal). +-10% is still a lot, 207V...253V. And it's RMS, not peak, but the latter is dominant for the PSU, at least under low load conditions (hence not much of a problem with class A).
It all comes from the EU-wide change to canonical 400V tri-phase... which poses a lot of problems with smaller tri-phase motors designed for 380V. These are likely to overheat and burn, because they are designed to run near saturation.
There is funny stuff in jacco's second link:
"The mains voltage has a surprising effect on the performance of a CD player. The motor speed is voltage controlled not frequency controlled with a crystal reference as most people would expect.
Even though the motor supply voltage is regulated, the mains voltage does affect it, making it play slightly faster or slower.
The effect on the music is quite large, making it sound either fast and exciting or slow and relaxed. I discovered this whilst experimenting to find out why a ‘Pandora’ isolating transformer, that was claimed to improve CD sound quality, did affect the sound. I discovered that the ‘Pandora’ was simply increasing the mains voltage by 24 volts, hence increasing the play speed and making the sound appear more ‘exciting’."
Oouuchh! is all I can say to that "expert statement"...
Back to Topic, and back to TickTock's question:
The "X-factor" is not the relevant aspect in the context of the power supply... rather it's the fact that this will be a bridged class A output stage. Only these draw constant current from the supply and need the PSU ground connection only as a reference point, with no load current flowing. In contrast, a non-bridged stage also draws a constant current, but only in an overall sense, not on the individual supply rails (at least these see only true reflected load currents, not the nasty half-wave rectified load currents as in class AB). Needless to say I'm a big fan of bridged class A...
- Klaus
It all comes from the EU-wide change to canonical 400V tri-phase... which poses a lot of problems with smaller tri-phase motors designed for 380V. These are likely to overheat and burn, because they are designed to run near saturation.
There is funny stuff in jacco's second link:
"The mains voltage has a surprising effect on the performance of a CD player. The motor speed is voltage controlled not frequency controlled with a crystal reference as most people would expect.
Even though the motor supply voltage is regulated, the mains voltage does affect it, making it play slightly faster or slower.
The effect on the music is quite large, making it sound either fast and exciting or slow and relaxed. I discovered this whilst experimenting to find out why a ‘Pandora’ isolating transformer, that was claimed to improve CD sound quality, did affect the sound. I discovered that the ‘Pandora’ was simply increasing the mains voltage by 24 volts, hence increasing the play speed and making the sound appear more ‘exciting’."
Oouuchh! is all I can say to that "expert statement"...
Back to Topic, and back to TickTock's question:
The "X-factor" is not the relevant aspect in the context of the power supply... rather it's the fact that this will be a bridged class A output stage. Only these draw constant current from the supply and need the PSU ground connection only as a reference point, with no load current flowing. In contrast, a non-bridged stage also draws a constant current, but only in an overall sense, not on the individual supply rails (at least these see only true reflected load currents, not the nasty half-wave rectified load currents as in class AB). Needless to say I'm a big fan of bridged class A...
- Klaus
> I was thinking about building the output stage with Lu1014Ds cascoded with the IRFP240s.
LU1014 cascoded needs 0V on the gate when used with a source resistor of about 0.68 ohm. IRFP240 as used in the A-J schematics has a corresponding gate voltage of about 4.5V. Not really a drop-in, shall we say ?
Patrick
LU1014 cascoded needs 0V on the gate when used with a source resistor of about 0.68 ohm. IRFP240 as used in the A-J schematics has a corresponding gate voltage of about 4.5V. Not really a drop-in, shall we say ?
Patrick
Alep 2 with Aleph J combined?
Hi J-builders,
Maybe this has been discussed somewhere, but i could not find it.
Has anyone designed an Aleph 2 with the Aleph J input?
I would like the 100 Watt power of the Aleph 2, but I would also like the improved sonics of the Aleph J. How can this be done?
Regards,
Lucas
Hi J-builders,
Maybe this has been discussed somewhere, but i could not find it.
Has anyone designed an Aleph 2 with the Aleph J input?
I would like the 100 Watt power of the Aleph 2, but I would also like the improved sonics of the Aleph J. How can this be done?
Regards,
Lucas
Re: Alep 2 with Aleph J combined?
that means in Jaccovitty slang ............ that you need cascodes on jfet's bottom ( to save them of excessive voltage) and nice follower stage to achieve enough current for driving all these hungry gates in output
hmmmm - Papa will probably call that follower just 1/2 of stage
Lucas_G said:
jacco vermeulen said:
that means in Jaccovitty slang ............ that you need cascodes on jfet's bottom ( to save them of excessive voltage) and nice follower stage to achieve enough current for driving all these hungry gates in output
hmmmm - Papa will probably call that follower just 1/2 of stage
> I was thinking about building the output stage with Lu1014Ds cascoded with the IRFP240s.
LU1014 cascoded needs 0V on the gate when used with a source resistor of about 0.68 ohm. IRFP240 as used in the A-J schematics has a corresponding gate voltage of about 4.5V. Not really a drop-in, shall we say ? <
Of course not. ( Not that limited understanding ). By posting I hoped that someone would maybe come up with a clever way around it. Coupling caps or whatever.
SandMarc
LU1014 cascoded needs 0V on the gate when used with a source resistor of about 0.68 ohm. IRFP240 as used in the A-J schematics has a corresponding gate voltage of about 4.5V. Not really a drop-in, shall we say ? <
Of course not. ( Not that limited understanding ). By posting I hoped that someone would maybe come up with a clever way around it. Coupling caps or whatever.
SandMarc
> but someone will be faster, certainly........
One possible solution is, for example, you can put a 4V5 10W Zener Diode below the source resistor.
Not that this is the best solution with the least distortion......
Oh, another one :
Hang a 4mA constant current diode (e.g. J511) from each of the drains of the JFET diff pair to 10V below the negative rail.
The rest I should leave as mental jogging exercises.
Patrick
One possible solution is, for example, you can put a 4V5 10W Zener Diode below the source resistor.
Not that this is the best solution with the least distortion......
Oh, another one :
Hang a 4mA constant current diode (e.g. J511) from each of the drains of the JFET diff pair to 10V below the negative rail.
The rest I should leave as mental jogging exercises.
Patrick