just found out : alternative to ztx450 is bc550. c2 and c3 are 220uF at 35v. zener = 1N4739A. Thanks to aleph j bom v1.1....is this the latest?
Sorry Sam. thought we were still on the soft start.
Look at the schematic, and imagine full output voltage swing. It won't do rail to rail, but maybe close, so these caps should be rated for at least 50V, preferably 63 or 80. Some will cut it closer assuming that they won't go rail to rail, which accounts for 35V rating. Personally, if the higher voltage caps will fit...
PM -
Calculate the zener dissipation. The current is set by R5, which has ~39V across it. (48V rail to rail - 9.1V) ==> you have 8.2 mA. P=V*I, so you dissipate <.1W in the zener. You want something capable of >.2W, and a .5W 9.1V 1n5239 is pretty standard for a $.05 or so. (or the 1W 1N4739A for a penny more)
I don't suggest 1/2W, but was pointing out that some will say that any of the 1/4W resistors could be made 1/2W. I used .6W resistors in a Leach amp and couldn't tell the difference, but it could have been that they were small form factor resistors with bodies the same size as the standard 1/4W ones I used in previous amps.
Watch the pin outs substituting the BC550 -
http://www.diodes.com/datasheets/ZTX450.pdf
http://www.fairchildsemi.com/ds/BC/BC550.pdf
Look at the schematic, and imagine full output voltage swing. It won't do rail to rail, but maybe close, so these caps should be rated for at least 50V, preferably 63 or 80. Some will cut it closer assuming that they won't go rail to rail, which accounts for 35V rating. Personally, if the higher voltage caps will fit...
PM -
Calculate the zener dissipation. The current is set by R5, which has ~39V across it. (48V rail to rail - 9.1V) ==> you have 8.2 mA. P=V*I, so you dissipate <.1W in the zener. You want something capable of >.2W, and a .5W 9.1V 1n5239 is pretty standard for a $.05 or so. (or the 1W 1N4739A for a penny more)
I don't suggest 1/2W, but was pointing out that some will say that any of the 1/4W resistors could be made 1/2W. I used .6W resistors in a Leach amp and couldn't tell the difference, but it could have been that they were small form factor resistors with bodies the same size as the standard 1/4W ones I used in previous amps.
Watch the pin outs substituting the BC550 -
http://www.diodes.com/datasheets/ZTX450.pdf
http://www.fairchildsemi.com/ds/BC/BC550.pdf
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i have plenty of 1N4739 (without the 'A') at 9.1v...left overs from my aleph 5. Assume they are the same??
Walter
Z-Diode 24V 0,5W // Re1?? the resistor 0.5 w at 20k? zener same as above mentioned?
Walter
Z-Diode 24V 0,5W // Re1?? the resistor 0.5 w at 20k? zener same as above mentioned?
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The BC's will be fine, they just won't match the silkscreen when installed correctly (in case you hadn't figured that out)
i just need to put it in the opposite direction.
Peter's board resistor's spacing are too close for 1/2 w.
Peter's board resistor's spacing are too close for 1/2 w.
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hi all
can i parralell the 2sj109 on my aleph j
will they work ok and do they need to be matched
i am running 3 pair of output devices per channel so i want to make sure it will be ok and i think 1x 2sj109 will be borderline
i will also up the bias as much as io can to get the output to double into 4 ohm , can i have a reccomendation on the bias required to acheive this ?
heatsinks are not a problem as i live close to conrad engineering and can run as much as required
thanks in advance for any help
regards sheafer
can i parralell the 2sj109 on my aleph j
will they work ok and do they need to be matched
i am running 3 pair of output devices per channel so i want to make sure it will be ok and i think 1x 2sj109 will be borderline
i will also up the bias as much as io can to get the output to double into 4 ohm , can i have a reccomendation on the bias required to acheive this ?
heatsinks are not a problem as i live close to conrad engineering and can run as much as required
thanks in advance for any help
regards sheafer
Hi Sheafer,
I paralleled them using closely matched quads, it is necessary.
Doubling the power into 4 ohms vs 8ohms will take more than doubling the bias. Take a look at the Aleph 5 which goes from 60/8 to 90/4. The current gain of the current source is vastly different.
If you just want to build a bigger Aleph J, NP has suggested building two stereo amps and paralleling the channels. I tried it and it works but I believe you need to match everything in both channels as closely as possible to promote current sharing.
I paralleled them using closely matched quads, it is necessary.
Doubling the power into 4 ohms vs 8ohms will take more than doubling the bias. Take a look at the Aleph 5 which goes from 60/8 to 90/4. The current gain of the current source is vastly different.
If you just want to build a bigger Aleph J, NP has suggested building two stereo amps and paralleling the channels. I tried it and it works but I believe you need to match everything in both channels as closely as possible to promote current sharing.
hi bill
so i presume for what i am after it would be better to just build the ajx version instead
wil the ajx double its power into 4 ohm ,i have the pd ajx boards so its not too much trouble to build
lets say i build the ajx with the standard 8 output devices per channel standard bias and a 18v/18v toriod per channel
what sort of power should i expect into 8 and 4 ohm and would this be more suitable for my esl speakers that the standard aleph j
sory to sound like a broken record with this i just want to make sure the amp i build is suitable for my needs
regards sheafer
so i presume for what i am after it would be better to just build the ajx version instead
wil the ajx double its power into 4 ohm ,i have the pd ajx boards so its not too much trouble to build
lets say i build the ajx with the standard 8 output devices per channel standard bias and a 18v/18v toriod per channel
what sort of power should i expect into 8 and 4 ohm and would this be more suitable for my esl speakers that the standard aleph j
sory to sound like a broken record with this i just want to make sure the amp i build is suitable for my needs
regards sheafer
sheafer,
Perhaps it would be better to define your 4R power needs and bias accordingly. Use the AXE-1-2 spreadsheet to determine your bias needs.
These single ended amps do not necessarily double 8R power into 4R loads. If that is a hard requirement (why?) you should investigate a push pull design. To get a single ended amp to double 8R power into 4R, your bias must be significantly higher than needed for 8R operation.
Perhaps it would be better to define your 4R power needs and bias accordingly. Use the AXE-1-2 spreadsheet to determine your bias needs.
These single ended amps do not necessarily double 8R power into 4R loads. If that is a hard requirement (why?) you should investigate a push pull design. To get a single ended amp to double 8R power into 4R, your bias must be significantly higher than needed for 8R operation.
I don't mean to start an argument here, but the X amps are push-pull, so it's down to whether you want single ended or push-pull to start with.
Whatever you decide you should tailor the build to the load you are going to present to it. Either can be changed to increase power into a 4ohm load but a little reengineering has to be done with the AC current gain. That is why I suggested studying the Aleph 5. I believe the spreadsheet covers all of it, and look up the thread about AC gain.
Whatever you decide you should tailor the build to the load you are going to present to it. Either can be changed to increase power into a 4ohm load but a little reengineering has to be done with the AC current gain. That is why I suggested studying the Aleph 5. I believe the spreadsheet covers all of it, and look up the thread about AC gain.
What I meant by push pull are amps with complimentary push pull or quasi-complimentary output stages where the output current isn't limited to the bias current (+ AC Current gain). Of course if you insist on class A operation, the bias current is required either way.
Technically the X amps' loads see a push pull voltage, but I think of it as bridged single ended output stages.
Technically the X amps' loads see a push pull voltage, but I think of it as bridged single ended output stages.
I agree completely. The genius of the Aleph current source is the ability to push the efficiency way past what is possible with CCSs with very little added distortion.
hi bob and bill
i think i will build the x in the 100w version and run lower rail voltage but higher bias to optimise for 4 0hm and see what happens
i love esl speakers and as such 4 to 2 ohm loads is what i have to build for
nothing to crazy with the watts into 8 ohm as 30 to 50 will do but the amp needs to be able to double power into 4 ohm to work well with a esl speaker
regards sheafer
i think i will build the x in the 100w version and run lower rail voltage but higher bias to optimise for 4 0hm and see what happens
i love esl speakers and as such 4 to 2 ohm loads is what i have to build for
nothing to crazy with the watts into 8 ohm as 30 to 50 will do but the amp needs to be able to double power into 4 ohm to work well with a esl speaker
regards sheafer