Ian it sounds like this is your first project, if thats the case then its not a good one to cut your teeth on. I'm not saying it cant be done, but it is rather ambitious.
3GGG - Updating the BOM to the X configuration isn't hard - look at the J schematic next to the JX. Notice a bit of symmetry? The parts around the power FETs double, but the inner gain section just adds few resistors (so you don't need to get another matched pair of jfets unless you want a spare. There are a couple of additional power resistors on the output to stabilize the DC.
Hi 3GGG,
the X'ed J just adds another Aleph-current source onto the empty drain of the differential pair and routes the feedback X'ed.
Be sure to get a working schematic first, before you start building or ordering.
Be warned the J-X is a big amp and will be a bit costly.
For parts, matched fets you can get from Jack (TechDIY) or me, I certainly have also the matched 2SK170BL and 2SJ74BL for the frontend.
Heatsinks I think you can get from Fischer Australia, toroids I don't have much idea.
Have fun, Hannes
the X'ed J just adds another Aleph-current source onto the empty drain of the differential pair and routes the feedback X'ed.
Be sure to get a working schematic first, before you start building or ordering.
Be warned the J-X is a big amp and will be a bit costly.
For parts, matched fets you can get from Jack (TechDIY) or me, I certainly have also the matched 2SK170BL and 2SJ74BL for the frontend.
Heatsinks I think you can get from Fischer Australia, toroids I don't have much idea.
Have fun, Hannes
Another thing I forgot: the X'ed amps can be a bit tricky to get a stable dc-offset.
How well that works ususally depends on good thermal connection between the two aleph current sources and on the amount of differential feedback. The latter one usually does not change for other reasons, but the former should be kept in mind.
With proper construction, single mV differential and say 100-200 mV absolute dc-offset can be achieved.
How well that works ususally depends on good thermal connection between the two aleph current sources and on the amount of differential feedback. The latter one usually does not change for other reasons, but the former should be kept in mind.
With proper construction, single mV differential and say 100-200 mV absolute dc-offset can be achieved.
my experiance
Hi Luke,
I have started many projects in the past but I have not always completed them the way I would of liked during planning the projects, but most of the projects I have done in the past are kits with step by step manuals, This is one of a few projects I have built from scratch, some of them never worked properly but I did not have a form like this to analyses the assembly and derive solutions for the errors made, this is my first big project so I am taking my time researching out all of the components and asking for help in the areas I dont understand completely.
Thanks for the help
Ian
Hi Luke,
I have started many projects in the past but I have not always completed them the way I would of liked during planning the projects, but most of the projects I have done in the past are kits with step by step manuals, This is one of a few projects I have built from scratch, some of them never worked properly but I did not have a form like this to analyses the assembly and derive solutions for the errors made, this is my first big project so I am taking my time researching out all of the components and asking for help in the areas I dont understand completely.
Thanks for the help
Ian
linking 3 piece pcb
Thank you for this information, it is something I just never knew and iI am at that point, I have just finnished wireing together the 36(thirty-six) 33,000uF capacitors together for the amp power supply, it was allot of work to get it done right, allot of trial and error untill I solved it.
Thank you for this information, it is something I just never knew and iI am at that point, I have just finnished wireing together the 36(thirty-six) 33,000uF capacitors together for the amp power supply, it was allot of work to get it done right, allot of trial and error untill I solved it.
I've learned the hard way and I now test every component before installing it on a board. Just because Digikey or Mouser puts a part in a neatly labeled bag doesn't mean its the correct part.
Case in point, while building the MOX active crossover, which has many resistors, I was tried of testing every resistor in the build. About 3/4 of the way through installing the resistors I stopped testing the values. After installing about 20 resistors, I went back and tested a bag. They were a completely different value- 6k instead of 12k. I had to trace back and make sure the others weren't wrong also.
Measure twice, cut once.
Just my two cents.
Vince
wiring a two bridge rectifier power supply
Hi,
I hope this is clear what I am asking ? The schematic I have followed used two bridge rectifiers per side, I assumed that the transformer had four output wires and two went to each bridge rectifier, then the positive output of one bridge rectifier went to the positive rail electrolytic capacitor positive terminal, my question is this, dose the negitive output from the same bridge rectifier go to the negitive rail electrolytic capacitor negitive terminal, or to the negitive side of the electrolytic capacitor on the positive rail side between the two electrolytic capacitors where the positive and negitive terminals are linked together that make up the power supply circuit ?
I know this is a stupid question that I should be comfortable with answering, but I do require some help here with this.
Thank You For Your Help
Ian
Hi,
I hope this is clear what I am asking ? The schematic I have followed used two bridge rectifiers per side, I assumed that the transformer had four output wires and two went to each bridge rectifier, then the positive output of one bridge rectifier went to the positive rail electrolytic capacitor positive terminal, my question is this, dose the negitive output from the same bridge rectifier go to the negitive rail electrolytic capacitor negitive terminal, or to the negitive side of the electrolytic capacitor on the positive rail side between the two electrolytic capacitors where the positive and negitive terminals are linked together that make up the power supply circuit ?
I know this is a stupid question that I should be comfortable with answering, but I do require some help here with this.
Thank You For Your Help
Ian
is the power supply schematic being used in error
Hi Hannes,
If you understand the power supply problem I have, can help me ? I have attached the schematic of the power supply I am using but I have subsituted chokes for resistors, it is imperritive that I seek your knoledge on the question I have raised about wiring together the two bridge rectifiers in each mono amp I am building, it looks like I attach the positive of one bridge rectifier to the negitive of the other bridge rectifier, this is what I am questioning because I feel uncomfortable with it ?
Any help from anyone will be usefull to me, Bill and Bob are you still here because I had to get another computer so I did not communicate for a while.
Thank you
Ian
Hi Hannes,
If you understand the power supply problem I have, can help me ? I have attached the schematic of the power supply I am using but I have subsituted chokes for resistors, it is imperritive that I seek your knoledge on the question I have raised about wiring together the two bridge rectifiers in each mono amp I am building, it looks like I attach the positive of one bridge rectifier to the negitive of the other bridge rectifier, this is what I am questioning because I feel uncomfortable with it ?
Any help from anyone will be usefull to me, Bill and Bob are you still here because I had to get another computer so I did not communicate for a while.
Thank you
Ian
Hey all, Just a quick sanity and math check on my Aleph JX intentions...
I am contemplating gutting my Aleph 5 for the Aleph JX. I am planning on reusing the power supply (+/-35VDC with CRC Filter) and putting 4.5mh chokes just after the rectifiers (for LCRC Filter) to get to +/-24VDC. I confirmed with PSUdesigner that it will indeed be around 24V. The class A nature of constant bias current should easily satisfy Lcrit issue, so I think this will work out fine.
Also, my Aleph 5 was modified to run full out Bias, so I think its dissipating 250w/side out the sinks. The Aleph JX will be 12 devices/channel, and I believe this is approximately the same dissipation, correct?
Thanks in advance, and look forward to this build.
edit - I think I miscalculated, and the Aleph JX will be 3.8A bias at 24v and dissipates of 185w x2 , the Aleph 5 is 3.1A at 35V and dissipates of 217w, so the Aleph JX will be total dissipation of 370w per channel? Does this seem correct? Yikes, I may not be able to use my existing chassis/sinks.
I am contemplating gutting my Aleph 5 for the Aleph JX. I am planning on reusing the power supply (+/-35VDC with CRC Filter) and putting 4.5mh chokes just after the rectifiers (for LCRC Filter) to get to +/-24VDC. I confirmed with PSUdesigner that it will indeed be around 24V. The class A nature of constant bias current should easily satisfy Lcrit issue, so I think this will work out fine.
Also, my Aleph 5 was modified to run full out Bias, so I think its dissipating 250w/side out the sinks. The Aleph JX will be 12 devices/channel, and I believe this is approximately the same dissipation, correct?
Thanks in advance, and look forward to this build.
edit - I think I miscalculated, and the Aleph JX will be 3.8A bias at 24v and dissipates of 185w x2 , the Aleph 5 is 3.1A at 35V and dissipates of 217w, so the Aleph JX will be total dissipation of 370w per channel? Does this seem correct? Yikes, I may not be able to use my existing chassis/sinks.
Last edited:
Hold on, after reading the Aleph J owners manual, it says it pulls 200 watts out the wall, so the Aleph JX should be double that, so 400 watts out the wall...how would I have to dissipate 700+ watts if it pulls 400? Are the Aleph J sold as Mono only?
I feel like I am missing something real simple here.
For S&G, I read from service manul that the Aleph 5 pulls 300w out of the wall, and when I put my In-Line Watt/Amp meter out on my Aleph 5 Clone (2 channel and bias at max), I am pulling 575 watts out of the wall...so I must be missing something...
Anyway, it looks like a standard Aleph J is 2/3 the power consumption/dissipation of the Aleph 5. So the Aleph JX should require only 1/3 more heatsinking of a standard Aleph 5.
I think I have that room...
I feel like I am missing something real simple here.
For S&G, I read from service manul that the Aleph 5 pulls 300w out of the wall, and when I put my In-Line Watt/Amp meter out on my Aleph 5 Clone (2 channel and bias at max), I am pulling 575 watts out of the wall...so I must be missing something...
Anyway, it looks like a standard Aleph J is 2/3 the power consumption/dissipation of the Aleph 5. So the Aleph JX should require only 1/3 more heatsinking of a standard Aleph 5.
I think I have that room...
Last edited:
The Aleph 5 should be less than 300 watts, unless you used .47ohm source resistors. If you did, each fet is over 40 watts diss., and you should have adjusted your sense resistor value also.
My 6 fet Aleph J runs at around 180 watts/ch with the standard J bias trim. Each fet is close to 30 watts diss.
I think I would consider dropping back to 4 fets in an X amp unless you need that much power. The Aleph J's AC current gain is set at around 42%, so quite a bit of output power can be picked up just going up to 50%.
Seems to me you would be better off getting the correct trafos than trying to cobble together a choke input PS, but thats just my opinion.
Again, I caution everyone about the current limiter resistor values.
My 6 fet Aleph J runs at around 180 watts/ch with the standard J bias trim. Each fet is close to 30 watts diss.
I think I would consider dropping back to 4 fets in an X amp unless you need that much power. The Aleph J's AC current gain is set at around 42%, so quite a bit of output power can be picked up just going up to 50%.
Seems to me you would be better off getting the correct trafos than trying to cobble together a choke input PS, but thats just my opinion.
Again, I caution everyone about the current limiter resistor values.
Last edited:
Is that 300 watts or 150 watts per channel on the Aleph 5?
Yes, I used .47ohm source resistors, and my FETS are running around 43 watts. And after a second look (ie waiting 5 minutes), I am pulling 625 watts (5.2A) out the wall.
There are definite advantages to a Choke input PS, correct? Better filtering?
So if my math is correct, my overdriven Aleph 5 is 43 watts/device x 6 devices = 258 watts/channel, and Standard Aleph JX would be 30 watts/device x 8 devices = 240 watts.
Looks like I just need to reduce #devices/channel from 12 to 8 and I am good to go.
Sorry if this is so obvious to all of you...
Last edited:
A standard A5 is a little less than 150W/ch, depending on the BJTs you used. If you used .47ohm source resistors you doubled the bias current. You also drastically changed the AC current gain ratio if you did not lower your sense resistors a like amount.
I don't know if there are any benefits to choke input other than lowering the output voltage. I know it will be very load dependent and I also don't know about heat dissipation or whether the average current draw would be equal to a true constant current draw. It probably would be in an X amp, but others will know for sure.
I don't know if there are any benefits to choke input other than lowering the output voltage. I know it will be very load dependent and I also don't know about heat dissipation or whether the average current draw would be equal to a true constant current draw. It probably would be in an X amp, but others will know for sure.
My first Aleph was pretty much exactly what you're describing.
I think you could still pull it off by lowering the rails. The signal swing is huge in a bridged amp. I would imagine 18-19 volts would put you in the ballpark of the Aleph 5, and if you had a little cushion with heatsink temps you could even crank the bias up a bit.
I think you could still pull it off by lowering the rails. The signal swing is huge in a bridged amp. I would imagine 18-19 volts would put you in the ballpark of the Aleph 5, and if you had a little cushion with heatsink temps you could even crank the bias up a bit.