If anyone could help, on the schematic of the AJ-X Power Supply it states that the resister values are 1.5ohms and 2.7ohms at 5watts, however in the artical with the schematic it uses resister values of 0.15ohms & 0.27ohms at 50watts, I believe the latter one is correct, is it ?
I have been thinking of many different ways that I would like to make this amplifier and I believe I will first just follow the schamatics given in the AJ-X artical, by the way is the artical still posted someware, I have a copy of it but am wondering why it just disappeared from the previos location, or did it ?
I have been thinking of many different ways that I would like to make this amplifier and I believe I will first just follow the schamatics given in the AJ-X artical, by the way is the artical still posted someware, I have a copy of it but am wondering why it just disappeared from the previos location, or did it ?
I am aware that many people are thinking of using fans, I am and found a good selection of quiet fans Quiet Case Fans - Zalman Fans & Noctua Fans & Fan Silencing Gaskets and a good fan controller that I will incorporate into my AJ-X for 3 or 4 120mm fans each monoblock ZM-MFC3 , I will have one fan on each of the two heatsinks per monoblock AAVID THERMALLOY|DB180-20|HEAT SINK, T SLOTS, 0.32°C/W | Newark Canada and the other fan for cooling the case and power supply heatsink FISCHER ELEKTRONIK|SK 56/ 200 SA|HEAT SINK, EXTRUDED | Newark Canada
, can someone tell me if I am overdoing it for the heat that this AJ-X amp will be creating because I dont want to be waisting money because I dont have much to spend these days but I would like to do this amp project the right way ?
, can someone tell me if I am overdoing it for the heat that this AJ-X amp will be creating because I dont want to be waisting money because I dont have much to spend these days but I would like to do this amp project the right way ?
dose the Aleph J-X & the Aleph J sound the same
The speakers I have are to use the Aleph amp above 100Hz, below 100Hz the subs have their own amps, above 100Hz my speakers are 98db per watt so I never use more than 8watts at home for 107db continues sound pressure. Can someone give me any information on the quality of A J-X & A J amplifiers sound if power is not an issue ?
Thank You for the responses I have had in the past month because it has helped me significantly make hard choices.
The speakers I have are to use the Aleph amp above 100Hz, below 100Hz the subs have their own amps, above 100Hz my speakers are 98db per watt so I never use more than 8watts at home for 107db continues sound pressure. Can someone give me any information on the quality of A J-X & A J amplifiers sound if power is not an issue ?
Thank You for the responses I have had in the past month because it has helped me significantly make hard choices.
Attachments
If they are part of a CRCRC filter, calculate the dissipation at 3.8A (nominal AJ-X bias per channel) and you'll see that the higher resistance values make no sense, they'd burn up and you'd have nothing left of your rail voltage.
hi all
ive calculated my jx using the spread sheet ,below are my results
volt @ fets = 16.2
bias per channel 10.2
current gain 50%
fets = 12 per channel
bias per fet = 1.7a
8 ohm = 50w
4 ohm = 87w
2 ohm = 104 w
dissapation per channel = 326w so 4x large conrad per channel /mono block
dissapation per fet = 27w
traffo will be custom 1kva 12/0/12 sec per mono block
source resistor = .29 ohm
current source is j74 and i am using a single j109 jfet
id love if someone could check the above for me just to confirm its ok
regards sheafer
ive calculated my jx using the spread sheet ,below are my results
volt @ fets = 16.2
bias per channel 10.2
current gain 50%
fets = 12 per channel
bias per fet = 1.7a
8 ohm = 50w
4 ohm = 87w
2 ohm = 104 w
dissapation per channel = 326w so 4x large conrad per channel /mono block
dissapation per fet = 27w
traffo will be custom 1kva 12/0/12 sec per mono block
source resistor = .29 ohm
current source is j74 and i am using a single j109 jfet
id love if someone could check the above for me just to confirm its ok
regards sheafer
your numbers look OK, but two things to consider
Transformer secondary - 12VAC will only give you 16.2V rails with a pure C filter. If you want to do something like CRC or CLC, add a couple volts to allow for the loss.
Rail voltage - a tradeoff for low impedance loads, but Pass has commented several times that IRFP240s aren't at their most linear below 20V. The mini A runs around 16V and people are happy with it. IIRC each of the biggest Conrad sinks can handle 100W, so you have a little room to play with rail voltage.
You'll have a lot better luck finding 0R3 resistors which will slightly decrease the bias. Increasing R11 and R33 can increase the bias to compensate.
Transformer secondary - 12VAC will only give you 16.2V rails with a pure C filter. If you want to do something like CRC or CLC, add a couple volts to allow for the loss.
Rail voltage - a tradeoff for low impedance loads, but Pass has commented several times that IRFP240s aren't at their most linear below 20V. The mini A runs around 16V and people are happy with it. IIRC each of the biggest Conrad sinks can handle 100W, so you have a little room to play with rail voltage.
You'll have a lot better luck finding 0R3 resistors which will slightly decrease the bias. Increasing R11 and R33 can increase the bias to compensate.
hi bob
thanks for looking it over
i am a little worried about the low rail voltage ,is there a substitute for the irfp240 that i could use that would work better and still take the high bias current ?
i will play with the spread sheet a little more and see what i can do to up the rail voltage and still have good power into 4 ohm
regards sheafer
thanks for looking it over
i am a little worried about the low rail voltage ,is there a substitute for the irfp240 that i could use that would work better and still take the high bias current ?
i will play with the spread sheet a little more and see what i can do to up the rail voltage and still have good power into 4 ohm
regards sheafer
I have finished my purchas orders for the Aleph J-X and they add up to over $2,000.00
Have I done something rong, I expected this amp to cost about $800.00 to make, not over $2,000.00 with taxs and shipping, where I have gone wrong, if I have done so ?
I am still going ahead with the Aleph J-X project, but has it cost anyone else over $2,000.00 for two mono Aleph J-X amps.
Have I done something rong, I expected this amp to cost about $800.00 to make, not over $2,000.00 with taxs and shipping, where I have gone wrong, if I have done so ?
I am still going ahead with the Aleph J-X project, but has it cost anyone else over $2,000.00 for two mono Aleph J-X amps.
The big ticket items are case, heat sinks, transformers, caps. Prices depend a lot on whether you are a surplus shopper or new parts shopper. I figure around $700 per chassis if I get good surplus stuff.
Just my 2 cents, but I noticed that every amp I have built that has a commercial equivalent costs me about 10% or so of the commercial version costs.
This is with a mix of new and surplus parts and DIY case.
This is with a mix of new and surplus parts and DIY case.
over $2,000.00 monoblock AJ-X Purchase Orders without the box or enclosure
I have attached copies of my purchase orders so you can see all of the parts required to build the mono Aleph J-X power amplifier, some of the parts ordered are for two monoblock amps depending on the supplier Purchase order techniques, I have not purchased yet waiting for some comments on the parts I have chosen, if I dont hear anything from anybody I will go ahead with what I have chosen on the attached Purchase Orders, all of the suppliers internet sites are in the titles of the files.
Thank You for your help if you can help me.
I have attached copies of my purchase orders so you can see all of the parts required to build the mono Aleph J-X power amplifier, some of the parts ordered are for two monoblock amps depending on the supplier Purchase order techniques, I have not purchased yet waiting for some comments on the parts I have chosen, if I dont hear anything from anybody I will go ahead with what I have chosen on the attached Purchase Orders, all of the suppliers internet sites are in the titles of the files.
Thank You for your help if you can help me.
looking at teh digikey order, 2 X CL60 should do, one for each monoblock.
Half the capacitance is more than enough, use CRC.
Maybe get your fets matched from here Tech DIY Company Store
Matching is important for this amp and you probably need more than youve bought.
Try finding heatsinks on ebay, there are often good sinks for good prices on this forum.
It should be hard trimming alot of your $2K if you shop around the swapmeet, surplus stores and ebay IMO.
Good luck with your build.
Half the capacitance is more than enough, use CRC.
Maybe get your fets matched from here Tech DIY Company Store
Matching is important for this amp and you probably need more than youve bought.
Try finding heatsinks on ebay, there are often good sinks for good prices on this forum.
It should be hard trimming alot of your $2K if you shop around the swapmeet, surplus stores and ebay IMO.
Good luck with your build.
There are a few duplicate parts, such as thermal grease from wakefield and AAvid, (one small tube will be plenty or not needed if you use silpad isolators), Rectifiers (you have several types for the PSU, for cost staving stick with the good old GPC type and the chokes from Newark and back ordered at Mouser, but included in your total.
BTW, you have selected common mode chokes when common mode is not needed. You can wire them for increased inductance, or find standard chokes. Air core chokes as used in speaker crossovers will work. As Luke suggested, using a CRC filter is probably cheaper.
I'll second Luke's recommendation to buy more IRFP240s - I see that is a one board order, but I'd buy at least 50 to try to get the best matches. Ideally, all 12 will match, but if need be match side to side gain stage and current source. They are packed in tubes of 25 IIRC, so buying multiples of ready packed tube means that you are more likely to get a bunch from the same manufacturing lot and therefore better matches.
There are also a few items in there that I don't understand - The vector board CBs and relays. Are you planning a circuit breaker in each rail? The vector board is expensive, what do you plan to use it for? Can you cut it and use one piece?
Why the fans and controllers? I think that your chosen sinks would be OK, but is it 2 per channel or 4? With 2 you'll need fans, 4 you can probably get away without. This is class A - the dissipation varies little. Save the cost of the controller, use a resistor to drop fans speed if needed or make a quick and dirty speed control with a leftover IRFP240 a cap and a couple resistors. You list 8 fans and 4 sinks, I wouldn't do more than one per heat sink.
You've also included the cost of some of your test equipment. You should amortize that over your next few builds. 😉
Have fun.
BTW, you have selected common mode chokes when common mode is not needed. You can wire them for increased inductance, or find standard chokes. Air core chokes as used in speaker crossovers will work. As Luke suggested, using a CRC filter is probably cheaper.
I'll second Luke's recommendation to buy more IRFP240s - I see that is a one board order, but I'd buy at least 50 to try to get the best matches. Ideally, all 12 will match, but if need be match side to side gain stage and current source. They are packed in tubes of 25 IIRC, so buying multiples of ready packed tube means that you are more likely to get a bunch from the same manufacturing lot and therefore better matches.
There are also a few items in there that I don't understand - The vector board CBs and relays. Are you planning a circuit breaker in each rail? The vector board is expensive, what do you plan to use it for? Can you cut it and use one piece?
Why the fans and controllers? I think that your chosen sinks would be OK, but is it 2 per channel or 4? With 2 you'll need fans, 4 you can probably get away without. This is class A - the dissipation varies little. Save the cost of the controller, use a resistor to drop fans speed if needed or make a quick and dirty speed control with a leftover IRFP240 a cap and a couple resistors. You list 8 fans and 4 sinks, I wouldn't do more than one per heat sink.
You've also included the cost of some of your test equipment. You should amortize that over your next few builds. 😉
Have fun.
comment on choosing a choke
Thank you for your help. I have been lead to believe that doing things the way they are doing them with the best tube amps is a way of choosing components for state of the art sound from the tranistor. Could you please comment on the choice of the choke I have found tube amp builders are using 7,000 Henrys at 12 Hz, they say it gives a significant increase in quality of the high frequency over all other chokes, is this true ?
Thank you for your help. I have been lead to believe that doing things the way they are doing them with the best tube amps is a way of choosing components for state of the art sound from the tranistor. Could you please comment on the choice of the choke I have found tube amp builders are using 7,000 Henrys at 12 Hz, they say it gives a significant increase in quality of the high frequency over all other chokes, is this true ?