9W is better figure
or just use IRFP240
use schematic of my Babelfish JX , along with servo and you're in game
or just use IRFP240
use schematic of my Babelfish JX , along with servo and you're in game
jea... I understand what you mean, but I would like to keep this on budget, use the parts that I have...
If I would nead to buy new toroid it will be like additional 70euro
will have to think
thanks for advices, I realy apreciate it 😀
If I would nead to buy new toroid it will be like additional 70euro
will have to think
thanks for advices, I realy apreciate it 😀
you mean this one ?
https://www.zenmod.in.rs/wp-content/uploads/2018/02/LTSpice-Babelfish-XJ-shrinked.jpg
you could not do it any more complex ?
I'm not saying anything for Donut and voltages ...... just saying what's better for you
with IRFP , one per quadrant , you hardly need proper matching ...... while with IRF you must double them , if you wish nice sleep
also , servo is everything but complicated
for input , if you don't have 2SJ , try finding J271 (or smd iteration of ) , buy them dozen or two and you'll find two pairs
aha , emiter follower between LTP and outputs is well worth trouble .....
with IRFP , one per quadrant , you hardly need proper matching ...... while with IRF you must double them , if you wish nice sleep
also , servo is everything but complicated
for input , if you don't have 2SJ , try finding J271 (or smd iteration of ) , buy them dozen or two and you'll find two pairs
aha , emiter follower between LTP and outputs is well worth trouble .....
will start to collect parts
used to have metched jfet but have sold them as I didn't plan to make any more amps 😎
used to have metched jfet but have sold them as I didn't plan to make any more amps 😎
that's damn simple , if you ask me
few additional parts comparing to common DiyA Aleph X , but works as charm
Zen
would J74BL with Idss 10.5 to 11.2mA work ?
I can get 2sj109BL but I think it would be painfull to instal it on the original green PCBs
would J74BL with Idss 10.5 to 11.2mA work ?
I can get 2sj109BL but I think it would be painfull to instal it on the original green PCBs
Pass DIY Addict
Joined 2000
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The original green boards bias the front end at 10mA per device, so the range of J74s that you have is ideal. You can also alter this bias by adjusting R23 & R25.
Not sure what rail voltages you're considering but you should keep an eye on
the dissipation of the jfets if you're not cascoding them.
the dissipation of the jfets if you're not cascoding them.
Big thank you...
To Zen Mod...
I used the DC servo built from 2 x BC639 and injected the voltage back to the junction R24/R26.
I have not yet change the Macmillan resistors - can now be higher in value.
Absolute DC changed from 2.2v cold to less than 0.2v. Relative DC is 7mv.
Very simple change and for me it was well worth doing.
Thanks again!
To Zen Mod...
I used the DC servo built from 2 x BC639 and injected the voltage back to the junction R24/R26.
I have not yet change the Macmillan resistors - can now be higher in value.
Absolute DC changed from 2.2v cold to less than 0.2v. Relative DC is 7mv.
Very simple change and for me it was well worth doing.
Thanks again!
I made a small board (20 x 25mm) that just plugs into the R24 position with a short piece of ribbon cable to pick up the voltage rails and speaker outputs. I swapped out the Macmillan resistors (from 4k7 to 100k) and reduced the LTP bias a little.
Absolute DC offset is now +/- 5mv. I think I’ll get some PCB’s made for this next time I put my next PCB order through, should be a neat little modification.
Absolute DC offset is now +/- 5mv. I think I’ll get some PCB’s made for this next time I put my next PCB order through, should be a neat little modification.
Hello to all of you Aleph X experts
After several years in the waiting in the “to be built area of my workshop”, I am finally completing construction of my Aleph X.
I have configured the layout using 12 Fets (IRF140) per channel – I happened to have about 50 matched pairs of these!!.
For the most mundane of reasons, I happen to have a pair of 1200VA toroid’s, with dual 28V secondary’s. This will equate to a DC voltage of about 37 volts (after rectification / filtering/ losses)
By my calculations, and assuming a bias of 6 amps, this equates to a dissipation of about 37 watts per fet, and a total dissipation of about 440 watts.
Power out will be:
8 ohms - 144 watts
4 ohms - 72 watts.
I don’t want to increase the bias current any further, as the dissipation gets out of hand.
I have no issue with heatsinking – have some VERY big brutes on hand.
My question is, has anyone built this amp using a higher supply voltage? and am I asking for trouble. Is this workable solution?
Or should I stop being a cheap skate and go buy the proper transformers.
I look forward to your comments
Kind Regards
George.
After several years in the waiting in the “to be built area of my workshop”, I am finally completing construction of my Aleph X.
I have configured the layout using 12 Fets (IRF140) per channel – I happened to have about 50 matched pairs of these!!.
For the most mundane of reasons, I happen to have a pair of 1200VA toroid’s, with dual 28V secondary’s. This will equate to a DC voltage of about 37 volts (after rectification / filtering/ losses)
By my calculations, and assuming a bias of 6 amps, this equates to a dissipation of about 37 watts per fet, and a total dissipation of about 440 watts.
Power out will be:
8 ohms - 144 watts
4 ohms - 72 watts.
I don’t want to increase the bias current any further, as the dissipation gets out of hand.
I have no issue with heatsinking – have some VERY big brutes on hand.
My question is, has anyone built this amp using a higher supply voltage? and am I asking for trouble. Is this workable solution?
Or should I stop being a cheap skate and go buy the proper transformers.
I look forward to your comments
Kind Regards
George.
Pass DIY Addict
Joined 2000
Paid Member
At first glance, the MPSA18 devices and the 9610's can both handle the rail voltage that you are proposing. I don't recall anyone building an Aleph-X with rail voltage that high, though. As there are different parts lists for a low-voltage (15v) and high-voltage (22v) version of this amp, I suspect some of the resistor values will need to be changed for going as high as 37v rails. I don't have a good starting place for you - perhaps others can make a suggestion.
The power output that you are looking at will generate some serious heat. My Aleph-X monoblocks bake off about 400w each. You can find a link in my signature. If you are looking to drive 8-ohm speakers, higher rail voltage and lower current is to your advantage. If you are looking to drive 4-ohm speakers, lower rail voltage and higher bias current will work better.
The power output that you are looking at will generate some serious heat. My Aleph-X monoblocks bake off about 400w each. You can find a link in my signature. If you are looking to drive 8-ohm speakers, higher rail voltage and lower current is to your advantage. If you are looking to drive 4-ohm speakers, lower rail voltage and higher bias current will work better.
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