As you should see in my post above, I replaced the 270 k pulll up resistor with something else to make the voltage at the emitter of the input transistor idle about 1/2 the rail voltage. This minimizes 2nd harmonic distortion on large signals if the operating point stays near there.
As I had a very high gain input transistor and needed compatibility with a high impedance PAS2 tube preamp, I also increased the pulldown resistor to achieve about 500k input impedance.
Hi Bruce,
Which do you prefer in terms of sound quality of this R.A. Penfold mosfet amp vs AUTONA AL125?
Regards,
PCB for # 278 . Done quickly, please point errors or ask me to do something differently.
thimios, is this what you are looking for
?
Hope this isnt too divergent from Mr. Mile's subject thread.
otherwise, request mods to delete the post.
regards
Prasi
thimios, is this what you are looking for
?Hope this isnt too divergent from Mr. Mile's subject thread
.otherwise, request mods to delete the post.
regards
Prasi
Attachments
Last edited:
IHMO The AL125 sounded much better. Maybe a member who has some spare time could do a board layout of the AL125 using MJL21194 flatpacks and pushing the rails to 100v which should give you app 100w into 8 and about 150 into 4 ohm. Th double bootstrap on the AL125 is also unique not something I have not seen a lot of. I did try bridging the modules with 2x AL125 with 2n3773 at 80v and doing away with the speaker bypass caps it worked perfectly for a while but one of the modules would start drifting so the midpoint voltage would have to be re adjusted.
PCB for # 278 . Done quickly, please point errors or ask me to do something differently.
thimios, is this what you are looking for
Hope this isnt too divergent from Mr. Mile's subject thread
otherwise, request mods to delete the post.
regards
Prasi
Can someone tell, if this amp will work with modern more easily available devices? Just an exercise towards curiosity!
.regards
Prasi
Attachments
Hi Prasi, like I said I did build the circuit and it did work although I did double up on the fets. I should imagine it would work just as well, if not better with the BUZ series fets or perhaps with a few modifications IRFP240/9240. Personally I did prefer the AL125 it seemed to have more bottom end. It would be great if someone could simulate it in LT spice ( something I am not too familiar with ). I have since found the original article for the AL125 module in the October 1980 copy of Pratical Electronics. As soon as I can scan and post it
Hi Prasi,i mean this amplifier.
First we need someone to simulate this using now available parts.
ok, lets wait!
Yes my friend, let's wait someone to help with the simulation, then i know a good friend ho can do the rest.
hello avtech,
8 usd base price for a pair of pcbs+shipping + paypal. So grand total of ~15 usd delivered via registered mail.
regards
Prasi
Yes my friend, let's wait someone to help with the simulation, then i know a good friend ho can do the rest.
, but I must say, its a bit confusing schematic with + and - shown as expressed by anti and also i/p and o/p ground connection not shown.
Last edited:
Prasi,do not take the effort of a pcb making before someone can post a clear schematic and make sure that is a working amplifier in simulation at least.
"-" is the "power ground". So connect the "-" to the VAS ground and all will be clear fast. Add a 4700uF -or so- output cap and you're good to go. The schem posted here is imho a more "true" one - an opinion based solely on my eyeballing expertise.
Google finds this: Archives: Vintage Audio – The Autona 125 module – Online Parts International
And this: Autona AL125 - Analog Ian
So if you're really into vintage ... imho a good idea would be to cobble up a derated 80W or so version with 4x TIP3055 and a BD139-16 instead of the BC441.
IF you are adamant to follow the autona circuit ...
Google finds this: Archives: Vintage Audio – The Autona 125 module – Online Parts International
And this: Autona AL125 - Analog Ian
So if you're really into vintage ... imho a good idea would be to cobble up a derated 80W or so version with 4x TIP3055 and a BD139-16 instead of the BC441.
IF you are adamant to follow the autona circuit ...