Buzz's Acro UL-II Monoblock Project
- Thread starter BuzzK
- Start date
with a lot of interest, nice project.
I'm thinking out loud and also looking for some opinions . . .
I've got most of the holes cut, except for the ones for the large caps. I'm ready to take the tops to a trophy shop and see if they can nicely label the 3 pots and the tube positions, before I anchor them to the chassis frame.
The Hammond power transformer is very much the "basic" model, i.e. doesn't have a fixed bias tap, and just enough current on the single 5.0 & 6.3 volt taps to run the KT88s at reduced power (I've got plenty of everything to drive EL34s or KT77s instead).
The original Acro used a 120V tap for the bias, so I found a small isolation transformer that will do.
In addition to the 10H choke, I've also ordered 30H & 60H chokes for "downstream" filtering. I haven't decided if I'm going to use both of them -- it may depend upon space.
I want the amp to be quiet, and I might use a rare 12AX7 variant (the brand new Blackburn Mullard E813CCs that were recently made, but only briefly before the British factory went dark again for good). John Broskie sells a nice 6.3 VDC regulator that uses 5.0VAC, and I just happen to have a Stancor 3A model that would be close to perfect. I need 0.9A total for a 6CG7 driver and the 12AX7 input type tubes. The output tubes will use AC filament voltage.
So already I'm contemplating a lot of iron, and with it, various magnetic fields.
My question is: is it safe to mount a small A/C tranny underneath a large one mounted on top of the chassis, i.e. are the magnetic fields likely to interact to any meaningful degree?
Other suggestions welcomed . . .
Thanks.
Buzz
I've got most of the holes cut, except for the ones for the large caps. I'm ready to take the tops to a trophy shop and see if they can nicely label the 3 pots and the tube positions, before I anchor them to the chassis frame.
The Hammond power transformer is very much the "basic" model, i.e. doesn't have a fixed bias tap, and just enough current on the single 5.0 & 6.3 volt taps to run the KT88s at reduced power (I've got plenty of everything to drive EL34s or KT77s instead).
The original Acro used a 120V tap for the bias, so I found a small isolation transformer that will do.
In addition to the 10H choke, I've also ordered 30H & 60H chokes for "downstream" filtering. I haven't decided if I'm going to use both of them -- it may depend upon space.
I want the amp to be quiet, and I might use a rare 12AX7 variant (the brand new Blackburn Mullard E813CCs that were recently made, but only briefly before the British factory went dark again for good). John Broskie sells a nice 6.3 VDC regulator that uses 5.0VAC, and I just happen to have a Stancor 3A model that would be close to perfect. I need 0.9A total for a 6CG7 driver and the 12AX7 input type tubes. The output tubes will use AC filament voltage.
So already I'm contemplating a lot of iron, and with it, various magnetic fields.
My question is: is it safe to mount a small A/C tranny underneath a large one mounted on top of the chassis, i.e. are the magnetic fields likely to interact to any meaningful degree?
Other suggestions welcomed . . .
Thanks.
Buzz
Last edited:
battradio
Electron trainer
You should have no problem with that , with 2.5 inches under the chassis it will have to be laid down to for it to fit which will also help prevent the magnet from coupling , you might find a5 volt toroid which will easily fit under the chassis and the magnet field is self contained .
http://www.antekinc.com/an-0105-10va-5v-transformer/ $10 + shipping
Last edited:
battradio
Electron trainer
You should have no problem with that , with 2.5 inches under the chassis it will have to be laid down to for it to fit which will also help prevent the magnet from coupling , you might find a surplus toroid which will easily fit under the chassis and the magnet field is self contained .
http://www.antekinc.com/an-0105-10va-5v-transformer/ you can use the two 120 windings for a smlaal isolation transfor or use it as a 2 amp 5 volt supply
Likely should have been a 6FQ7.
Dave
Dave
It's K's fault. He's the one that had to bring it up....... 
Dave
Dave
crispycircuit
Super Member
Do you have a schematic? I could use one for my mono organ amps.... Great work! Love the looks..... don't stall out on us.....
MickeySmile
Well-Known Member
Buzzk ,
You do silkscreen your self or you send it out? It looks very nice!
You do silkscreen your self or you send it out? It looks very nice!
I had a trophy shop engrave this one. I've always used 3rd parties for silkscreening. I used to use DATAK transfer labels and spray before they became unobtanium.
