1 channel AB763 chassis size

[dunner84]

I have all of my components to get this build started, but I have a concern about the chassis. I bent it out of a piece of aluminium that I had lying around in hopes of using it for this build, but after laying the iron out on it, I don't think it will be big enough.

It is 19" long and 6" deep. The circuit I am doing is the 1 channel ab763, but without the tremolo portion. I think the inside portion will be fine, but I am worried about crowding on the top side of the chassis.

Has anyone built this amp? What size chassis did you use? Does the topside look too crowded, or could this chassis work?

[dunner84]

Another view

[sluckey]

It'll fit. Just be careful planning your layout. I built one in a 17x4x3 chassis. See link...

     http://sluckeyamps.com/tdr/tdr.htm

[mresistor]

I built one in a 17 x 8 x 2 and I agree with Sluckey on planning. You'll have one less tube and a small section less on the board. My PT was a stand up, your's is going to protrude into the interior. The tubes have to go on there too. So how crowded it gets is really your call. Maybe a solid state recto?  In hindsight  I would have added a PPIMV and next time I think I'll build the board instead of using a pre-made one, so I can plan out turret location to suit the components I want to use. The capacitors I like are much bigger than the spaces for them on the pre-made boards. But I had this AB763 board sitting around, so I chopped off the normal channel and used it. the amp is very quiet and sounds really nice. Cabinet is not done yet as it's cold here and I cant open a can of fumes in the house. I mounted the reverb tank underneath the top of the cabinet - right side up, and made an aluminum cover for the bottom of the tank to deflect heat from the tubes.


http://i122.photobucket.com/albums/o250/privateacct/006_zpsxg075pve.jpg


http://i122.photobucket.com/albums/o250/privateacct/003_zpsvsdlhvkx.jpg


http://i122.photobucket.com/albums/o250/privateacct/IMG_3999_zpsfxh6s6ve.jpg

[dunner84]

Thank you for the replies, and wow! great looking builds!. I am feeling much better about using this chassis. I was really worried about the iron being too crowded, but looking at both of your builds, I think it will work.
I am mounting this upright in the cabinet like a tweed deluxe, so the tubes will all be on the backface, which frees up even more room on top.

The only other concern, or question I have is about the filter caps. The PT I am using is quite large, so I dont have the space on top. I am building my own turret board for this build, so I may be able to squeeze them inside the chassis, but I also thought about building a small, spearate chassis or box just for them, and mounting them separately.

Do you have any advice? If I get creative with the layout, I could place them on top of the chassis with all the iron. Is there anything I need to look out for either way? Magnetic field interference, long wire runs, etc...?

Thanks

[Paul1453]

Sluckey got it to work in less space.

I would copy his work as much as possible. 
He knows what works, and what causes problems.
Changes you make to his design, might only make things worse. 

If you copy his design exactly, he is very likely to know what issues can arise and how to fix them.
He seems quite willing to help if you run into trouble.

[dunner84]

Sluckeys build is almost identical to what I have planned for this amp. I usually add NFB switches, and this one will have a RAW control. I have also been toying with the idea of a fixed/cathode bias switch. It is more of a novelty, but I am curious to hear the difference "side-by-side".

The question I have now is about the master volume. I am glad you discovered the issue with the vibrato circuits added resistance. I doubt I would have ever found that. How is your master volume? would a post PI master still be able to work? Do you have a recomendation for either. I see you chose the Pre-PI. Is that based on preference or for ease of retrofit? If you had a chance to start all over again would you do it the same way? Sorry about the 100 questions, but I just learned a hard but valuable lesson in my last build about the importance of this planning stage.

Thanks again for all of the input

[sluckey]

With a 6" wide chassis you'll have plenty of room inside for the caps. Look at how Hoffman likes to do filter caps...

     http://el34world.com/Hoffman/AB763Project.htm

I did that pre PI MV just for ease, but it has been removed and replaced with a much more useful Raw control. IMO, a fixed/cat switch is a waste. You'll play with it for a week then it will probably be left in fixed position. The only thing I'd change would be the flimsy Hammond chassis I used.

[mresistor]

Sorry , it wasn't readily apparent to me you had planned on a tweed configuration, where the "top" of chassis isn't really "up".  Mine is more Marshall style head.

[DummyLoad]

put a 50/50 can next to the choke. obviously choke moves further back. choke ties across can cap. use MIEC brand caps on turret board or radial can caps to save board space.

--pete