Building a COMPACT Hoffman Blues Junior / Stacking Circuit Boards to Save Space

[jonyoungyi]

Hi, all, I just bought a Blues Junior PT & OT for a great price and am thinking of building Hoffman's Blues Junior Conversion from scratch (2nd time). This time, I'd like to keep things as compact as possible, fitting everything into a 13" x 8" x 2" (maybe 3") chassis. My question is:

Can I cut the layout in half and stack the cut half OVER the remaining circuit to save space?

I've done this successfully with Hoffman's Single Channel AB763 & 5E3 (I cut the first half of the pcb that goes to V1A and stacked on top of the PCB that went to V1B), but rather than rely on sheer luck, I'd like to hear from others' opinions on the matter. I'm assuming I risk running into some nasty oscillation, but I'm not 100% sure. Here's an example of what I'm talking about:

https://www.instagram.com/p/BOi7MK1ALio/?taken-by=doxasound

Also, if there's another 15 to 18 watt, Push Pull, Solid State Rectified, EL84 amp I should be building, I'm open to suggestions, too!

Thanks, all!

[sluckey]

Can I cut the layout in half and stack the cut half OVER the remaining circuit to save space?

You could do that. 2" may not be deep enough.

[jonyoungyi]

Can I cut the layout in half and stack the cut half OVER the remaining circuit to save space?

You could do that. 2" may not be deep enough.

Always so helpful Sluckey, thanks! I'm assuming it's not a good idea to stack the preamp section on top of the power section? :D

[MFowler]

You can always PTP wire the tone stack right in front of the pots to a terminal strip.


The phase inverter can be separated from the preamp section as well.


Mark

[tubenit]

Da Geezer's HoSo56 is a great amp!


I personally would never stack the layout board preamp over phase invertor layout area.  I don't mind stacking power rail caps over an OT or PT & the tone caps idea directly on the pots I've done numerous times. Just my preference & not necessarily "better".  I will say I don't like noisey amps.


With respect, Tubenit

[shooter]

fwiw, here's an example of vertical board + point to point.  you might need deeper for this idea

[jonyoungyi]

Da Geezer's HoSo56 is a great amp!


I personally would never stack the layout board preamp over phase invertor layout area.  I don't mind stacking power rail caps over an OT or PT & the tone caps idea directly on the pots I've done numerous times. Just my preference & not necessarily "better".  I will say I don't like noisey amps.


With respect, Tubenit

Ooooo, recommendation from Tubenit AND lower parts count than the Blues Junior Conversion?! :D

[jonyoungyi]

You can always PTP wire the tone stack right in front of the pots to a terminal strip.


The phase inverter can be separated from the preamp section as well.


Mark

I think I thought it would save 2 or 3 lugs on the circuit board, so wasn't something I considered, but now that I look at the schematic and thought about it, 2 or 3 lugs is great!

[jonyoungyi]

fwiw, here's an example of vertical board + point to point.  you might need deeper for this idea

Didn't think about this either haha Separating the boards!

[kagliostro]

Gibson GA40 Les Paul to reduce space has components on both sides of the board, but a friend that build one say that to service it is a pain

--

In some old amp I've seen board disposed at 90° like in the post of Shooter, in a few other ones, boards were disposed between 45° and 90°

to save a bit of height space, may be a solution in some cases, however you require to have a higher (than standard) chassis

Franco

[PRR]

http://hpmemoryproject.org/pict/timeline/bob_devries/sandwich_hr.jpg
https://upload.wikimedia.org/wikipedia/commons/c/c3/Cordwoodcircuit.agr.jpg
https://hackadaycom.files.wordpress.com/2017/03/moto.png?w=558&h=625
http://www.decadecounter.com/vta/pic/th537.jpg
http://www.glennsmuseum.com/ibm/pics/705_tube_module_many.jpg
https://lh3.googleusercontent.com/-ipKoiZOGOLg/WlBzkyeLcOI/AAAAAAABH-4/8UQMU70xMuQdjl7JquLt0mVQFjXgUtIIACHMYBhgL/w9999/module-front.jpg
http://www-03.ibm.com/ibm/history/ibm100/images/icp/Y811765A43424O57/us__en_us__ibm100__603calc__vacuum_tubes__620x350.jpg
http://www-03.ibm.com/ibm/history/ibm100/images/icp/G843082Z90578R90/us__en_us__ibm100__603calc__604_assembly__620x350.jpg

[92Volts]

I've done something point-to-point with terminal strips in a pretty small chassis: http://el34world.com/Forum/index.php?topic=22528

Half the power supply is on the back face of the chassis, half the preamp and the whole tone stack are on the front. I wanted to mount stuff to the sides until I realized the heads of the screws would interfere with sliding it into a cab. I believe it is 14"x7"x3".

Enormous pain in the ass to build but it's very quiet, since components are very close to the tubes. My only "problem" (other than making various wiring errors) was bringing the signal from the tone stack to the power tube. The shielded (instrument) cable seen in that photo shorted due to some combination of manhandling as I tried to reroute it, and the fairly high voltage signal it carries. Twice. Ended up using non-shielded wire which I needed to be careful with to avoid oscillation.

[jonyoungyi]

http://hpmemoryproject.org/pict/timeline/bob_devries/sandwich_hr.jpg
https://upload.wikimedia.org/wikipedia/commons/c/c3/Cordwoodcircuit.agr.jpg
https://hackadaycom.files.wordpress.com/2017/03/moto.png?w=558&h=625
http://www.decadecounter.com/vta/pic/th537.jpg
http://www.glennsmuseum.com/ibm/pics/705_tube_module_many.jpg
https://lh3.googleusercontent.com/-ipKoiZOGOLg/WlBzkyeLcOI/AAAAAAABH-4/8UQMU70xMuQdjl7JquLt0mVQFjXgUtIIACHMYBhgL/w9999/module-front.jpg
http://www-03.ibm.com/ibm/history/ibm100/images/icp/Y811765A43424O57/us__en_us__ibm100__603calc__vacuum_tubes__620x350.jpg
http://www-03.ibm.com/ibm/history/ibm100/images/icp/G843082Z90578R90/us__en_us__ibm100__603calc__604_assembly__620x350.jpg

Omg... they're beautiful! Although, some pictures make me want to quit hahaha

[jonyoungyi]

I've done something point-to-point with terminal strips in a pretty small chassis: http://el34world.com/Forum/index.php?topic=22528

Half the power supply is on the back face of the chassis, half the preamp and the whole tone stack are on the front. I wanted to mount stuff to the sides until I realized the heads of the screws would interfere with sliding it into a cab. I believe it is 14"x7"x3".

Enormous pain in the ass to build but it's very quiet, since components are very close to the tubes. My only "problem" (other than making various wiring errors) was bringing the signal from the tone stack to the power tube. The shielded (instrument) cable seen in that photo shorted due to some combination of manhandling as I tried to reroute it, and the fairly high voltage signal it carries. Twice. Ended up using non-shielded wire which I needed to be careful with to avoid oscillation.

Wow, that looks great! And thanks for posting the results, especially about how quiet everything was! I'm thinking I'd need to use shielded wire for some areas, too, so good to know that high voltage could cause shorts!

[shooter]

when I seen the poor transistor (circled) I had an instantt image like this one

[jonyoungyi]

when I seen the poor transistor (circled) I had an instantt image like this one

hahahaha almost the same color as the cat too!

Too bad tomorrow is Thursday, here :'(