Blues Briefcase

18watt-specific Tech Talk - Building, Fixing, Parts, Mods...

Moderators: CurtissRobin, colossal, zaphod_phil, Daviedawg, Graydon

User avatar
JMPGuitars
Super Duper Admin
Super Duper Admin
Posts: 3954
Joined: Tue 09/18/12 8:00 pm
Location: South Central, MA
Contact:

Re: Blues Briefcase

Post by JMPGuitars »

Here's my 2 cents:

Strip the lining on the inside of the briefcase. Add between 1/4" to 1/2" void-free plywood to the entire main panel that the speaker is being mounted on. Glue it on, and use weights on top and/or clamps to keep it pressed tight.

After that's done, drill the speaker mounting holes / speaker hole.

I would try to not cut out the tweed to the full size of the hole. If you can lift the tweed from the panel, and save an extra couple inches, you'll be able to wrap the tweed and cover the entire speaker hole edge.

This will give the speaker a much better sound than floating on a weak briefcase side. Also more stable for the rest of the stuff you're mounting.

Thanks,
Josh

PS. My wife made me do this: hurray :baby: :?: :evil: :D :D :o 8O
3 x
'I installed a skylight in my apartment yesterday... The people who live above me are furious.' - Steven Wright

Modern Ground Schemes
Soldering Technique
B+ Voltage Reduction
Amplifier Tools & Parts Info


Web Design: DolceVittoria.com
Guitars / Amps / Effects: JMPGuitars.com
(anti)Social: Facebook · Instagram
Items for Sale

User avatar
crgfrench
Frequent poster
Frequent poster
Posts: 827
Joined: Fri 04/27/18 3:02 am

Re: Blues Briefcase

Post by crgfrench »

Yes. I'm going to see after I cut the hole. Thanks!
0 x

User avatar
crgfrench
Frequent poster
Frequent poster
Posts: 827
Joined: Fri 04/27/18 3:02 am

Re: Blues Briefcase

Post by crgfrench »

I cut the hole with a saber saw and mounted the Celestion on the inside and the grill on the outside with 4 through bolts. The briefcase is solid! I discovered it's 1/8" birch ply with the fur bonded to the inside and the tweed bonded to the outside. Same high quality solid construction as their tweed guitar cases. Will get some pix of the speaker when I get home from work.
20190604_154001.jpg
You do not have the required permissions to view the files attached to this post.
0 x

User avatar
JMPGuitars
Super Duper Admin
Super Duper Admin
Posts: 3954
Joined: Tue 09/18/12 8:00 pm
Location: South Central, MA
Contact:

Re: Blues Briefcase

Post by JMPGuitars »

I don't recommend having less than 3/8" for a speaker baffle, and even that is on the thin side. Are you mounting the speaker on the same side as the circuit and transformers?
0 x
'I installed a skylight in my apartment yesterday... The people who live above me are furious.' - Steven Wright

Modern Ground Schemes
Soldering Technique
B+ Voltage Reduction
Amplifier Tools & Parts Info


Web Design: DolceVittoria.com
Guitars / Amps / Effects: JMPGuitars.com
(anti)Social: Facebook · Instagram
Items for Sale

User avatar
crgfrench
Frequent poster
Frequent poster
Posts: 827
Joined: Fri 04/27/18 3:02 am

Re: Blues Briefcase

Post by crgfrench »

JMPGuitars wrote:
Fri 06/07/19 5:00 pm
Are you mounting the speaker on the same side as the circuit and transformers?
Yes -- if you open the briefcase and turn it on its side it looks exactly like a combo setup, tubes sticking down from the chassis towards the speaker magnet. Like this pic:
Screenshot_20190607-185403_Gallery.jpg
You do not have the required permissions to view the files attached to this post.
0 x

User avatar
JMPGuitars
Super Duper Admin
Super Duper Admin
Posts: 3954
Joined: Tue 09/18/12 8:00 pm
Location: South Central, MA
Contact:

Re: Blues Briefcase

Post by JMPGuitars »

I don't know how much you plan on cranking that up, but with such a thin wall, the transformers and chassis will be subject to much more vibration. Excess vibration can lead to a lot of issues.

Typically the speaker baffle is thinner than the rest of the cabinet construction to allow for speaker response. Even 3/8" would be considered thin.

The chassis and transformers are mounted on to a stiffer piece of wood to reduce excess vibrations.

Personally I would mount the speaker opposite the rest, on a 3/8" or thicker baffle (1/4" added/glued to the wall would be fine). I would also recommend using lock washers and thread locking liquid on the bolts to make sure nothing comes undone from the vibrations.

If you do it the way you have it, it may be fine, but a little extra work now goes a long way to avoid problems.
0 x
'I installed a skylight in my apartment yesterday... The people who live above me are furious.' - Steven Wright

Modern Ground Schemes
Soldering Technique
B+ Voltage Reduction
Amplifier Tools & Parts Info


Web Design: DolceVittoria.com
Guitars / Amps / Effects: JMPGuitars.com
(anti)Social: Facebook · Instagram
Items for Sale

User avatar
crgfrench
Frequent poster
Frequent poster
Posts: 827
Joined: Fri 04/27/18 3:02 am

Re: Blues Briefcase

Post by crgfrench »

Thanks Josh -- good suggestions and I appreciate the feedback (no pun intended).
I keep seeing people using nail polish which is cool but I like loctite 242. Have not applied any here yet, since I disassemble and reassemble iteratively during my builds and I'm still in the "fitting up" phase here. I also like to use nylock nuts when possible. For #6 and smaller nuts I use star tooth lockwashers or keps nuts and for #8 and larger I use split ring lockwashers.

The essence of this briefcase amp is "cheap, simple, ultra compact and under-engineered". Think "Barefoot Willie found an old briefcase and some tubes in a dumpster on the south side of Chicago and he's throwing them together because he can't afford a Champ to play on the corner for wine money" rather than "the Mesa Boogie production line"... it's a gritty, grungy craft brew not a Bordeaux.

Here are some pix of the speaker installation -- the rubber ring is a little distorted around the bolts, I might trim a bit off the bottom side of the ring at each bolt to smooth that out, or maybe not. I might just remove the ring altogether to give it a rougher look.
20190607_235449.jpg
20190607_235521.jpg
20190607_235553.jpg
20190607_235541.jpg
You do not have the required permissions to view the files attached to this post.
0 x

User avatar
JMPGuitars
Super Duper Admin
Super Duper Admin
Posts: 3954
Joined: Tue 09/18/12 8:00 pm
Location: South Central, MA
Contact:

Re: Blues Briefcase

Post by JMPGuitars »

If you do decide to add some wood, you can get that fabric at a fabric store and use spray glue to adhere it to the wood. Then you'll still have the look you're going for. ;)
0 x
'I installed a skylight in my apartment yesterday... The people who live above me are furious.' - Steven Wright

Modern Ground Schemes
Soldering Technique
B+ Voltage Reduction
Amplifier Tools & Parts Info


Web Design: DolceVittoria.com
Guitars / Amps / Effects: JMPGuitars.com
(anti)Social: Facebook · Instagram
Items for Sale

User avatar
crgfrench
Frequent poster
Frequent poster
Posts: 827
Joined: Fri 04/27/18 3:02 am

Re: Blues Briefcase

Post by crgfrench »

Chassis initial mounting, still need to drill for pots & jacks
20190608_234223.jpg
20190608_233334.jpg
20190608_234322.jpg
You do not have the required permissions to view the files attached to this post.
0 x

User avatar
crgfrench
Frequent poster
Frequent poster
Posts: 827
Joined: Fri 04/27/18 3:02 am

Re: Blues Briefcase

Post by crgfrench »

JMPGuitars wrote:
Fri 06/07/19 8:54 pm
I don't know how much you plan on cranking that up
https://youtu.be/4xgx4k83zzc
2 x

User avatar
JMPGuitars
Super Duper Admin
Super Duper Admin
Posts: 3954
Joined: Tue 09/18/12 8:00 pm
Location: South Central, MA
Contact:

Re: Blues Briefcase

Post by JMPGuitars »

My suitcase goes to 11!

I'd get some form of grill cloth on that grill. Or paint the grill if you want it open.
1 x
'I installed a skylight in my apartment yesterday... The people who live above me are furious.' - Steven Wright

Modern Ground Schemes
Soldering Technique
B+ Voltage Reduction
Amplifier Tools & Parts Info


Web Design: DolceVittoria.com
Guitars / Amps / Effects: JMPGuitars.com
(anti)Social: Facebook · Instagram
Items for Sale

User avatar
crgfrench
Frequent poster
Frequent poster
Posts: 827
Joined: Fri 04/27/18 3:02 am

Re: Blues Briefcase

Post by crgfrench »

Installed the AC inlet/fuse/power switch tonight
20190612_035052.jpg
20190612_035037.jpg
20190612_034826.jpg
You do not have the required permissions to view the files attached to this post.
0 x

User avatar
crgfrench
Frequent poster
Frequent poster
Posts: 827
Joined: Fri 04/27/18 3:02 am

Re: Blues Briefcase

Post by crgfrench »

Made the panel cutout, it's tight at 7" x 1.5". Just perfect for 2 jacks and 4 pots. The chassis side is 8" x 2" abutting inside. Just need to find some small trim for it. Not sure which knobs to use but I'm leaning toward the 1939 black bakelite chickenhead ones. Still need to drill the chassis for jacks & pots.
20190613_140957.jpg
20190613_140849.jpg
20190613_140821.jpg
20190613_140757.jpg
You do not have the required permissions to view the files attached to this post.
0 x

User avatar
crgfrench
Frequent poster
Frequent poster
Posts: 827
Joined: Fri 04/27/18 3:02 am

Re: Blues Briefcase

Post by crgfrench »

JMPGuitars wrote:
Sun 06/09/19 6:59 am
I'd get some form of grill cloth on that grill. Or paint the grill if you want it open.
In the Aftermath of this excellent feedback, I decided to take the advice of Keith Richards and Paint It Black. Happily, it is already, so nothing more to do on that front!

By the way, did y'all know about that time Keith electrocuted himself in 1965 playing "The Last Time" in California -- brushed his guitar strings against an ungrounded mic stand, blew him backstage in a flaming blue electric arc, ended the whole show. Almost killed the poor bloke!
0 x

User avatar
crgfrench
Frequent poster
Frequent poster
Posts: 827
Joined: Fri 04/27/18 3:02 am

Re: Blues Briefcase

Post by crgfrench »

Drilled chassis for pots & jacks
20190614_030410.jpg
20190614_025542.jpg
20190614_025526.jpg
You do not have the required permissions to view the files attached to this post.
0 x

zuceno
Newbie
Newbie
Posts: 37
Joined: Thu 05/30/19 7:34 am

Re: Blues Briefcase

Post by zuceno »

crgfrench wrote:
Thu 06/13/19 1:59 pm
By the way, did y'all know about that time Keith electrocuted himself in 1965 playing "The Last Time" in California -- brushed his guitar strings against an ungrounded mic stand, blew him backstage in a flaming blue electric arc, ended the whole show. Almost killed the poor bloke!
Only the good die young!
1 x

User avatar
crgfrench
Frequent poster
Frequent poster
Posts: 827
Joined: Fri 04/27/18 3:02 am

Re: Blues Briefcase

Post by crgfrench »

JMPGuitars wrote:
Fri 06/07/19 5:00 pm
I don't recommend having less than 3/8" for a speaker baffle, and even that is on the thin side. Are you mounting the speaker on the same side as the circuit and transformers?
The good news is, with the tweed and the fur it is 3/8". I'm certain this red crushed velvet fur is growing to contribute meaningfully to a creamy blues tone.
0 x

User avatar
JMPGuitars
Super Duper Admin
Super Duper Admin
Posts: 3954
Joined: Tue 09/18/12 8:00 pm
Location: South Central, MA
Contact:

Re: Blues Briefcase

Post by JMPGuitars »

crgfrench wrote:
Fri 06/14/19 8:43 pm
I'm certain this red crushed velvet fur is growing to contribute meaningfully to a creamy blues tone.
LMAO I agree! Check out this amp mod video I did in 2011: https://youtu.be/_pM1KmdKPHE
1 x
'I installed a skylight in my apartment yesterday... The people who live above me are furious.' - Steven Wright

Modern Ground Schemes
Soldering Technique
B+ Voltage Reduction
Amplifier Tools & Parts Info


Web Design: DolceVittoria.com
Guitars / Amps / Effects: JMPGuitars.com
(anti)Social: Facebook · Instagram
Items for Sale

User avatar
crgfrench
Frequent poster
Frequent poster
Posts: 827
Joined: Fri 04/27/18 3:02 am

Re: Blues Briefcase

Post by crgfrench »

JMPGuitars wrote:
Sat 06/15/19 7:26 am
crgfrench wrote:
Fri 06/14/19 8:43 pm
I'm certain this red crushed velvet fur is growing to contribute meaningfully to a creamy blues tone.
LMAO I agree! Check out this amp mod video I did in 2011: https://youtu.be/_pM1KmdKPHE
OMG That grill cloth! Love it -- nice video Josh, thanks for sharing.
1 x

User avatar
crgfrench
Frequent poster
Frequent poster
Posts: 827
Joined: Fri 04/27/18 3:02 am

Re: Blues Briefcase

Post by crgfrench »

I finally installed the sockets onto the chassis,; I only had 4 of this shielded kind and one went missing so I had to order a replacement. So now 2 fully shielded CV4004s and 2 base-shielded EL844s.

Next steps are to wire the board and reinstall it into the chassis, wire the transformers and rectifier diodes.
Screenshot_20190702-135349_Gallery.jpg
You do not have the required permissions to view the files attached to this post.
1 x

Post Reply