Blues Briefcase
Moderators: zaphod_phil, Daviedawg, Graydon, CurtissRobin, colossal
- JMPGuitars
- Super Duper Admin
- Posts: 3969
- Joined: Tue 09/18/12 8:00 pm
- Location: South Central, MA
- Contact:
Re: Blues Briefcase
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.
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
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
- crgfrench
- Frequent poster
- Posts: 827
- Joined: Fri 04/27/18 3:02 am
Re: Blues Briefcase
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.
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.
You do not have the required permissions to view the files attached to this post.
0 x
- JMPGuitars
- Super Duper Admin
- Posts: 3969
- Joined: Tue 09/18/12 8:00 pm
- Location: South Central, MA
- Contact:
Re: Blues Briefcase
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
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
- crgfrench
- Frequent poster
- Posts: 827
- Joined: Fri 04/27/18 3:02 am
Re: Blues Briefcase
Chassis initial mounting, still need to drill for pots & jacks
You do not have the required permissions to view the files attached to this post.
0 x
- crgfrench
- Frequent poster
- Posts: 827
- Joined: Fri 04/27/18 3:02 am
- JMPGuitars
- Super Duper Admin
- Posts: 3969
- Joined: Tue 09/18/12 8:00 pm
- Location: South Central, MA
- Contact:
Re: Blues Briefcase
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.
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
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
- crgfrench
- Frequent poster
- Posts: 827
- Joined: Fri 04/27/18 3:02 am
Re: Blues Briefcase
Installed the AC inlet/fuse/power switch tonight
You do not have the required permissions to view the files attached to this post.
0 x
- crgfrench
- Frequent poster
- Posts: 827
- Joined: Fri 04/27/18 3:02 am
Re: Blues Briefcase
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.
You do not have the required permissions to view the files attached to this post.
0 x
- crgfrench
- Frequent poster
- Posts: 827
- Joined: Fri 04/27/18 3:02 am
Re: Blues Briefcase
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!JMPGuitars wrote: ↑Sun 06/09/19 6:59 amI'd get some form of grill cloth on that grill. Or paint the grill if you want it open.
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
- crgfrench
- Frequent poster
- Posts: 827
- Joined: Fri 04/27/18 3:02 am
Re: Blues Briefcase
Drilled chassis for pots & jacks
You do not have the required permissions to view the files attached to this post.
0 x
-
- Newbie
- Posts: 37
- Joined: Thu 05/30/19 7:34 am
Re: Blues Briefcase
Only the good die young!crgfrench wrote: ↑Thu 06/13/19 1:59 pmBy 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!
1 x
- crgfrench
- Frequent poster
- Posts: 827
- Joined: Fri 04/27/18 3:02 am
Re: Blues Briefcase
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.JMPGuitars wrote: ↑Fri 06/07/19 5:00 pmI 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
- JMPGuitars
- Super Duper Admin
- Posts: 3969
- Joined: Tue 09/18/12 8:00 pm
- Location: South Central, MA
- Contact:
Re: Blues Briefcase
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
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
- crgfrench
- Frequent poster
- Posts: 827
- Joined: Fri 04/27/18 3:02 am
Re: Blues Briefcase
OMG That grill cloth! Love it -- nice video Josh, thanks for sharing.JMPGuitars wrote: ↑Sat 06/15/19 7:26 amLMAO I agree! Check out this amp mod video I did in 2011: https://youtu.be/_pM1KmdKPHE
1 x
- crgfrench
- Frequent poster
- Posts: 827
- Joined: Fri 04/27/18 3:02 am
Re: Blues Briefcase
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.
Next steps are to wire the board and reinstall it into the chassis, wire the transformers and rectifier diodes.
You do not have the required permissions to view the files attached to this post.
1 x
- crgfrench
- Frequent poster
- Posts: 827
- Joined: Fri 04/27/18 3:02 am
Re: Blues Briefcase
There is room for another OT in the briefcase so I'm thinking of adding a Classictone 40-18031 or a Hammond 125ESE like this:
You do not have the required permissions to view the files attached to this post.
0 x
- crgfrench
- Frequent poster
- Posts: 827
- Joined: Fri 04/27/18 3:02 am
Re: Blues Briefcase
Class AB usually runs cooler than Class A so to complement the single-ended / double-ended switch I might add 2 more brown devils connected via this switch
https://tubedepot.com/products/three-po ... ary-switch
Like this:
https://tubedepot.com/products/three-po ... ary-switch
Like this:
You do not have the required permissions to view the files attached to this post.
0 x
- crgfrench
- Frequent poster
- Posts: 827
- Joined: Fri 04/27/18 3:02 am
Re: Blues Briefcase
I know, I know, this is so wrong. But I had to translate bias into something normal musicians understand, like Scoville Heat Units.
You do not have the required permissions to view the files attached to this post.
0 x
- JMPGuitars
- Super Duper Admin
- Posts: 3969
- Joined: Tue 09/18/12 8:00 pm
- Location: South Central, MA
- Contact:
Re: Blues Briefcase
Those numbers are way off. SHU: Ghost is 1M, Scorpion is 2M, and the Reaper is 2.2M. If you wanted to go directly from SHU to Ohms, then they'd all be Pepperoncini.
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
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
- crgfrench
- Frequent poster
- Posts: 827
- Joined: Fri 04/27/18 3:02 am
Re: Blues Briefcase
Notice below the switch it's clarified, "SHU x 1,000". Like on a tachometer.JMPGuitars wrote: ↑Wed 07/03/19 9:05 amThose numbers are way off. SHU: Ghost is 1M, Scorpion is 2M, and the Reaper is 2.2M. If you wanted to go directly from SHU to Ohms, then they'd all be Pepperoncini.
0 x