Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Woodrow F Call on March 21, 2026, 06:41:50 pm
-
Well, I travel a good bit for work. I fly with a guitar, but am starting to think about shipping a amp to the job for going to jams.
I'm thinking about building a simple 18 watt or maybe a EL34 Champ of some kind. Probably a 10" combo to get the size down, so I can pack it in a pelican case or even luggage.
Likely going to use a 270EX PT and either a 125E or 125ESE OT since I have those not doing anything.
I'll have effects pedals, so cleaner headroom is probably what I'll go for here.
I'm thinking 1" pine cabinet, 3/4 birch speaker baffle..... not sure about dimensions yet. Open back combo.
Anyone got some thoughts or tips? Cabinet size is definitely something I could use some help on. Speaker options?
-
You may get some ideas on my website. Maybe Dual Lite?
https://sluckeyamps.com/index.htm
-
I would suggest you work out your objectives and requirements before getting into your design. For example:
• You want it small so do you REALLY need 18 watts? You don't want to lug around 18 watts when 10 might do. This also affects the weight of your speaker.
• You want it small so do you REALLY need to take up 2” of height and width with 1” pine? Are there thinner and lighter alternatives?
• You want it light so do you REALLY need a 3/4” birch baffle for a 10” speaker?
• Do you want your amp to fit your transformers or your transformers to fit your requirements?
• Do you want to build an amp before determining what specifically you would use to transport it and the actual cost, dimensions, and finished weight of it? Checked
baggage gets pretty beat up. Is a strong amp cabinet or more padding a better approach? Is damage to the electronics more a concern than damage to the cabinet?
May I suggest you work backwards. Determine your maximum finished weight and size. Find a transportation container that you won’t mind lugging around. Work out your padding and determine your maximum amp dimensions and maximum weight. Then work from there to work out your case material and your amps inside dimensions. Only then, design you amp to fit your “jam” needs.
-
I would suggest you work out your objectives and requirements before getting into your design. For example:
• You want it small so do you REALLY need 18 watts? You don't want to lug around 18 watts when 10 might do. This also affects the weight of your speaker.
• You want it small so do you REALLY need to take up 2” of height and width with 1” pine? Are there thinner and lighter alternatives?
• You want it light so do you REALLY need a 3/4” birch baffle for a 10” speaker?
• Do you want your amp to fit your transformers or your transformers to fit your requirements?
• Do you want to build an amp before determining what specifically you would use to transport it and the actual cost, dimensions, and finished weight of it? Checked
baggage gets pretty beat up. Is a strong amp cabinet or more padding a better approach? Is damage to the electronics more a concern than damage to the cabinet?
May I suggest you work backwards. Determine your maximum finished weight and size. Find a transportation container that you won’t mind lugging around. Work out your padding and determine your maximum amp dimensions and maximum weight. Then work from there to work out your case material and your amps inside dimensions. Only then, design you amp to fit your “jam” needs.
Well, money doesn't grow on trees..... kinda the reason for the transformers I have.
I can definitely go thinner on the wood. Would half inch be too little?
I could go with a EL34 Champ or something similar, but I do really like the 18 Watt I have, I figure going to the 10" speaker will cut the volume a bit, but this is for an any drummer I come up against kind of idea. Some places a champ would be fine, some an 18watt with a 12" ain't enough.
Under 25lbs would be great and something like a height of 17 and width of 15 that way it'll fit in luggage if need be. Definitely smaller than a Princeton reverb in overall size. It'll probably get shipped most of the time.
-
You may get some ideas on my website. Maybe Dual Lite?
https://sluckeyamps.com/index.htm
Where can I find a blank chassis like the one used in the dual lite? I can find a bigger one for like a plexi, but a shorter one would be great..
-
I don't know. The guy I got mine from is out of business.
-
You may get some ideas on my website. Maybe Dual Lite?
https://sluckeyamps.com/index.htm (https://sluckeyamps.com/index.htm)
Where can I find a blank chassis like the one used in the dual lite? I can find a bigger one for like a plexi, but a shorter one would be great..
These (https://www.hawkusa.com/manufacturers/hammond-mfg/enclosures/chassis/1444-12825?srsltid=AfmBOopQYKZmfl4yE6p13_kTfprptkG7sOsrntTlmUMl2qAlVXNU-qbN) should work. Attach some L brackets if you want an outward facing flange for mounting. They are kind of flimsy but will be ok if your transformers aren't too heavy, you may want to fab a backing plate for the power transformer.
Steve O'connor with Synaptic Amps has custom cut and fold chassis for me in the past. IIRC, I was paying around $100/chassis for 2, a bit less for 5 or more. Don't know if he's still taking orders, my last order was in May, 2023.
https://www.synapticamps.com/
--Pete
-
You may get some ideas on my website. Maybe Dual Lite?
https://sluckeyamps.com/index.htm (https://sluckeyamps.com/index.htm)
Cool amp!
-
You may get some ideas on my website. Maybe Dual Lite?
https://sluckeyamps.com/index.htm (https://sluckeyamps.com/index.htm)
Where can I find a blank chassis like the one used in the dual lite? I can find a bigger one for like a plexi, but a shorter one would be great..
These (https://www.hawkusa.com/manufacturers/hammond-mfg/enclosures/chassis/1444-12825?srsltid=AfmBOopQYKZmfl4yE6p13_kTfprptkG7sOsrntTlmUMl2qAlVXNU-qbN) should work. Attach some L brackets if you want an outward facing flange for mounting. They are kind of flimsy but will be ok if your transformers aren't too heavy, you may want to fab a backing plate for the power transformer.
Steve O'connor with Synaptic Amps has custom cut and fold chassis for me in the past. IIRC, I was paying around $100/chassis for 2, a bit less for 5 or more. Don't know if he's still taking orders, my last order was in May, 2023.
https://www.synapticamps.com/
--Pete
I've used those before. They are fine for stuff that isn't going to get shipped, but I think they are a little light duty for the purpose of this amp.
The synaptic ones look good though.
-
I used synaptic about a year ago. He's a perfectionist. Highly recommended.
-
With those OTs, any champ-ish style amp with 1 x 12AX7 and 1 output tube.
Depending on the output tube you use, I'd expect the 270EX with a FW Bridge will make somewhere between 310 and 380VDC.
You probably won't get a lot of watts out of it
If you went to a 15-20W PP OT, you could make a one-channel reverbless, trem-less blackface deluxe with couple of pre-amp tubes and 2 x 6V6s driving a 12" speaker that could be good for 15W. i.e. an input channel with a 12AX7 where each triode bookends treble/bass/volume pots, and driving a 12AT7 long-tail pair blackface inverter, driving a pair of fixed bias 6V6s (or JJ6V6Ss). But you'd still want a FW bridge rectifier with the 270EX to make 370-380-ish VDC.
But with a bit of imaginative PTP layout, you 'could' cram that into tinyish combo box (say 14" x 13" x 9") weighing less than carry-on luggage that would probably fit into an overhead plane locker and get through airport x-ray security. YMMV
-
This one goes well
MAR-CHAMP (https://el34world.com/Forum/index.php?topic=31786.msg350106#msg350106)
Got a few tricks as well
-
Looks like the 125E is a 15W push-pull OT?
In that case, maybe something like a matchless spitfire or similar?
https://el34world.com/charts/Schematics/files/Matchless/Matchless_spitfire.pdf
Would suggest to change the crossline master for a PPIMV, and maybe a couple other tweaks.
For chassis, you could use the Hoffman stout chassis which is now sold by Mojotone
https://mojotone.com/products/hoffman-stout-chassis-v2?variant=41689805488224
With a couple of their adapter plates for the 9-pin sockets on the EL84s and a blanking plate for the PT cutout.
-
I'd consider this:
A 14-18 watt amp converted from a Hammond AO-39 organ amp. Easy to find on Ebay.
Sluckey has the best instructions I've seen for doing this.
The chassis is small and rigid. The iron is good. Some other parts will be usable.
I have built several:
18w light
Vox 10/15 light
Supro 16 light - 7963 and/or 6CZ5 power tubes
Gibson GA-40 light - 5879 preamp tube - 6CM6 power tubes
Will take pedals well - GA-40 needs no overdrive pedal :icon_biggrin:
I also have built a Spitfire, but in a different chassis. It does loud/clean and takes pedals well.
No reason to use a baffle board any thicker than 3/8" baltic birch plywood.
I would use cedar or cypress for the cab - no tolex - if you can do dovetail joints will be beautiful with a clear finish and will be quite a bit lighter than pine.
-
FWIW I built the dual lite a few years ago (wow maybe more? Time flies…) and I definitely recommend it. I think it sounds so good, and was a fairly straightforward build. Plus for gigging you have some tonal versatility. The only issue I had was with getting the rotary switch wired and the wonderful Mr. Luckey was right here to answer my equations.
If you want to go even more portable take a look at his Smoky. I think I’m gonna build one of those for my son with spare parts I have lying around.
-
this was built as a tinker'n amp, the current owner says it's loud:)
there was a thread on the build somewhere here at Doug's place
-
this was built as a tinker'n amp, the current owner says it's loud:)
there was a thread on the build somewhere here at Doug's place
I was thinking about something like this, but the tube datasheets I saw didn't have anything on SE operation. Looking at the drawing, I'm wondering if I have enough iron.
-
with SE builds, I typically just buy the 25W iron, whether the amps a 10W or 25
I'm an Engineer by trade, can't tell a D from an E musically, so I look at "cool" pieces of schematics, stitch them together, play n tweak enough to then pass it on to the guitar test drivers, rinse n repeat till the guitarists either grin, or say it plays well as a 1-trick pony
the owner burnt out something his tech got it up n run'n n last contact "This might be better than either my GA-18rvt, or the tube Crate...It's really LOUD"
-
Where can I find a blank chassis like the one used in the dual lite? I can find a bigger one for like a plexi, but a shorter one would be great..
Hammond has some chassis boxes in thin aluminum that I've used a few of. Work really well and very light weight. Got them thru CE Dist / Tubesandmore
-
Weber has really decent stainless steel chassis in the close out area every now and then. There’s a Marshall JTM chassis there for $45 currently.
https://www.tedweber.com/6m50ch/
Just sayin’