Snfoilhat
Tele-Afflicted
These cabinet photos look great, the colors and composition and the sort of 45 degree exploded diagram style. Thanks for sharing this
Journey of my Bassman Micro build
- Thread starter joulupukki
- Start date
The wiring of the power amp master volume shouldn't matter. I made a mistake on the layout--I meant to wire it like the schematic. I thought I fixed the layout error but I'll have to double-check.
joulupukki
Tele-Meister
Well shoot, maybe I should be building the EF80 version. No wonder it’s being talked about so much. I guess in order to do that (besides ordering different tubes and other small parts) I‘d need a different power transformer. If the MT 18w TMB kit ever comes I won’t really lack on power option though.
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joulupukki
Tele-Meister
One thing I’ll have to sort out is that I think I’m not going to go with a headphone output, nor a line out jack since I have a Torpedo Captor X I can use for both of those. What I do want to do is put in a mini toggle switch for switching between 4 and 8 ohms. I found another thread that talks about this (https://www.tdpri.com/threads/bassman-micro-build-thread-w-pictures.1055088/page-5), but I’m not sure I fully understand yet the connections I’ll need to make. But, I’ve got time to figure that out.
Or maybe since you'll have a big amp soon enough, a true Micro that gets distortion at reasonable levels would be a useful addition to your amp stable...
joulupukki
Tele-Meister
Exactly. I re-read Rob’s Bassman Micro site and if I’m understanding it right, the 12AU7 would be around a 3-4 watt amp, using a 12BH7 would be 4-5 watt, and the EF80 is around a 2 watt amp. Am I missing something there (different than what I stated earlier)?
From the site about the “5F6A-M Bassman Micro LTP”:
About the “Bassman Micro LTP EF80”:
Yes, sorry, I don't know about watts. And don't take my word for it -- I *thought* Rob said recently the EF80 version would be louder. I could be wrong.
Bitsleftover
Tele-Holic
I built mine with the post PI MV and it works a charm. Maybe not right at the bottom end of the scale, but it’ll take the majority of the volume off while maintaining a good tone. I mainly use it for keeping a constant volume between playing clean or dirty. I use an attenuator to do the grunt of the work.
I also added a Diode/Tube rectifier switch and can’t tell which is selected without looking at the switch position.
I’m not sure it’s possible to use a figure that will replicate a JTM level of negative feedback vs a bassman level etc. the power sections are just too different in my humble opinion. I found a figure that made the presence control work well and did away with the switch.
Great looking head cab by the way!
I also added a Diode/Tube rectifier switch and can’t tell which is selected without looking at the switch position.
I’m not sure it’s possible to use a figure that will replicate a JTM level of negative feedback vs a bassman level etc. the power sections are just too different in my humble opinion. I found a figure that made the presence control work well and did away with the switch.
Great looking head cab by the way!
joulupukki
Tele-Meister
I’ll definitely be putting in this volume knob.
Good to know. I won’t worry about adding the SS option and just keep it tube-based. Thanks for that info.
joulupukki
Tele-Meister
Ok, I think I understand what’s going on in this build with the output speaker impedance switch (https://www.tdpri.com/threads/bassman-micro-build-thread-w-pictures.1055088/post-10423887). It’s switching between 8 ohms and 15 ohms with a SPDT switch easily because it shares one common wire (#4 - Yellow) between those two outputs.
For the Hammond 125B OT these are the wires for 4 and 8 ohms:
4 ohms:
#5 - Violet
#6 - White
8 ohms:
#2 - Orange
#4 - Yellow
Is it possible to switch between these two with a single output jack? If so, what kind of jack, switch, and wiring?
For the Hammond 125B OT these are the wires for 4 and 8 ohms:
4 ohms:
#5 - Violet
#6 - White
8 ohms:
#2 - Orange
#4 - Yellow
Is it possible to switch between these two with a single output jack? If so, what kind of jack, switch, and wiring?
joulupukki
Tele-Meister
Ok, maybe what I ought to do is follow this same thing and switch between 8 and 16 ohms. My main goal is to be able to have the option of using both of my 1x12 speaker cabs I built (each has an 8 ohm speaker in them).
The back of my speaker cabs have two 1/4” jacks that are currently wired in parallel. What if I were to use one of the cabs and wire those jacks in series? That way if I were to plug both of them in, they’d be 16 ohms and I could switch the output of my amp to 16 ohms to match. Or, if I’m just using one speaker, I’d switch it to 8 ohm.
Assuming that would all work, is this the right wiring I’d need to do?
The back of my speaker cabs have two 1/4” jacks that are currently wired in parallel. What if I were to use one of the cabs and wire those jacks in series? That way if I were to plug both of them in, they’d be 16 ohms and I could switch the output of my amp to 16 ohms to match. Or, if I’m just using one speaker, I’d switch it to 8 ohm.
Assuming that would all work, is this the right wiring I’d need to do?
joulupukki
Tele-Meister
Actually, would I need to use a shorting jack on that speaker cab jack plate and have a dedicated Input & Output (shorting jack would be on the output)? Like this:
joulupukki
Tele-Meister
Burning the midnight oil today to wrap up the Bassman Micro amp head cabinet. I’ve gotta find some black screws for the handles and maybe some black screws for the back, but other than that it’s ready for whenever I can get the chassis put together.
Also, part of the electronics came today … and the rest should arrive tomorrow.
I documented most today’s steps in that Volley thread I linked to earlier in case you wanna see more details. But, here are a bunch of pics from today…
Here’s the two amp head cabs I’ve built. This one for the Bassman Micro and the British style 18w. I hope I can get the actual amps put together soon!
Oh, and the metal mesh is now installed on my 18w head as well (finally got some and took care of stapling it into both amps tonight).
Also, part of the electronics came today … and the rest should arrive tomorrow.
I documented most today’s steps in that Volley thread I linked to earlier in case you wanna see more details. But, here are a bunch of pics from today…
Here’s the two amp head cabs I’ve built. This one for the Bassman Micro and the British style 18w. I hope I can get the actual amps put together soon!
Oh, and the metal mesh is now installed on my 18w head as well (finally got some and took care of stapling it into both amps tonight).
willholt92
Tele-Meister
Beautiful work on the cabs, I really need to get on with doing mine for my JTM micro.
I wish I had access to a table saw that could run dado stacks, it would make finger jointing so much easier but it's not easy to get hold of them in the UK (yet..... although it might be soon with safety standards changing)
What size round over bit did you use? 1/2"?
I wish I had access to a table saw that could run dado stacks, it would make finger jointing so much easier but it's not easy to get hold of them in the UK (yet..... although it might be soon with safety standards changing)
What size round over bit did you use? 1/2"?
joulupukki
Tele-Meister
Thank you. Yes I did a 1/2" roundover. I maybe should have done 3/4" but that bit that I have for my router isn't the best. I actually used the Porter Cable dovetail jig with a router to do the finger joints (just using a straight 1/2" bit). It's maybe a little slower than a dado stack, but it works just the same. I'm excited to get the electronics put together.
What piping did you use?
joulupukki
Tele-Meister
I used this for the gold piping:
Metallic Tinsel Grill Piping
hard to find speaker cabinet parts and accessories
www.speakerbuildersupply.com
...and this for the beading across the top:
Cabinet vinyl string bead .090''
hard to find speaker cabinet parts and accessories
www.speakerbuildersupply.com
joulupukki
Tele-Meister
My transformers and chassis came today (Hammond 1444-1372). Wow, it's a close fit, but not too tight ... whew! Also, I didn't realize the chassis would already have mounting holes drilled in the bottom. They barely miss where the cabinet feet are mounted.
Below is the front panel arrangement I'm thinking of (ignore the wrong input jack type and the fact that I don't yet have the pilot light).
Below is the front panel arrangement I'm thinking of (ignore the wrong input jack type and the fact that I don't yet have the pilot light).
joulupukki
Tele-Meister
Here's the design I'm looking to do on the front faceplate. I drew it vector-based in Photoshop and now just need to figure out how to convert it to EPS so I can get a quote for pulling it off.
Looks like I need to order a different pilot light. I ordered the Fender-style with red jewel light, but that probably won't work with the design I'm looking to do (so it looks more like a Marshall).
Looks like I need to order a different pilot light. I ordered the Fender-style with red jewel light, but that probably won't work with the design I'm looking to do (so it looks more like a Marshall).
joulupukki
Tele-Meister
I’m also working on the layout of the innards … not done, but here’s the progress so far…
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