Micro Bassman Build

N

Nic

Well-known member
I have been less active since a few months, part of it is because I'm more selective on my builds, part of it is because of life happening and the third part of it is because I've been planning on building an amp for some time and the process is very slow.

I'm not finished, but I figured I'll slowly start posting my process. So much nice amps builds here lately :)

So, what gave me the courage to start this journey was M. Rob Robinette website. Yeah it looks like it been made in the late 90's, but there is a TON of useful information there. I said courage because I was afraid of the high voltage... I still am, but think that by taking my time and all precautions, I'll be able to complete a simple build such as his micro amps.

One thing to be said, I did not think that there would be that much money involved in this and it's part of the reasons this build is taking time and I've not build so much pedals.

I thought of making a really nice chassis using sheet steel... Hahaha, what a fool was I ! :ROFLMAO: After a few cuts and tries at bending, I've aborted this idea. I just do not have the tools to make it looking good, and not the patience I guess. So I said what the hell, a nice aluminium chassis is around 40$.

So here was my first idea ...
20230215_231223.jpg

And the BUD Industries chassis after most the drilling had been done.
20230528_095305.jpg

To be continued...
 
Next was the board layout. I've decided to go for the Cathodyne phase inverter version. I figured that on my first attempt at amplifier, I would be better to start with lower components to mess up. One thing that I found interesting and will be adding is the rectifier type switch, simple mod requiring only two more diodes and a switch. For my planned enclosure, I had to flip Rob layout vertically... I drilled it and installed my eyelets and populated the board. When I realized that my enclosure plans where going to change, I flipped the board and re-populated it correctly.

I must say now that most components, the board, eyelets where purchased at Next Gen Guitars and I had a great service, really fast shipping. I was able to add to caps after ordering and when the order arrived, two jack were missing, which they sent express.

Switches, Power cable connector and fuse holder came from Tayda.

Enclosure and Transformers came from mouser.

20230307_144411.jpg 20230727_224358.jpg

20230527_091110.jpg

Time to test fit things
20230604_221035.jpg

Still needing the power transformer at that point.
20230604_221011.jpg

While waiting on the PT, I've built the light bulb current limiter, will become handy when needed.

To be continued.
 
Painting the enclosure was a P.I.T.A. Never seemed to have nice weather, and when I had I was in a kind of a hurry, really did not come that bad, but it's far from perfect and I'm not happy about it. At some point I had to let it go.

And right now, I'm at this point... taking times when it's possible to head the iron and make a few connections at a time...

It goes slowly but surely.

20230801_145752.jpg

You may have seen those graphics somewhere.

20230801_145642.jpg

And I did make myself some kind of a logo.

20230801_145714.jpg
 
Finished wiring everything yesterday, now I will try to take the time today to check every connection for errors before doing a first start with the bulb limiter. Hope everything goes well.

Had some connections not really pretty, but overall not that bad for a first time.
20230815_233548.jpg
 
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Question : is this pair (OT yellow/orange) supposed to have continuity ?

I've got continuity everywhere, even when the switch is open.

Everything else has been verified and good to go, but not sure about this.

20230816_113748.jpg
 
Nic said:
Question : is this pair (OT yellow/orange) supposed to have continuity ?

I've got continuity everywhere, even when the switch is open.

Everything else has been verified and good to go, but not sure about this.
Click to expand...
Transformers are funny on continuity, but the short answer is yes. Your meter is measuring DCR, and to a DC signal the coil of a transformer is just a long wire, so it will naturally have continuity. But the transformer is working with AC signals, which is why it's okay.
 
vigilante398 said:
Transformers are funny on continuity, but the short answer is yes. Your meter is measuring DCR, and to a DC signal the coil of a transformer is just a long wire, so it will naturally have continuity. But the transformer is working with AC signals, which is why it's okay.
Click to expand...
Excellent, I've seen it was the same with the heater wires and figured it was normal but had my doubts before putting current in it.

I'll try powering it up later. Need to double check I've wired the power cord connector right.

Thank you!
 
Nic said:
Painting the enclosure was a P.I.T.A. Never seemed to have nice weather, and when I had I was in a kind of a hurry, really did not come that bad, but it's far from perfect and I'm not happy about it. At some point I had to let it go.

And right now, I'm at this point... taking times when it's possible to head the iron and make a few connections at a time...

It goes slowly but surely.

View attachment 53851

You may have seen those graphics somewhere.

View attachment 53852

And I did make myself some kind of a logo.

View attachment 53853
Click to expand...
Well I think the paint came out great. Whenever I'm painting something I repeat the mantra "I am not Michelangelo and this is not the Sistine chapel" otherwise I'd spend an eternity painting a door frame.

How did you achieve the face plate? Are those decals?
 
IT'S ALIVE !

I just received my tubes this morning and took some time to start it up on the bulb limiter first. As everything looked fine I fired it with my headphones plugged in, again no problems detected so far, so I plugged in the bass and then my wife's strat and both sounds really nice through the headphones. Maybe not gainy enough for the guitar, but later a couple other tubes could take care of that.

20230829_125036.jpg

Guess who will soon be ordering a 12" speaker... and will have to build a cab... you gotta stay busy !
 
Nic said:
IT'S ALIVE !

I just received my tubes this morning and took some time to start it up on the bulb limiter first. As everything looked fine I fired it with my headphones plugged in, again no problems detected so far, so I plugged in the bass and then my wife's strat and both sounds really nice through the headphones. Maybe not gainy enough for the guitar, but later a couple other tubes could take care of that.

View attachment 55520

Guess who will soon be ordering a 12" speaker... and will have to build a cab... you gotta stay busy !
Click to expand...
That is a piece of art! can't wait to see it in a cabinet
 
I have a question for you fellow amp builders. I know M. Robinette states this amp is would output 1 to 2 watts with a 12au7 in power and 12ax7/12ay7 in preamp.

I could crank both volume and master un my headphones and it would be loud, but not what I would consider too loud. I used my rumble 25 8" to test through speaker and once again it gets loud, but not that much. I juat want to know if it's normal because the wife vox AC4 can get REALLY loud even at 1/4W ...
 
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music6000 said:
12AU7 will give you the least Volume & Gain, Try going up in stages with 12AX7 being the pinnacle.
Click to expand...
Ok, not that I'm complaining, I think the volume is just right for home. Just wanting to make sure it's doing what it's supposed to do. I'll surely try 1xBH and 2xAX at some point.

And, I now have quite a few pedals to spice things up!
 
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