The Amp Garage

I have an old boss hm2 that is suppose to be powered by either a 9v battery or a 12v wall wart. But... It works just fine with a 9v power supply as long as: The power supply is not really isolated. And many of them are really not even though they are marketed that way. The power supply has some othe...

How is the overdrive pedal being powered? It could be that the power supply of the pedal and the amp are causing a ground loop and picking up 60hz hum.

Mike

… I'll make another post once I better understand the results I got by dropping a simple 0.68uf cap across the 10k cathode resistor. That alone should have made quite a difference :shock: ?! Oh it did! You see the whole subject of input/output impedance used to make my eyes glaze over. So, I mostly...

I don’t think you’ve got sufficient gain stages to make one of them unbypassed cold biased. Hotter bias and at least partial bypass of the second stage should help to get some preamp overdrive. Bear in mind that the clipping (3rd) stage of a 2203/4 uses a 820R cathode resistor; stock it’s unbypasse...

Maybe consider this idea... Convert your AB763 tremolo circuit to the Trem-O-Nator circuit. Better sounding trem plus you free up V5B to possibly use in the Normal channel. I'm very seriously working over the details of retrofitting a Trem-O-Nator. Thanks for putting togeather all the wonderful doc...

If your goal is no distortion/clipping then I'd not overthink it too much. Build the whole amp. Then find the point at which clipping starts on the output by adjusting the volume control set the volume to the point where it is just short of clipping. Then with the amp off, measure the pot. Say you a...

For a lot of amp topologies, things tend to break down at the power tubes first and then work their way backwards towards the input. So, (most of the time), you can put a scope on the output. Then inject a reasonable signal into the input and turn up the gain until you start to see the signal distor...

Got it all wired up. It works! Only trouble I had during start up was a bad solder joint in my filament string. These EH 12ax7s just don't glow enough and I missed this when testing earlier in the build. The fact that I was getting voltage on the plates but no current through v1 and v2 quickly lead ...

Looks like you handled that project just fine! Looks nice!

And nice picture of the front panel showing where the dang wires for the tremolo pots get routed! For some reason it is almost impossible to find a good shot of that.

Mike

Folks, What' s the consensus on using a power soak attenuator like the Bugera PS1 Passive 100-watt Power Attenuator? Can it damage your amp? And can you run 2 in series to cut it down to 1/4 volume but sustain its tone? When you cut an amps output power by half you only drop the volume by 3db. Half...

Got a little bit more wired up. Both the tremolo and hotrod channels are now wired up along with the reverb driver. guts2.jpg I suppose that at this point one could probably plug a small 8 ohm speaker into the reverb transformer secondary and have a low power amp to test out. But there are still too...

After some real world distractions, I've found some time to get a bit more work done on it. The boards are now mounted and the front face pots, switches and jacks have been partially wired up. I've also connected all the positive connections from the doghouse cap board and the main board. top1.jpg p...

5k and 100R feedback network? Even off the 16R tap, that’s a negligible degree of feedback, basically open loop. Leo seems to have used 820R and 100R on a 2 ohm tap. Somewhere I remember seeing a rule of thumb that advised doubling the 820R if the impedance was doubled (this may not have been good ...

xtian wrote: ↑Wed Jan 18, 2023 8:48 pm Your photos remind me of Under The Skin.

LOL. I had some lights and a backdrop already set up for another project. So, I just took the pictures with that setup. Followups will probably be on my bench .

Mike

Having never built or played a classic black face Fender, I decided to build one for my next project. I like amps in the 50 watt range so I decided to build a vibroverb in a head cabinet. The schematic I'm using is below. Like many of us, I could not resist the chance to tinker with the circuit a bi...