Tube Amp Archive

I sorta buy into Merlin's theory about Fenders standby switch being put in not to save the tubes from anything. But instead to save the under rated caps in the power supply. Back then, big caps with a high voltage rating were really really expensive (compared to today). So, often the filter caps dow...

After having been sidetracked by other (less fun) things. I've had some time to work on this again. So, here is a bit of a report on my progress. The boards I ordered came in in about a week. And the cost (with shipping and my new customer discount) was one dollar per board. Pretty dang cool. Here i...

Can you post the whole amp Kicad file? Sure. Of course, there is no pcb component as I'm going to do a build using turret boards. And this schematic is just a cleaned up copy into kicad of one I found out on the net. So, I claim nothing for it's accuracy :). However it appears that it would work. I...

Updated the kicad zip file again. It turns out that the uxcell 35mm faders I found cheap on Amazon were similar but not exact matches for the bourns footprints. So, I got to learn how to use the footprint editor. Then a few tracks were changed to account for the pin differences. Oh and I found the 3...

Do you want actual Mesa Boogie Graphic EQ measurements? If so, I can give you them, because I own a Boogie 50 Caliber+. Measurements off of a real boogie would be great! It would allow me to better scale my image and pick faders with the correct lengths. Below is a picture which has some dimensions...

Consider looking for OP amps in SOIC packages that fit easily on the back beneath fader. This not only saves space but simplifies your trace layout. Surprisingly easy to work with in DIY bench solder assembly. . The thought of soldering surface mount stuff normally confuses and frightens me :). How...

the two 220k resistors appear to be going negative to negative and positive to positive on the caps, is that correct? They are also going + to - in series with each cap. The key is to pay attention to the red wire under the board. Look at it for a while and you will see that it is exactly the same....

Sounds like you are on the right track. The resistors are there to act as a voltage divider and make sure that each cap sees exactly 1/2 of the voltage applied across both of them. If they were not there, then the voltage at the junction of the caps would depend upon each caps equivalent series resi...

I've done a bit more work and updated the mbeq.zip file in the first post. The whole board now uses 0.5mm traces. I was able to get the spacing up to 0.35mm. After this the rules checker really starts to get crazy :). So, I called it good enough. board-no-mask.png I think I still want to swap the si...

Mike, Maybe you could collaborate with Amp Garage member "frusciante89" (Andrea Antonello), who supplies great PCBs and is now designing a Mesa Boogie PCB. I think I may have seen some PCBs mentioned on another forum some months back. Perhaps these were Andrea's? I for sure want to do most of my bu...

Nuts! It looks like kicad made a whole new project in the same directory where I copied bits of the schematic from. So, I was actually doing the edits there instead of the location I thought I was. I've fixed this and updated the mbeq.zip file in my first post. In this updated version I was able to ...

Thanks for the feedback! I really appreciate it. It was my hope to just ignore the whole net thing and just stumble around with the defaults. :) But playing around with it a bit makes it a little easier to understand. Should I set the minimum separation higher than 0.2mm while I'm at it? Or is that ...

So, through a course of events I don't fully understand, It looks like my next build will be one of these: mb-mark2c+.pdf I'm fairly serious about it and to motivate myself to actually start it, I've bought a chassis: chassis.jpg I plan to build most of it using turret boards. It is kinda small but ...

Sounds like you are going about things right to me. A 200mV signal might be a bit on the hot side but it is in the ballpark. I have found that many/most early amp designs breakup first in the power tubes and then work there way backwards towards the input. You can see this by attaching the scope to ...

V2 doesn't seem to be but V3 is getting hot. The voltages look off (especially for V2). If it were working correctly it would be conducting and you should have a volt or two on pin 3. See this page for a very general voltage chart: https://mhuss.com/MyJCM/vchart.html Note that this is for an 82 amp...