Having completed the power supply I felt confident and decided I’d try a tube amplifier. Since this is my first attempt I’m sticking to something relatively easy, like a single ended 5 watt thing. I found a schematic for the Bad Cat Mini II amplifier on schematicheaven.com and also discovered a thread on freestompboxes.org where a couple of members had actually built this thing.
It took me a long time, but I managed to source all the parts eventually.
This is very much a learning experience and gut shots of an actual Bad Cat Mini II amplifier helped me figure out approximately how to lay out the various parts in a practical manner. Turns out the chassis I ordered is a lot bigger than it had to be, but that’s OK. Would have been a lot worse the other way around.
I’ve spent some time reading up on amplifier specific issues and considerations. I tried to implement star grounding, but none of the switchcraft jacks I’ve used are isolated. Once I’ve got the speaker cabinet ready I’ll have to evaluate whether I need to isolate these to reduce hum. Gave the amp a test run with an old speaker I had lying around and it worked quite well on first attempt, albeit at a very low volume. After some investigation it turned out I had the filament wiring on the 12AX7’s slightly wrong, but having fixed this the amp now works like a wonder. Time to get started on the cabinet…
Update (27.10.2010): Here’s my parts list for this project.
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After many a month of sitting on a shelf my 5 watt Mini II clone finally received a proper house.
I’m quite happy with it, being my first attempt at an amp, but there’s lots of room for improvement. Building the housing turned out to be a lot more challenging than I first imagined, but this might come down to a complete lack of experience. I expect the next amp project to go a lot smoother in this regard.
In retrospect the housing should have extended a bit further backwards to help protect the power switch and speaker selector. Oh, and I might also place a board across the back to prevent my kid from touching anything back there.
Now I need to build a speaker cabinet…
HI Harald,
My name is Stephan, I would like very to communicate with you concerning this amp project, could you respond to me buy E@mail please at s***n@v***n.ca.
Thanks a lot
Stephan
Wish I was joking, but I probably spend as much or even more on shipping and import tax than I do on parts and hardware. If you’re in the US and can get reasonable shipping (I can’t) you can probably build it for 1/3 – 1/2 the cost. Norway has to be one of the most expensive countries on the planet, and everything has to be imported because we don’t have any electronics stores/suppliers. *End of rant*
No secret sources, I’ve listed all of the ones I have used and can recommend on the right-hand side here.
Yikes… expensive.
Can’t claim much knowledge or experience, but afaik, here in California, the only parts that should have cost >$1 would be: pots ($2-4 / ea), tubes ($7 – infinity / ea), and trannies (30, 40 bucks maybe?).
….So I was totally expecting you to say something in the lines of “well, I know places, so it cost <$100, but for you mere mortals, maybe 200 bucks".
Or were you being ironic, in the "shipping and customs were such a pain it felt like I just dropped a grand on it", but with the actual numbers rather more reasonable?
About $999 😉 But keep in mind that’s buying all the parts from the US, UK or Germany, paying just as much, if not more on shipping, and on top of that having to pay 25% import tax (even on the shipping cost) + customs fees. Norway is not the place you want to build amps if you can choose 🙁
Wow, and this tiny circuit clones a $999 amp? Huh… how much did parts cost?
Oh wow you can just ignore that one 😀 i guess you shouldn’t think of these things after your bedtime 🙂 waiting to get my hands on this build!
Hi,
In that parts list you have there, doesn’t the resistors have a bit unnecessary high power rating? From my calculations i got that only few resistors had to be rated over 1/2W.
I hope someone might be able to help me.
I’m about to purchase a bad cat mini cat 2 from USA and get it sent to Australia. Now I understand that I will need to purchase a step down transformer but I am a little confussed. Does anyone know what the Pre Amp Volts/ Amps or V/A is on the Bad Cat Mini Cat 2? Apparently I need to know this to ensure I get the correct step down transformer.
Can anyone please help?
Matt
I’m sorry Jose, but I don’t understand spanish. English please.
Hola estoy realmente impresionado con el proyecto muy bueno, quisiera saber si es posible hacer este mismo amp pero que tenga mas potencia como por ejemplo llegar a 30 vatios, me ayudarías bastante gracias saludos
The output transformer is a Hammond 125CSE and the power transformer is a generic 230V primary, 230V – 6.3V secondary I found at http://www.musikding.de
thanks for added parts list. Wich power- and output-transformer do you use? Thanks again. Regards, Heiko
Couldn’t have made these layouts without your software, Bancika. Keep up the good work!
Hi,
Nice builds and layouts! I’m bancika from DIY-fever, just saw that you have link to my site, so I placed one on mine in return.
Cheers,
Bane