I am kind of caught up on builds at the moment and had some free time to play with some new ideas. A Local friend turned me onto a few of the Subminiature tubes and I though I would see what I could make with them. I decided to see if I couldn't build a miniature bedroom amp. The idea then evolved into putting a complete Express on a small PCB board that measures 4" x 8" (Less power supply) I came up with the design on the board and ectched up a prototype to test the amp with . This test board is single sided and will have jumpers for the top copper side. I will have some professional boards made up if the thing sounds worth persueing. I know there has been some use of the 6112 preamp tubes in Wrecks before but I am also using the Sub mini 5902 beam power pentode tubes in a PP configuration. The pots are all 1/4w. I'll try and keep this thread updated if anyone is interested. I am calling this one the Lil' Devil
Here are a few pics of the prototype board with all the parts installed (Minus the top Jumpers). All resistors are 1/2w except for the 1w screen resistors and the 1k3w that replaced the 25w. I included a pic of my Ipod Nano next to the board to give you an idea of the size.
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Last edited by UR12 on Sun Aug 03, 2008 3:44 pm, edited 1 time in total.
bigmik wrote:that is about the coolest thing i have seen in a while ,how do you think this stuff up? can't wait to see and hear the final product.
Thanks! I guess I just have a warped mind I can't wait to hear it either
VacuumVoodoo wrote:Spring loaded 8 pin DIL sockets for tubes. Cool.
Yes, In the true spirit of Ken Fisher I decided to to use what I had laying around. They fit the bill so I went with it. If they cause me any trouble I will either solder them to a 8 pin dip header and plup them into the sockets that way or just solder them directly to the board without sockets the way they were intended to be installed.
Did you put our regular Express in the washing machine and hit the wrong temperature button?
Like small amps!
Wonder how she sounds like. My Lil'Wreck uses on 12AX7/ECC83 and half of 12AU7/ECC82 as SE output and quite low voltages <170V. It's nice, but triodes are not pentodes nor do they sound exactly like 'em.
I just ordered trannys so I guess they will be in next wednesday. At that rate I should have it fired up one day next week. I went with Hammond off the shelf trannys to start with a 129ax for power and a 125a for the OT. I'll be running the outputs at either 5.6k or 6.8k.
I am looking for a good 5 or 6 inch guitar speaker. If anyone has any suggestions I would love to hear them.
This could be a really fun amp to play. I'll be reading closely. Thanks for sharing!
Regarding your words about speakers, I know Weber offers two 6" speakers, one ceramic ($30), and one alnico ($45), for use in the small, early Fender type amps. 15 watts each, and the alnico has three different cone options.
Well, if you've got a platform you can easily try it on, do keep us informed. I've got something else on the go right now, and a lot of other drama going on as well, so I can't really try it right away.
Hopefully, it would come closer to the pentode sound. I can't say I've ever heard triode output sound that I liked (does "triode mode" on a pentode amp even count for this?), and I don't know of a small pentode that's in new production/readily available except the EF86 - haven't read too much good about those..
They fit the bill so I went with it. If they cause me any trouble I will either solder them to a 8 pin dip header and plup them into the sockets that way or just solder them directly to the board without sockets the way they were intended to be installed.
LOL
