2Watt Sub Miniature Plexi

General discussion area for tube amps.

Moderators: pompeiisneaks, Colossal

Post Reply
User avatar
UR12
Posts: 1570
Joined: Mon Nov 28, 2005 7:22 pm

2Watt Sub Miniature Plexi

Post by UR12 »

I have had so much fun playing with the subminiature tubes I decided to try miniaturizing a JTM45 next. I got the 1st prototype board etched last night and am waiting on some small PCB drill bits to come in before I can drill the board and populate the components. While I am waiting I thought I would bounce a few ideas off you guys and see if it sounds like it would fly or maybe you may have a better approach or an added feature that I could add. I am trying to design this so it fits in the same chassis as the Lil Devil and so far that is my only limiting factor.

The amp/PCB I have designed has 2 channels just like it's big brother. Unfortunatly I didn't have enough room for two seperate vol controls. I though about concentric controls on one pot shaft but haven't found a supplier for those yet. So the amp as is stands right now has a single shaft dual pot for the Vol I and VOL II and it controls both channels. I plan to add a small 3 pos switch like the Bright switch on a Express. The switch will enable you to select between Channel I, Both Channels or Channel II. Kind of a built in A/B/Y thing. I could also put this on a foot switch if you leave the front panel switch in the both position you could then use a footswitch. Only problem is this really doesn't allow for two different vol settings for each channel.

I'll try and post a few pics as I go along
Last edited by UR12 on Fri Jan 29, 2010 3:52 pm, edited 2 times in total.
User avatar
Structo
Posts: 15446
Joined: Wed Oct 17, 2007 1:01 am
Location: Oregon

Re: 2Watt Sub Miniature Plexi

Post by Structo »

Or jumper the channels like a lot of guys end up doing inside the amp. :D

Does sound like an interesting project.
Tom

Don't let that smoke out!
User avatar
UR12
Posts: 1570
Joined: Mon Nov 28, 2005 7:22 pm

Re: 2Watt Sub Miniature Plexi

Post by UR12 »

Structo wrote:Or jumper the channels like a lot of guys end up doing inside the amp. :D

Does sound like an interesting project.
In the middle position on the switch the channels are both engaged or jumped.
User avatar
gearhead
Posts: 928
Joined: Sun Mar 19, 2006 2:54 am
Location: Virginia (Fairfax)

Re: 2Watt Sub Miniature Plexi

Post by gearhead »

Might be too late, but you might try putting a "balance" knob on the back. Would dictate the mix of regular and bright channels. At least for me, tend to adjust the mix of the two and keep it there.
User avatar
UR12
Posts: 1570
Joined: Mon Nov 28, 2005 7:22 pm

Re: 2Watt Sub Miniature Plexi

Post by UR12 »

gearhead wrote:Might be too late, but you might try putting a "balance" knob on the back. Would dictate the mix of regular and bright channels. At least for me, tend to adjust the mix of the two and keep it there.
Never too late. I am still prototyping. I ended up makeing 5 board revisions before the Lil Devil was done. This first one will be the basic design and then I want to start to add some of the better marshall style mods to see what it can do. I have also been thinking about the 2 input with cascading stages in the front end. That also may be a way to go.
dr. who
Posts: 479
Joined: Fri Feb 16, 2007 8:36 am

Re: 2Watt Subminiature Plexi

Post by dr. who »

UR12 wrote:I have had so much fun playing with the subminiature tubes I decided to try miniaturizing a JTM45 next. I got the 1st prototype board etched last night and am waiting on some small PCB drill bits to come in before I can drill the board and populate the components. While I am waiting I thought I would bounce a few ideas off you guys and see if it sounds like it would fly or maybe you may have a better approach or an added feature that I could add. I am trying to design this so it fits in the same chassis as the Lil Devil and so far that is my only limiting factor.

The amp/PCB I have designed has 2 channels just like it's big brother. Unfortunatly I didn't have enough room for two seperate vol controls. I though about concentric controls on one pot shaft but haven't found a supplier for those yet. So the amp as is stands right now has a single shaft dual pot for the Vol I and VOL II and it controls both channels. I plan to add a small 3 pos switch like the Bright switch on a Express. The switch will enable you to select between Channel I, Both Channels or Channel II. Kind of a built in A/B/Y thing. I could also put this on a foot switch if you leave the front panel switch in the both position you could then use a footswitch. Only problem is this really doesn't allow for two different vol settings for each channel.

I'll try and post a few pics as I go along
Here's someone who can do the concentric pot just like you want-
Vlado Hansal
hansal@mec-pickups.de
Last edited by dr. who on Thu Jan 28, 2010 7:34 pm, edited 1 time in total.
dr. who
Posts: 479
Joined: Fri Feb 16, 2007 8:36 am

Re: 2Watt Subminiature Plexi

Post by dr. who »

DBL post
MCK
Posts: 618
Joined: Mon Apr 27, 2009 4:49 am

Re: 2Watt Sub Miniature Plexi

Post by MCK »

Amazing! This will be great! Thanks much!
User avatar
UR12
Posts: 1570
Joined: Mon Nov 28, 2005 7:22 pm

Re: 2Watt Sub Miniature Plexi

Post by UR12 »

Thanks for the heads up on the pots. I contacted another mfg and he is sending me a sample . I was given a price of $18.50 ea if I order 100 and that doesn't include the knobs :shock: . I also found some small drill bits at Harbor Freight (God I love that place :lol: ) and hope to have the board drilled this evening so I can start populating it. The ones I had on order didn't ship until yesterday.
MCK
Posts: 618
Joined: Mon Apr 27, 2009 4:49 am

Re: 2Watt Sub Miniature Plexi

Post by MCK »

Thats it! I'm ordering 4 x 6" Alnico's from Weber and starting to build a slanted 4 x 6". I have no idea how it will sound but I have to have my mini Plexi half stack. Great idea to use the same chassis as Lil' Devil.
User avatar
UR12
Posts: 1570
Joined: Mon Nov 28, 2005 7:22 pm

Re: 2Watt Sub Miniature Plexi

Post by UR12 »

MCK wrote:Thats it! I'm ordering 4 x 6" Alnico's from Weber and starting to build a slanted 4 x 6". I have no idea how it will sound but I have to have my mini Plexi half stack. Great idea to use the same chassis as Lil' Devil.
I have a 1 x 12 cab coming in that I want to try the amp through if it ever gets here. Even though I will be using the same chassis I think I will try and do a scaled down version of the Marshall head cab instead of the Lil Devil style cab.
frequencycentral
Posts: 57
Joined: Wed Oct 22, 2008 11:27 pm

Re: 2Watt Sub Miniature Plexi

Post by frequencycentral »

.....
Last edited by frequencycentral on Mon Apr 12, 2010 6:29 pm, edited 1 time in total.
MCK
Posts: 618
Joined: Mon Apr 27, 2009 4:49 am

Re: 2Watt Sub Miniature Plexi

Post by MCK »

UR12 wrote: I have a 1 x 12 cab coming in that I want to try the amp through if it ever gets here. Even though I will be using the same chassis I think I will try and do a scaled down version of the Marshall head cab instead of the Lil Devil style cab.
Marshall head cab style is what I have in mind too. Please let us know how it goes with the EVM12L once you get it. All the best
User avatar
UR12
Posts: 1570
Joined: Mon Nov 28, 2005 7:22 pm

Re: 2Watt Sub Miniature Plexi

Post by UR12 »

frequencycentral wrote:Dana - what tubes are you using for this amp? 5902 and 6112?

Rick

Yes, 5902 and 6112

MCK wrote: Marshall head cab style is what I have in mind too. Please let us know how it goes with the EVM12L once you get it. All the best
I am still waiting on the speaker cab to come in but I'll keep ya posted.


Here is a couple of pics. I will be drilling the rest of the holes in the PCB today and maybe get some of the board populated tonight.
You do not have the required permissions to view the files attached to this post.
MCK
Posts: 618
Joined: Mon Apr 27, 2009 4:49 am

Re: 2Watt Sub Miniature Plexi

Post by MCK »

Looks cool!!!
Post Reply