Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: tubenit on October 19, 2012, 11:30:10 am
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Guys,
So, I have this Tweed BluezMeister (great sounding amp!) in a tweed style chassis. I think it was an 18w chassis blank,IIRC?
I'm going to go back into that chassis and install Doug's relay boards so I can switch both clean/OD & midboost (instead of just clean/OD like it currently is).
And since I'm going back in .......... I thought about other mods to make?
I've been using a D-lator type active FX box with it and it sounds superb with that. So much so that I am thinking that I'd love to have this small combo amp have the FX on board to keep it a quick, small, grab & go amp.
The thing about the D-lator is that it makes a fabulous master volume and I can substitute the "return" pot for a master volume pot.
Yet the chassis space is REALLY tight given everything going on.
So, I'm pondering the idea of "floating" a double decked active FX board above (mostly) the LTPI section of the current layout board. I do have room for the added tube and the socket hole is currently punch out and "capped" with a plate.
Question: Has anyone here ever tried double decking an active FX loop board? Or double decking a layout board of any kind? Or know of a production amp that double decks boards successfully without added noise or oscillation?
I'd really have alot going on in the amp with clean/OD, relay switching and active FX in a small tweed style chassis ............ AND I'd love to make all that work if possible. I don't know if this is a realistic effort to attempt. The amp sounds wonderful as is and it's VERY quiet with floor noise at idle. I like that!
I think I've figured out how to attempt this in a way that I can easily undo it if it doesn't work. In other words, make this an experiment that's not so intrusive that it can't be undone with reasonable minimal effort.
Thoughts????
With respect, Tubenit
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I've thought about it, and I think someone built a Champ-reverb (with 6BM8 for reverb) where the reverb was built on a board that was stacked: http://music-electronics-forum.com/t22660/ (http://music-electronics-forum.com/t22660/)
I think it would save quite a bit of real-estate, but I suspect layout could be critical. :think1:
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I haven't done double-deck boards but I've done both sides of a vertically mounted board with success.
-John
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May be your double staked board can have benefit using an intermediate iron shield connected to ground
(a thin piece of galvanized iron sheet)
K
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Tubenit, you can point-to-point a lot of the loop if you are able to locate the tube socket near the knobs/jacks.
Here's a portion of a layout where I did that. It's a slightly stripped down 2-knob version of the Dumbleator loop with a bypass switch. I built this and it's working fine for me.
http://i50.tinypic.com/2rwnu6w.jpg (http://i50.tinypic.com/2rwnu6w.jpg)
-John
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Tubenit, you can point-to-point a lot of the loop if you are able to locate the tube socket near the knobs/jacks.
That looks like a fantastic idea, but unfortunately won't work in my small cramped tweed style chassis.
I have the chassis out to put in the new relay boards (hopefully tomorrow). Looking over it, double decking the FX over the LTPI looks like a possible option from a physical space vantage point. Whether there are oscillation or hum problems from that ............. I don't know?
With respect, Tubenit
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It shouldn't be a problem as long as you properly consider all the normal wiring/lead dress issues.
That is, are you keeping related circuits together? Are you keeping lead length short (especially grid wires), and not passing high-level late signals near low-level early inputs? Are you keeping the wire runs related to the grids and their grid reference resistors short?
As long as your loop enters/exits right at the phase inverter, I don't think it should be a problem with mounting a second board layer there. I'm envisioning short metal standoffs between the two boards, with maybe a single screw through each top board hole, through the spacer, through the lower board, through the lower board's standoff, through the chassis and secured with a nut outside.
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I tried it in a build and I had oscillation issues, but that was for other reasons, not due to the double decker setup. I am sure it can be done just fine as long as you follow good layout practice. Instead of 2D you are just connecting stuff in 3D..shouldn't be any different...
Greg