6v6 JCM800 Layout - Build Finished!

[jayfitt]

Hi all,

My next build is a 20 watt 6v6 jcm800ish amp. I'm going to put it in a Hammond 12x8x2 enclosure, so I need the board to be about the same size as the Hoffman stout boards.

I've attached the layout. Can anyone see any issues or problems?

Thanks
jay

[sluckey]

Posting your schematic also would be a big help.

[jayfitt]

Added schematic to the first post. It's modified from your JMP/2204 schematic and the board is laid much like your plexi.

Thanks
-jay

[darkbluemurder]

Since the first two stages are cascaded in this layout, the outputs of V1a and V1b are out of phase with each other. I would put them a little farther away from each other by placing the filter cap between them. Otherwise the layout seems fine.


Good luck,
Stephan

[jayfitt]

Thanks Stephen. I already ordered the board but may have enough room to move somethings if it's an issue.

Jay

[jayfitt]

I finished this build about a week ago. I’ve updated the layout in the first post since I discovered a few errors during the build process.

I’m really digging the sound and spent the last week dialing it in. I ended up ditching the the 0.68uf bypass cap v2a as I found it a bit harsh. My goal was to have a small grab-n-go amp that could get me all the sounds I needed without pedals (if i was feeling really lazy). My band plays grungy rock so I needed a bit more gain at times. For the gain part I added an on-off-on gain structure switch (a la Friedman) on v1a where I can switch between 2.7k/0.68uf, 10k, or 3.2k (I may raise this). The 2.7k/0.68uf setting gets me where I need to be, along with a bit of squealing feedback if I’m not careful.

I was also surprised by the amount of clean headroom it had. A month ago I scored a handful of 1M dual concentric pots, so I decided to put in foot switchable gain and master pots. You can see this in the last pic below, the silver knobs are the gain and master (you can also kinda make out the structure switch hidden between them).  I found an old post by Geezer, used his layout and boom - a “channel switcher”! Works perfectly with my Marshall foot switch, even lights the LED. But then I tried to use my Line 6 HX Effects…..horrible ground loop noise when plugged in to the foot switch jack. I picked up a Behringer hum canceling box and placed it between the HX unit and amp. The hum is gone and the HX can switch “channels” fine but there is little hiss and my amp picks up AM radio at lowish volumes. I’m guessing this is a side effect of lifting the ground between the amp and HX unit.

It’s a definitely a fun amp to play. I used it at band practice this past Monday, just the amp - no pedals,  and was very happy with it.



-j

[sluckey]

Nice looking amp!