G7 build with 6SJ7

[gemini86]

Hey there...It's been a long time in the making, but I think I'm finally ready to share my latest G7 build.

Much thanks to the forum and Jakob E. for introducing the G7 project. It's the standard G7 circuit, but with a JAN 6SJ7 tube, being that they're very cheap. It's a little microphonic but, with a shockmount, it's not a problem. The circuit board is hand drawn, which I highly recommend for small PCBs like this. I did the layout in KICAD then printed the silkscreen layer with all the component holes, drilled it, then drew the traces with a sharpy (I  recommend using an actual resist pen, as I had problems with the sharpie fading in the etchant). The capsule is just a Chinese piece, but the output transformer is pure UNOBTAINIUM! (unless you live near a radio shack, part #273-1365) I might change this later, but firstly I wanted to see how it would sound, but after breaking in the tube with it, I actually really like the sound of the mic overall. The upper mids and highs are smooth and plosives are NOT an issue at all with this mic. Every other mic I have, I have to turn my head almost completely to keep from popping, and they all have a big peak in the 2k range(actually I'm pretty sure it's my voice).

Thanks again to the forum for making all this possible!

 

[gemini86]

Gut shot

 

[gemini86]

Tube mounting

 

[gemini86]

last one.

 

[3nity]

Wow!!
You outta post a sample with this mic...this is a nice build!!
Thanks.

 

[gemini86]

I uploaded a demo to my sound cloud. Please be kind, and note that it is a writing demo only, still in progress, but it's what I have on hand.

http://soundcloud.com/gemini86-1/plagurism-factory-demo

 

[gary o]

Coool, great work.....did you have to change component values for the 6SJ7 are they same as EF86 ?

 

[tchgtr]

Nice!...and I'm guessing there's nothing unusual about the PS, or you would've said something.
Don't know how I missed this the first time around.

 

[gemini86]

I did plot the load lines for the 6sj7 vs the ef86 and found they looked quite similar at the same operating point used in this circuit so no changes were made initially.  I did, however, just recently change the grid r from 1g to about 33m. The 6sj7 seems to be much quieter now, with little to no change in response.

The psu is straight forward, nothing special except being built inside a bread baking pan.

 

[tchgtr]

The psu is straight forward, nothing special except being built inside a bread baking pan.

I like the way you work
My Royer 1 build used an old lock box from a thrift store. About 1/5 the the cost of an ammo case.

 

[gary o]

me too I have a cat food can mic and a chocolate tin mic

I have a point to point G 7 in choc tin but my old ef 86s are noisy I might try the 6sj7......thanks

 

[gemini86]

It's not the perfect tube for that circuit, but it works well... It's dirt cheap on ebay, so I bought about eight of them... out of 8, I have 2 that are nice and quiet, no microphonics.

I want to get a few 5693 to try also... [edit] Nevermind....looks like the price on the 5693 more than tripled in the last 6 months... Stupid ebay...