Collins 6Q-1

[Matt C]

I stand corrected; after adjusting the humdinger pot (I knew I included that for a reason...) the noise at full gain is more like -93 dBfs.  That seems reasonably good.

 

[baadc0de]

I stand corrected; after adjusting the humdinger pot (I knew I included that for a reason...) the noise at full gain is more like -93 dBfs.  That seems reasonably good.

So, that's a pot between heaters with a grounded wiper?

 

[Matt C]

I stand corrected; after adjusting the humdinger pot (I knew I included that for a reason...) the noise at full gain is more like -93 dBfs.  That seems reasonably good.

So, that's a pot between heaters with a grounded wiper?

yes. in this case it worked well to reduce the amount of 60Hz hum on the output.

 

[Matt C]

finally got this thing completely put together and functional. Not really a "clone" since I wasn't going for original parts and all that, but the audio circuit is essentially identical to the schematic.  at some point I might rewire the pad and polarity switches, or add an input impedance switch, but everything is working well and I didn't have any real problems to troubleshoot. The layout is a bit unusual, but doing it this way let me keep the input lines as far away as possible from the PSU, and the filament wires didn't have to cross audio wires at any point.  As you can see, this thing may be lacking in physical beauty (my metal working tools are minimal and this is my first time putting something together "from scratch"), but personally I like the homemade look. Noise performance seems to be pretty solid, both channels show up at around -91 dBFS. 

here's a brief run down of some of the parts used, and some pictures of the finished thing.

Blank 2RU case from Collective Cases (thanks Dan)
Cinemag CMQEE-3440A mic input transformers
Edcor WSM 15k/600 output transformers
Turret Boards made from 1/8" Garolite (ordered from McMaster-Carr), the turrets themselves are from Hoffman Amps.
the tubes came from ebay and tubedepot
paper-in-oil output coupling caps came from ebay too.
power transformer from Antek

 

[Seamus]

Love it!

 

[letterbeacon]

Great work!

 

[Dr Gris]

Very nice, congrats!!

How much B+ are you feeding them with?

Best
M

 

[Matt C]

How much B+ are you feeding them with?

with both channels hooked up, B+ is around 143 Vdc

thanks everyone!