Federal AM864 - My build

Gavin Pursinger · Jul 5, 2023

Attack/release are 1meg and 2.2.mfd...my ear says it is right for singers...I won't track with it right away...just Chanel patch it on return til I get to know it better

thomasdf · Jul 6, 2023

The description you are making for the audio seems right on. I've had an original one and built a clone years ago, which ended up as a donor for other projects. But I have plans to build another one some day from scratch parts. IIRC it wasn't very subtle and quite agressive but yet sounded a bit wooly somehow, very tubey. Nothing like an opto or a 6386 varimu, but def a lovely useful color in my setup.

Re the finish, I did some research and apparently you can get that with high temperature wrinkle paint... It's pretty expensive and needs baking but should look cool. I'll give it a try soon on a STA level clone, hopefully.

scott2000 · Jul 6, 2023

Gavin Pursinger said:
.need to explore my control voltage as it is high compared to manual specs

Here's a quote from PRR
"However the "current control" is your main control of knee sharpness and ratio. If you set it to zero volts, it has a very soft knee and low ratio. For limiting, you have to set it to a fairly high voltage. For high-ratio limiting, maybe near 20V. It wasn't made to do that, as shown by the pretty lame control amp. I suspect 2 or 3 volts gives a good range of no-action, and above that a range of lower dynamic range. If you are compressing clean tracks for effect, maybe you want compression to start early and soft, so 1V might be your setting."

Gavin Pursinger · Jul 6, 2023

Thank you very much for all this info...my control voltage is at 11 when the 1ma meter is at 1.0 if I get it down to 3vdc the meter is so low on the scale it is useless...unit sounds 'cleanest' up in the 8 to 100 range...I need to make an h ad for the 2 volt audio meter as I don't want to fry it...I tried tying a 600 ohm resister across it but that certainly did not help the sound quality. I should pull the 6sq7 to see what it sound like w/ no gr....I do like this thing@@...thx

xazrules · Jul 6, 2023

thanks for the info, i'll keep it as my next project.

thomasdf said:
The description you are making for the audio seems right on. I've had an original one and built a clone years ago, which ended up as a donor for other projects. But I have plans to build another one some day from scratch parts. IIRC it wasn't very subtle and quite agressive but yet sounded a bit wooly somehow, very tubey. Nothing like an opto or a 6386 varimu, but def a lovely useful color in my setup.

Re the finish, I did some research and apparently you can get that with high temperature wrinkle paint... It's pretty expensive and needs baking but should look cool. I'll give it a try soon on a STA level clone, hopefully.

can you post link or examples of the paint job? what is wrinkle paint? what's the purpose of baking?

Gavin Pursinger · Jul 7, 2023

The finish on this salvage front panel has a kind of sandy grit in it...I think the panel is low grade steel as it chewed up my titanium drill bit..here is my best picture ... my 1 ma meter for gr does not have polarity marks on it and I may have wired it backwards ? Ain't this fun ;- )