Saturday, September 25, 2021

TRIDENT: A-Range Channel Output Amplifier

After some success with the Trident mic preamp (AKA the Revox A77 Preamp), I thought I might try another section of the console - this time the EQ / Channel output amplifier.

It looks interesting on LTspice, as towards the end of the gain range, you get a distinct bump in the mid-range.   At the moment I've left the values on LTspice fairly stock, except of course for running at 9v.  

Like other projects - if successful, I'll post a working vero layout.  If not...  well, I'll move onto the next one, or better yet, finish the growing number of incomplete projects that I have.

I’m calling it the Sea King for the moment, which is perhaps a bit presumptions, as I don't even know if this will work well enough to warrant a name.


TRIDENT A-RANGE CHANNEL OUTPUT AMPLIFIER SCHEMATIC

TRIDENT A-RANGE CHANNEL OUTPUT AMPLIFIER SCHEMATIC


LTSPICE

working notes reference schematic below:  

  • input and output caps can be smaller
  • Reducing C13 reduces bass
  • Increase C12 to reduce highs
  • C15 can be as low as 10u without any real impact (in spice anyway)
  • gain pot may need to be quite small - def not 5k, more like 500ohm
  • changing R18 moves the mid hump / and low end to some degree, as well as some change to gain, might be interesting as a pot (1k resistor + 20k pot)
  • Try a single diode for biasing, R24 may not be required (low value trimmer on original)

Trident channel amp modded schematic v2a






PROTOTYPE V1 - SEA KING ON VISUAL ANALYZER

caution re levels - start low
 
This starts with adjustments to R18 using a 25k pot, with the gain set fairly high, then changes to the gain control.  

 

 



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