Quad FM4 increase output level

  • No one logged in.

29-Oct-2017 02:38 PM

Lingo

Lingo

Posts: 27

How to increase Quad FM4 output level to 1.0v? Because if use other brand preamp might need to 1.0v~1.5v, but Quad FM4 output level only 0.3~0.5v. Thanks for helping.

  Reply

30-Oct-2017 03:21 AM

EJP

EJP

Posts: 1405

You can get 6dB more signal out of an FM4 by modifying the circuit around the LM4500 multiplex decoder IC as shown in Figure 4 and the accompanying table of the LM4500 datasheet.

EJP
  Reply

31-Oct-2017 10:47 AM

Lingo

Lingo

Posts: 27

I check FM4 service manual, If want gain 6dB (default is 3 dB), change as follow :
 C44,C45=6.80nF,
 R55,R56=27KR,
 R52,R53=10KR.  
Thanks EJP

  Reply