reduce loudness circult

[Philip C]

Hi, I have a loudness circuit which need to reduce "output". how may I achieve this by fixed resistors by around 6-9db? How to calculate values? View attachment PM6006 Integrated Amplifier Service Manual PG9.pdf

 

[rayma]

Changing the feedback network could cause high frequency instability.
A series 50k to 100k before the volume control would do this safely.

 

[Philip C]

Thanks for your speedy reply!
if I put a 50K resistors after C2503/2504 (100V 0.1uf), would it not change the original circuit when in "no loudness mode"?

 

[rayma]

I think it will be ok, give it a try.

 

[Philip C]

If I want to remove the "treble lift" in the loudness circuit, should I remove and short C2501 / C2502?

 

[Philip C]

anyone please?

 

[rayma]

Looks like you would just remove them, but don't short them.

 

[Philip C]

thanks and will report on findings later!

 

[HumbleDeer]

The "Loudness' Circuit is oftentimes what they call the hearing curve compensation. It is a special dynamic type of EQ that adjusts the sound to the human hearing sensitivity when levels are below a certain threshold. Not enabling it should have it disabled. It is not active when it is not enabled.

 

[Charles Darwin]

If I want to remove the "treble lift" in the loudness circuit, should I remove and short C2501 / C2502?

Switch the 'Loudness' off and use the bass eq to boost instead.

I see no need to go inside the thing.

 

[HumbleDeer]

The Loudness Comp is supposedly proportional, so another solution to your concern could be to just play it louder

 

[Philip C]

Sorry for my late reply as I was busy with work. The amp now sounds better so far.

I would like to express my thank everyone for their advice on this thread as I have gained much on understanding the circuit.

Last question : What does changing R2501 / R2503 achieve, that is after adding 50 K adjustable resisters after C2503 / C2504.


Best Regards.

 

[rayma]

If you have removed those capacitors, the resistors do nothing.
When the capacitors are in circuit, the resistors set the loudness treble level.