Soundstream MC120 power ON/OFF pop

[picco76]

Hi guys, i have one Soundstream MC120 with power ON and power OFF pop (bump).
It's normal for this amplifier?
I don't found MC120 schematics, maybe MC245 is similar?
Thanks in advance

 

[Perry Babin]

Do you have the 245? The 140 is below. I have no clue what the 120 is so you'll have to compare them.

 

[picco76]

Hi Perry, yes i have 245 schematics. Should be similar.. the 140 don't have anti-bump circuit, right?

 

[Perry Babin]

I don't see any muting.

 

[picco76]

Ok, then can be normal this "pop"..

 

[Perry Babin]

Some older amplifiers had a slight turn on/off noise. I don't know how severe this one is (would have to hear it in person, not on video) and would have to have experience with that specific model. I can't help there. Maybe someone who knows these old amps can help.

 

[picco76]

Yes i know, for example, HK CA260 have pop when turn on, and this mc120 have the same level (approximately), this is the first old soundstream on the my hand..

 

[cheezemanrich]

Early CA, D, and MC series without the output relays had the pop/bump. Later models had a relay which delayed the turn on and opened the output with the remote terminal.
Here is some info in Post#23:

B

Thread 'DC output in Soundstream MC245'

2007-04-06 3:10 pm

Hi everybody,

Recently I just bought a used SS amp MC 245. It has a little problem with the pop noise ONLY during on and off. However, the popping noise come from all channels EXCEPT the subwoofer output. I noticed that the sub out has its own relay, but not so for the other 4 channels. Anyone be kind enough to guide me to trace the culprit??

The DC output are small, but still it's annoying. Across 4 channels, it puts out 0.4 - 0.5 v. Help😀

Thanks

• bayiganteng
• Replies: 22
• Forum: Car Audio

 

[cheezemanrich]

Here is the circuit used to drive the later model relays.

 

[MOER]

Add in diff amp degeneration resistors of about 100R each emitter.
Increase the the 750R to R209 to 1K. Q202 then needs an emitter resistor of 82R.
Change R213 to 120R
Add in a resistor of 10K from Q205 collector to ground.

Who ever the "genius" was who designed this amplifier placed diode D1 before the fuse, so any reversal of the power connections will generally blow open D1 and then destroy the MOSFETs. Move D1 to the transformer side of the fuse.