I have an Opti4000D (same board as the SS XXX6500 I hear)
The problem is, that some frequency's sounded a bit like they had a 'stutter' to them. It only seemed to happen from about vol 18/26.
I adjusted the gain to zero and kept the headunit low then adjusted the volume to see if it was the amp or headunit. I then tried this with the gain. I have now found it is the amplifier at fault.
When I turned the gain up to a certain point and the bass went from sounding like a clean signal to a noise which I can only describe being like someone had dubbed over my CD with another bass-heavy track. It was still making bass, just not what I was playing...
It does not do this with the RCA's unplugged.
The amplifier switches on and works every time.
I have since checked ALL fets and output transistors and everything gives correct readings.
Has anybody seen this problem before?
The problem is, that some frequency's sounded a bit like they had a 'stutter' to them. It only seemed to happen from about vol 18/26.
I adjusted the gain to zero and kept the headunit low then adjusted the volume to see if it was the amp or headunit. I then tried this with the gain. I have now found it is the amplifier at fault.
When I turned the gain up to a certain point and the bass went from sounding like a clean signal to a noise which I can only describe being like someone had dubbed over my CD with another bass-heavy track. It was still making bass, just not what I was playing...
It does not do this with the RCA's unplugged.
The amplifier switches on and works every time.
I have since checked ALL fets and output transistors and everything gives correct readings.
Has anybody seen this problem before?
Yes. I have actually put another amp in the car temporarily while I diagnose this...
It works fine.
It works fine.
The two amps use a different input circuit and may not react the same to a bad shield ground. Check the shield ground and confirm that it's essentially 0 ohms for the head unit.
This seems more like a preamp level problem than anything else.
This seems more like a preamp level problem than anything else.
Hi Perry, did a few checks with the DMM today.
The RCA shields came back with 0.02Ohms so I assumed that they were OK. I checked and swapped the RCA's for some other known good ones.
I'm not sure if this means anything, I am hoping you can shed some light on it.
I checked the resistance between the RCA outer jacket (whilst plugged in to the amp) and ground. I got about 18-19Ohms. Does this sound about right?
I also noticed that touching a ground source the the shields on the amp (either input or output) gave a slight 'thud' at the sub...
You guessed it, I did a few gut shots of inside the amp which I'm about to upload. There are a few items that appear to have either been added on or fixed at some point... I'll get these uploaded now. Thanks
The RCA shields came back with 0.02Ohms so I assumed that they were OK. I checked and swapped the RCA's for some other known good ones.
I'm not sure if this means anything, I am hoping you can shed some light on it.
I checked the resistance between the RCA outer jacket (whilst plugged in to the amp) and ground. I got about 18-19Ohms. Does this sound about right?
I also noticed that touching a ground source the the shields on the amp (either input or output) gave a slight 'thud' at the sub...
You guessed it, I did a few gut shots of inside the amp which I'm about to upload. There are a few items that appear to have either been added on or fixed at some point... I'll get these uploaded now. Thanks
PS: Maybe some more useless information but, the resistance between the RCA plugs at the amp end (but not connected) and ground read -16.7Ohms
Again, I'm not sure if this is relevant or not?
Again, I'm not sure if this is relevant or not?
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Did you say that you had ~18 ohms from the amp's RCA shield to the amp's main ground (no RCAs plugged in)?
Yes, chassis to RCA
I have just been out to see if I could find anything else.
It would seem the problem is ALL frequencies at around 2-3 clicks volume (Alpine 4v pre outs). Not sure of the amps voltage output at this stage though. It plays cleanly above and below this 'patch'
I have just been out to see if I could find anything else.
It would seem the problem is ALL frequencies at around 2-3 clicks volume (Alpine 4v pre outs). Not sure of the amps voltage output at this stage though. It plays cleanly above and below this 'patch'
Disconnect all speaker wires from the terminal block on the amp and disconnect the RCAs from the amp. Measure the resistance across R34 in the amp. It's near the small transformer.
Does the blue capacitor near it show any signs of stress or damage (is it warped, bulging, melted)?
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