Lanzar Optidrive 4000D problem

Custom Chris · 19th June 2011, 09:36 PM

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?

Perry Babin · 19th June 2011, 10:54 PM

Have you confirmed that the shield ground on your head unit is intact?

Custom Chris · 19th June 2011, 11:28 PM

Yes. I have actually put another amp in the car temporarily while I diagnose this...
It works fine.

Perry Babin · 20th June 2011, 12:08 AM

Was the second amp identical?

Custom Chris · 20th June 2011, 12:12 AM

No, it was a pair of Kenwood 9152D's strapped.

Perry Babin · 20th June 2011, 12:29 AM

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.

Custom Chris · 20th June 2011, 01:07 AM

OK thanks Perry. Will check and report back.

Custom Chris · 20th June 2011, 08:42 PM

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

Custom Chris · 20th June 2011, 08:45 PM

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?

Custom Chris · 20th June 2011, 10:39 PM

19th June 2011, 09:36 PM	#1
Custom Chris diyAudio Member Join Date: May 2011	Lanzar Optidrive 4000D problem 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?

19th June 2011, 10:54 PM	#2
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Have you confirmed that the shield ground on your head unit is intact? __________________ Links >> Basic Car Audio Amp Repair * Basic Car Audio Electronics * New Site * Basic Switching Power Supply Design * Basic Computer Skills << Links

20th June 2011, 12:08 AM	#4
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Was the second amp identical? __________________ Links >> Basic Car Audio Amp Repair * Basic Car Audio Electronics * New Site * Basic Switching Power Supply Design * Basic Computer Skills << Links

20th June 2011, 12:29 AM	#6
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	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. __________________ Links >> Basic Car Audio Amp Repair * Basic Car Audio Electronics * New Site * Basic Switching Power Supply Design * Basic Computer Skills << Links

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19th June 2011, 11:28 PM	#3
Custom Chris diyAudio Member Join Date: May 2011	Yes. I have actually put another amp in the car temporarily while I diagnose this... It works fine.

20th June 2011, 12:12 AM	#5
Custom Chris diyAudio Member Join Date: May 2011	No, it was a pair of Kenwood 9152D's strapped.

20th June 2011, 01:07 AM	#7
Custom Chris diyAudio Member Join Date: May 2011	OK thanks Perry. Will check and report back.

20th June 2011, 08:42 PM	#8
Custom Chris diyAudio Member Join Date: May 2011	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

20th June 2011, 08:45 PM	#9
Custom Chris diyAudio Member Join Date: May 2011	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?

20th June 2011, 10:39 PM	#10
Custom Chris diyAudio Member Join Date: May 2011

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